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Home My WebLink AboutREPORT 02JESSIE GLEN Stormwater Pollution Prevention Plan October 2005 Prepared for JPS Holdings. LLC 18124 Riviera Place SW Seattle. WA 98166 (206) 799-3051 Prepared by ESM Consulting Engineers. LLC 33915 1st Way South. Suite 200 Federal Way. WA 98003 253.838.6113 tel 253.838.7104 fax www.esmcivil.com 0 '"'" ~ c;, CJ '" ~ <0 "'" ~ :<:: ~ fa i:::~ s$ Orn '->ll.J ::g!!5 ?@ '" ~ JESSIE SLEN Stormwater Pollution Prevention Plan October 2005 Prepared for JPS Holdings. LLC 18124 Riviera Place SW Seattle. WA 98166 (206) 799-3051 Prepared by ESM Consulting Engineers. LLC 339151st Way South. Suite 200 Federal Way. WA 98003 , 253.838.6113 tel 253.838.7104 fax 55M www.esmcivil.com SECTION 1 SECTION 2 SECTION 3 SECTION 4 TABLE OF CONTENTS Stormwater Pollution Prevention Plan Erosion/Sedimentation Control Design Vicinity Map Application for General Permit to Discharge Stormwater Associated with Construction Activity (Notice of Intent) Washington State Department of Ecology Guidance Document for Applying for Ecology's General Permit to Discharge Stormwater Associated with Construction Activity 2005 King County, Washington Surface Water Design Manual Appendix D -Erosion and Sediment Control Standards Geotechnical Report Temporary Erosion and Sediment Control Plans 1:IESM-JOBSI116610011005Idocumentlswppp.doc SECTION 1 The Temporary Erosion and Sediment Control (T.E.S.C.) Plan consists of the using the latest techniques for stabilizing a construction site during construction. The recommendations for erosion control measures are shown on the plans and maybe referenced for your use in Section 4. Following this page are a Vicinity Map and the Application for General Permit to Discharge Stormwater Associated with Construction Activity (Notice of Intent) (' , o 7;:,; ~ .. ~. W /~ 0,8 <N ., ,;;;':! " . ~ W •• /~ c:-ESM SE 186TH ST SE 188TH ST SE SE 192ND ST SE 196TH ST VICINITY MAP CONSULTING ENGINEERS 33915 1st Way South Federal Way, WA 9eooa NOT TO SCALE LLC BOTHEu 425 ~!S-61" www.esmcivil.com FtDtRAL WAY 1"'1 alfI-&I13 CLE ELUI,! !>O9 ~'4_ 1905 /' .!! Civil Engineering Land Surveying Lend Planning JOB NO. DRAWING NAME DATE: DRAWN SHEET OF n 1166-001-005 EN-03 2005-09-13 EAP ... i5 Public: Wo .. l<;s Project l.4on0ge""en1 Lcmdseope At'e-hitecture ~~L-~~~~~ ____ ~ __ ~ ____ ~ __ ~ __ ~-=~~~~~~~~ ________________________________________________________ -1 Application for General Permit to Discharge Stormwater Associated with Construction Activity (Notice of Intent) o Change of Information Permit # 803 - (Please print in ink or type) Please Read NOI Instructions Before Filling Out This Form I. Contact Person II. Owner/Representative of Site (All correspondence will be mailed here) Contact Name Phone No. Owner's Name Phone No. Joe Singh 206.799.3051 Joe Singh 206.799.3051 Company Company Name JPS Holdings. L.L.C. JPS Holdings, L.L.C. Mailing Address Mailing Address 18124 Riviera Place SW 18124 Riviera Place SW City State Zip + 4 City State Zip + 4 Seattle WA 98166 Seattle WA 98166 III. Site Location/Address IV. 8·1 I ling Address Site Name Contact Name Phone No. Jessie Glen Joe SinQh 206.799.3051 Street Address (or Location Description) Company Name Property is located east of 116th Avenue SE, west of 120th JPS Holdings, L.L.C. Avenue SE, and north of SE 192nd Street in unincorporated Kinq CountY, on the east Hill of Kent. City (or nearest city) Zip + 4 Mailing Address Renton 98058 18124 Riviera Place SW County City State Zip + 4 Pierce County Seattle WA 98166 Provide legal description if no address for site (attach separate sheet if necessary) A legal description is enclosed. v. Receivin Water Information (check all that apply) A. Does your construction site discharge storrnwater to: 1. It8J] Storm drain system -Owner of storm drain system (name)~ 2. IIB:IIlndirectly or directly to surface waters ID River IDI Lake IIB:II Creek IDI Estuary IDI Ocean IDI Wetland) 3. D Directly to ground waters of Washington state. IDI Dry Well [] Drainfield IDI Other (Infiltration Pond) Initial discharge is to an unnamed receiving water? IDI Yes IDI No (Site Infiltration) C. Location of discharges (Use any of the following to most accurately identify location of discharge. Attach a supplemental sheet if more than one discharge point and/or numerous receiving waters.): 1. Map enclosed (Mark discharge point on map and provide distance from receiving water.) (Specify degrees, minutes, and seconds.) 2. NEY. SEY.; Section 22 Township 23N Range 05E __ % __ y.; Section __ Township __ Range __ 3. Latitude __ Longitude __ Latitude __ Longitude __ Latitude Lon itude VI. Construction Activit Information 1. Total size of site 7.70 acres Total area to be disturbed 3.31 Acres How many phases? 1 2. Will any portion of the project be sold to private developers? II2JI Yes ID No 3. Projected startup date: November/2005 month/year Proposed completion date: October/2006 month/year 4. Will there be dewatering activity? DYes disposed of: __ II2lI No If yes, give brief description of location of such activity and how water will be 5. Check all construction (soil disturbing activities) that apply. Attach a supplemental sheet if necessary. II2J1 Clearing II8II Utilities Il8lI Landscaping Homes (How many?) IISJI Grading II2II Stormwater Facilities [t2D Trails [t2D Single-family ~ IISJI Demolition Roads/Streets [t8lI Parks Multi-family IIB:II Other limG1BM~ 1DI0ther __ 1DI0ther __ o Importing Soil o Exporting Soil o Stockpiling !OJ Retaining Walls IEJI Piping Systems Filling Wetland IDIlndustrial Buildings IDI Townhomes __ Type __ IDI Condominiums __ Site VII. Stormwater Pollution Prevention Plan OOther __ OOther __ A. Best Management Practices (BMPs) (Check all that apply.) Attach supplemental list if needed to include other BMPs. IEJI Silt Fencing 0 Wheel Wash Area 0 Riprap Channel Lining 0 Slope Reduction IDI Vegetated Strips IDI Nets and Blankets ~ Interceptor Trenches/Ditches IDI Chemical Treatment o Straw Bales OSwale 0 Culverts 0 Kiln Dust o Mulching 0 Diverted Flows IEJI Pipes IEJI Dust Control IEJI Hydroseed 0 Dikes 0 Benms IEJI Other_ ID Plastic Covering IDI Check Dams IDI Terracing IISJI Other Rock construction entrance B. Stormwater Pollution Prevention Plan (SWPPP) Has a SWPPP been developed that includes a narrative and drawings? ~ Yes If NO, will a plan be developed prior to the start of construction? IDI Yes DNa DNa If you answered "NO" to the above question, notify Ecology in writing when a final Plan has been developed. A permit will not be issued until a confirmation letter has been received by Ecology. The SWPPP is to be implemented when construction activity commences on your ro·ecL VIII. If the SEPA process has not been completed at the time of NOI submittal, a foJJow~up letter must be sent to Ecology with the following information prior to Ecology granting permit coverage. Has a SEPA review been completed? Type of SEPA document IEJI Yes IEJI DNS DNa o Final EIS Agency issuing DNS, Final EIS, or Exemption King County; Date September 16 2005 Are you aware of an appeal of the adequancy of the SEPA document? (If yes, please attach explanatory letter.) DYes o Exempt o MONS SEPA requirements must be complied with prior to permit issuance. IX Public Notice The public notice must be published at least once each week for 2 consecutive weeks, in a single newspaper, which has general circulation in the county in which the construction is to take place. See the NOI instructions for the public notice language requirements. Permit coverage will not be granted sooner than 31 days after the date of the second public notice. Note: This NOI must be submitted to Ecology on or before the date of the first public notice. PUBLIC NOTICE JPS Holdings. L.L.C. (Name oj Owner; or name of owner % engineering firm, architect, etc) 18124 Riviera Place SW. Seattle. Washington 98166 (Address oj owner, or % Representative) is seeking exemption of the Washington Department of Ecology's NPDES General Permit for Stormwater Discharges Associated with Construction Activities. The proposed 7.70 acre (Total acres) project, known as Jessie Glen (Project name) is located east of 116th Avenue SE, west of 120th Avenue SE, and north of SE 192nd Street (Street address, intersection, crossroads, or other descriptive site location) l!:! unincorporated King County, on the east Hill of Kent (Name oJnearest city). Approximately 3.31 acres (Number oJdisturbed acres) will be disturbed for construction of ~ublic right~of-wa~ and 49 single famil~ residential lots. (List all construction activity, e.g., clearing, importing/exporting materials, demolition, grading, stormwater facilities, roads, utilities, number buildingdhomes and type, sidewalks, landscaping.) Demolition shall consist of removing existing fence within the right of wa~ of 116th Avenue SE and 120th Avenue SE. Clearing and grading will be ~eformed for the construction of the groQosed roadways, utilities, ~ark and trails. The develoger will utilize intercegtor ditches to direct runoff towards proposed catch basins with filter fabric installed around the perimeter of the inlets. Temgora[y sediment trags will be provided. (Brief description of how the stormwater will be cleaned and controlled), A tightline drainage system will convey stormwater into a water guality and infiltration stormwater facili~ and discharge to Soos Creek a~rroximately Y.s mile east of the site. (Clarify the direction of the stormwater flows) (List wetlands, unnamed and named receiving waters and storm drains; clarify if buffers will be used to protect sensitive waterbodies.) Any person desiring to present their views to the Department of Ecology concerning this application, may notify Ecology in writing within 30 days from the last date of publication of this notice. Comments may be submitted to: Dept. of Ecology, Stormwater Unit, PO Box 47696, Olympia, W A 98504-7696 Provide the exact dates (mm/dd/yy) that the first and second public notices will appear in the newspaper: Date of the first notice 10 J 22 J 05 ; Date of second notice 1Q 1 291 05 Name of the newspaper which will run the public notices King County South Journal Ecology is no longer reQuirin.a the submittal of the affidavit of publication. 2 I Complete the above public notice information or provide a copy ofthe notice to be published. X. Regulatory Status A. lUI NPDES Permit (e.g., industrial stormwater) C. ILU Air Notice of Construction, Permit, or Order Permit No. --Agency __ B. ID State Waste Discharge Permit D. lUI StateJUSEPA Hazardous Waste 10 No. Permit No. ---- XI. Certification of Permittee(s) "I certify under penalty a/law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsiblefor gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. J am aware that there are significant penalties for submitting false information, including the possibility affine and imprisonment for knowing violations. " owner/Representat!?e,s Printed Name Title ~f!~ IltjP oat? Sign and return this document to the following address; for questions call (360) 407-6437: Washington Department of Ecology, Water Quality Program, Slormwater Unit, PO Box 47696, Olympia, WA 96504-7696 The Department of Ecology is an equal opportunity agency and does not discriminate on the basis of race, creed, color, disability, age, religion, national origin, sex, marital status, disabled veteran's status, Vietnam Era veteran's status, or sexual orientation. (Rev. 3/01) IIEsm8lengrlESM-JOBSl116610011005ldocumenllnoLDOC 3 I LEGAL DESCRIPTION -Jessie Glen Legal descriptions taken from First American Title Insurance Company, File Number 4261-473774, 1111/2004 APN: 619840-0080-04 (parcel "An) APN: 619840-0100-00 (parcel "Bn) APN: 619840-0120-06 (parcel "Cn) APN: 619840-0140-02 (parcel "Dn) APN: 619840-0320-04 (parcel "En) Parcel "An: Lot 4 in Block I of the Northwestern Garden Tracts Div. No.4, according to play recorded August 24, 1950 in volume 47 of plats aIPage(s) 74, in King County, Washington. Parcel UBJ1 : Lot 5 in Block 1 of Northwestern Garden Tracts Div_ No.4, according to plat recorded August 24, 1950 in Volume 47 of plats at Page(s) 74, in King County, Washington. Parcel ~~cn: The East 30 feet ofl.ot 6 in Block I of Northwestern Garden Tracts Div. No 4, according to plat recorded August 24, 1950 in Volume 47 of plats at Page(s) 74, in King County, Washington. Parcel liD": Lot 7 in Block I of Northwestern Garden Tracts Div. No.4, according to plat recorded August 24,1950 in Volume 47 of plats at Page(s) 74, in King County, Washington; Except the North 70 reet of the West 225 feet thereof; And Except the West 300 reet of the remainder or said Lot 7_ Parcel "D· 1 ": A non-exclusive easement for ingress and egress Cleated by instrument recorded December 27, 1993 under Recording Nos. 9312272113 and 9312272116. Parcel ~~E": Lot 7 in Block 2 of North western Garden Tracts Div. No.4, according to plat recorded August 24, 1950 in Volume 47 of plats at Page(s) 74, in King County, Washington; Washington State Department of Ecology Guidance Document for Applying for Ecology's General Permit to Discharge Stormwater Associated with Construction Activity Guidance Document for Applying for Ecology's General Permit to Discharge Stormwater Associated with CONSTRUCTION Activity Who Should Read This Brochure? • Developers • Contractors • Consultants • Home Builders • Local Governments Linda Matlock Technical Services Unit Construction Stormwater Permits Department of Ecology Water Quality Program PO Box 47696 I Olympia, WA 98504-7696 L ___ ~_ 360.407.6437 FAX 360.407.6426 Imat461@ecy_wa.gov Ecology is an equal opportunity employer Revised May 2004 INSIDE Why does Ecology have a stormwater permit ...................... 1 Who needs to apply? ........ " .............................. . .1 What type of construction activities need Ecology's permit? 1 How to apply the five acre Ihreshold _"",_."""""""".""""." 1 Individual stormwater permits ........................................... 2 Projects with less than five acres....... . ................... 2 What types of sites do not need the permit ..... . ................. 2 Penalties... ........................................... ..2 When to apply......... . ............ 2 Before submitting your application ...................................... 2 Submit application to ..... Permit fees ........... _ ............................. 2 .. ................... 3 When and how to terminate your permit ..... . ........ 3 What does the permit require? .. .. ...... 3 Erosion and Sediment Control Plan ..... . . .......... 3 Objectives of the ESC Plan. .. ......... 3 ESC Plan contents and requirements .......................... .3 Spill Prevention and Emergency Cleanup Plan .................... 4 Chemical treatment of stormwater ....................................... 4 Public notice requirements .............................................. 5 Where to get help.. . ................. 6 Ecology regional offices contacts.. . ............ 6 Stormwater manual information .. ............. 7 How to get copies of stormwater manual.. . ...... a Instructions and application ...................................... Included ~, "I prtnted on recycled paper Publication No. 99-37 NOTICE Construction permit is being revised The guidance information contained in this booklet will change when the current general storm water permit for construction is re-issued. Once the newly revised permit goes into effect, there will be a new application form. Phase II rules may require monitoring stormwater discharging from your project and reporting to Ecology, plus other new requirements. Mixing zones may apply. The threshold will be lowered to include 1 - 5 acre sites that discharge stormwater to a receiving water or storm drain that discharges to receiving waters of the state. Ecology has not decided whether a separate stormwater permit will be issued for the I - 5 acre sites or be included with the revision of the current general stormwater permit for construction. Updated stormwater information will be posted on Ecology's website. When the final decisions have been made on what will be required in the newly revised permit (and if a separate permit will be issued for the I - 5 acre projects), a new guidance booklet will be developed to assist you when applying for permit coverage in the future. Why does Ecology have a stormwater permit for construction? Ecology's stormwater permit for construction activities is required by federal regulations (40 CFR, Parts 122, 123, and 124 Subchapter D which implements the Federal Clean Water Act 1987, Section 402 (P». The goal of the permit is to reduce or eliminate stormwater pollution and other impacts to surface waters from construction sites. Who needs to apply? The site owner is the permittee and is responsible for applying and complying with the permit. At construction sites for which a lease, easement, or other use agreement has been obtained from the site owner, the entity obtaining the use agreement is required to apply. Note: Ecology's stormwater permit is required even though you may have acquired permit(s) from the local government for your construction site. Ecology's permit does not supersede more stringent requirements of the local government. 'll municipalities statewide are required to apply _ or permit coverage if they have construction projects with five or more acres of disturbed soil and with a discharge of stormwater to a receiving water of the state. What type of construction activities need Ecology's permit? Any soil disturbing activity, such as clearing, grading, excavating, and/or demolition that will disturb five acres or more of land area and have a discharge of stormwater from the site into surface water(s), or into storm drainage systems which discharge to a surface water. (Surface waters may include wetlands, ditches, rivers, unnamed creeks, lakes, estuaries, marine waters.) Land Conversion. A site that has five or more acres ofland that is being converted from a silvicultural (forested area) to a residential/commercial 'evelopment is required to have overage under the storm water permit for construction. Consider activities such as logging, clearing, pulling stumps, grading, construction of berms, detention ponds or swales, or any other soil disturbing activity. If there is a potential, or a definite discharge of stormwater from the site, to a receiving water and/or storm drains, the project requires stormwater permit coverage. Schedule earthwork for the dry season. Road Projects. Permit coverage is required for road projects that have a potential to cause an environmental impact to surface waters of the state. Constructing Infiltration System. Plans may be to infiltrate stormwater on site. If the stormwater cannot be retained on site until the infiltration system is constructed, permit coverage is required. How to apply the five acre threshold Normally, a stormwater permit is not required when less than five acres of total land area will be disturbed. However, if the construction is "part of a larger common plan of development or sale," defined as a contiguous area where multiple separate and distinct construction activities may be taking place on different schedules under one plan, the total area that will be disturbed must be considered. For example, if the total land area to be disturbed in the phased construction of a subdivision totals five acres or more, Ecology's stormwater permit must be obtained prior to beginning construction on the first phase. Note: Only those phases for which the SEP A (State Environmental Policy Act) requirements have been completed, may receive permit coverage. For construction of subdivisions, the five acre threshold which triggers the permit requirements applies only to land which is disturbed by the land owner, land owner's representative, or a contractor to the land owner. If the owner (or the owner's representative or contractor) is only installing roads and utilities, only land disturbed for that construction should be calculated to determine whether the five acre threshold will be exceeded. Land to be disturbed by independent contractors who purchase lots from the owner should not be considered when deciding the owner's Page 1 responsibilities, unless the individual lots are disturbed (e.g., by grading) prior to being sold. "f an independent contractor has purchased ontiguous individual lots which will disturb a total of five acres or more, that contractor must obtain a stormwater permit from Ecology. Individual stormwater permits Large construction sites may be required to have coverage under an individual stormwater permit written specifically for the site. Ecology's regional office staff makes the final determination. Projects with less than five acres Any construction activity discharging stormwater which Ecology determines to be a significant contributor of pollutants to waters of the state may be required to have permit coverage regardless of the project size. What type of sites do not need the permit? ® Sites at which the total area to be disturbed is less than five acres. <) Sites at which all the stormwater is retained on site (discharges to the ground through infiltration basins, dry weIls, drain field, or other means of discharge to the ground). ® Any part of a facility with a stormwater discharge resulting from remedial action conducted by the U.S. Environmental Protection Agency (USEPA) or Ecology or a potentially liable/responsible person under an order or consent decree issued under the Comprehensive Environmental Response, Compensation, and Liability Act. ® Emergency construction required to protect public health and safety. ® Construction activity for routine maintenance of existing facilities to maintain original line and grade, or hydraulic capacity. ® Nonpoint source silvicultural (forestry) activities. Federally-owned or operated projects, projects on tribal land, or projects discharging directly to tribal waters which have USEPA approved Water Quality Standards. Page 2 ® Facilities covered under existing NPDES individual or general permits in which stormwater management or treatment associated with construction activity is already addressed. Penalties for failure to apply for and comply with the permit Owners of construction sites should be aware that the discharge of stormwater without Ecology's permit is a violation of state and federal law and may bring enforcement action by Ecology or citizens' law suits. Failure to comply with the permit requirements is also subject to legal action. Ecology can issue penalties of up to $10,000 a day for each violation. When to apply At least 38 to 60 days prior to any clearing, grading, excavating and/or demolition activities. Before submitting your application for a stormwater permit, you should: 0" Develop a Storm water Pollution Prevention Plan. 0" Comply with the State Environmental Impact Statement (SEPA). 0" Draft your public notice. 0" Submit a draft of the Nor and public notice to Ecology for review prior to publishing the public notice. Drafts may be faxed to 360.407.6426. Submit lication to: Mailing Address Department of Ecology Water Quality Program Stormwater Unit PO Box 47696 Olympia WA 98504-7696 Physical Address Department of Ecology 300 Desmond Drive Lacey WA 98503 The Notice ofIntent (Nor) is the official permit application. The Nor is a simple three page form which requests information about your site. (A Nor is included with this pamphlet.) Permit fees There is no application fee; however, state law ~quires that all permittees pay an annual permit ee. The annual permit fee is $353. Fees are set by state regulation, and may be changed only by amendment of the regulation. Permittees will be billed soon after receiving their permit. Thereafter, Ecology bills permittees annually. Call Bev Poston, Fee Administrator, at 360.407.6425 if you have questions concerning fees. When and how to terminate your permit Request termination of permit after all soils have been stabilized with a permanent vegetative cover (or equivalent permanent stabilization measure), all temporary control measures have been removed, and all paving is complete. Wooden peQs sodding Sod should be laid perpendicular to direction of slope Revegetation is an excellent form of erosion control A Notice of Termination form is located in the back of the permit. Mail the form to Department of Ecology, Water Quality Program, Stormwater Unit, PO Box 47696, Olympia WA 98504-7696. fl•· Permitfees continue until Ecology receives " the Notice of Termination form. '.~ What does the permit require? The permit requires implementation of a Stormwater Pollution Prevention Plan (SWPPP). A SWPPP for construction activities is primarily a temporary erosion and sediment control plan (ESC). This plan is to be implemented when soil disturbing activity commences. The WPPP shall be updated and maintained throughout _.e entire life of the construction project. Erosion and Sediment Control Plan The SWPPP shall be monitored, updated, and maintained throughout the duration of construction activity. The primary focus of the SWPPP is to focus on sediment and erosion control, along with controlling the velocity of the stormwater discharge. The SWPPP, the permit application, inspection reports, the permit, and any related information shall be kept on or near the construction site. A contact person shall be designated who will be available 24 hours a day to respond to inquiries or directives from Ecology. Objectives of the Erosion and Sediment Control (ESC) Plan ® To implement Best Management Practices (BMPs) for identifYing, reducing, eliminating, or preventing sediment and erosion problems on site. ® Prevent violations of surface and ground water quality and sediment management standards. ® Prevent impacts to receiving waters from peak rates and volumes of stormwater runoff. ESC Plan contents and requirements (abbrev.) 1. The ESC Plan shall include stabilization BMPs. Stabilization practices may include: temporary/permanent seeding, mulching, geotextiles, sod stabilization, vegetative buffer strips, protection of trees, and preservation of mature vegetation. The plan shall ensure the following: Ii'! All exposed and unworked soils shall be stabilized by suitable and timely application ofBMPs. Ii'! Existing vegetation should be preserved where attainable. Ii'! Cut and fill slopes shall be designed and constructed to . .. . mlmmlze erosIOn. Ii'! Stabilization should be adequate to prevent erosion of conveyance outlets and stream banks. Page 3 o All storm drain inlets made operable during construction shall be properly maintained. o Sediment (mud) onto paved roads from construction site shall be kept to a minimum. Adjacent road surfaces shall be cleaned on a regular basis. 2. Structural practices shall include a description of BMPs to divert flows from exposed soils, store flows, or otherwise limit runoff and pollutants from exposed areas of the site. Examples include: silt fences, earth dikes, drainage swales, sediment traps, check dams, subsurface drains, pipe slope drains, level spreaders, storm drain inlet protection, rock outlet protection, reinforced soil retaining systems, gabions and sediment basins. The plan shall ensure the following: o Prior to leaving the site, stormwater shall pass through a sediment pond or sediment trap, or other appropriate BMPs. o Adjacent properties shall be protected from sediment deposition. o Sediment ponds and traps, perimeter dikes, sediment barriers, and other BMPs intended to trap sediment on- site shall be constructed as a first step in grading. o Properties and waterways downstream from the construction site shall be protected from impacts due to stormwater runoff. o All temporary erosion and sediment control BMPs shall be removed within 30 days after final site stabilization. Trapped sediment shall be removed or stabilized on site. o All BMPs shall be inspected, maintained, and repaired as needed. All on-site erosion and sediment control measures shall be inspected at least once every seven days and within 24 hours after any storm event of greater than 0.5 inches of rain per 24 hour period. Page 4 Spill Prevention and Emergency Cleanup Plan HEY. WE JUST HAD I~\~~ /' A SPill F o Avoid spills due to overfilling, tipping chemicals, paints, liquids, or rupture of petroleum products, oils, waste materials, and batteries. Store such materials on durable impervious bermed areas o Recycle waste materials All pollutants other than sediment that occur on-site during construction shall be handled and disposed of in a manner that does not cause contamination of stormwater. Chemical treatment of stormwater A request shall be submitted to Ecology at least 30 days prior to the proposed use of experimental BMPs. Refer to page 6 of this pamphlet for the regional contact person. Public notice requirements Along with your NO! application, submit a typed or ·gible copy of the public notice which will be submitted to the newspaper, the dates it will be published, and the name of the newspaper. The notice must be published once each week for two consecutive weeks in a single newspaper which has circulation in the county in which the construction is to take place. The notice must be reviewed by Ecology prior to publication aod contain the following: ® A statement that the applicant is seeking coverage under the Washington Department of Ecology's National Pollutant Discharge Elimination System (NPDES) General Permit for Stormwater Discharges Associated with Construction Activities. ® The name and address of the applicant. ® The name, address (or location description) of the construction site. ® A description of the applicant's construction activities and areas from which a stormwater discharge will occur, name(s) of receiving water(s). ® The statement: "Any person desiring to present their views to the Department of Ecology concerning this application, or interested in the Department's action on this application, may notify the Department of Ecology in writing within 30 days of the last date of publication of this notice. Comments can be submitted to: Department of Ecology, PO Box 47696, Olympia, W A 98504-7696." Permit coverage will not be graoted sooner than 31 days from the date of the second public notice. Ecology is no long requiring the submittal of the affidavit of publication. The applicaot must instead provide the dates that the first and second public notices will appear and the name of the newspaper which will run the public notices. A copy of the notice to be published must also be submitted along 'vith the NOr. Sample Newspaper Notice (Public Notice or Legal Section) ABC Construction Company, 555 Sixth Ave NE, Any town W A 98000, is seeking coverage under the Washington Department of Ecology's NPDES General Permit for Stormwater Discharges Associated with Construction Activities. The proposed I 50-acre project, known as Clearview Heights, is located on the comer of 55 th and Sunny Drive, in the City of Any town. Approximately 120 acres will be disturbed for construction of stormwater facilities, roads, utilities, sidewalks, a park aod single-family homes. Stormwater will be collected in an on-site detention system and bio-filtration swale, prior to discharge to Anywhere Creek and wetlaods. The wetlands will be protected by established buffers. A pre-developed discharge rate of stormwater will flow to the wetlands. Any person desiring to present their views to the Department of Ecology concerning this application, may notify Ecology in writing within 30 days of the last date of publication of this notice. Comments may be submitted to: Department of Ecology, Stormwater Unit, PO Box 47696, Olympia WA 98504-7696. (Dates of publication in the Times, July 21 & July 28,1999.) The notice and NO! may be faxed to Ecology for review prior to publication. The fax number is 360.407.6426. The notice may be published prior to completion of the State Environmental Policy Act (SEPA) has been finalized. Page 5 Where to get help For questions on the application or ~rmination form Linda Matlock ....................... 360.407.6437 Email: Imat461@ecy.wa.gov Shirley Rollins ...................... 360.407.7330 Email: sroI461@ecy.wa.gov For permit fee questions Bev Poston ......................... 360.407.6425 Email: bpos@ecy.wa.gov FAX machine and request line numbers FAX machine ....................... 360.407.6426 Request line ......................... 360.407.7156 Ecology Regional Offices For questions concerning a specific construction site: Call the Ecology staff person assigned to your county. For example, call if: ® You need clarification on whether your SWPPP is adequate. ® Significant erosion or discharge of sediment is occurring despite your efforts. ® You need clarification on appropriate experimental BMPs, such as chemical treatment or kiln dust. ® The construction activity is finished and assistance is needed to determine if the site is stabilized sufficiently to terminate the permit. Page 6 Northwest Regional Office -Bellevue Kitsap, Snohomish Ken Fukutomi. ............................ 425.649. 7167 King Don Seeberger .......................... 425.649.4424 Island, San Juan, Skagit Bob Wright ................................ .425.649.7060 Bellingham Field Office Whatcom Andrew Craig ............................. 360.676.2217 Southwest Regional Office -Olympia Grays Harbor, Lewis, Pacific Janet Boyd ................................. 360.407.0245 Clallam, Jefferson, Mason, Thurston Betsy Dickes .............................. 360.407.6294 Pierce Margaret Hill .............................. 360.407.0246 Vancouver Field Office Clark, Cowlitz, Skamania, Wahkiakum Rusty Post ................................. 360.690.4787 Eastern Regional Office -Spokane Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman Dennis Murray ........................... 509.329.3493 Central Regional Office -Yakima Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima Ray Latham ............................... 509.575.2807 '" Kerry Can-oll ;s the coordinator for the southwest region; contact her if you cannot reach the inspector assigned to your area. Note: Some ofthe permit managers' responsibilities in the southwest regional office overlap into adjoining counties due to WRIA boundaries. The counties cited for each manager is a general guidance on who to contact. Guidance information for developing your Stormwater Pollution Prevention Plan 'tormwater Management Manual for Western Vashington This manual is useful to developers, engineers, and construction contractors who need guidance to control erosion and sedimentation from construction projects. Under the Fuget Sound Water Quality Management Plan, local governments within Puget Sound are to adopt requirements which are at least equivalent to the minimum requirements listed in Volume I of the manual. Where Ecology has determined those local government requirements to be equivalent, compliance with those local requirements ensures compliance with Ecology's permit. Please note that local governments may have more stringent requirements than the requirements in Ecology's permit. Ecology is currently developing a stormwater management manual for eastern Washington. The '11anual is due for issuance in the fall of 2003. ,'he Stormwater Management Manual consists of the following five volumes: Volume I: Volume II: Minimum Technical Requirements and Site Planning Construction Storm water Pollution Prevention Volume III: Hydrologic Analysis and flow Control DesignIBMPs Volume IV: Source Control BMPs Volume V: Runoff Treatment BMPs Key Changes in the Revised Manual • Thresholds for the selection of best management practices (BMPs) are written to allow for the most appropriate sizing and placement of flow control and treatment BMPs. Fewer projects will require engineered structures, but all projects will be required to use appropriate BMPs. • Runoff flow control requirements will now address problems of both increased peak flow and the duration of high flows. This will require the use of more sophisticated stormwater runoff models and will generally result in the construction of larger runoff control facilities. • Higher levels of treatment will be required to remove and reduce pollution from runoffto lakes and smaller streams to provide more assurance that the treated storm water runoff is not harmful to fish and other aquatic life and is protective of the environment. • New BMPs have been added for controlling runoff from construction sites and for preventing stormwater pollution at the source. These BMPs will help to further remove contaminants from runoff. • Ecology proposes to establish a Technical Review Committee to evaluate new treatment technologies and to maintain an updated list of approved treatment technologies. Best Management Practices result in clean stormwater runqif. Help protect our water. Page 7 How to Get Printed Copies of the Stormwater Manual 'he following are four options for obtaining copies of the stormwater manual: o Credit card orders Visit the Washington State Department of Printing at the following web site. Cost is $57.25. https:/Iwws2.wa.gov/prt/printwa/wsprtldefault.asp o Mail check or money order for $57.25 to: Washington State Department of Printing PO Box 798 Olympia, WA 98507-0798 Include your name, mailing address, phone number, and the name of the publication (Stormwater Manual). Allow two weeks for delivery. If you have any questions about ordering the manual, call the Department of Printing at 360.753.6820. :r Download the manual from the web The manual is divided into five volumes. You can download the manual by volume. You will need Version 4 or later of Adobe Acrobat Reader. (You can download a free copy Acrobat Reader.) http://www.ecy.wa.gov/programs/wg/stormwater/manual.html o Obtain the manual on CD Send email to mewi461@ecy.wa.gov. Page 8 Application for General Permit to Discharge Stormwater Associated with o Change of Information WUHINGTON STAff D ! P ~ R 1 1M' E N r 0 f ECOLOGY Construction Activity (Notice of Intent) Permit # S03-00 __ Print ~ in ink or type. Please read NOllnstructions before completing this form. . Contact Person Contact Name Phone No. Tille Company Mailing Address (All correspondence will be mailed here) II Owner/Representative of Site Owner's Name Tille Company Name Mailing Address Phone No. City State Zip + 4 City State Zip + 4 Email address Fax No. Email address Fax No. IllS' L Ite ocatlon /Add ress I Ing Ad dress Site Name Contact Name Phone No. Street Address (or Location Description) Tille Company Name City (or nearest city) Zip Mailing Address County City State Zip +4 Provide legal description if no address for site (attach separate sheet if necessary). V. Receivin Water Information (check all that a A. Does your construction site discharge stormwater to: 1. 0 Storm drain system -Owner of storm drain system (name) : ____________________ _ 2. [] Indirectly or directly to surface waters: 0 River D Lake DCreek 0 Estuary 0 Ocean 0 Wetland 3. [J Oirectly to ground waters of Washington state: [J Dry Well oOrainfield 0 Other B. Name(s) of receiving water(s): Initial discharge is to an unnamed receiving water? 0 Yes 0 No (C Ditch C Wetland CJ Unnamed Stream) C. location of discharges. (Use all of the following to identify location of discharge. Attach a supplemental sheet if more than one discharge point and/or numerous receiving waters.): 1. Map enclosed (Mark discharge point on map and provide distance from receiving water.) 2. Specify degrees, minutes, and seconds. Section: __ Township: __ Range: __ Section: __ Township: __ Range: __ Section: __ Township: __ Range: __ 3. Latitude: _____ _ Longitude: _____ _ Lalitude: _____ _ Longitude: _____ _ Lalitude: _____ _ Longitude: _____ _ ECY 020·85 (Rev. 03104) List receiving waters. Page 1 VI. Construction Activity Information 1. Total size of site: acres Total area to be disturbed' acres How many phases? __ 2. Will any portion of the project be sold to private developers? 0 Yes ONo 3. Projected startup date: ____ _ Proposed completion date: ___ _ 4. Will there be dewatering activity? [] Yes DNo Check all construction (soil disturbing activities) that applies. Attach a supplemental sheet if necessary o Clearing bI Homes (how many) 0 Landscaping 0 Stormwater Facilities ):0 Condominiums o Demolition '> Multi-family o Parks D Trails ). Single-family o Exporting Soil :> Town homes o Piping Systems o Utilities o Filing Wetland o Importing Soil 0: Retaining Walls o Other: ______ _ o Grading o Industrial Buildings Cl RoadsfStreets o Other: ______ _ '> Type: ,. Site: o Stockpiling D Other: VII. Stormwater Pollution Prevention Plan A. Best Management Practices (BMPs) (check all that apply). Attach supplemental list if needed to include other BMPs. o Berms D Diverted Flows c:J Plastic Covering o Swale DI Check Dams o Hydroseed ICI Polyacrylamides D Terracing o Chemical Treatment D Interceptor Trenches/Ditches D Riprap Channel lining o Vegetated Strips o Culverts ID Kiln Dust o Sediment Pond o Wheel Wash Area bI Detention Pond o Mulching [J Silt Fencing Ll Other: o Dikes o Nets and Blankets Id Slope Reduction C10ther: o Dust Control LJPipes Ll Straw Ba les OOther: __ B. Stormwater Pollution Prevention Plan (SWPPP) Has a SWPPP been developed that includes a narrative and drawings? 0 Yes 0 No If NO, will a plan be developed prior to the start of construction? [J Yes ID No A permit cannot be issued unless the permittee indicates that the SWPPP is completed or certifies that it will be developed prior to the commencement of the construction activity VIII. State Environmental Polic Act SEPA requirements must be complied with prior to submittal of the stormwater permit application. If exempt, provide documentation that justifies SEPA exemption. Has a SEPA review been completed? Type of SEPA document: 0 DNS DYes o Final EIS DNo o MONS [J Exempt o Supplemental o Addendum Agency issuing DNS, Final EIS, Supplemental, Addendum, or Exemption: ______________ _ Date: _____ Supplemental Date: _____ Addendum Date: ____ _ Are you aware of an appeal of the adequacy of the SEPA document? If YES, please attach explanatory letter. ECY 020-85 (Rev. 03/04) DYes DNo Page 2 IX. Public Notice The public notice must be published at least once each week for two consecutive weeks, in a single newspaper of general circulation in the county in which the construction is to take place. See the NOI instructions for the public notice language requirements. Permit coverage will not be granted sooner than 31 days after the date of the second public notice. Note: The NOT and public notice must be reviewed and approved by Ecology before the date of the first public notice. The NOl and public notice may be faxed to (360) 407·6426 or sent via email to [,ll1at461@ccy.,wa,go\,. The public notice may also be typed separately as an attachment. PUBLIC NOTICE __ (Name oj owner; or name of owner % engineeringjirm, architect, etc). __ (Address of owner or % Representative is seeking coverage under the Washington Department of Ecology's NPDES General Permit for Storm water Discharges Associated with Construction Activities. The proposed __ (Fotal acres) project, known as __ (Project name) is located at __ (Street address, intersection, crossroads, or other descriptive site location) in __ (Name o/nearest city). Approximately __ (Number of disturbed acres) will be disturbed for construction of __ (List all construction activity, e.g., clearing, grading, stockpiling (approx C.y. and location), importing/exporting materials (c.y.). demolition, grading, stormwater facilities, roads, utilities. number buildings/homes and Iype, sidewalks, landscaping.) Storm water will be __ (Brief description of how the stormwater will be cleaned and controlled), prior to discharging __ (Clarify the direction of the stormwater flows; include distance to receiving waters. List wetlands, unnamed and named receiving waters and storm drains; clarify if buffers wiJI be used to protect sensitive water bodies) Any person desiring to present their views to the Department of Ecology concerning this application may notify Ecology in writing within 30 days from the last date of publication ofthis notice. Comments may be submitted to: Department of Ecology Stormwater Unit PO Box 47696 Olympia, WA 98504-7696 Provide the exact dates (mmldd/yy) that the first and second public notices will appear in the newspaper: Date of the first notice __ 1 __ 1 __ Date of second notice 1 __ 1_- Name of the newspaper that will run the public notices: Ecology is no longer requiring the submittal of the affidavit of publication. Complete the above public notice information or provide a copy of the notice to be published. Status OJ NPDES Permit (e.g., industrial stormwater or individual NPDES) Permit No: 803, _____ or WA, ____ _ o State Waste Discharge Permit No: ST ____ _ o Air Notice of Construction, Permit, or Order Agency: ____ _ CJ StatelUSEPA Hazardous Waste ID No: ECY 020-85 (Rev. 03/04) Page 3 XI. Certification of Permittee(s) "1 certifY under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted The information submitted is, to the best of my knowledge and belief true, accurate, and complete. 1 am aware that there are significant penalties for submittingfalse information, including the possibility affine and imprisonment for knowing violations. JJ Owner/Representative's Printed Name Owner/Representative's Signature Sign and return this document to the following address: Washington Department of Ecology Water Quality Program Slormwater Unit -Construction PO Box 47696 Olympia, WA 96504-7696 For questions, please call (360) 407-6437 or send email to Imat461@e~Q-,,!. Title Date The Department Df Ecology is an equal opportunity agency and does not discriminate on the basis of race, creed, c%r, disability, age, religion, national origin, sax, madtal status, disabled veteran's status, Vietnam Era veteran's status, or sexual orientation. ECY 020-85 (Rev. 03/04) Page 4 Introduction How to apply for a General Permit to Discharge Stormwater Associated with Construction Activity These instructions will help you prepare an application, referred to as Notice ofIntent (NOI), for coverage under a National Pollutant Discharge Elimination System (NPDES) General Permit for stormwater discharges associated with construction activity in the state of Washington, This NPDES General Permit (general permit) applies to storm water discharges to surface waters and to storm drains, Municipalities of less than 100,000 population need to apply for construction sites that they own or operate, Owners of construction sites of fewer than five acres, or those that will retain onsite and discharge to the ground all stormwater associated with construction activity, are not required to apply for coverage under the construction storm water general permit. Who Must Apply • The owner of a construction site where five acres or more of total land area will be disturbed must apply for coverage under the general permit if there will be a discharge of stormwater associated with construction activity to a surface water or to a storm drain, • At sites for which a lease, easement, or other use agreement has been obtained from the site owner, the entity obtaining the use agreement must apply, In cases where the owner(s) ofa site is (are) represented by a developer, the developer should apply. • At sites where fewer than five acres oftotal land area will be disturbed, the owner is not required to apply unless the construction is "part of a larger common plan of development or sale." "Part of a larger common plan of development or sale" means a contiguous area where multiple separate and distinct construction activities may be taking place at different times on different schedules under one plan. • Industrial facilities already covered by the Industrial Baseline General Permit for their industrial activity that are planning construction which will disturb five or more acres of total land area, must complete this NO!. When to Apply The NOI shall be submitted to Ecology on or before the date ofthe first public notice and at least 38 days prior to the start of construction activities (see Section IX), Ecology must have the permit application during the public comment period in order to provide the public access to the applications as required by WAC 173- 226-130(5), Note: Ecology cannot grant permit coverage until 31 days after the date of the second Public Notice. Ecology intends to notifY applicants by mail of their status concerning coverage under the permit within 10 working days of its receipt of a complete NO!. An NOI is only deemed complete after a final SEPA determination has been made, the applicant has certified that a SWPPP will be developed prior to the start of construction, the 30-day public comment period has been satisfied, and all other NOI information has been supplied, Upon receipt of a complete NOI, Ecology will notify the applicant of their status either through written authorization of permit coverage or by sending a letter to the applicant giving a date when permit coverage ECY 020·85 (Rev. 03/04) Page 1 will automatically commence. Coverage will begin on the date of Ecology's written authorization or will automatically commence on the date specified in Ecology's letter. Where to Apply Mail the signedNOI to the following office: Washington Department of Ecology Water Quality Program Stormwater Unit· Construction P.O. Box 47696 Olympia, WA 98504·7696 Applicants who discharge stormwater associated with construction activity to a storm drain operated by any of the following municipalities must also submit a copy of the NO] to the municipality: Seattle, King County, Snohomish County, Tacoma, Pierce County, Clark County, Spokane County, and Washington State Department of Transportation. Fees There is no application fee. You will be billed for permit fees after the permit is issued. Call (360) 407·6425 or send email to bpos461@ecv.wa.gov for questions relating to fees. ECY 020-85 (Rev. 03/04) Page 2 Instructions for Completing the Notice of Intent The Notice ofIntent (NO!) is an official document committing the pennittee to compliance with the requirements oftbe General Pennit. It should be completed accurately, completely and legibly. Please print in ink or type. Change of Information: Check this box if infonnation included in a previously submitted NOI application in which pennit coverage was granted has changed. An example of a change could be a new contact person, billing address, or total area to be disturbed. Include your assigned penn it number in the upper right hand comer of the NO!. Your assigned pennit number is in the upper right hand comer of the first (title) page of your pennit. Complete only those sections of the NOI that require changes. Please submit a transmittal letter which confinnslexplains the change of infonnation in the NO!. Permit Number: Use only if you are reporting a "Change ofInfonnation" or transferring ownership of penni!. Section I. Contact Person Give the name, address, and telephone number of a local person who is available 24 hours a day to respond to emergencies, and to inquiries or directives from Ecology. The contact person should be someone who is completely familiar with the site and charged with overseeing compliance with the pennit requirements. This person could be an employee, a consultant, a developer, or a contractor. Section II. Owner/Representative of Site Give the name, address and telephone number of the person, company, firm, public corporation, municipality or any other entity which owns or legally represents the site. If the owner is the same as the contact person, enter "same as contact person" on the first line. The pennit and all other correspondence will be sent to this address. An exception to this infonnation is the billing address. Section III. Site Address Enter the street address or location description (e.g., Intersection ofB & C streets) for the construction site. Also include the county. Construction sites which do not have a street address must also provide a legal description of the location, either in the space provided or as an attachment. Section IV. Billing Address Indicate where the annual and [mal pennit fee invoices should be sent. Also provide a contact person who can answer any questions on the billing invoices. Section V. Receiving Water Information Part A. Check the appropriate boxes for receiving water infonnation for the stonnwater discharges from the construction site. Part A.1. Check this box if stonnwater leaving your site enters a stann drain system, and indicate the name of the owner of the stonn drain system such as a municipality, flood control district, utility or private entity (e.g., industrial park). Part A.2. Check this box if stonnwater flows directly or indirectly into or over adjacent properties, through ditches or right-of-ways to surface waters of the state; the definition of a surface water includes lakes, rivers, ponds, streams, salt waters, and wetlands. Part A.3. Check this box if stonnwater from your site is discharged to the ground. Indicate by what method by checking one of the three choices. If you discharge stonnwater only to the ground, you are not required to apply for coverage under the general penni!. ECY 020-85 (Rev. 03/04) Page 3 Part B. Indicate the name of the first downstream receiving water(s) which has an assigned name. If stormwater is discharged to more than one receiving water, the names of each receiving water must be listed. Indicate whether the stormwater is initially discharged to an unnamed receiving water(s) prior to flowing into the named receiving water(s) by placing a check in the appropriate box. If the discharge is to an unnamed surface water which does not eventually drain to a named surface water (e.g., a pond with no outlet), enter a description of the receiving water (e.g., ponds, creek, etc.) and check "Yes." Part C. Identify the points or areas of stormwater discharge. Provide the latitude and longitude for each point discharge. If you are not able to provide that information, provide the section, township and range information and locate your discharge on a map of sufficient scale and accuracy to identify the points of discharge and distance from receiving water(s); provide name of water body. If you discharge to a storm water drainage system, identify where the points of discharge are for the drainage system; give name of receiving water. Section VI. Construction Activity Information Give the total land area in acres and total area that will be disturbed during all phases ofthe construction project. This includes all clearing, grading, and excavating, and any other activity that disturbs the surface of the land. Include how many phases. Once the site is prepared for development (for example utilities and roads installed) will the project be sold? (Once you are no longer responsible for the site, request the permit be canceled by submitting a termination form.) Give the projected monthlyear when the construction activity will begin, and the anticipated monthlyear of completion of all soil disturbing and soil stabilization activity. Notify Ecology if dewatering is planned. Mark all soil disturbing activity anticipated. Add to the list activities that are pertinent to your project. Section VII.A. Best Management Practices Indicate how the stormwater will be cleaned and controlled before it discharges to storm drains and receiving waters. (This includes ditches and wetlands.) Section VII.B. Stormwater Pollution Prevention Plan (SWPPP) Applicants must develop and implement the SWPPP before beginning construction activities. Applicants may indicate completion of the SWPPP on the NO! form or certify that development of a SWPPP will occur before construction begins. If this is not done, Ecology must be notified that a SWPPP will be developed prior to the start of construction before permit coverage can be granted. A stormwater pollution prevention plan (SWPPP) for construction sites is a documented plan primarily intended to control erosion and sedimentation caused by construction activity. These plans are not submitted to Ecology, but kept on-site or within reasonable access to the site, to be made available to Ecology and local governmental agencies upon request. Section VllI. State Environmental Policy Act (SEPA) Compliance Ecology cannot cover the applicant under the General Permit until the following SEP A information has been provided and the SEPA process has been satisfied. Provide the following information: • Whether SEPA review has been completed or the project is exempt. • The type of SEPA document prepared, i.e., a Determination of Non significance (ONS) or a Final Environmental Impact Statement (EIS). The name ofthe agency that issued the DNS or the Final EIS, or that decided the project was exempt from SEP A. Usually this agency is a representative of local government such as a city or county. • Provide the date the agency issued the DNS or Final E1S. ECY 020-85 (Rev. 03/04) Page 4 • Whether you are aware of an administrative or judicial appeal of the adequacy of the SEP A document. If you check the "yes" box, provide a letter explaining the issues and status of the appeal. If necessary, the SEPA follow-up information may be supplied in writing after submission of the NO!. Section IX. Public Notice The applicant must complete the 3D-day public notice requirement prior to receiving permit coverage. The notice must be published at least once each week for two consecutive weeks, in a single newspaper of general circulation in the county in which the construction is to take place. It must include the following information: • A statement that the applicant is seeking coverage under the Washington Department of Ecology's NPDES General Permit for Stormwater Discharges Associated with Construction Activities; • The name, address and location of the construction site; • The name and address of the applicant; • A description of the applicant's construction activities and areas from which a stormwater discharge will occur and name(s) of receiving water(s); and • This statement: "Any person desiring to present their views to the Department of Ecology concerning this application, or interested in the department's action on this application may notifY the Department of Ecology in writing within 30 days of the last date of publication of this notice. Comments can be submitted to: Department of Ecology, P.O. Box 47696, Olympia, WA 98504-7696." Please note: ./ Ecology is no longer requiring the submittal of the affidavit of publication. However, a typed copy of what will be submitted to the newspaper must be sent along with the NO!. The dates that the first and second public notices will run and the name of the newspaper in which the public notices will appear must also be provided . ./ That state law requires a 30 day public comment period prior to permit coverage, therefore permit coverage will not be granted sooner than 31 days after the date of the second public notice. The public notice may be published simultaneously with other notices such as State Environmental Policy Act notices and Shoreline Permit notices, provided the NOI is sent to Ecology on or before the date of the first public notice. Section X. Regulatory Status Parts A, B, and C request information on any existing NPDES (including a stormwater permit for industrial activity), State Waste Discharge, and Air permits issued to the facility. In Washington, air emission permits are issued by local agencies or Ecology. They can be referred to by various names such as a permit, an order, or a Notice of Construction. In part D, indicate if your facility has been assigned a StatelUSEPA Hazardous Waste ID number, and list that number. Section Xl. Certification by Permittee(s) This section should be read closely by the applicant. The responsible official or authorized representative of the owner must print his or her name for clarity, then sign and date the document. In the case of corporations, the NOI must be signed by a responsible corporate officer or a authorized representative, if such representative is responsible for the overall operation of the site from which the discharge originates. For a partnership, the NOI must be signed by a general partner. ECY 020-85 (Rev. 03104) Page 5 For a sole proprietorship, the NO! must be signed by the proprietor. For a municipal, state or other public agency, the NO! must be signed by either a principal executive officer, ranking elected official or other duly authorized employee. Questions Questions concerning proper completion of this form may be directed to the Department of Ecology by calling (360) 407-6437 or send email to Imat461@ecy.wa.gov. ECY 020-85 (Rev. 03/04) Page 6 2005 King County, Washington Surface Water Design Manual Appendix D -Erosion and Sediment Control Standards Appendix D Erosion and Sediment Control Standards ® King County Department of Natural Resources and Parks King County, Washington Surface Water Design Manual APPENDIXD EROSION AND SEDIMENT CONTROL (ESC) STANDARDS KING COUNTY, WASHINGTON SURFACE WATER DESIGN MANUAL King County Department of Natural Resources and Parks January 24, 2005 APPENDIXD Section 0.1 Erosion and Sediment Control 0-3 Principles EROSION AND Section 0.2 General ESC Requirements 0-5 SEDIMENT CONTROL Section 0.3 ESC Measures 0-7 STANDARDS Section 0.3.1 Clearing Limits 0-8 Section 0.3.2 Cover Measures D-l0 Section D.3.3 Perimeter Protection 0-30 Section 0.3.4 Traffic Area Stabilization D-38 Section D.3.5 Sediment Retention 0-44 Section 0.3.6 Surface Water Collection D-56 Section 0.3.7 Dewatering Control D-65 Section 0.3.8 Oust control D-65 Section 0.3.9 Flow Control 0-67 Section 0.4 ESC Performance and 0-69 Compliance Provisions Section D.4.1 ESC Performance 0-69 Section 0.4.2 Flexible Compliance D-69 KING COUNTY, WASHINGTON Section 0.4.3 Roads and Utilities Compliance 0-69 SURFACE WATER Section 0.4.4 Alternative and Experimental D-70 Measures DESIGN MANUAL Section 0.5 ESC Implementation 0-71 Requirements Section 0.5.1 ESC Plan 0-71 Section D.5.2 Wet Season Requirements D-71 Section 0.5.3 Critical Areas Restrictions 0-72 Section D.S.4 Maintenance Requirements D-73 Section 0.5.5 Final Stabilization 0-74 Section D.S.6 NPDES Requirements D-75 Section 0.5.7 Forest Practice Permit 0-75 Requirements Section 0.6 Erosion and Sediment Control 0-77 Plans Section 0.7 Small Site ESC 0-81 Section D.7.1 Introduction to Small Site ESC 0-81 Section D.7.2 Small Site ESC Requirements 0-82 Section 0.7.3 Submittal Requirements 0-85 Section 0.8 Reference Section 0-89 Section D.8.1 ESC Maintenance Report 0-89 Section D.8.2 Standard ESC Plan Notes D-92 Section 0.8.3 Recommended Construction 0-93 Sequence Section D. 8.4 References 0-93 2005 Surface Water Design Manual -Appendix D 1124/2005 KING COUNTY, WASHINGTON, SURF ACE WATER DESIGN MANUAL APPENDIXD EROSION AND SEDIMENT CONTROL STANDARDS The purpose of erosion and sediment control (ESC) is to prevent to the maximum extent practicable,' the transport of sediment to streams, wetlands, lakes, drainage systems, and adjacent properties during and following construction of a proposed project or other land disturbing activity.' In many circumstances it is difficult to completely prevent the transport of sediment to these features, eitl,er because of the difficulty in removing silt and clay-sized particles from runoff or because of large, infrequent storms that overwhelm the ESC facilities. It is the responsibility of those involved in the design and construction of any project to utilize a variety of strategies to minimize erosion and the transport of sediment to the maximum extent practicable. These strategies shall include overall project planning that reduces the risk of erosion through appropriate design and scheduling (see Section D.l) and traditional structural and cover measures, such as those described in Section D.3. Erosion and sediment control is necessary because erosion rates associated with uncontrolled construction sites are much higher than normal rates-often a thousand or more times that of undeveloped land. The erosion rates increase during construction due to the removal of soil cover, alteration of soil characteristics, and changes in site topography. These vastly accelerated erosion rates, together with the higher rates typical of urbanized areas, result in excessive deposition of sediment in water resources and drainage facilities. This excessive erosion and consequent sediment deposition can result in devastating impacts to surface waters such as smothering of salmonid spawning beds, algal blooms in lakes, and flooding due to obstruction of drainage ways. Applying erosion and sediment controls to construction sites can greatly reduce the delivery of sediment to surface waters. The chart on the next page shows how controls can significantly reduce the concentration of sediment leaving the project site.' Even with good controls, the concentration of sediment leaving the site will still be significantly higher than either undeveloped or developed conditions and this may result in significant adverse impacts; however, the likelihood of such impacts are dramatically less than ifno controls are used. 1 Maximum extent practicable means the use of best management practices that are available and capable of being designed, constructed and implemented in a reliable and effective manner including, but not limited to, consideration of site conditions and cost. 2 Land disturbing activity means any activity that results in a change in the existing soil cover (both vegetative and non~ vegetative and/or the existing soil topography. Land disturbing activities include, but are not limited to demolition, construction, clearing, grading, filling, excavation, and compaction. Land disturbing activity does not include tilling conducted as part of agricultural practices, landscape maintenance, or gardening. 33 Project site means that portion of a site and any offsite areas subject to proposed project activities, alterations, and improvements. Site means a single parcel, or two or more contiguous parcels that are under common ownership or documented legal control. used as a single parcel for purposes of applying for authority from King County to carry out a development/project proposal. For projects located primarily within dedicated rights-of-way, site includes the entire width of right-at-way within the total length ot right-at-way subject to improvements proposed by the project. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-I APPENDlXD 112412005 EROSION AND SEDIMENT CONTROL STANDARDS Organization of Appendix 0 Appendix D is organized as follows: • Section D.l, "Erosion and Sediment Control Principles" (p. D-3) • Section D.2, "General ESC Requirements" (p. D-5) • Section D.3, "ESC Measures" (p. D-7) • Section D.5, "ESC Implementation Requirements" (p. D-71) • Section D.6, "Erosion and Sediment Control Plans" (p. D-77) • Section D.7, "Small Site ESC" (p. D-81) • Section D.8, "Reference Section" (p. D-89) MEDIAN STORM SEDIMENT CONCENTRATIONS (METROPOLITAN WASHINGTON COUNCIL OF GOVERNMENTS, 1990) 4500 4.145 13, .§. 4000 UNCONTROLLED -NO EROSION OR SEDIMENT CONTROL z 3500 0 EROSION -EROSION CONTROL ONL Y ;:: 3000 SEDIMENT -SEDIMENT A NO EROS ION CONTROL ..: 0: URBANIZED -POST CONSTRUCTION (NURP. 1987) .... z 2500 NA TURA L -PREDEV EL OPMENT w u z 0 2000 u 1500 .... z w 1000 :0 i5 w 500 '" 50 25 0 UNCONTROLLED EROSION SEDIMENT URBANIZED NATURAL CONSTRUCTION SITE CONDITION 2005 Surface Water Design Manual-Appendix D D-2 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL D.l EROSION AND SEDIMENT CONTROL PRINCIPLES This section provides basic information on the principles of erosion and sediment control that shall be applied to all projects in King County. This section is intended to highlight ce11ain principles that are particularly critical to achieving effective control and that are the basis for the Surface Water Design Manual's Core Requirement #5: Erosion and Sediment Control. Projects that are consistent with these principles will generally meet the intent of the Core Requirement and this appendix, even if the details of the project are not entirely consistent with County standards. If a more complete treatment of ESC is needed, there are a number of useful references available (for example, Goldmau et aI., 1986). Additionally, information on permanent erosion control in natural channels is available in the Guidelines for Bank Stabilization Projects (King County, 1993). • Design the project to fit the natural topography, soils, and drainage patterns, Through such practices as limiting disturbance of steeper slopes, avoiding disturbance of natural drainage ways, or using soils with a high infiltration rate to treat polluted runoff, the characteristics ofthe site can be used to minimize erosion and sediment transport • Emphasize erosion control rather than sediment control, Erosion control minimizes the entrainment of sediment by runoff or in the air due to wind, while sediment control removes entrained sediment from runoff. Erosion control is more efficient and cost-effective because it is nearly impossible to entirely remove sediment from runoff once it is entrained. Examples of erosion control include covering disturbed soils and controlling surface runoff using measures such as dikes and lined ditches. One illustration of the relative effectiveness of erosion control is straw mulch, which can reduce sediment concentrations in runoff over 90%. Since it is nearly impossible to entirely prevent erosion, it will also be necessary to incorporate sediment control facilities such as sedimentation ponds and silt fences. Sediment controls vary in their effectiveness, but typically reduce sediment concentrations 50 to 75%. However, sediment controls have little effect on the very fine sediment that causes turbidity, whereas cover measures, such as straw mulch, can be highly effective in reducing turbidity. • Minimize the extent and duration of area exposed, Restricting clearing to only those areas necessary for construction is probably the single most effective form of erosion control. Additionally, exposing areas only as long as necessary reduces the risk of erosion substantially. This can be accomplished by planning the project so that areas are disturbed only when construction is imminent, and by mulching or seeding disturbed areas as soon as grading is completed. • Keep runoff velocities low, While erosion of exposed soil begins with a single raindrop or the wind, the largest volumes of eroded materials are typically associated with concentrated runoff forming rills and gullies. One of the best ways to minimize erosion, therefore, is to reduce the possibility of concentrated runoff by intercepting runoff and conveying it in a non-erosive manner to a sediment pond or trap. This can include the use of dikes, swales, and benches to intercept runoff on slopes and ditches or drains to convey the intercepted runoff. • Retain sediment on site, Sediment retention is less effective than erosion control measures, such as cover, but it is nevertheless a vital part of most projects because it is impossible to completely prevent erosion and the entrainment of sediment by runoff Sediment can be retained by allowing it to settle out in ponds and traps or by filtering runoff from small areas through vegetation or use of a silt fence. Note that settling and filtration typically only remove sand-sized and coarse silt particles. Fine silts and clays cannot be removed in these ways, unless the runoff is released to vegetated areas or if chemical treatment, such as alum, or chitosan introduction or electrofloculation, are used. • Thoroughly monitor the site and maintain all ESC measures. Maintenance and vigilance are the most vital components of effective ESC management. All measures require regular maintenance, monitoring and inspection. The overall site also needs to be constantly examined to ensure that all 2005 Surface Water Design Manual-Appendix D 112412005 D-3 SECTION D.I EROSION AND SEDIMENT CONTROL PRINClPLES \/24/2005 areas are protected, that the measures are working together to provide maximum protection, and that all areas are mulched andlor vegetated as soon as possible. • Schedule major earthwork during the dry season. The climate in the Puget Sound region is unique in that there are generally well-defined wet and dry seasons (see Figure D.3.I.A) and the wei season' is characterized by a large number of low-intensity, but frequent and long-lasting, stonns. As a result, construction in the dry season' is a very effective fonn of erosion control. If construction does occur in the wet season, the need for regular maintenance is even more imperative. I 0.3 0.2 0.1 FIGURE D.3.I.A YEARLY RAINFALL PATTERN AVERAGE DAILY RAINFALL 45 YEARS OF SEATAC RAINFALL .j , i ~ • i 1 ••• ! i. -1" , . • Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 4 Wet season means October 1 Sf to April 30 1h , 5 Dry season means May 15t to September 30th . I 2005 Surface Water Design Manual-Appendix D D-4 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL D.2 GENERAL ESC REQUIREMENTS To satisfy the King County requirements for ESC, the following steps are required of all construction projects: I. In accordance with Sections 2.3.1 and 2.3.3 of the Sur/ace Waler Design Manual (SWDM), prepare and submit a technical information report (T1R) and an ESC plan for King County review. Incorporate any King County review comments as necessary to comply with Core Requirement #5, Section 1.2.5 of the SWDM and the Erosion and Sediment Control Standards in this appendix. 2. Construct initial ESC measures on site according to the approved ESC plan. 3. Inspect and maintain all ESC measures throughout construction in accordance with the inspection and maintenance standards of Section D.5.4 (p. D-73). 4. Make any changes or additions necessary during construction to ensure that ESC measures perform in accordance with Core Requirement #5 and Sections D.3 and D.5. 5. Prior to final construction approval, meet all the conditions in Section D.S.S (p. D-74) for final stabilization. Proposed projects subject to Small Project Drainage Review as determined in Section 1.1.2.1 may satisfy King County ESC requirements by meeting the Small Site ESC requirements specified in Section D.7 (p. D-SI) and reiterated in Appendix C of the Surface Water Design Manual titled, "Small Project Drainage Requirements. n 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-S KING COUNTY, WASHTNGTON, SURFACE WATER DESIGN MANUAL D.3 ESC MEASURES This section details the ESC measures that are required to minimize erosion and sediment transporr off a construction site. These ESC measures represent Best Management Practices (BMPs), for the control of erosion and entrained sediment as well as other impacts related to construction such as increased runoff due to land disturbing activities. The measures and practices are grouped into nine sections corresponding to each of the nine categories of ESC measures in Core Requirement #5, Section 1.2.5 of the King County Surface Water Design Manuol. The introductory paragraphs at the beginning each section present the basic requirement for that category of measures, the purpose of those measures, installation requirements relative to construction activity, guidelines for the conditions of use, and other information relevant to all measures in the section/category. Compliance with each of the nine categories of the ESC measures, to the extent applicable and necessary to meet the performance criteria in Section 0.4, and compliance with the ESC implementation requirements in Section 0.5, constitutes overall compliance with King County's ESC Standards. Note: Additionol measures sholl be required by the County if the existing standards are insufficient to protect adjacent properties, drainage facilities, or water resources. The standards for each individual ESC measure are divided into four sections: I. Purpose 2. Conditions of Use 3. Design and Installation Specifications 4. Maintenance Requirements. A code and symbol for each measure have also been included for ease of use on ESC plans. Note that the "Conditions of Use" always refers to site conditions. As site conditions change, ESC measures must be changed to remain in compliance with the requirements of this appendix. Whenever compliance with King County ESC Standards is required, all of the following categories of ESC measures must be considered for application to the project site as detailed in the following sections: 1. Clearing Limits: Prior to any site clearing or grading, areas to remain undisturbed during project construction shall be delineated on the project's ESC plan and physically marked on the project site. 2. Cover Measures: Temporary and pennanent cover measures shall be provided when necessary to protect disturbed areas. The intent of these measures is to prevent erosion by having as much area as possible covered during any period of precipitation. 3. Perimeter Protection: Perimeter protection to filter sediment from sheet flow shall be provided downstream of all disturbed areas prior to upslope grading. 4. Traffic Area Stabilization: Unsurfaced entrances, roads, and parking areas used by construction traffic shall be stabilized to minimize erosion and tracking of sediment offsite. 5. Sediment Retention: Surface water collected from all disturbed areas of the site shall be routed through a sediment pond or trap prior to release from the site, except those areas at the perimeter of the site small enough to be treated solely with perimeter protection. Sediment retention facilities shall be installed prior to grading any contributing area. 6. Surface Water Collection: Surface water collection measures (e.g., ditches, berms, etc.) shall be installed to intercept all surface water from disturbed areas, convey it to a sediment pond or trap, and discharge it downstream of any disturbed areas. Areas at the perimeter of the site, which are small enough to be treated solely with perimeter protection, do not require surface water collection. Significant sources of upstream surface water that drain onto disturbed areas shall be intercepted and 6 Best Management Practices (BMPs) means the best available and reasonable physical, structural, managerial, or behavioral activities, that when singly or in combination, eliminate or reduce the contamination of surface and/or ground waters. 2005 Surface Water Design Manua\-Appendix D 1124/2005 D-7 SECTION D.3 ESC MEASURES conveyed to a stabilized discharge point downstream of the disturhed areas. Surface water collection measures shall be installed concurrently with or immediately following rough grading and shan be designed, constructed, and stabilized as needed to minimize erosion. 7. Dewatering Control: The water resulting from construction site de.watering activities must be treated prior to discharge or disposed of as specified. 8. Dust Control: Preventative measures to minimize wind transport of soil shall be implemented when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources. 9. Flow Control: Surface water from disturbed areas must be routed through the project's onsite flow control facility or other provisions must made to prevent increases in the existing site conditions 2· year and IO·year runoff peaks discharging from the project site during construction. D.3.1 CLEARING LIMITS D.3.1.1 1124/2005 Prior to any site clearing or grading, those areas that are to remain undisturbed during project construction shall be delineated. At a minimum, clearing limits shall be installed at the edges of all critical area buffers and any other areas required to be left uncleared such as portions of the site subject to clearing limits under KCC 16.82.150, areas around significant trees identified to be retained, and other areas identified to be left undisturbed to protect sensitive features. Purpose: The purpose of clearing limits is to prevent disturbance of those areas of the project site that are not designated for clearing or grading. This is important because limiting site disturbance is the single most effective method for reducing erosion. Clearing limits may also be used to control construction traffic, thus reducing the disturbance of soil and limiting the amount of sediment tracked off site. When to Install: Clearing limits shall be installed prior to the clearing andlor grading of the site. Measures to Use: Marking clearing limits by delineating the site with a continuous length of brightly colored survey tape is sometimes sufficient. The tape may be supported by vegetation or stakes, and it shall be 3 to 6 feet high and highly visible. Critical areas and their huffers require more substantial protection and shall be delineated with plastic or metal safety fences or stake and wire fences. Fencing may he required at the County's discretion to control construction traffic or at any location where greater protection is warranted. Permanent fencing may also be used if desired by the applicant. Silt fence, in combination with survey flagging, is also an acceptable method of marking critical areas and their buffers. PLASTIC OR METAL FENCE Code: FE Symbol: ~E~ Purpose Fencing is intended to (I) restrict clearing to approved limits; (2) prevent disturbance of critical areas, their buffers, and other areas required to be left undisturbed; (3) limit construction traffic to designated construction entrances or roads; and (4) protect areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits, plastic or metal fence may be used: I. At the boundary of critical areas, their buffers, and other areas required to be left uncleared. 2. As necessary to control vehicle access to and on the site (see Sections D.3.4.1 and D.3.4.2). 2005 Surface Water Design Manual-Appendix D D·S D.3.1 CLEARING LIMITS Design and Installation Specifications 1. The fence shall be designed and installed according to the manufacturer's specifications. 2. The fence shall be at least 3 feet high and must be highly visible. 3. The fence shall not be wired or stapled to trees. Maintenance Requirements I. If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. 2. Disturbance of a critical area, critical area buffer, native growth retention area, or any other area required to be left undisturbed shall be reported to the County for resolution. D.3.1.2 STAKE AND WIRE FENCE Code: SWF Symbol: Purpose Fencing is intended to (I) restrict clearing to approved limits; (2) prevent disturbance of critical areas, their buffers, and other areas required to be left undisturbed; (3) limit construction traffic to designated construction entrances or roads; and (4) protect any areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits, stake or wire fence may be used: I. At the boundary of critical areas, their buffers, and other areas required to be left uncleared. 2. As necessary, to control vehicle access to and on the site (see Sections D.3.4.1 and D.3.4.2). Design and Installation Specifications See Figure D.3.I.A for details. Maintenance Requirements I. If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. 2. Disturbance of a critical area, critical area buffer, native growth retention area, or other area required to be left undisturbed shall be reported to the County for resolution. 3. The County may require more substantial fencing if the fence does not prevent encroachment into those areas that are not to be disturbed. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-9 SECTIOND.3 ESC MEASURES ! FIGURE D.3.I.A STAKE AND WIRE FENCE I SURVEY FLAGGING DO NOT NAIL OR STAPLE WIRE TO TREES T~~~---IJ-C'o- 3' MIN. Il-e------l 0' -20'-----+1 METAL FENCE POST J """"'11 =I-;ftl =I"TT"II =1Ti=11 =;-1 TI=II =1"1 TI=II =i+-T-T=II =-1 ;-;-'=11 =-11n=1 =rl11""T=1 =rT11-,!h1 =rT11-r=1 T -III 111-111-111-111-11 111-111-111-111-II-II 12" MIN. t D.3.2 COVER MEASURES 1/24/2005 Temporary and permanent cover measures shall be provided to protect all disturbed areas, including the faces of cut and fill slopes. Temporary cover shall be installed if an area is to remain unworked for more than seven days during the dry season (May I to September 30) or for more than two consecutive working days during the wet season (October I to April 30). These time limits may be relaxed if an area poses a low risk of erosion due to soil type, slope gradient, anticipated weather conditions, or other factors. Conversely, the County may reduce these time limits ifsite conditions warrant greater protection (e.g., adjacent to significant aquatic resources or highly erosive soils) or if significant precipitation (see Section 0.5.2) is expected. Any area to remain unworked for more than 30 days shall be seeded or sodded, unless the County determines that winter weather makes vegetation establishment infeasible. During the wet season, slopes and stockpiles at 3H: I V or steeper and with more than ten feet of vertical relief shall be covered if they are to remain unworked for more than 12 hours. Also during the wet season, the material necessary to cover all disturbed areas must be stockpiled on site. The intent of these cover requirements is to have as much area as possible covered during any period of precipitation. Purpose: The purpose of covering exposed soils is to prevent erosion, thus reducing reliance on less effective methods that remove sediment after it is entrained in runoff. Cover is the only practical method of reducing turbidity in runoff. Structural measures, such as silt fences and sediment ponds, are only capable of removing coarse particles and in most circumstances have little to no effect on turbidity. When to Install: Any exposed soils that will remain unworked for more than the time limit set above shall be covered by the end of the working day. If the exposed area is to remain unworked for more than 30 days, the area shall be seeded with the temporary seed mix or an equivalent mix that will provide rapid protection (see Section 0.3.2.5). If the disturbed area is to remain unworked for a year or more or if the area has reached final grade, permanent seed mix or an equivalent mix shall be applied. Measures to Use: Cover methods include the use of surface roughening, mulch, erosion control nets and blankets, plastic covering, seeding, and sodding. Mulch and plastic sheeting are primarily intended to protect disturbed areas for a short period oftime, typically days to a few months. Seeding and sodding are measures for areas that are to remain unworked for months. Erosion nets and blankets are to be used in conjunction with seeding steep slopes. The choice of measures is left to the designer; however, there are restrictions on the use of these methods, which are listed in the "Conditions of Use" and the "Design and Installation Specifications" sections for each measure. 2005 Surface Water Design Manual-Appendix D D-IO D.3.2 COVER MEASURES The methods listed are by no means exhaustive. Variations on the standards presented here are encouraged if other cost-effective products or methods provide substantially equivalent or superior performance. Also, the details of installation can, and should, vary with the site conditions. A useful reference on the application of cover measures in the Puget Sound area is Homer, Guedrey, and Kortenhof (1990). D.3.2-1 SURFACE ROUGHENING Purpose The purpose of surface roughening is to aid in the establishment of vegetative cover and to reduce runoff velocity, increase infiltration, and provide for sediment trapping through the provision of a rough soil surface. The rough soil surface may be created by operating a tiller or other equipment on the contour to form horizontal depressions or by leaving slopes in a roughened condition by not fine grading. Conditions of Use I. All slopes steeper than 3: I and greater than 5 vertical feet require surface roughening. 2. Areas with grades steeper than 3: I should be roughened to a depth of 2 to 4 inches prior to seeding. 3. Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until seeding takes place. 4. Slopes with a stable rock face do not require roughening. 5. Slopes where mowing is planned should not be excessively roughened. Design and Installation Specifications There are different methods for achieving a roughened soil surface on a slope, and the selection of an appropriate method depends upon the type of slope. Roughening methods include stair-step grading, grooving, contour furrows, and tracking. See Figure D.3.2.A for information on tracking and contour furrows. Factors to be considered in choosing a method are slope steepness, mowing requirements, and whether the slope is fonned by cutting or filling. Sole reliance on roughening for temporary erosion control is of limited effectiveness in intense rainfall events. Stair-step grading may not be practical for sandy, steep, or shallow soils. 1. Disturbed areas that will not require mowing may be stair -step graded, grooved, or !eft rough after filling 2. Stair Step grading is particularly appropriate in soils containing large amounts of soft rock. Each "step" catches material that sloughs from above, and provides a level site where vegetation can become established. Stairs should be wide enough to work with standard earth moving equipment. Stair steps must be on contour or gullies will form on the slope. 3. Areas that will be mowed (slopes less steep than 3:1) may have small furrows left by disking, harrowing, raking, or seed-planting machinery operated on the contour. 4. Graded areas with slopes greater than 3:1 but less than 2:1 should be roughened before seeding. This can be accomplished in a variety of ways, including "track walking" or driving a crawler tractor up and down the slope, leaving a pattern of cleat imprints parallel to slope contours. 5. Tracking is done by operating equipment up and down the slope to leave horizontal depressions in the soil. 2005 Surface Water Design Manual -Appendix D 1124/2005 D-11 SECTION 0.3 1/24/2005 ESC MEASURES Maintenance Standards Periodically check roughened, seeded, planted, and mulched slopes for rills and gullies, particularly after a significant stann event. Fill these areas slightly above the original grade, then re-seed and mulch as soon as possible. FIGURE D.3.2.A SURFACE ROUGHING I I COIHOUR FURROWS I SURFACE ROUGHU·II~IG BY TRp.CKII·jG NID CONTOUR FURROWS 2005 Surface Water Design Manual-Appendix D D-!2 D.3.2 COVER MEASURES D.3.2.2 MULCHING Code: MU Symbol: --o-----{@I--____ _ Purpose The purpose of mulching soils is to provide immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating soil temperatures. There is an enonnous variety of mulches that may be used. Only the most common types are discussed in this section. Conditions of Use As a temporary cover measure, mulch should be used: I. On disturbed areas that require cover measures for less than 30 days 2. As a cover for seed during the wet season and during the hot summer months 3. During the wet season on slopes steeper than 3H: I V with more than 10 feet of vertical relief. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table D.3.2.A. Note: Thicknesses may be increasedfor disturbed areas in or near critical areas or other areas highly susceptible to erosion. Maintenance Standards 1. The thickness of the cover must be maintained. 2. Any areas that experience erosion shall be remulched andlor protected with a net or blanket If the erosion problem is drainage related, then the drainage problem shall be assessed and alternate drainage such as interceptor swales may be needed to fix the problem and the eroded area remulched. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-B SECTION D.3 ESC MEASURES ... ·,&.ii't '.'.' ... ,"'-' C , .......................... , •.•.•••..•••.. ~ •.. , '. .' ..... ..•.. •... '. «... "',' ". .... . . .... ' ... '. • ........T~BLJ<;n·H1-MIJ~CHSTAND1-RDSAN,1) GUlI)ELINES . '.,' '.' •..... " . ..... '. Mulch Quality Standards Application Rates Remarks Material Straw Air-dried; free from 2"-3" thick; 2-3 Cost-effective protection when applied with adequate undesirable seed and bales per 1 000 sf thickness. Hand-application generally requires coarse material or 2-3 tons per acre greater thickness than blown straw. Straw should be crimped to avoid wind blow. The thickness of straw may be reduced by half when used in conjunction with seeding. Wood Fiber No growth inhibiting Approx. 25-30 Ibs Shall be applied with hydromulcher. Shall not be Cellulose factors per 1000 sf or used without seed and tackifier unless the application 1000-1500 Ibs per rate is at least doubled. Some wood fiber with very acre long fibers can be effective at lower application rates and without seed or tackifier. Compost No visible water or 2" thick min.; More effective control can be obtained by increasing dust during handling. approx. 100 tons thickness to 3". Excellent mulch for protecting final Must be purchased per acre (approx. grades until landscaping because it can be directly from supplier with 800 Ibs per cubic seeded or tilled into soil as an amendment. Sources Solid Waste Handling yard) for compost are available from the King County Permit. Commission for Marketing Recyclable Materials at (206) 296-4439. Compost may not be used in Sensitive Lake' basins unless analysis of the compost shows no phosphorous release. Hydraulic This mulch category Apply at rates from The BFM shall not be applied immediately before, Matrices includes hydraulic 3,000 Ibs per acre during or immediately after rainfall so that the matrix (Bonded slurries composed of to 4,000 Ibs per will have an opportunity to dry for 24 hours after Fiber Matrix) wood fiber, paper fiber acre and based on installation. Application rates beyond 2,500 pounds or a combination of manufacturers may interfere with germination and are not usually the two held together recommendations recommended for turf establishment. BFM is by a binding system. generally a matrix where all fiber and binders are in The BFM shall be a one bag, rather than having to mix components from mixture of long wood various manufacturers to create a matrix. BFMs can fibers and various be installed via helicopter in remote areas. They are bonding agents. approximately $1,000 per acre cheaper to install. Chipped Site Average size shall be 2" minimum This is a cost-effective way to dispose of debris from Vegetation several inches. thickness clearing and grubbing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above approx. 10% because of its tendency to be transported by runoff. It is not recommended within 200 feet of surface waters. If seeding is expected shortly after mulch, the decomposition of the chipped vegetation may tie up nutrients important to grass establishment. 7 Sensitive lake means a lake that has proved to be particularly prone to eutrophication; the County gives this deSignation when an active input plan has been adopted to limit the amount of phosphorous entering the lake. 1/24/2005 2005 Surface Water Design Manual -Appendix D D-I4 D.3.2 COVER MEASURES D.3.2.3 NETS AND BLANKETS Code: NE Symbol: Purpose Erosion control nets and blankets are intended to prevent erosion and bold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. [n addition, some nets and blankets can be used to pennanently reinforce turf to protect drainage ways during high flows. Nets are strands of material woven into an open, but high-tensile strength net (for example, jute matting). Blankets are strands of material that are not tightly woven, but instead fonn a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control nets and blankets should be used: 1. For pennanent stabilization of slopes 2H: I V or greater and with more than 10 feet of vertical relief 2. In conjunction with seed for final stabilization of a slope, not for temporary cover. However, they may be used for temporary applications as long as the product is not damaged by repeated handling. In fact, this method of slope protection is superior to plastic sheeting, which generates high-velocity runoff (see Section D.3.2.4). 3. For drainage ditches and swales (highly reconunended). The application of appropriate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can capture a great deal of sediment due to their open, porous structure. Synthetic nets and blankets may be used to pennanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. Design and Installation Specifications I. See Figure D.3.2.B and Figure D.3.2.C for typical orientation and installation of nettings and blankets. Note: Installation is critical to the effectiveness of these products. If good ground contact is not achieved. runofTcan concentrate under the product, resulting in significant erosion. 2. With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer thoroughly consults the manufacturer's information and that a site visit takes place in order to insure that the product specified is appropriate. 3. Jute matting must be used in conjunction with mulch (Section D.3.2.2J. Excelsior, woven straw blankets, and coir (coconut fiber) blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. Other types of products will have to be evaluated individually. In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. 4. Purely synthetic blankets are allowed but shall only be used for long-tenn stabilization of waterways. The organic blankets authorized above are better for slope protection and short-tenn waterway protection because they retain moisture and provide organic matter to the soil, substantially improving the speed and success of re-vegetation. 2005 Surface Water Design Manual-Appendix D 1124/2005 D-15 SECTION D.3 ESC MEASURES I Maintenance Standards I. Good contact with the ground must be maintained, and there must not be erosion beneath the net or blanket. 2. Any areas of the net or blanket that are damaged or not in close contact with the ground shall be repaired and stapled. 3. If erosion occurs due to poorly controlled drainage, the problem shall be fixed and the eroded area protected. FIGURE D,3.2.B WATERWAY INSTALLATION DO NOT STRETCH BLANKETS/MATIINGS TIGHT - ALLOW THE ROLLS TO MOLD TO ANY IRREGULARITIES SLOPE SURFACE SHALL BE SMOOTH BEFORE PLACEMENT FOR PROPER SOIL CONTACT ANCHOR, STAPLE, AND INSTALL CHECK SLOTS AS PER MANUFACTURER'S RECOMMENDATIONS AVOID JOINING MATERIAL IN THE CENTER OF THE DITCH liME. FERTILIZE AND SEED BEFORE INSTALLATION Z!~~~o;.:.,::::::", MIN. 6" OVERLAP FIGURE D.3.2.C SLOPE INSTALLATION SLOPE SURFACE SHALL BE SMOOTH BEFORE IF THERE IS A BERM AT THE ;~;~;g:~;~;~::;;:~~i:~LAT~:::ACT _~.~-'-~'~:'~'~~" ;t'''~~J: i3-:~~t-;:~ir:.: .. :.:..? ''.i~:;;;;,?~~,,:::,::-.::::.~;o.~-,,;._, ~0~Lg~E S~~P~H:N~tR~R / 12" INTERVALS 7~::--';?il~':C==~ MIN. 6" OVERLAP DO NOT STRETCH BLANKETS/MATIINGS TIGHT - ALLOW THE ROLLS TO MOLD TO ANY IRREGULARITIES FOR SLOPES LESS THAN 3H:1V, ROLLS MAY BE PLACED IN HORIZONTAL STRIPS STAPLE OVERLAPS MAX. 5' SPACING BRING MATERIAL DOWN TO A LEVEL AREA, TURN THE END UNDER 4" AND STAPLE AT 12h INTERVALS LIM£. FERTILIZE AND SEED BEFORE INSTALLATION. PLANTING OF SHRUBS, TREES. ETC. SHOULD OCCUR AFTER INSTALLATION. I I 1/24/2005 2005 Surface Water Design Manual -Appendix D D-16 D.3.2 COVER MEASURES D.3.2.4 PLASTIC COVERING Code: PC Symbol: -.. ----l§f---.. - Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. Conditions of Use 1 . Plastic covering may be used on disturbed areas that require cover measures for less than 30 days. 2. Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable/or long-term applications. 3. Clear plastic sheeting may be used over newly-seeded areas to create a greenhouse effect and encourage grass growth. Clear plastic should not be used for this purpose during the summer months because the resulting high temperatures can kill the grass. 4. Due to rapid runoff caused by plastic sheeting, this method shall not be used upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. Note: There have been many problems with plastic, usually attributable to poor installation and maintenance. However, the material itself can cause problems, even when con'ectly installed and maintained, because it generates high-velocity nlnoff and breaks down quickly due to ultraviolet radiation. In addition, if the plastic is not completely removed, it can clog drainage system inlets and outlets. It is highly recommended that alternatives to plastic sheeting be used whenever possible and that its use be limited. Design and Installation Specifications 1. See Figure 0.3.2.0 for details. 2. Plastic sheeting shall have a minimum thickness of 0.06 millimeters. 3. If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be installed at the toe of the slope in order to reduce the velocity of runoff. I rOE IN SHEETING IN Ir.fINIIdUId ,,"X4" TRENCH FIGURE D.3.2.D PLASTIC COVERING ---- TIRES, SANDBAGS. OR EQUIVALENT 1.4.6. Y BE USED TO WEIGHT PLASTIC SEIlUS BElWEEN SHEETS IolUST OVERLAP A IollN1MUid or 12" AND BE WEIGHTED OR TAPED I 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-17 SECTIOND.3 ESC MEASURES Maintenance Standards for Plastic Covering 1. Tom sheets must he replaced and open seams repaired. 2. If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and replaced. 3. When the plastic is no longer needed, it shall be completely removed. D.3.2.S STRAW WATTLES 1/24/2005 .. Code: SW Symbol: Purpose Wattles are erosion and sediment control barriers consisting of straw wrapped in biodegradable tubular plastic or similar encasing material. Wattles may reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sediment. Straw wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length. The wattles are placed in shallow trenches and staked along the contour of disturbed or newly constructed slopes. Conditions of Use I. Install on disturbed areas that require immediate erosion protection. 2. Use on slopes requiring stabilization until perroanent vegetation can be established. 3. Can be used along the perimeter of a project, as a check dam in unlined ditches and around temporary stockpiles 4. Wattles can be staked to the ground using willow cuttings for added revegetation. 5. Rilling can occur beneath and between wattles if not properly entrenched, allowing water to pass below and between wattles Design and Installation Specifications I. It is critical that wattles are installed perpendicular to the flow direction and parallel to the slope contour. 2. Narrow trenches should be dug across the slope, on contour, to a depth of 3 to 5 inches on clay soils and soils with gradual slopes. On loose soils, steep slopes, and during high rainfall events, the trenches should be dug to a depth of 5 to 7 inches, or y, to 2/3 of the thickness ofthe wattle. 3. Start construction of trenches and installing wattles from the base ofthe slope and work uphill. Excavated material should be spread evenly along the uphill slope and compacted using hand tamping or other method. Construct trenches at contour intervals of 3 to 30 feet apart depending on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches should be constructed. 4. Install the wattles snugly into the trenches and abut tightly end to end. Do not overlap the ends. 5. Install stakes at each end of the wattle, and at 4 foot centers along the entire length of the wattle. 6. If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. 7. At a minimum, wooden stakes should be approximately % x ';' x 24 inches. Willow cuttings or 3/8 inch rebar can also be used for stakes. 2005 Surface Water Design Manual-Appendix D D-18 D.3.2 COVER MEASURES 8. Stakes should be driven through the middle ofthe wattle, leaving 2 to 3 inches of the stake protruding above the wattle. Maintenance Standards I. Inspect wattles prior to forecasted rain, daily during extended rain events, after rain events, weekly during the wet season, and at two week intervals at all othertimes of the year. 2. Repair or replace split, tom, raveling, or slumping wattles 3. Remove sediment accumulations when exceeding Y, the height between the top of the wattle and the ground surface. 2005 Surface Water Design Manual-Appendix D 112412005 D-19 SECTION D.3 ESC MEASURES I 1/24/2005 FIGURE D.3.2.E STRAW WA TTLES STRAW ROLLS MUST BE PLACED ALONG SLOPE COIHOURS ADJACENT ROLLS SHALL TIGHTLY ABUT A. / 10'-25' ROLL SPACING DEPENDS ON SOIL TYPE AND SLOPE STEEPNESS I WE NOTES: (3-Sm) ;1 r-SEDIMENT, ORGANIC ~~ATTER. AI~D I'JATIVE SEEDS ARE CAPTURED BEHIND THE ROLLS 3"-5" (75-125mm) STRAW WATTLES 1. STRAW ROLL INSTALLATION REQUIRES THE PLACEMUH i\lm SECURE STAKII<G OF THE ROLL IN A TRENCH. ]" , 5" (75-125mm) DEEF·. DUG ON COfHOUR. RUNOFF MUST 1,(lT BE ALLOWED TO RUN UI"DER OR AROUND ROLL. 8"-10" DIA. (200-250mm) I 2005 Surface Water Design Manual -Appendix D D-20 D.3.2.6 D.3.2 COVER MEASURES TEMPORARY AND PERMANENT SEEDING Code: SE Symbol: -"--i@)----- Purpose Seeding is intended to reduce erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use I. Seeding shall be used throughout the project on disturbed areas that have reached final grade or that wiJl remain unworked for more than 30 days. 2. Vegetation-lined channels shall be seeded. Channels that will be vegetated shou\d'be installed before major earthwork and hydroseeded or covered with a Bonded Fiber Matrix (BFM). 3. Retention/detention ponds shall be seeded as required. 4. At the County's discretion, seeding without mulch during the dry season is allowed even though it will take more than seven days to develop an effective cover. Mulch is, however, recommended at all times because it protects seeds from heat, moisture loss, and transport due to runoff. 5. At the beginning of the wet season, all disturbed areas shall be reviewed to identify which ones can be seeded in preparation for the winter rains (see Section D.5.2). Disturbed areas shall be seeded within one week of the beginning of the wet season. A sketch map of those areas to be seeded and those areas to remain uncovered shall be submitted to the DDES inspector. The DDES inspector may require seeding of additional areas in order to protect surface waters, adjacent properties, or drainage facilities. 6. At final site stabilization, all disturbed areas not otherwise vegetated or stabilized shall be goeded and mulched (see Section D.S.5). Design and Installation Specifications I. The best time to seed is April I through June 30, and September 1 through October 15. Areas may be seeded between July I and August 31, but irrigation may be required in order to grow adequate cover. Areas may also be seeded during the winter months, but it may take several months to develop a dense groundcover due to cold temperatures. The application and maintenance of mulch is critical for winter seeding. 2. To prevent seed from being washed away, confinn that all required surface water control measures have been installed. 3. The seedbed should be firm but not compacted because soils that are well compacted will not vegetate as quickly or thoroughly. Slopes steeper than 3H:IV shan be surface roughened. Roughening can be accomplished in a variety of ways, but the typical method is track walking, or driving a crawling tractor up and down the slope, leaving cleat imprints parallel to the slope contours. 4. In general, 10-20-20 N-P-K (nitrogen-phosphorus-potassium) fertilizer may be used at a rate of 90 pounds per acre. Slow-release fertilizers are preferred because they are more efficient and have fewer environmental impacts. It is recommended that areas being seeded for final landscaping conduct soil tests to determine the exact type and quantity of fertilizer needed. This will prevent the over- application of fertilizer. Disturbed areas within 200 feet of water bodies and wetlands must use slow- release low-phosphorus fertilizer (typical proportions 3-1-2 N-P-K). 5. The following requirements apply to mulching: a) Mulch is always required for seeding slopes greater than 3H:IV (see Section D.4.2.1). 2005 Surface Water Design Manual ~ Appendix D 1/24/2005 D-21 SECTION D.3 112412005 ESC MEASURES b) If seeding dnring the wet season, mulch is required. c) The use of mulch may be required during the dry season at the County's discretion if grass growth is expected to be slow, the soils are highly erodible due to soil type or gradient, there is a water body close to the disturbed area, or significant precipitation (see Seclion 0.5.2) is anticipated before the grass will provide effective cover. d) Mulch may be applied on top of the seed or simultaneously by hydroseeding. 6. Hydroseeding is allowed as long as tackifier is included. Hydroseeding wilh wood fiber mulch is adequate during the dry season. During the wet season, lhe application rate shall be doubled because the mulch and taekifier used in hydroseeding break down fairly rapidly. It may be necessary in some applications to include straw with the wood fiber, but this can be detrimental to gennination. 7. Areas to be permanently landscaped shall use soil amendments. Good qualily topsoil shall be tilled into the top six inches to reduce the need for fertilizer and improve the overall soil quality. Most native soils will require the addilion of four inches of well-rotted compost to be tilled into the soil to provide a good quality topsoil. Compost used should meet Ecology publication 98-38 specifications for Grade A quality compost. 8. The seed mixes listed below include recommended mixes for both temporary and pennanent seeding. These mixes, with the exception of the wetland mix, shall be applied at a rate of 120 pounds per acre. This rate may be reduced if soil amendments or slow-release fertilizers are used. Local suppliers should be consulted for their recommendations because the appropriate mix depends on a variety of factors, including exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by lhe County may be used. Table 0.3.2.B presents the standard mix for those areas where just a temporary vegetative cover is required. ~0:~TiBL~~.3'2;~TEMp'()~RVERO~~ONO:iNTR()LSE~J),~}{ • •...... ,\ ... ; ..... ' •. 'i:.·· .. ,e.·.i ·,· % Weight % Purity % Germination Chewings or red fescue 40 98 90 Festuca rubra var. commutata or Festuca rubra Annual or perennial rye 40 98 90 Lolium multiflorum or Lolium perenne Redtop or colonial bentgrass 10 92 85 Agrostis alba or Agrostis tenuis White dutch clover 10 98 90 Trifolium repens 2005 Surface Water Design Manual-Appendix D D-22 D.3.2 COVER MEASURES Table D.3.2.C provides just one recommended possibility for landscaping seed . ... ' , ...... •• .' . . :' ......•. ,.. .-,.~ ".' .... ~'-' ......... . ' .. . ' . ' . . .... TABLE D.3,2,CLANDSCAPINGSEED MIX' ' . " . , ....... % Weight % Purity % Germination Perennial rye blend 70 98 90 Lolium perenne Chewings and red fescue blend 30 98 90 Festuca rubra var. commutata or Festuca rubra This turf seed mix in Table D.3.2.D is for dry situations where there is no need for much water. The advantage is that this mix requires velY little maintenance. I ..... ' ........•. TABLEU.3.2.D LOW~GROWING TURF SEEDM." , ............. . . . . ' .. , . . ". '.' . "'.: ., ). .' . % Weight % Purity % Germination Dwarf tall fescue (several varieties) 45 98 90 Festuca arundinacea var. Dwarf perennial rye (Barclay) 30 98 90 Lolium perenne var. barclay Red fescue 20 98 90 Festuca rubra Colonial bentgrass 5 98 90 Agrostis tenuis :; Table D.3.2.E presents a mix recommended for bioswales and other intennittently wet areas. Sod shall generally not be used for bioswales because the seed mix is inappropriate for this application. Sad may be used for lining ditches to prevent erosion, but it will provide little water quality benefit during the wet season. . ' .... TABLE D.3.2.E ,BIOSWALE SEED MIX' . " ... , . " ... . '" '., . . ." .'. . ' ..... . % Weight % Purity % Germination Tailor meadow fescue 75-80 98 90 Festuca arundinacea or Festuca elatior Seaside/Creeping bentgrass 10-15 92 85 Agrostis pa/ustris Redtop bentgrass 5-10 90 80 Agrostis alba or Agrostis gigantea • Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-23 SECTION DJ 1/24/2005 ESC MEASURES The seed mix shown in Table DJ.2.F is a recommended low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wetlands (if planting in wetland areas, see Section 6.3.1 oflhe Surface Water Design Manual). Other mixes may be appropriate, depending on the soil type and hydrology of the area. Apply this mixtnre at a rate of60 pounds per acre. , I ·>i.TABLE D3:2.Ji' WIi;T..AREA SEED MIX" ...... .•.... ' .. ' ..•..•.••... '., ....•. ". . .. .... •• % Weight % Purity % Germination Tali or meadow fescue 60-70 98 90 Festuca arundinacea or Festuca elalior Seaside/Creeping bentgrass 10-15 98 85 Agroslis paluslris Meadow foxtail 10-15 90 80 Alepocurus pralensis Aisike clover 1-6 98 90 Trifolium hybridum Redtop bentgrass 1-6 92 85 Agroslis alba , Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix The meadow seed mix in Table D.3.2.G is recormnended for areas that will be maintained infrequently or not at all and where colonization by native plants is desirable. Likely applications include rural road and utility right-of-way, Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. The appropriateness of clover in the mix may need to be considered as this can be a fairly invasive species. If the soil is amended, the addition of clover may not he necessary. ....... .. ' ......".;. • ••• TABLED.3.2.G .·MEAJjowsE~DI~U~;"; (.. •• :..':' ...••••.• ' .•..••.. ., .. ;. . ... '.' '.,. " . " ". ......• ..... . '. % Weight % Purity % Germination Redtop or Oregon bentgrass 40 92 85 Agrostis alba or Agroslis oregonensis Red fescue 40 98 90 Festuca rubra White dutch clover 20 98 90 Trifolium repens Maintenance Standards for Temporary and Permanent Seeding , l I. Any seeded areas that fail to establish at least 80 percent cover within one month shan be reseeded. If reseeding is ineffective, an alternate method, such as sodding or netslblankets, shall be used, If winter weather prevents adequate grass growth, this time limit may be relaxed at the discretion of the County when critical areas would otherwise be protected. 2005 Surface Water Design Manual--Appendix D D-24 D.3.2 COVER MEASURES 2. After adequate cover is achieved, any areas that experience erosion shall be re-seeded and protected by mulch. If the erosion problem is drainage related, the problem shall be fixed and the eroded area re-seeded and protected by mulch. 3. Seeded areas shall be supplied with adequate moisture, but not watered to the extent that it causes runoff. D-3.2.7 SODDING Code: SO Symbol: Purpose The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize drainage ways where concentrated overland flow will occur. Conditions of Use Sodding may be used in the following areas: I. Disturbed areas that require short-term or long-term cover 2. Disturbed areas that require immediate vegetative cover 3. All waterways that require vegetative lining (except biofiltration swales-the seed mix used in most sod is not appropriate for biofiltration swales). Waterways may also be seeded rather than sodded, and protected with a net or blanket (see Section D.3.2.3). Design and Installation Specifications Sod shall be free of weeds, of uniform thickness (approximately I-inch thick), and shall have a dense root mat for mechanical strength. The following steps are recommended for sad installation: I. Shape and smooth the surface to final grade in accordance with the approved grading plan. 2. Amend two inches (minimum) of well-rotted compost into the top six inches of the soil if the organic content ofthe soil is less than ten percent. Compost used should meet Ecology publication 98-38 specifications for Grade A quality compost. 3. Fertilize according to the supplier's recommendations. Disturbed areas within 200 feet of water bodies and wetlands must use non-phosphorus fertilizer. 4. Work lime and fertilizer I to 2 inches into the soil, and smooth the surface. 5. Lay strips of sad beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H: I V. 6. Roll the sodded area and irrigate. 7. When sodding is carried out in alternating strips or other patterns, seed the areas between the sod immediately after sodding. Maintenance Standards If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and protected with a net or blanket. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-25 SECTION D.3 ESC MEASURES D.3.2.8 POLYACRYLAMIDE FOR SOIL EROSION PROTECTION 1/24/2005 Purpose Polyacrylamide (PAM) is used on construction sites to prevent soil erosion. Applying PAM to bare soil in advance of a rain event significantly reduces erosion and controls sediment in two ways. First, PAM increases the soil's available pore volume, thus increasing infiltration through flocculation and reducing the quantity of stormwater runoff. Second, it increases flocculation of suspended particles and aids in their deposition, thus reducing stormwater runoff turbidity and improving water quality. Conditions of Use 1. PAM shall not be directly applied to water or allowed to enter a water body. 2. PAM may be applied to wet soil, but dry soil is preferred due to less sediment loss. 3. PAM will work when applied to saturated soil but is not as effective as applications to dry or damp soil. 4. PAM may be applied only to the following types of bare soil areas that drain to a sediment trap or a sediment pond: • Staging areas • Stockpiles • Pit sites • Balanced cut and fill earthwork • Haul roads prior to placement of crushed rock surfacing • Compacted soil road base 5. PAM may be applied only during the following phases of construction: • During rough grading operations • After final grade and before paving or final seeding and planting • During a winter shut down of site work. In the case of winter shut down, or where soil will remain unworked for several months, PAM should be used together with mulch. 6. Do not use PAM on a slope that flows directly to a stream or wetland. The stormwater runoff shall pass through a sediment control measure prior to discharging to surface waters. Design and Installation Specifications I. PAM must be applied using one of two methods of application, "preferred" or "alternative." The specifications for these methods are described under separate headings below. 2. PAM may be applied in dissolved form with water, or it may be applied in dry, granular or powdered form. The preferred application method is the dissolved form. 3. PAM is to be applied at a maximum rate of \I, pound PAM per 1000 gallons of water per I acre of bare soil. Table D.3.2.H may be used to determine the PAM and water application rate for disturbed soil areas. Higher concentrations of PAM do not provide any additional effectiveness. 4. Do not add PAM to water discharging from the site. 5. PAM shall be used in conjunction with other ESC measures and not in place oftl,em. When the total drainage area is greater than or equal to 3 acres, PAM treated areas shall drain to a sediment pond per Section D.3.S.2. For drainage areas less than 3 acres, PAM treated areas must drain to a sediment trap per Section D.3.S.1. Other normally required sediment control measures such as perimeter protection 2005 Surface Water Design Manual -Appendix D D-26 D.3.2 COVER MEASURES measures (Section D.3.3) and surface water collection measures (Section D.3.6) shall be applied (0 PAM treated areas. 6. All areas not being actively worked shall be covered and protected from rainfall. PAM shall not be the only cover BMP used. 7. Keep the granular PAM supply out of the sun. Granular PAM loses its effectiveness in three months after exposure to sunlight and air. 8. Care must be taken to prevent spills of PAM powder onto paved surfaces. PAM, combined with water, is very slippery and can be a safety hazard. During an application of PAM, prevent over-spray from reaching pavement as the pavement will become slippery. If PAM powder gets on skin or clothing, wipe it off with a rough towel rather than washing with water. Washing with water only makes cleanup more difficult, messier, and time consuming. 9. The specific PAM copolymer formulation must be anionic. Cationic PAM shall not be used in any application because of known aquatic toxicity concerns. Only the highest drinking water grade PAM, certified for compliance with ANSIINSF Standard 60 for drinking water treatment, may be used for soil applications. The Washington State Department of Transportation (WSDOT) lists approved PAM products on their web page. All PAM use shall be reviewed and approved by DDES. 10. The PAM anionic charge density may vary from 2 -30 percent; a value of 18 percent is typical. Studies conducted by the United States department of Agriculture (USDA)! ARS demonstrated that soil stabilization was optimized by using very high molecular weight (12 -15 mg!mole), highly anionic (>20% hydrolysis) PAM. 11. P A1vf must be "water soluble" or "li near" or "non-crass-linked." Cross-linked or water absorbent PAM, polymerized in highly acidic (pH<2) conditions, are used to maintain soil moisture content. ' ... . .... TABLEDj.2.H·PAMANnWATER APPLlCATIONRxrESC ..... ' ..... ..... .' . ... . Disturbed Area (ac) PAM (lbs) Water (gal) 0.50 0.25 500 1.00 0.50 1,000 1.50 0.75 1,500 2.00 1.00 2,000 2.50 1.25 2,500 3.00 1.50 3,000 3.50 1.75 3,500 4.00 2.00 4,000 4.50 2.25 4,500 5.00 2.50 5,000 Preferred Application Method I. Pre-measure the area where PAM is to be applied and calculate the amount of product and water necessary to provide coverage at the specified application rate (112 pound PAMII ,000 gallons!acre). 2. Dissolve pre-measured dry granular PAM with a known quantity of clean water in a bucket several hours or overnight. PAM has infinite solubility in water, but dissolves very slowly. Mechanical mixing will help dissolve PAM. Always add PAM to water -not water to PAM. 3. Pre-fill the water truck about 1!8 full with water. The water does not have to be potable, but it must have relatively low turbidity -in the range 0[20 NTU or less. 2005 Surface \Vater Design Manual-Appendix D 1/24/2005 D-27 SECTION D.3 ESC MEASURES 4. Add PAMlWater mixture to the truck. 5. Completely fill the water truck to specified volume. 6. Spray PAMlWater mixture onto dry soil until the soil surface is uniformly and completely wetted. Alternate Application Method PAM may also be applied as a powder at the rate of 5 pounds per acre. This must be applied on a day that is dry. For areas less than 5-10 acres, a hand-held "organ grinder" fertilized spreader set to the smallest setting will work. Tractor mounted spreaders will work for larger areas. Maintenance Standards 1. PAM may be reapplied on actively worked areas after a 48-hour period 2. Reapplication is not required unless PAM treated soil is disturbed or unless turbidity levels show the need for an additional application. If PAM treated soil is left undisturbed, a reapplication may be necessary after two months. More PAM applications may be required for steep slopes, silty and clay soils, (USDA classification Type "C" and "D" soils), long grades, and high precipitation areas. When PAM is applied first to bare soil and then covered with straw, a reapplication may not be necessary for several months. D.3.2.9 COMPOST BLANKETS 1124/2005 Code: COBL Symbol: -.~-{~,;~)-- '---" Purpose Compost blankets are intended to: • Provide immediate temporary protection from erosion by protecting soil from rainfall and slowing flow velocity over the soil surface. • Enhance temporary or permanent plant establishment by conserving moisture, holding seed and topsoil in place, providing nutrients and soil microorganisms, and moderating soil temperatures. • Compost blankets, applied at the proper thickness and tilled into the soil, are also an option for amending soils for pennanent landscaping. • Compost generally releases and adds phosphorous to stormwater. Therefore, compost blankets are not recommended for use in watersheds where phosphorous sensitive water resources are located. Unless prior approval is given by the County. they should not be used in Sensitive Lake Watersheds. Conditions of Use 1. Compost blankets may be used unseeded on disturbed areas that require temporary cover measures up to 1 year. Compost applied as temporary cover may be reclaimed and re-used for permanent cover. 2. Compost provides cover for protecting final grades until landscaping can be completed as it can be directly seeded or tilled into soil as an amendment. 3. Compost blankets meet mulch requirements for seed. 4. Seed may be applied to a compost blanket at any time for pennanent or temporary stabilization of disturbed areas. Seed may be applied prior to blanket application, on top of blankets, or injected and mixed into the compost as it is applied. 5. Compost blankets may be applied on slopes up to 2H: 1 V. 2005 Surface Water Design Manual ~-Appendix D D-28 D.3.2 COVER MEASURES Design and Installation Specifications I. Compost shall be applied at a minimum of 2 inches thick, unless otherwise directed by an ESC supervisor or King County. At an application of 2 inches, this will equal approximately 100 tons per acre (compost generally weighs approximately 800 Ibs per cubic yard). Thickness shall be increased at the direction of the design engineer for disturbed areas in or near critical areas or other areas highly susceptible to erosion. 2. Compost shall meet criteria in WAC 173-350-220 (10) for Designation of Composted Materials. 3. Compost shall be obtained from a supplier meeting the requirements ofW AC 173-350-220. 4. Compost blankets shall be applied over the top of the slope to which it is applied, to prevent water from running under the blanket 5. Compost blankets shall not be used in areas exposed to concentrated flow (e.g. channels, ditches, dikes) Maintenance Standards I. The specified thickness of the blanket/cover must be maintained. 2. Any areas that show signs of erosion must be re-mulched. If the erosion problem is drainage related, then tbe drainage problem must first be remedied and then the eroded area re-mulched. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-29 SECTION D.3 ESC MEASURES D.3.3 PERIMETER PROTECTION Perimeter protection to filter sediment from sheetwash shall be located downslope of all disturbed areas and shall be installed prior to upslope grading. Perimeter protection includes the use of vegetated strips as well as, constructed measures, such as silt fences, fiber rolls, sand/gravel barriers, brush or rock filters, triangular silt dikes and other methods. During the wet season, 50 linear feet of silt fence (and the necessary stakes) per acre of disturbed area must be stockpiled on site. Purpose: The purpose of perimeter protection is to reduce the amount of sediment transported beyond the disturbed areas of the construction site. Perimeter protection is primarily a backup means of sediment control. Most, if not all, sediment-laden water is to be treated in a sediment trap or pond. The only circumstances in which perimeter control is to be used as a primary means of sediment removal is when the catchment is very small (see below). When to Install: Perimeter protection is to be installed prior to any upslope clearing and grading. Measures to Use: The above measures may be used interchangeably and are not the only perimeter protection measures available. If surface water is collected by an interceptor dike or swale and routed to a sediment pond or trap, there may be no need for the perimeter protection measures specified in this section. Criteria for Use as Primary Treatment: At the boundary of a site, perimeter protection may be used as the sole form of treatment when the f10wpath meets the criteria listed below. If these criteria are not met, perimeter protection shall only be used as a backup to a sediment trap or pond. Average Slope 1.5H: I V or less 2H:1 V or less 4H: I V or less 6H:1 V or less iOH: 1 V or less Slope Percent 67% or less 50% or less 25% or less 16.7% or less 10% or less Flowpath Length 100 feet 115 feet ISO feet 200 feet 250 feet D.3.3.1 SILT FENCE 1/24/2005 Code: SF Symbol: x X X X X Purpose Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use I. Silt fence may be used downslope of all disturbed areas. 2. Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment trap or pond. The only circumstance in which overland flow may be treated solely by a silt fence, rather than by a sediment trap or pond, is when the area draining to the fence is small (see "Criteria for Use as Primary Treatment" on page D-30). Design and Installation Specifications 1. See Figure D.3.3.A and Figure D.3.3.B for details. 2005 Surface Water Design Manual -Appendix D D-30 D.33 PERIMETER PROTECTION 2. The geotextile used must meet the standards listed below. A copy of the manufacturer's fabric specifications must be available on site. AOS (ASTM 04751) 30-100 sieve size (0.60-0.t5 mm) for slit film 50-100 sieve size (0.30-0.15 mm) for other fabrics Water Permittivity (ASTM 04491) 0.02 sec·1 minimum Grab Tensile Strength (ASTM 04632) 180 Ibs. min. for extra strength fabric 100 Ibs. min. for standard strength fabric Grab Tensile Elongation (ASTM 04632) 30% max. Ultraviolet Resistance (ASTM 04355) 70% min. 3. Standard strength fabric requires wire backing to increase the strength of the fence. Wire backing or closer post spacing may be required for extra strength fabric if field performance warrants a stronger fence. 4. Where the fence is installed, the slope shall be no steeper than 2H: IV. 5. If a typical silt fence (per Figure D.3.3.A) is used, the standard 4 x 4 trench may not be reduced as long as the bottom 8 inches of the silt fence is well buried and secured in a trench that stabilizes the fence and does not allow water to bypass or undennine the silt fence. Maintenance Standards I. Any damage shall be repaired immediately. 2. If concentrated flows are evident uphill of the fence, they must be intercepted and conveyed to a sediment trap or pond. 3. It is important to check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. 4. Sediment must be removed when the sediment is 6 inches high. 5. If the filter fabric (geotextile) has deteriorated due to ultraviolet breakdown, it shall be replaced. FIGURE D.3.3.A SILT FENCE JOINTS IN FILTER FABRIC SHALL BE SPUCED AT POSTS. USE STAPLES, WIRE RINGS, OR EQUIVALENT TO ATIACH FABRIC TO POSTS. 2"x2" BY 14 Ga. WIRE OR EQUIVALENT, IF STANDARD -~~ STRENGTH FABRIC USED FILTER FABRIC-~-j 1------,------1 T~ / U ;MAX \ MINIMU~;f;;:~o;;;;:3/"1I~15" POST SPACING MAY BE INCREASED WASHED GRAVEL TO 8' IF WIRE BACKING IS USED NOTE: FILTER FABRIC FENCES SHALL BE INSTALLED ALONG CONTOUR WHENEVER POSSIBLE 2"x4" WOOD POSTS, STEEL FENCE POSTS, REBAR. OR EQUIVALENT I 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-31 SECTION D.3 ESC MEASURES 1/24/2005 FIGURE D3.3.B SILT FENCE INSTALLATION BY SLICING SILT F(flCE FLOW c>- NOTES: 100% COMPACTION EACH SIDE 1. POST SP.ACIHG: 7' MAX. ON OPEN RUNS 4' MAX. ON POOLlI,G AREAS. ') POST DEPTH: AS MUCH BELOW GROUND AS FABRIC ABOVE GROUIJD. 3. PONDII'-JG HEIGHT MAX. 24" ATTACH FABRIC TO UPSTREAM SIDE OF POST. 4. DRIVE OVER EACH SIDE OF SILT FENCE 2 TO 4 TIMES WITH DEVICE EXERTIHG 60 p.s.1. OR GREATER. 5. NO MORE THAN 24" OF A 36" FABRIC IS ALLOWED ABOVE GROUND. 6. VIBRATORY PLOW IS NOT ACCEPTABLE BEep,USE OF HORIZONTAL COI~PACTIOI·1. -=:le---OPERATION HORIZOI'-JTAL CHISEL POII'-JT (76mm WIDTH) Anp,CHI~EI,T DET;I.lLS TOP OF FABRIC BELT T TOP 8" DIAGONAL ATTACHMENT DOUBLES STRENGTH t 1. GATHER FABRIC AT POSTS, IF NEEDED. 2. UTILIZE THREE TIES PER POST, ALL WITHIN TOP 8" OF FABRIC. 3. POSITION EACH TIE DIAGOfIALLY, PUI'ICTURIHG HOLES VERTICALLY A MINIMUM OF I" APp.RT. 4 HANG EACH TIE 01, .~ POST I,IPPLE N-ID TIGHTEI, SECURELY. USE CABLE TIES (50 LBS) OF SOFT WIRE. ROLL OF SILT FEI,CE PLOW FABRIC ABOVE. GROUND 200-300mm ] SILT FEI,CE INSTALLATION BY SLlCIIIG METHOD 2005 Surface Water Design Manual-Appendix D D-32 D.3.3 PERIMETER PROTECTION D.3.3.2 BRUSH BARRIER Code: BB Symbol: Purpose The purpose of brush barriers is to reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use I. Brush barriers may be used downslope of all disturbed areas. 2. Brush barriers are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment trap or pond. The only circumstance in which overland flow may be treated solely by a barrier, rather than by a sediment trap or pond, is when the area draining to the barrier is small (see "Criteria for Use as Primary Treatment" on page 0-30). Design and Installation Specifications 1. See Figure O.3.3.C for details. 2. King County may require filter fabric (geotextile) anchored over the brush berm to enhance the filtration ability of the barrier. Maintenance Standards I. There shall be no signs of erosion or concentrated runoff under or around the barrier. If concentrated flows are bypassing the barrier, it must be expanded or augmented by toed-in filter fabric. 2. The dimensions of the barrier must be maintained. ! FIGURE D.3.3.C BRUSH BARRIER IF REQUIRED, DRAPE FILTER fABRIC ~"-- OVER BRUSH AND SECURE IN 4"x4" MIN. TRENCH WITH COMPACTED ~ ~ -.. BACKf"lLl ~~ '--~ "'----",----0 '----:---..- --............. ...... ANCHOR DOWNHILL EDGE Of ~ FILTER fABRIC WITH STAKES, _____ SANDBAGS, OR EOUIVALENT -----/'-O"""'''"'Ilii'~''T11~~~ 2' MIN. 5' WIDE BRUSH BARRIER WITH MAX. 6" DIAMETER WOODY DEBRIS. 'II MIN. HEIGHT ALTERNATIVELY TOPSOIL STRIP PINGS MAY BE USED TO FORM THE BARRIER. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-33 SECTION D.3 ESC MEASURES D.3.3.3 VEGETATED STRIP Code: VS Symbol: Purpose Vegetated strips reduce the transport of coarse sediment from a constmction site by providing a temporary physical barrier to sediment and reducing the mnoffvelocities of overland flow. Conditions of Use I. Vegetated strips may be used downslope of all disturbed areas. 2. Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment trap or pond. The only circumstance in which overland flow may be trealed solely by a strip, rather than by a sediment trap or pond, is when the area draining to the strip is small (see "Criteria for Use as Primary Treatment" on page D-30). Design and Installation Specifications I. The vegetated strip shall consist of a 25-foot minimum width continuous strip of dense vegetation with a permeable topsoil. Grass-covered, landscaped areas are generally not adequate because the volume of sediment overwhelms lhe grass. Ideally, vegetated strips shall consist ofundislurbed native growth with a well-developed soil that allows for infiltration ofmnoff. 2. The slope within the strip shall not exceed 4H: I V. 3. The uphill boundary ofthe vegetated strip shall be delineated with clearing limits as specified in Section D.3.J (p. D-8). Maintenance Standards I. Any areas damaged by erosion or constmction activity shall be seeded immediately and protected by mulch. 2. If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded, sad must be installed using the standards for installation found in Section DA.2.S. Ifthere are indications that concentrated flows are traveling acrOSs the buffer, surface water controls must be installed to reduce the flows entering the buffer, or additional perimeter protection must be installed. D.3.3.4 TRIANGULAR SILT DIKE (GEOTEXTILE ENCASED CHECK DAM) 1124/2005 Code: TSD Symbol: .. Purpose Triangular silt dikes (TSDs) may be used as check dams, for perimeter protection, for temporary soil stockpile protection, for drop inlet protection, or as a temporary interceptor dike. Silt dikes, if attached to impervious surfaces with tack or other adhesive agent may also be used as temporary wheel wash areas, or concrete washout collection areas. Conditions of Use I. May be used for temporary check dams in ditches. 2005 Surface Water Design Manual -Appendix D D-34 D.3.3 PERIMETER PROTECTION 2. May be used on soil or pavement with adhesive or staples. 3. TSDs have been used to build temporary sediment ponds, diversion ditches, concrete washout facilities, curbing, water bars, level spreaders, and benns. Design and Installation Specifications I. TSDs must be made of urethane foam sewn into a woven geosynthetic fabric. 2. TSDs are triangular, 10 inches to 14 inches high in the center, with a 20-inch to 28-inch base. A 2- foot apron extends beyond both sides of the triangle along its standard section of 7 feet. A sleeve at one end allows attachment of additional sections as needed 3. Install TSDs with ends curved up to prevent water from flowing around the ends 4. Attach the TSDs and their fabric flaps to the ground with wire staples. Wire staples must be No. II gauge wire or stronger and shall be 200 mm to 300 mm in length. S. When multiple units are installed, the sleeve of fabric at the end of the unit shall overlap the abutting unit and be stapled. 6. TSDs must be located and installed as soon as construction will allow. 7. TSDs must be placed perpendicular to the flow of water. 8. When used as check dams, the leading edge must be secured with rocks, sandbags, or a small key slot and staples. 9. When used in grass-lined ditches and swales, the TSD check dams and accumulated sediment shall be removed when the grass has matured sufficiently to protect the ditch or swale unless the slope of the swale is greater than 4 percent. The area beneath the TSD check dams shall be seeded and mulched immediately after dam removal. Maintenance Standards I. Triangular silt dikes shall be monitored for perfonnance and sediment accumulation during and after each runoff producing rainfall event. Sediment shall be removed when it reaches one half the height of the silt dike. 2. Anticipate submergence and deposition above the triangular silt dike and erosion from high flows around the edges of the dike/dam. Immediately repair any damage or any undercutting of the dike/dam. D.3.3.S COMPOST BERMS Code: COBE Symbol: Purpose Compost benns are an option to meet the requirements of perimeter protection. Compost benns may reduce the transport of sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Compost benns trap sediment by filtering water passing through the benn and allowing water to pond, creating a settling area for solids behind the berm. Organic materials in the compost can also reduce concentrations of metals and petroleum hydrocarbons from construction runoff. Due to the increase in phosphorous seen in the effluent data from compost benns, they should be used with some cautions in areas that drain to phosphonls sensitive water bodies, and should only be used in Sensitive Lake watersheds, such as Lake Sammamish, with the approval from the County or the local jurisdiction. 2005 Surface Water Design Manual-Appendix D 112412005 D-35 SECTION DJ 1/24/2005 ESC MEASURES Conditions of Use I. Compost berms may be used in most areas requiring sediment or erosion control where runoff is in the form of sheet flow or in areas where silt fence is nonnally considered acceptable. Compost berms may be used in areas where migration of aquatic life such as turtles and salamanders are impeded by the use of silt fence. 2. Compost berms are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed via a drainage system to a sediment pond or trap. 3. For purposes of long-term sediment control objectives, benns may be seeded at the time of installation to create an additional vegetated filtering component. Design and Installation Specifications I. Compost berms shall be applied using a pneumatic blower device or equivalent, to produce a uniform cross-section and berm density. 2. Compost berms shall be triangular in cross-section. The ratio of base to height dimensions shall be 2:1. 3. The minimum size of a compost benn is a 2-foot base with a I-foot height. 4. Compost berms shall be sized and spaced as indicated in the table below. SLOPE SLOPE Maximum Slope Length or Berm Size Required Berm Spacing (linear feet) (height x base width) 0% -2% Flatter than 50: I 250 Iftx2ft 2% -10% 50:1-10:1 125 Iftx2ft 10% -20% 10:1 -5:1 100 Iftx2ft 20% -33% 5:1-3:1 75 Iftx2ft 33% -50% 3:1-2:1 50 l.5ftx3ft 5. Compost benns shall not be used on slopes greater than 2H: I V 6. Compost shall meet criteria in WAC 173-350-220 (10) for Designation of Composted Materials 7. Compost shall be obtained from a supplier meeting the requirements of WAC 173-350-220. 8. Compost particle size distribution shall be as follows: 99% passing a I inch sieve, 90% passing a % inch sieve and a minimum of 70% greater than the 3/8 inch sieve. A total of 98% shall not exceed 3 inches in length. 9. Benns shall be placed on level contours to assist in dissipating flow into sheet flow rather than concentrated flows. Benns shall not be constructed to concentrate runoff or channel water. Sheet flow of water shall be perpendicular to the benn at impact. No concentrated flow shall be directed towards compost benns. 10. Where possible, berms shall be placed 5 feet or more from the toe of slopes to allow space for sediment deposition and collection. 11. In order to prevent water from flowing around the ends ofthe benns, the ends of the benn shall be constructed pointing upslope so the ends are at a higher elevation than the rest of the benn. 12. A compost blanket extending 10-15 feet above the berm is reconunended where the surface above the benn is rutted or uneven, to reduce concentrated flow and promote sheet flow into the berm. 2005 Surface Water Design Manual-Appendix D D-36 D.3.3 PERIMETER PROTECTION Maintenance Standards 1. Compost benns shall be regularly inspected to make sure they retain their shape and allow adequate flow-through of stonnwater. 2. When construction is completed on site, the berms shall be dispersed for incorporation into the sailor left on top of the site for final seeding to occur. 3. Any damage to benns must be repaired immediately. Damage includes flattening, compacting, rills, eroded areas due to ove110pping. 4. If concentrated flows are evident uphill of the benn, the flows must be intercepted and conveyed to a sediment trap or pond. 5. The uphill side of the benn shall be inspected for signs of the benn clogging and acting as a barrier to flows and causing channelization of flows parallel to the benn. If this occurs, replace the benn or remove the trapped sediment. 6. Sediment that collects behind the benn must be removed when the sediment is more than 6 inches deep. D.3.3.6 COMPOST SOCKS Code: COSO Symbol: Purpose Compost socks reduce the transport of sediment from a construction site by providing a temporary physical barrier to sediment-laden water and reducing the runoff velocities of overland flow. Compost socks trap sediment by filtering water that passes through the sock and allows water to pond behind the sock, creating a settling area for solids. Organic materials in the compost also may reduce metal and petroleum hydrocarbon concentrations in construction runoff. Compost socks function similarly to compost benns; however, because the compost is contained in a mesh tube, they are appropriate for both concentrated flow and sheet flow. Compost socks may be used to channel concentrated flow on hard surfaces. Conditions of Use 1. Compost socks may be used in areas requiring sediment or erosion control where runoff is in the fonn of sheet flow or in areas that silt fence is nonnally considered acceptable. Compost socks may also be used in sensitive envirorunental areas where migration of aquatic life, including turtles, salamanders and other aquatic life may be impeded by the used of silt fence. 2. Compost socks are not intended to treat substantial amounts of overland flow. However, compost socks may be subjected to some ponding and concentrated flows. If intended primarily as a filtration device, the socks should be sized and placed so that flows do not overtop the socks. 3. For purposes oflong tenn sediment control objectives, compost socks may be seeded at the time of installation to create an additional vegetated filtering component. Design and Installation Specifications I. Compost socks shall be produced using a pneumatic blower hose or equivalent to fill a mesh tube with compost to create a unifonn cross-section and benn density. 2. Socks shall be filled so they are firmly -packed yet flexihle. Upon initial filling, the socks shall be filled to have a round cross-section. Once placed on the ground, it is recommended to apply weight to the sock to improve contact with the underlying surface. This may cause the sock to assume an oval shape. 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-37 SECTION D.3 ESC MEASURES 3. Compost socks shall be a minimum of 8 inches in diameter. Larger diameter socks are recommended for areas where ponding is expected behind the sock. 4. Compost socks shall not be used on slopes greater than 2H: I V. 5. Compost shall meet criteria in WAC 173-350-220 (10) for Designation of Composted Materials. 6. Compost shall be obtained from a supplier meeting the requirements of WAC 173-350-220. 7. Compost particle size distribution shall be as follows: 99% passing a I inch sieve, 90% passing a Yo inch sieve and a minimum of 70% greater than the 3/8 inch sieve. A total of 98% shall not exceed 3 inches in length. 8. In order to prevent water from flowing around the ends of compost socks, the ends must be pointed upslope so the ends of the socks are at a higher elevation than the remainder of the sock. Maintenance Standards I. Compost socks shall be regularly inspected to make sure the mesh tube remains undamaged, the socks retain their shape, and allow adequate flow through of surface water. If the mesh tube is torn, it shall be repaired using twine, zip-ties, or wire. Large sections of damaged socks must be replaced. Any damage must be repaired immediately upon discovery of damage. 2. When the sock is no longer needed, the socks shall be cut open and the compost dispersed to be incorporated into the sailor left on top of the soil for final seeding to occur. The mesh material must be disposed of properly as solid waste. If spills of oil, antifreeze, hydraulic fluid, or other equipment fluids have occurred that have saturated the sock, the compost must be disposed of properly as a waste. 3. Sediment must be removed when sediment accumulations are within 3 inches of the top of the sock. D.3.4 TRAFFIC AREA STABILIZATION 1124/2005 Unsurfaced entrances, roads, and parking areas used by construction traffic shall be stabilized to minimize erosion and tracking of sediment off site. Stabilized construction entrances shall be installed as the first step in clearing and grading. At the County's discretion, road and parking area stabilization is not required during the dry season (unless dust is a concern) or if the site is underlain by coarse-grained soils. Roads and parking areas shall be stabilized immediately after initial grading. Purpose: The purpose of traffic area stabilization is to reduce the amount of sediment transported off site by construction vehicles and to reduce the erosion of areas disturbed by vehicle traffic. Sediment transported off site onto paved streets is a significant problem because it is difficult to effectively remove, and any sediment not removed ends up in the drainage system. Additionally, sediment on public right-of- way can pose a serious traffic hazard. Construction road and parking area stabilization is important because the combination of wet soil and heavy equipment traffic typically fonns a slurry of easily erodible mud. Finally, stabilization also is an excellent fonn of dust control in the summer months. When to Install: The construction entrance is to be installed as the first step in clearing and grading. Construction road stabilization shall occur immediately after initial grading of the construction roads and parking areas. Measures to Use: There are two types of traffic area stabilization: (I) a stabilized construction entrance and (2) construction road/parking area stabilization. Both measures must be used as specified under "Conditions of Use'l for each measure. 2005 Surface Water Design Manual ~ Appendix D D-38 D.3.4 TRAFFIC AREA STABILIZATION D.3.4.1 STABILIZED CONSTRUCTION ENTRANCE Code: CE Symbol: Purpose Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by motor vehicles or nmoff by constructing a stabilized pad of quarry spalls at entrances to construction sites. Conditions of Use Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling on paved roads or other paved areas within 1,000 feet afthe site. Design and Installation Specifications I. See Figure D.3.4.A for details. 2. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the following standards: Grab Tensile Strength (ASTM 04751) 200 psi min. Grab Tensile Elongation (ASTM 04632) 30% max. Mullen Burst Strength (ASTM D3786-80a) 400 psi min. AOS (ASTM 04751) 20-45 (U.S. standard sieve size) 3. Hog fuel (wood based mulch) may be substituted for or combined with quarry spalls in areas that will not be used for pennanent roads. The effectiveness of hog fuel is highly variable, but it has been used successfully on many sites. It generally requires more maintenance than quarry spalls. Hog fuel is not recommended for entrance stabilization in urban areas. The inspector may at any time require the use of quarry spalls if the hog fuel is not preventing sediment from being tracked onto pavement or if the hog fuel is being carried onto pavement. Hog fuel is prohibited in permanent roadbeds because organics in the subgrade soils cause difficulties with compaction. 4. Fencing (see Section D.3.!) shall be installed as necessary to restrict traffic to the construction entrance. 5. Whenever possible, the entrance shall be constructed on a finn, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. Maintenance Standards I. Quarry spalls (or hog fuel) shall be added if the pad is no longer in accordance with the specifications. 2. If the entrance is not preventing sediment from being tracked onto pavement, then alternative measures to keep the streets free of sediment shall be used. This may include street sweeping, an increase in the dimensions ofthe entrance, or the installation ofa wheel wash. !fwashing is used, it shall be done on an area covered with crushed rock, and wash water shall drain to a sediment trap or pond. 3. Any sediment that is tracked onto pavement shall be removed immediately by sweeping. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when sweeping is ineffective and there is a threat to 2005 Surface Water Design Manual-Appendix D 112412005 D-39 SECTlOND.3 ESC MEASURES public safety. If it is necessary to wash the streets, a small sump must be constructed. The sediment would then be washed into the sump where it can be controlled and discharged appropriately. 4. Any quarry spalls that are loosened from the pad and end up on the roadway shall be removed immediately. 5. If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing (see Section D.3.1) shan be installed to control traffic. FIGURE D,3.4.A STABILIZED CONSTRUCTION ENTRANCE AS PER KING COUNTY ROAD STANDARDS, DRIVEWAYS SHALL BE PAVED TO THE EDGE OF R-O-W PRIOR TO INSTALLATION OF THE CONSTRUCTION ENTRANCE TO AVOID DAMAGING OF THE ROADWAY IT IS RECO .... ENDED THAT THE ENTRANCE BE CROWNED SO THAT RUNOFF DRAINS OFF THE PAD INSTALL DRIVEWAY CULVERT IF THERE IS A ROADSIDE DITCH PRESENT. AS PER KING COUNTY ROAD STANDARDS 4"-8" OUARRY SPALLS -_.../ 12" "IN. THICKNESS 1124/2005 D-40 PROVIDE FULL WIDTH OF INGRESS/EGRESS AREA 2005 Surface Water Design Manual-Appendix D ~ I D.l.4 TRAFFIC AREA STABILIZATION D.3.4.2 CONSTRUCTION ROAD/PARKING AREA STABILIZATION ~ Code: CRS Symbol: ~ Purpose Stabilizing subdivision roads, parking areas, and other onsite vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or runoff. Conditions of Use I. Roads or parking areas shall be stabilized wherever they are constructed, whether pennanent or temporary, for use by construction traffic. 2. Fencing (see Section D.3.I) shall be installed, if necessary, to limit lbe access of vehicles to only tbose roads and parking areas that are stabilized. Design and Installation Specifications I. A 6-inch depth of2-to 4-inch crushed rock, gravel base, or crushed surfacing base course shall be applied immediately after grading or utility installation. A 4-inch course of asphalt treated base (ATE) may also be used, or the road/parking area may be paved. It may also be possible to use cement or calcium chloride for soil stabilization. If the area will not be used for pennanent roads, parking areas, or structures, a 6-inch depth of hog fuel may also be used, but this is likely to require more maintenance. Whenever possible, construction roads and parking areas shall be placed on a finn, compacted subgrade. Note: If the area will be used/or permanent road or parking installation later in the project, the subgrade will be subject to inspection. 2. Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain transversely. Drainage ditches shall be provided on each side of the roadway in the case of a crowned section, or on one side in the case of a super-elevated section. Drainage ditches shall be designed in accordance with the standards given in Section D.3.6.3 (p. D-60) and directed to a sediment pond or trap. 3. Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet-flows into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not adequate. If this area has at least 50 feet of vegetation, then it is generally preferable to use the vegetation to treat runoff, rather than a sediment pond or trap. The 50 reet shall not include vegetated wetlands. If runoff is allowed to sheet flow through adjacent vegetated areas, it is vital to design the roadways and parking areas so that no concentrated runoff is created. 4. In order to control construction traffic, the County may require that signs be erected on site infonning construction personnel that vehicles, other than those perfonning clearing and grading, are restricted to stabilized areas_ 5. If construction roads do not adequately reduce trackout to adjacent property or roadways, a wheel wash system will be required. Maintenance Standards Crushed rock, gravel base, hog fuel, etc. shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-41 SECTION D.3 ESC MEASURES D.3.4.3 WHEEL WASH 1/24/2005 Code: WW Purpose Wheel wash systems reduce the amount of sediment transported onto paved roadways and into surface water systems by construction vehicles. Conditions of Use When a stabilized construction entrance is not preventing sediment from being tracked onto pavement: • Wheel washing is generally an effective erosion and sediment control method and BMP when installed with careful attention to topography. For example, a wheel wash can be detrimental if installed at the top of a slope abutting a right-of-way where the water from the dripping truck wheels and undercarriage can run unimpeded into the street. • Pressure washing combined with an adequately sized and properly surfaced wash pad with direct drainage discharge to a large 10 foot x 10-foot sump can be very effective. Design and Installation Specifications A suggested detail is shown in Figure D.3.4.B. I. A minimum of 6inches of asphalt treated base (ATB) over crushed base material or 8 inches over a good subgrade is recommended to pave the wheel wash area. 2. Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. 3. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. 4. Midpoint spray nozzles are only needed in very muddy conditions. 5. Wheel wash systems should be designed with a small grade change, 6 to 12 inches for a 10-foot wide pond, to allow sediment to flow to the low side of the pond and to help prevent re-suspension of sediment. 6. A drainpipe with a 2 to 3 foot riser should be installed on the low side of the wheel wash pond to allow for easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a closed-loop system. 7. Polyacrylamide (PAM) added to the wheel washwater at a rate of 0.25 -0.5 pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is already being used for dust or erosion control and is being applied by a water truck, the same truck may be used to change the washwater. Maintenance Standards I. The wheel wash should start out each day with clean, fresh water. 2. The washwater should be changed a minimum of once per day. On large earthwork jobs where more than 10-20 trucks per hour are expected, the washwater will need to be changed more often. 3. Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system, such as a closed-loop recirculation system or land application, or to the sanitary sewer system with proper local sewer district approval or pennits. 2005 Surface Water Design Manual-Appendix D D-42 DJ.4 TRAFFIC AREA STABILIZATION FIGURE D,3.4,B WHEEL WASH AND PAVED CONSTRUCTION ENTRANCE f3" TRASH PUMP WITH FLOATS 6" SEWER PIPE WITH A ON SUCTION HOSE BUnERFLY VALVES -....:.-.. " I ~ 2" SCHEDULE 40 ,g'xS' SUMP WITH 5' fi' "" r ~ 1-1/2" SCHEDULE 40 OF CATCH L I-II g' ,4 .,;.' FOR SPRAYERS 2% SLOPE • '--15' ATB 5L-1! SLOPE 1/ : r'-.1IDPOIIH SPRAY IWZZLES, ~:1 :: IF NEEDED SLOPE I I I-O-:'-Ji'----2% SLOPE , , " \ ' , 1:1 j,. L-. " ". \ ' J ~ I "'-____ oj,c'" \ '--6" ATB CONSTRUCTIOI'J SLOPE A ' \ EI"TRANCE GROLlI'm FROI;! SPLASHING WATER APROI, TO PROTECT L B,~LL VALVES -\ "--ASPHALT CLIRB ON THE Q SLEEVE UNDER ROAD~ LOW ROAD SIDE TO DIRECT WATER BAC~: TO POND 1 PLAN VIEW 1 1 ELEVATION ViEW] LOCATE IIWERT OF TOP PIPE l' ABDVE BOnOM OF WH EEL WASH \ 18' 8'x8' SUMP ---.\ \ WATE~ t t \ \''., ./::? 3' " / /\ 5' 1-·1 \ t 11' \ -t \ ['RAIIJ PIPE \~1 .1 SLOPE ISE(TIOI', A-A 1 NOTES: I. BUILD 8')·.8' SUMP TO Accm·IOOATE CLENJIHG 8Y TR/,CKHOE. WHEEL WASH 2005 Surface Water Design Manual-Appendix D 112412005 D-43 SECTION D.3 ESC MEASURES D.3.S SEDIMENT RETENTION Surface water collected from disturbed areas of the site shall be routed through a sediment pond or trap prior to release from the site. An exception is for areas at the perimeter of the site with drainage areas small enough to be treated solely with perimeter protection (see Section D.3.3, p. D-30). Also, if the soils and topography are such that no offsite discharge of surface water is anticipated up to and including the developed 2-year runoff event, sediment ponds and traps are not required. A I 0-yearI15-minute peak flow shall be used for sediment pond/trap sizing if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection (see below). At the County's discretion, sites may be worked during the dry season without sediment ponds and traps if there is some other form of protection of surface waters, such as a I DO-foot forested buffer between the disturbed areas and adjacent surface waters. Protection of catch basins is required for inlets that are likely to be impacted by sediment generated by the project and that do not drain to an onsite sediment pond or trap. Sediment retention facilities shall be installed prior to grading of any contributing area. Purpose: The purpose of sediment retention facilities is to remove sediment from runoff generated from disturbed areas. When to Install: The facilities shall be constructed as the first step in the clearing and grading of the site. The surface water conveyances may then be connected to the facilities as site development proceeds. Measures to Use: There are three sediment retention measures in this section. The first two, sediment traps and ponds, serve the same function but for different size catchments. All runoff from disturbed areas must be routed through a trap or pond except for very small areas as specified in Section D.4.3. The third measure is for catch basin protection. It is only to be used in limited circumstances and is not a primary sediment treatment facility. It is only intended as a backup in the event of failure of other onsite systems. Use of Permanent Drainage Facilities: All projects that are constructing permanent facilities for runoff quantity control are strongly encouraged to use the rough-graded or final-graded permanent facilities for ponds and traps. This includes combined facilities and infiltration facilities. When permanent facilities are used as temporary sedimentation facilities, the surface area requirements of sediment traps (for drainages less than 3 acres) or sediment ponds (more than 3 acres) must be met. If the surface area requirements are larger than the surface area of the permanent facility, then the pond shall be enlarged to comply with the surface area requirement. The permanent pond shall also be divided into two cells as required for sediment ponds. Either a permanent control structure or the temporary control structure described in Section D.3.5.2 may be used. If a permanent control structure is used, it may be advisable to p3l1ially restrict the lower orifice with gravel to increase residence time while still allowing dewatering of the pond. If infiltration facilities are to be used, the sides and bottom of the facility must only be rough excavated to a minimum of three feet above final grade. Excavation should be done with a backhoe working at "arms length" to minimize disturbance and compaction of the infiltration surface. Additionally, any required pretreatment facilities shall be fully constructed prior to any release of sediment-laden water to the facility. Pretreatment and shallow excavation are intended to prevent the clogging of soil with fines. Final grading of the infiltration facility shall occur only when all contributing drainage areas are fully stabilized (see Section D.S.5, p. D-74). Selection of the Design Storm: In most circumstances, the IS-minute peak flow from the developed 2- year runoff event is sufficient for calculating surface area for ponds and traps and for determining exemptions from the sediment retention and surface water collection requirements (Sections D.3.5 and D.3.6, respectively). In some circumstances, however, the I O-yearIlS-minute peak flow should be used. Examples of such circumstances include the following: • Sites that are within 1i4 mile of salmonid streams, wetlands, and designated sensitive lakes such as Lake Sammamish • Sites where significant clearing and grading is likely to occur during the wet season 1124/2005 2005 Surface Water Design Manual-Appendix 0 D-44 D.3.5 SEDIMENT RETENTION • Sites with downstream erosion or sedimentation problems. Natural Vegetatiou: Whenever possible, sediment-laden water shall be discharged into onsite, relatively level, vegetated areas. This is the only way to effectively remove fine particles from runoff. This can be particularly useful after initial treatment in a sediment retention facility. The areas of release must be evaluated on a site-by-site basis in order to determine appropriate locations for and methods ofreleasing runoff. Vegetated wetlands shall not be used for this purpose. Frequently, it may be possible to pump water from the collection point at the downhill end of the site to an upslope vegetated area. Pumping shall only augment the treatment system, not replace it because of the possibility of pump failure or runoff volume in excess of pump capacity. D.3.S.1 SEDIMENT TRAP Code: ST Symbol: Purpose Sediment traps remove sediment from runoff originating from disturbed areas of the site. Sediment traps are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually only result in a small reduction in turbidity. Conditions of Use A sediment trap shall be used where the contributing drainage area is 3 acres or less. Design and Installation Specifications I. See Figure D,3.5.A for details. 2. Ifpennanent nmoff control facilities are part of the project, they should be used for sediment retention (see "Use of Penn anent Drainage Facilities" on page D-44). 3. To detennine the trap geometry, first calculate the design surface area (SA) of the trap, measured at the invert of the weir. Use the following equation: where SA = FS(Q,lVs ) Q, = Design inflow (cfs) based on the IS-minute peak discharge from the developed 2- year runoff event from the contributing drainage area as computed in the hydrologic analysis. The 1O-yearIl5-minute peak flow shall be used if the project size, expected liming and duration of construction, or downstream conditions warrant a higher level of protection. lfno hydrologic analysis is required, the Rational Method may be used (Section 3.2.1 oflhe Surface Water Design Manuaf). Vs = The settling velocity (ft/sec) ofthe soil particle of in teres!. The 0.02 rum (medium silt) particle Witll an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a settling velocity (Vs) of 0.00096 ft/sec. FS = A safety factor of2 to account for non-ideal settling, Therefore, the equation for computing surface area becomes: SA = 2 x Q,IO.00096 or 2080 square feet per cfs of inflow Note: Even if permanent/acilities Gre used, they must still have a surface area that is at least as large as that derivedfi'om the above formula. If they do not, the pond must be enlarged. 2005 Surface Water DeSign Manual-Appendix D 1/2412005 D-45 SECTION D.3 1124/2005 ESC MEASURES 4. To aid in detennining sediment depth, all traps shall have a staff gage with a prominent mark one foot above the bottom of the trap. Maintenance Standards I. Sediment shall be removed from the trap when it reaches I foot in depth. 2. Any damage to the trap embankments or slopes shall be repaired. FIGURE D.3.S.A SEDIMENT TRAP SURrACE AREA DETERMINED AT rop or WEIR l' MIN. ---T---------[ 3.5'-5' _.-____ J~.......:.+_':.o..:i:+~~,;...;..-=L ----'--...:;:c:.:.: 1.5' MIN. rLAr BOnDI.! NOTE: TRAP MAY BE rORMED BY BERM OR BY PARTIAL OR COMPLETE EXCAVATION NATIVE SOIL COMPACTED BACKFILL GEOTEXTILE CROSS-SECTION TRAP OUTLET DISCHARGE TO_S~"'i!I!-I~I~D CONVEYANCE, LEVEL SPREADER I 2005 Surface Water Design Manual-Appendix D D-46 D.3.5 SEDIMENT RETENTION D.3.S.2 SEDIMENT POND Code: SP Purpose Symbol: OA/UAXb C"XAUAAOb Sediment ponds remove sediment from runoff originating from disturbed areas of the site. Sediment ponds are typically designed to only remove sediment as small as medium silt (0.02 mm). As a consequence, they usually reduce turbidity only slightly. Conditions of Use A sediment pond shall be used where the contributing drainage area is 3 acres or more. Design and Installation Specifications I. See Figure D.3.5.B, Figure D.3.5.C, and Figure 0.3.5.0 for details. 2. If permanent runoff control facilities are part of the project, they should be used for sediment retention (see "Use of Permanent Drainage Facilities" on page D-44). Determining Pond Geometry I. Obtain the discharge from the hydrologic calculations of the l5-minute peak flow for the 2-year runoff event (Q,). The 1 0-yearI15-minute peak flow shall he used if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection. If no hydrologic analysis is required, the Rational Method may be used (Section 3.2.1 of the Surface Water Design Manual). 2. Determine the required surface area at the top of the riser pipe with the equation: SA = 2 x Q,IO.00096 or 2080 square feet per cfs of inflow See Section D.3.5.1 (p. 0-45) for more information on the derivation of the surface area calculation. 3. The basic geometry of the pond can now be determined using the following design criteria: • ReqUired surface area SA (from Step 2 above) at top of riser • Minimum 3.5-foot depth from top of riser to bottom of pond • Maximum 3:1 interior side slopes and maximum 2:1 exterior slopes. The interior slopes may be increased to a maximum of 2: 1 if fencing is provided at or above the maximum water surface • One foot of freeboard between the top of the riser and the crest of the emergency spillway • Flat bottom • Minimum one foot deep spillway • Length-to-width ratio between 3: 1 and 6: 1. Sizing of Discharge Mechanisms Principal Spillway: Detennine the required diameter for the principal spillway (riser pipe). The diameter shall be the minimum necessary to pass the 15-minute peak flow from the developed I O-year runoff event (Q,o)' Use Figure 5.3.4.H (SWDM Chapter 5) to determine this diameter (h = one foot). Note: A permanent control structure may be used instead qf a temporary riser. 2005 Surface Water Design Manual-Appendix D \/24/2005 D-47 SECTION DJ 1124/2005 ESC MEASURES Emergency Overflow Spillway: Detennine the required size and design of the emergency overflow spillway for the developed lOO-yearI!S-minute peak flow using the procedure in Section 5.3.1 ("Emergency Overflow Spillway" subsection) of the Surface Water Design Manual. Dewatering Orifice: Detennine the size of the dewatering orifice(s) (minimum I-inch diameter) using a modified version of the discharge equation for a vertical orifice and a basic equation for the area ofa circular orifice. I. Detennine the required area of the orifice with the following equation: A = A,(2h)05 o O.6x3600Tg 05 4.81(10-6 )A,.Jh where orifice area (square feet) pond surface area (square feet) head of water above orifice (height of riser in feet) dewatering time (24 hours) acceleration of gravity (32.2 feet/second 2) 2. Convert the required surface area to the required diameter D (inches) of the orifice: D = 24X~: = 13.54x..JA: 3. The vertical, perforated tubing connected to the dewatering orifice must be at least 2 inches larger in diameter than the orifice to improve flow characteristics. The size and number of perforations in the tubing should be large enough so that the tubing does not restrict flow. The flow rate should be controlled by the orifice. Additional Design Specifications o The pond shall be divided into two roughly equal volume cells by a penneable divider that will reduce turbulence while allowing movement of water between cells. The divider shall be at least one- half the height of the riser and a minimum of one foot below the top of the riser. Wire-backed, 2-to 3-foot high, extra strength filter fabric (see Section D.3.3.1) supported by treated 4"x4"s may be used as a divider. Alternatively, staked straw bales wrapped with filter fabric (geotextile) may be used. If the pond is more than 6 feet deep, a different mechanism must be proposed. A riprap embankment is one acceptable method of separation for deeper ponds. Other designs that satisfY the intent of this provision are allowed as long as the divider is penneable, structurally sound, and designed to prevent erosion under or around the barrier. o To aid in determining sediment depth, one-foot intervals shall be prominently marked on the riser. o If an embankment of more than 6 feet is proposed, the pond must comply with the criteria under "Embankments" in Section 5.3.1 of the Surface Water Design Manual. Maintenance Standards I. Sediment shall be removed from the pond when it reaches I foot in depth. 2. Any damage to the pond embankments or slopes shall be repaired. 2005 Surface Water Design Manual-Appendix D D-48 I D.3.5 SEDIMENT RETENTION FIGURE D.3.S.B SEDIMENT POND PLAN VIEW I<E'Y DIVIDER INTO SLOPE TO PRM"IT FLOW -'ROUND SIDES THE POND lEN[;TH SHALL BE .3 TO 6 TIMES THE WJ(IIdUIl POND WIDTH NOTE: POND IoI"'Y BE rORIAEO BY 8(1'1111 OR BY PARTIAl OR COI.IPLITE EXCAVATION (IA(RGf"lCY OVERFLOW SPillWAY DISCHARGE TO STABILIZED CONVEYANCE:. OUTLET OR LEVEL SPREADER FIGURE D.3.S.C SEDIMENT POND CROSS SECTION RISER PIPE (PRINCIPAL SPILLWAY) OPEN AT TOP WITH TRASIi RACK PER FIG. 5.3.I.C DEWATERING DEVICE (SEE RISER DETAIL) CREST OF 6' MIN. WIDTH EMERGENCY SPILLWAY EMBANKMENT COMPACTED 95';:. PERVIOUS MATERIALS SUCH AS GRAVEL OR CLEAN SAND SHALL NOT BE USED. WIRE-BACI<ED SILT FENCE, DEWATERING STAKED HAY8ALES WRAPPED ORIFICE WITH fiLTER fABRIC, OR CONCRETE BASE (SEE RISER DETAJL) DISCHARGE TO STABIUZEO COmEYANCE, OVTlET OR LEVEL SPREADER EQUIVALENT OMD[R I 2005 Surface Water Design Manual-Appendix D 1/2412005 D-49 SECTION D.3 1124/2005 ESC MEASURES FIGURE D.3.S.D SEDIMENT POND RISER DETAIL POLYETHYLENE CAP PERfORATED POL '(ETHYLENE DRAIw.GE TUBING. DIAMETER MIN. 2" LARGER THAN DEWATERING ORIfiCE. TUBING SHALL COI.4PL Y WITH ASH" Hi!!!7 AND AASfiTO M294. PROVIDE ADEQUATE STRAPPING WATERTIGHT COUPLING CORRUGATED METAl RISER lB" MIN. L CONCRETE BASE ~ 2X RISER CIA. 1.A1N.-----t D-50 3.5' lAIN. DEWATERING ORIFICE, SCHEDULE 40 STEEL STUB MIN. DIAMETER AS PER CALCULATIONS ALTERNATIVELY, METAL STAKES AND WIRE I,IAY BE USEO TO PREVENT FLOTATION 2005 Surface Water Design Manual -Appendix D D.3.5 SEDIMENT RETENTION D.3.5.3 STORM DRAIN INLET PROTECTION Code: FFP or CBlor CBP Symbol: R or'lnr Purpose Storm drain inlets are protected to prevent coarse sediment from entering stonn drainage systems. Temporary devices around stonn drains assist in improving the quality of water discharged to inlets or catch basins by ponding sediment-laden water. These devices are effective only for relatively small drainage areas. Conditions of Use I. Protection shall be provided for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless the runoff that enters the catch basin will be conveyed to a sediment pond or trap. 2. Inlet protection may be used anywhere at the applicant's discretion to protect the drainage system. This will, however, require more maintenance, and it is highly likely that the drainage system will still require some cleaning. 3. The contributing drainage area must not be larger than one acre. Design and Installation Specifications 1. There are many options for protecting storm drain inlets. Two commonly used options are filter fabric protection and catch basin inserts. Filter/abric protection (see Figure D.3.5.E) is filter fabric (geotextile) placed over the grate. This method is generally very ineffective and requires intense maintenance efforts. Calch basin inserts (see Figure DJ.5.F) are manufactured devices that nest inside a catch basin. This method also requires a high frequency of maintenance to be effective. Both options provide adequate protection, but filter fabric is likely to result in ponding of water above the catch basin, while the insert will not. Thus, filter fabric is only allowed where ponding will not be a traffic concern and where slope erosion will not result if the curb is overtopped by ponded water. Trapping sediment in the catch basins is unlikely to improve the water quality of runoff if it is treated in a pond or trap because the coarse particles that are trapped at the catch basin settle out very quickly in the pond or trap. Catch basin protection normally only improves water quality where there is no treatment facility downstream. In these circumstances, catch basin protection is an important last line of defense. It is not, however, a substitute for preventing erosion. The placement of filter fabric under grates is generally prohibited and the use of filter fabric over grates is strictly limited and discouraged. 2. It is sometimes possible to construct a small sump around the catch basin before final surfacing of the road. This is allowed because it can be a very effective method of sediment control. 3. Block and gravel filters, gravel and wire mesh filter barriers, and bag barriers filled with various filtering media placed around catch basins can be effective when the drainage area is I acre or less and flows do not exceed 0.5 cfs. It is necessary to allow for overtopping to prevent flooding. Many manufacturers have various inlet protection filters that are very effective in keeping sediment-laden water from entering the stonn drainage system. The following are examples of a few common methods. a) Block and gravel filters (Figure D.3.5.G) are a banier formed around an inlet with standard concrete block and gravel, installed as follows: • Height is I to 2 feet above the inlet. 2005 Surface Water Design Manual-Appendix D 1124/2005 D-51 SECTION D.3 \/24/2005 ESC MEASURES • Recess the first row of blocks 2 inches into the ground for stability. • Support subsequent rows by placing a 2x4 through the concrete block opening. • Do not use mortar. • Lay some blocks in the bottom rowan their side for dewatering the pooled water. • Place cloth or mesh with ,/, inch openings over all block openings. • Place gravel below the top of blocks on slopes of 2: 1 or flatter. • An alternate design is a gravel donut. b) Gravel and wire mesh filters consist of a gravel barrier placed over the top of an inlet. This structure generally does not provide overflow. Install as follows: • Cloth or comparable wire mesh with ,/, inch openings is placed over inlet. • Coarse aggregate covers the cloth or mesh. • Height/depth of gravel should be 1 foot or more, 18 inches wider than inlet on all sides. c) Curb inlet protection with a wooden weir is a barrier formed around an inlet with a wooden frame and gravel, installed as follows: • Consttuct a frame and attach wire mesh (V, inch openings) and filter fabric to the frame. • Pile coarse washed aggregate against the wire/fabric. • Place weight on frame anchors. d) Curb and gutter sediment barriers (Figure D.3.S.H) consist of sandbags or rock berms (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape, installed as follows: • Bags of either burlap or woven geotextile fabric, filled with a variety of media such as gravel, wood chips, compost or sand stacked tightly allows water to pond and allows sediment to separate from runoff. • Leave a "one bag gap" in the top row of the barrier to provide a spillway for overflow. • Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 x 3 and at least 2 feet from the inlet. • Construct a horseshoe shaped sedimentation trap on the outside of the berm to sediment trap standards for protecting a culvert inlet. 4. Excavated drop inlet sediment traps are appropriate where relatively heavy flows are expected and overflow capability is needed. If emergency overflow is provided, additional end-of-pipe treatment may be required. Excavated drop inlets consist of an excavated impoundment area around a storm drain. Sediment settles out of the stormwater prior to enter the drain. Install according to the following specifications: a) b) c) d) e) f) g) The impoundment area should have a depth of 1 -2 feet measured from the crest of the inlet structure. Side slopes of the excavated area must be no steeper than 2: 1. Minimum volume of the excavated area should be 35 cubic yards. Install provisions for draining the area to prevent standing water problems. Keep the area clear of debris. Weep holes may be drilled into the side of the inlet. Protect weep holes with wire mesh and washed aggregate. 2005 Surface Water Design Manual-Appendix D D-52 D.3.5 SEDIMENT RETENTION h) Weep holes must be sealed when removing and stabilizing excavated area. il A temporary dike may be necessary on the down slope side ofthe structure to prevent bypass flow. Maintenance Standards I. Any accumulated sediment on or around inlet protection shall be removed immediately. Sediment shall not be removed with water, and all sediment must be disposed of as fill on site or hauled off site. 2. Any sediment in the catch basin insert shall be removed when the sediment has filled one-third of the available storage. The filter media for the insert shall he cleaned or replaced at least monthly. 3. Regular maintenance is critical for all forms of catch basinlinlet protection. Unlike many fonns of protection that fail gradually, catch basin protection will fail suddenly and completely ifnot maintained properly. FIGURE D.3.S.E FILTER FABRIC PROTECTION STANDARD STRENGTH FILTER FABRIC ~ =111 [D"" I I I <:;GRATE I ::!I IT NOTE: ONLY TO BE USED WHERE PONDING OF WATER ABOVE THE CATCH BASIN WILL NOT CAUSE TRAFFIC PROBLEMS AND WHERE OVERFLOW WILL NOT RESULT IN EROSION OF SLOPES. ~III ~III ~III fiLTER MEDIA 1 FOR DEWATERING_ ~III ~III II 2005 Surface Water Design Manua\-Appendix D CATCH BASIN 11= II~ II FIGURE D.3.S.F CATCH BASIN INSERT I I POROUS BOTTOt.i D-53 III~ III~ III~ III~ III~ II NOTE: THIS DETAIL IS ONLY SCHEMATIC. ANY INSERT IS ALLOWED THAT HAS A MIN. 0.5 C.F. OF STORAGE, THE MEANS TO DEWATER THE STORED SEDIMENT, AN OVERFLOW, AND CAN BE EASilY MAINTAINED. I I 1124/2005 SECTION D.3 1I24/2005 ESC MEASURES FIGURE D.3.S.G BLOCK AND GRA VEL CURB INLET PROTECTION c-BACI( OF SIDEWALK \ CURB FACE 3/4" DRAIN 2x4 WOOD STUD --; \ (20mm) ----~ WIRE SCREEN OR FILTER FABRIC 3/4" ORAl I', GRNJEL (20mm) POHD HEIGHT A ! CATCH BASIN COVER ) CURB IflLET A CONCRETE BLOCKS I PLAt, VIEW I CATCH BASIN COVER OVERFLOW WIRE SCREU, OR FILTER FABRIC fWTES, 2x4 WOOD STUD (100x50 TIMBER STUD) CURB INLET CATCH BASIN I SECTION A-A I 1. USE BLOCK Aim GRAVEL TYPE SEDIMEI,T BARRIER WHEH CURB INLET IS LOCATED 11'1 GENTLY SLOPING SEGMENT. WHERE WATER CAN PDND AI,D ALLOW SEDIMEI'IT TO SEPA.RATE FRm~ RUNOFF. 2. BARRIER SHALL ALLOW FOR OVERFLOW FROM SEVERE STORM EVEr'T. 3. INSPECT BARRIERS AI,D REMOVE SEDIMENT AFTER EACH STORI.! EVEI-IT. SEDIMENT mo GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEDIMELY. BLOCV AND GRAVEL CURB INLET PROTECTION 2005 Surface Water Design Manual ~ Appendix D D-54 D.3.5 SEDIMENT RETENTION FIGURI<: D.3.S.H CURB AND GUTTER BARRIER PROTECTION RUHOFF ------ RIJGIOFF I,IOTES 64CK OF SIDEWALI< SAtmB4GS TO OVERLAP OI,TO CURB GR."VEL FILLED SANDBAGS STACKED TIGHTLY CURB INLET DRAII'I GRATE CURB FACE GUDER 1. PLACE CURB TYPE SEDIMEHT 8ft,PRIERS ON GEHTL'( SLOPII~G STREET SEGMEI'ITS, WHERE WATER CAN POtm .AND ALLOW SEDIMNENT TO SEPARATE FROM RUNOFF. 2. SANDBAGS OF EITHER BURLAP OR WOVEN GEOTEXTILE Fft.BRIC, ARE FILLED WITH GRAVEL, UWERED Al-ID PACI<ED TIGHTLY. ~. LEAVE ft, ONE SAl'~D8AG GAP II, THE TOP ROW TO PROVIDE A SPILLWAY FOR OVERFLOW. +. II,SPECT BARRIEF:S AtlD RD.WVE SEOIMEIH AFTER EACH STOPtA EVEi'IT. SEDIMDJT AND GRAVEL ~WST BE REMOVED FROM THE TRAVELED WA,'( 1I~~1EDI,~TELY. ~IJRR NJD GliDER BARRIER 2005 Surface Water Design Manual·-Appendix D D·55 1/24/2005 SECTION D.3 ESC MEASURES D.3.6 SURFACE WATER COLLECTION 1124/2005 All surface water from disturbed areas shall be intercepted, conveyed to a sediment pond or trap, and discharged downslope of any disturbed areas. An exception is for areas at the perimeter of the site with drainage areas small enough to be treated solely with perimeter protection (see Section D.3.3). Also, if the soils and topography are such that no offsite discharge of surface water is anticipated up to and including the developed 2-year runoff event, surface water controls are not required. A I O-yearll 5-minute peak flow shall be used for sizing surface water controls if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection (see the introduction to Section D.3.S). At the County's discretion, sites may be worked during the dry season without surface water controls, if there is some other form of protection of surface waters, such as a I DO-foot forested buffer between the disturbed areas and adjacent surface waters. Significant sources of upslope surface water that drain onto disturbed areas shall be intercepted and conveyed to a stabilized discharge point downslope of the disturbed areas. Surface water controls shall be installed concurrently with rough grading. Purpose: The purpose of surface water control is to collect and convey surface water so that erosion is minimized, and runoff from disturbed areas is treated by a sediment pond or trap. Surface water control essentially consists of three elements: 1. Interception of runoff on and above slopes 2. Conveyance of the runoffto a sediment pond or trap (if the runoff was collected from a disturbed area) 3. Release of the runoff downslope of any disturbed areas. When to Iustall: Surface water controls shall be constructed during the initial grading of an area and must be in place before there is any opportunity for storm runoff to cause erosion. Measures to Install: Interceptor dikes/swales intercept runoff, ditches and pipe slope drains convey the runoff, and riprap or level spreaders help release the runoff in a non-erosive manner. Each measure is to be used under different circumstances so there is very little overlap. However, the two options for releasing water in a non-erosive manner, outlet protection and level spreaders, can be somewhat interchangeable. See Figure D.3.6.A for a schematic drawing demonstrating the use of these measures. 2005 Surface Water Design Manual-Appendix D D-56 D.3.6 SURFACE WATER COLLECTION FIGURE D.3.6.A SKETCH PLAN OF SURFACE WATER CONTROLS FLOW s I PIPE SLOPE DRAIN INTERCEPTOR DIKE TOP OF SLOPE OUTLET PROTECTION TOE OF SLOPE .0 SILT fENCE D.3.6.1 INTERCEPTOR DIKE AND SWALE Code: ID or IS Symbol: -t"--<@--I~-or -t~--<@--I~_ Purpose Interceptor dikes and swales intercept storm runoff from drainage areas on or above disturbed slopes and convey it to a sediment pond or trap. They may also be used to intercept runoff from undisturbed areas and convey the runoff to a point below any exposed soils. Interception of surface water reduces the possibility of slope erosion. Interceptor dikes and swales differ from ditches (see Section D.3.6.3) in that they are intended to convey smaller flows along low-gradient drainage ways to larger conveyance systems such as ditches or pipe slope drains. Conditions of Use Interceptor dikes and swales are required in the following situations: 1. At the top of all slopes in excess of3H: 1 V and with more than 20 feet of vertical relief. 2. At intervals on any slope that exceeds the dimensions specified in this section for the horizontal spacing of dikes and swales. Design and Installation Specifications 1. See Figure D.3.6.B for details of an interceptor dike and Figure D.3.6.C for an interceptor swale. 2005 Surface Water Design Manual -Appendix D 112412005 0-57 SECTION D.3 ESC MEASURES 1/24/2005 2. Interceptor dikes and swales shall be spaced horizontally as follows: A verage Slope Slope Percent FIowpath Length 20H: 1 V or less 3-5% 300 feet (10 to 20)H:IV 5-10% 200 feet (4to 10)H:IV 10-25% 100 feet (2 to 4)H:lV 25-50% 50 feet 3. For slopes steeper than 2H:I V with more than 10 feet of vertical relief, henches may be constructed or closer spaced interceptor dikes or swales may be used. Whichever measure is chosen, the spacing and capacity of the measures must be designed by the engineer and the design must include provisions for effectively intercepting the high velocity runoff associated with steep slopes. 4. If the dike or swale intercepts runofffrom disturbed areas, it shall discharge to a stable conveyance system that routes the runoff to a sediment pond or trap (see Section D.3.5). If the dike or swale intercepts runoff that originates from undisturbed areas, it shall discharge to a stable conveyance system that routes the runoff downslope of any disturbed areas and releases the water at a stabilized outlet. 5. Construction traffic over temporary dikes and swales shall be minimized. Maintenance Standards 1. Damage resulting from runoff or construction activity shall be repaired immediately. 2. If the facilities do not regularly retain storm runoff, the capacity and/or frequency of the dikes/swales shall be increased. FIGURE D.3.6.B INTERCEPTOR DIKE DIKE MATERIAL COMPACTED ~ 90% MODIFIED PROCTOR I ~ --1 18 " MIN. __ 2: 1 MAX. SLOPE DIKE SPACING DEPENDS ON SLOPE GRADIENT FIGURE D.3.6.C INTERCEPTOR SW ALE 2:1 MAX. SLOPE SWALE SPACING DEPENDS ON SLOPE GRADIENT , III =111= I 2005 Surface Water Design Manual-Appendix D D-58 D.3.6 SURF ACE WATER COLLECTION D.3.6.2 PIPE SLOPE DRAINS Code: PD Symbol: ~EI ==~ .. == Purpose Pipe slope drains are designed to carry concentrated runoff down steep slopes without causing erosion, or saturation of slide-prone soils. Pipe slope drains may be used to divert water away from or over bare soil to prevent gullies, channel erosion, and saturation of slide prone soils Conditions of Use Pipe slope drains should be used when a temporary or permanent stormwater conveyance is needed to move water down a steep slope to avoid erosion. Pipe slope drains may be: I. Connected to new catch basins and used temporarily until all permanent piping is installed. 2. Used on any slope with a gradient of 2H: 1 V or greater and with at least 10 feet of vertical relief. 3. Used to drain water collected from aquifers exposed on cut slopes and convey it to the base of the slope. 4. Used to collect clean runoff from plastic sheet cover and direct away from any exposed soils. 5. Installed in conjunction with silt fence to drain collected water to a controlled area. 6. Used to divert small seasonal streams away from construction. Pipe slope drains have been used successfully on culvert replacement and extension projects. Large flex pipe may be used on larger streams during culvert removal, repair, or replacement. 7. Connected to existing downspouts and roof drains used to divert water away from work areas during building renovation, demolition, and construction projects. 8. Rock-lined ditches or other pennanent, non-erosive conveyances used to convey runoff down steep slopes that are not steep slope hazard areas. Design and Installation Specifications 1. See Figure D.3.6.D for details. 2. The capacity for temporary drains shall be sufficient to handle the 15-minute peak flow from a developed 10-year runoff event. Up to 30,000 square feet may be drained by each 6-inch minimum diameter pipe without computation of the peak flow. Up to 2 acres may be drained by each 12-inch minimum diameter pipe. Otherwise, the peak flow will need to be computed using the Rational Method described in Section 3.2.1 of the Swface Waler Design Manual (SWDM). 3. The maximum drainage area allowed for any sized pipe is 10 acres. For larger areas, more than one pipe shall be used or a rock-lined channel shall be installed (see SWDMSection 4.4.1, "Open Channels"). 4. The soil around and under the pipe and entrance section shall be thoroughly compacted. 5. The flared inlet section shall be securely connected to the slope drain and be fused or welded, or have flange-bolted mechanical joints to ensure a watertight seal. Ensure that the entrance area is stable and large enough to direct flow into the pipe. 6. Slope drains shall be continuously fused, welded, or flange-bolted mechanical joint pipe systems with proper anchoring to the soil. 7. Where slope drains cross steep slope hazard areas or their associated buffers, the installation shall be on the ground surface, accomplished with minimum alteration. In most circumstances, this requires 2005 Surface Water Design Manual ~ Appendix D 1/2412005 D-59 SECTION D.3 ESC MEASURES that slope drains be constructed of corrugated metal, ePE, or equivalent pipe and installed by hand (see SWDM Section 4.2. I). Any area disturbed during installation or maintenance must be immediately stabilized. 8. If the pipe slope drain will convey sediment-laden runoff, the runoff must be directed to a sediment retention facility (see Section D.3.5). If the runoff is not from a disturbed area or is conveyed from a sediment trap or pond, it must be conveyed to a stabilized discharge point (see Section D.3.6.5). 9. Re-establish cover immediately on areas disturbed by the installation. Maintenance Standards I. The inlet shall not be undercut or bypassed by water. If there are problems, the head wall shall be appropriately reinforced. 2. No erosion shall occur at the outlet point. If erosion occurs, additional protection shall be added. FIGURE D.3.6.D PIPE SLOPE DRAIN DIKE MATERIAL COMPACTED _~-/,,, 90% IoiODlflED PROCTOR DISCHARGE TO A STABILIZED WATERCOURSE, SEDIMENT RETENTION fACILITY OR STABIUZEO OUTLET PROVIDE RIPRAP PAD OR EaUIVALENT ENERGY DISSIPATION INTERCEPTOR DIKE 12' IoIIN"] STANDARD FLARED END SECTION INLET AND All SECTIONS MUST BE SECURELY FASTENED TOGETHER \ WITH GASK[lED WATERTIGHT FITTINGS I D.3.6.3 SUBSURFACE DRAINS 1124/2005 Purpose To intercept, collect, and convey ground water to a satisfactory outlet, using a perforated pipe or conduit below the ground surface. Subsurface drains are also known as "French Drains" The perforated pipe provides a dewatering mechanism to drain excessively wet soils, provide a stable base for construction, improve stability of structures with shallow foundations, or to reduce hydrostatic pressure and to improve slope stability. Conditions of Use Use when excessive water mllst be removed from the soil. The soil permeability, depth to water table, and impervious layers are all factors that may govern the use of subsurface drains. Design and Installation Specifications I. Two types of drains may be used as follows: D·60 2005 Surface Water Design Manual ~ Appendix D D.3.6 SURF ACE WATER COLLECTION a) Relief drains are used either to lower the water table in large, relatively flat areas, improve the growth of vegetation, or to remove surface water. They are installed along a slope and drain in the direction of the slope. They may be installed in a grid pattern, a herringbone pattern, or a random pattern. b) Interceptor drains are used to remove excess groundwater from a slope, stabilize steep slopes, and lower the water table below a slope to prevent the soil from becoming saturated. They are installed perpendicular to a slope and drain to the side of the slope. They usually consist of a single pipe or single pipes instead of a patterned layout. 2. Size of Drains -Size subsurface drains to carry the required capacity without pressurized flow. Minimum diameter for a subsurface drain is 4 inches. 3. Outlet -Ensure that the outlet of a drain empties into a channel or other watercourse above the normal water level. Maintenance Standards I. Subsurface drains shall be checked periodically to ensure that they are free flowing and not clogged with sediment or roots. 2. The outlet shall be kept clear and free of debris. 3. Surface inlets shall be kept open and free of sediment and other debris. 4. Trees located too close to a subsurface drain often clog the system with roots. If a drain becomes clogged, relocate the drain or remove the trees as a last resort. Drain placement should be planned to minimize this problem. 5. Where drains are crossed by heavy equipment, the line shall be checked to ensure that it is not crushed and have adequate cover protection. D.3.6.4 DITCHES Code: DI Symbol: Purpose Ditches convey intercepted runoff from disturbed areas to and from sediment ponds or traps. They also convey runoff intercepted from undisturbed areas around the site to a non-erosive discharge point. Conditions of Use Ditches may be used anywhere that concentrated runoff is to be conveyed on or around the construction site. Temporary pipe systems may also be used to convey runoff. Design and Installation Specifications 1. Channels and ditches shall be sized to accommodate the 1 5-minute peak flow from the developed 10- year runoff event with 0.5 feet of freeboard. If no hydrologic analysis is required for the site, the Rational Method may be used [see Section 3.2.1 of the Swiaee Water Design Manual (SWDM)]. 2. See SWDM Section 4.4.1 for open-channel design requirements. 3. The only exception to the requirements of SWDMSection 4.4.1 is the use of check dams, rather than grass lining, for channels in which the design flow velocity does not exceed 5 fps. See Figure D.3.6.E for details on check dam installation. 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-61 SECTION D.3 ESC MEASURES Maintenance Standards I. Any sediment deposition of more than 0.5 feet shall be removed so that the channel is restored to its design capacity. 2. !fthe channel capacity is insufficient for the design flow, it must be determined whether the problem is local (e.g., a constriction or bend) or the channel is under-designed. !fthe problem is local, the channel capacity must be increased through construction of a berm(s) or by excavation. !fthe problem is under-design, the design engineer shall be notified and the channel redesigned to a more conservative standard to be approved by King County. 3. The channel shall be examined for signs of scouring and erosion of the bed and banks. If scouring or erosion has occurred, affected areas shall be protected by riprap or an erosion control blanket or neL I FIGURE D.3.6.E CHECK DAMS 1124/2005 ROCK MUST COMPLETELY COVER THE BOnDI.! AND SIDES OF THE DITCH 6" MIN. 2"-4" ROCK :ill" 1 IT] m I = ~ L -----;:!l:ID-. "-"'=III--=llnll-__ ""-111=111 III II = _ '-11'=111 -III III =_ L = THE DISTANCE SUCH THAT POINTS "'-II 1=111-111 II: A AND B ARE OF EQUAL ELEVATION --111-=1 T 24" MIN. t CROSS SECTION CHECK DAM SPACING 2005 Surface Water Design Manual-Appendix D D-62 D.3.6 SURFACE WATER COLLECTION D.3.6.S OUTLET PROTECTION Code: OP Symbol: Purpose Outlet protection prevents scour at conveyance outlets. Conditions of Use Outlet protection is required at the outlets of all ponds, pipes, ditches, or other approved conveyances, and where runoff is conveyed to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch. Design and Installation Specifications For the standard pipe slope drains in Section D.3.6.2 and other smaller conveyance systems, the standard rock pad (6 feet by 8 feet) made of I-foot thick quarry spall is adequate. For all other outlets, the outlet protection shall meet the requirements of the "Outfalls" section of Core Requirement #4 and Section 4.2.2 of the Surface Water Design Manual. Maintenance Standards for Outlet Protection If there is scour at the outlet, the eroded area shall be protected with more conservative measures proposed by the design engineer and approved by King County. D.3.6.6 LEVEL SPREADER Code: LS Symbol: I I HtfHtH Purpose Level spreaders convert concentrated runoff to sheet flow and release it onto areas stabilized by existing vegetation. Conditions of Use Level spreaders may be used where runoff from undisturbed areas or sediment retention facilities is discharged. This practice applies only where the spreader can be constructed on undisturbed soil and the area below the level lip is vegetated and low gradient (see below). Note: Level spreaders are conceptually an ideal way to release stormwater since the vegetaaon and soil allow for the removal offinesfi-om runoff that cannot be removed by settling or filtration. Unfortunately, the pe/jormance record of spreaders in thefield is dismal. They are frequently under-designed and, despite the best installations, are rarely perfectly level, which results in the release of storm water at a particular point. This concentrated run~ff can result in catastrophic erosion downslope. Given such design failures, the use a/spreaders is not encollraged. However, where slopes are gentle and the water volume is relatively low, spreaders may stil! be the best method. When proposing their use, the deSigner shall carefully evaluate the sitefor possible concerns. Design and Installation Specifications I. See Figure D.3.6.F for detail. Other designs may be used subject to County approval. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-63 SECTION D.3 ESC MEASURES 2. If runoff velocity as it enters the level spreader is more than 4 fps for the developed lO-yearIl5- minute peak flow, a rip rap apron must be provided to dissipate energy before the runoff enters the spreader (Section D.3.6.5). 3. The total spreader length shall be at least the square root of the catchment area. The maximum length for an individual spreader is 50 feet, limiting the catchment area that a single spreader may serve to 2500 square feet. Although this is very small, four 50-foot level spreaders next to one another could serve nearly an acre (40,000 square feet). Multiple spreaders shall not be placed uphill or downhill from one another in a configuration that would allow water released from one spreader to enter a downslope spreader. 4. The area below the spreader for a horizontal distance of 100 feet shall not exceed 20 percent and shall be completely vegetated with no areas of instability or erosion. The topography for a horizontal distance of 50 feet below the spreader shall be uniform so that runoff is not funneled into a swale or channel immediately after its release. 5. The level spreader shall be seeded and mulched in accordance with Section D.3.2 (p. D-IO). Maintenance Standards I. Any damage to the spreader shall be immediately repaired. 2. The downslope area shall be checked for signs of erosion and to verify that the spreader is not functioning as a point discharge. Any eroded areas shall be immediately stabilized, and the cause determined and eliminated if possible. If the erosion is recurrent and the design, even when properly installed and maintained, is not adequate to prevent erosion, a new method of releasing runoff shall be installed in accordance with the standards of this appendix. Any new design must be approved by King County. I FIGURE D.3.6.F LEVEL SPREADER 1/24/2005 DENSELY VEGETATED FOR A MIN. Of 100' AND SLOPE LESS THAN 5: 1 SPREADER MUST BE LEVEL MIN.---<- CROSS SECTION TREATED 2~Xl0· MAY BE ABUTTED END TO END FOR MAX. SPREADER LENGTH Of 50' , 8" t.4tN. REBAR SUPPORTS s' t.tIN. SPACING DETAIL OF SPREADER 2005 Surface Water Design Manual -Appendix. D D-64 D.3,7 DEWATERING CONTROL D.3.7 DEWATERING CONTROL Any runoff generated by dewatering shan be treated through construction of a sediment trap (Section D.3,5.1) when there is sufficient space or by releasing the water to a well vegetated, gently sloping area. Since pumps are used for dewatering, it may be possible to pump the sediment-laden water well away from the surface water so that vegetation can be more effectively utilized for treatment Discharge of sediment-laden water from dewatering activities to surface and storm waters is prohibited, If dewatering occurs from areas where the water has come in contact with new concrete, such as tanks, vaults, or foundations, the pH of the water must be monitored and must be neutralized prior to discharge. Purpose: To prevent the untreated discharge of sediment-laden water from dewatering of utilities, excavated areas, foundations, etc. When to Install: Dewatering control measures shan be used whenever there is a potential for runoff from dewatering of utilities, excavations, foundations, etc, Measures to install: 1, A straw bale filter shall be placed around the discharge from a dewateting pump. 2, If there is not space for a sediment trap or 25 feet of suitable vegetation, other filtration methods shall be required consistent with KCC 9.12, Dewatering structures shall be sized to allow water to flow through the filtering media without overflowing the structure, 3. Portable sediment tanks, such as Baker tanks, may be necessary to capture and treat sediment-laden runoff generated by dewatering, 4. Runoff from dewatering may have to be discharged to the sanitary sewer especially if the site is a known contaminated site and has a history of sailor groundwater contamination, specifically petroleum hydrocarbons, pH abnormalities, or metals contamination, An approval for discharge to the sanitary sewer must be secured from the local sewer agency. D.3.8 DUST CONTROL Preventative measures to minimize the wind transport of soil shall be taken when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources or adjacent properties. Purpose: To prevent wind transport of dust from exposed soil surfaces onto roadways, drainage ways, and surface waters. When to Install: Dust control shall be implemented when exposed soils are dry to the point that wind transport is possible and roadways, drainage ways, or surface waters are likely to be impacted. Dust control measures may consist of chemical, structural, or mechanical methods, Measures to Install: Water is the most common dust control (or palliative) used in the area, When using water for dust control, the exposed soils shall be sprayed until wet, but runoff shall not be generated by spraying. Calcium chloride, Magnesium chloride, Lignin derivatives, Tree Resin Emulsions, and Synthetic Polymer Emulsions may also be used for dust control. Exposed areas shall be re-sprayed as needed, Oil shall not be used for dust control. The following table lists many common dust control measures, Some of the measures are not reconunended for use in King County and must have prior approval prior to use from the DDES inspector assigned to specific projects. 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-65 SECTION D.3 ESC MEASURES ··.·.···•· ••• ··.· .• ·'L·.· •• ·•·•···• •.•• <;'.·. ·'.,i.·~:·:.';tTABLE.l)j.8.A.DUSTCONT~OLMEASURES*./'.;.i..i·: .. ,.>.·.·.: •. ·· •.. ·.• .. · .••..• METHOD CONSIDERATIONS SITE PREPARATION RECOMMENDED APPLICATION RATE Water -Most commonly used practice For all liquid agents: 0.125 gal/sq yd every -Evaporates quickly -Blade a small surface 20 to 30 minutes -Lasts less than 1 day -Crown or slope surface to avoid ponding -Compact soils if needed -Uniformly pre-wet at 0.03 -0.3 gallsq yd -Apply solution under pressure. Overlap solution 6 -12 inches -Allow treated a rea to cure 0-4 hours -Compact area after curing -Apply second treatment before first treatment becomes ineffective Salts -Restricts evaporation Apply 38% solution at Calcium -Lasts 6-12 months 1.21 Llm2 (0.27 gal/yd2) Chloride -Can be corrosive or as loose dry granules (CaCI) -Less effective in low humidity per manufacturer -Can build up in soils and leach by rain Magnesium -Restricts evaporation Apply 26 32% solution Chloride -Works at higher temperatures and lower at 2.3 Llm2 (0.5 (MgCI) humidity than CaCI gal/yd2) -May be more costly than CaCI Sodium -Effective over smaller range of Per Manufacturer Chloride conditions (NaCI) -Less expensive -Can be corrosive -Less effective in low humidity Silicates -Generally expensive -Available in small quantities -Require Second application Surfactants -High evaporation rates -Effective for short time periods -Must apply frequently Copolymers -Forms semi-permeable transparent 750 940 Llha (80 crust 100 gal/a c) -Resists ultraviolet radiation and moisture induced breakdown -Last 1 to 2 years Petroleum -Used oil is prohibited as a dust control Use 57 63% resins as Products method base. Apply at 750- -Bind soil particles 940 Llha (80-100 -May hinder foliage growth gal/ac) -Environmental and aesthetic concerns -Hiqher cost Lignin -Paper industry waste product Loosen surface 25-50 Sulfonate -Acts as dispersing agent mm (1 -2 inches) Need -Best in dry climates 4-8% fines -Can be slippery -Will decrease Dissolved Oxygen in waterways therefore cannot be used adjacent to surface water systems Vegetable -Coat grains of soils. so limited binding Per Manufacturer Oils ability -May become brittle -Limited availabilitv Spray on -Available as organic or synthetic Per Manufacturer Adhesives -Effective on dry, hard soils -Forms a crust -Can last 3 to 4 years 1/24/2005 2005 Surface Water Design Manual -Appendix D D-66 D.3.9 FLOW CONTROL D.3.9 FLOW CONTROL Surface water from disturbed areas must be routed through the project's onsite flow control facility or other provisions must made to prevent increases in the existing site conditions 2-year and IO-year runoff peaks discharging from the project site during construction. Purpose: The purpose of surface water flow control is to mitigate increases in runoffpeaks that occur during construction as a result of clearing vegetation, compacting the soil, and adding impervious surface. Such increases can cause or aggravate downstream flooding and erosion. When to Install: Surface water flow control shall be installed or otherwise provided prior to any clearing andlor grading of the site, except that required to construct the surface water flow control facilities. Measures to Use: The project's onsite flow control facility or other equivalent storage facility that meets the peak-matching perfonnance criteria stated above. 2005 Surface Water Design Manual -Appendix D 112412005 D-67 KING COUNTY. WASHINGTON, SURF ACE WA TER DESIGN MANUAL D.4 ESC PERFORMANCE AND COMPLIANCE PROVISIONS The changing conditions typical of construction sites call for frequent field adjustments of existing ESC measures or additional ESC measures in order to meet required perfonnance. In some cases, strict adherence to specified measures may not be necessary or practicable based on site conditions or project type. The provisions contained in this section specify the minimum performance required and the circumstances under which the County may add to or vary from the ESC standards in this appendix to meet this performance. D.4.1 ESC PERFORMANCE ESC measures shall be applied and maintained so as to prevent, to the maximum extent practicable, the transport of sediment from the project site to downstream drainage systems or surface waters or into onsite wetlands, streams, or lakes. This performance is intended to be achieved through proper selection, installation, and operation of the above ESC measures as detailed in the ESC Standards (detached Appendix D) and approved by the County. However, the ESC supervisor or the County may determine at any time during construction that such approved measures are not sufficient and additional action is required based on one of the following criteria: I. IF a turbidity test of stonn and surface water discharges leaving the project site or entering onsite wetlands, streams, or lakes indicates a turbidity level greater than 25 NTU (nephelometric units) above the background levels of offsite storm and surface water flows entering the project site, OR if stann and surface water discharges from onsite activity areas exceed 25 NTU, THEN corrective actions and/or additional measures beyond those specified in Section D.3 shall be implemented as deemed necessary by the County inspector or ESC supervisor. Note: The ESC supervisor shall have a turbidity meter onsite and shall use it whenever runqlf occurs from onsite activities and during storm events. 2. IF a turbidity test indicates a turbidity level greater than 100 NTU, THEN County inspection staff shall be notified immediately and corrective actions and/or additional measures beyond those specified in Section D.3 shan be implemented as deemed necessary by the County. 3. IF the County detennines that the condition of the construction site poses a hazard to adjacent property or may adversely impact drainage facilities or water resources, THEN additional measures beyond those specified in Section D.3 may be required by tl,e County. D.4.2 FLEXIBLE COMPLIANCE Some projects may meet the intent of Core Requirement #5 while varying from specific ESC requirements in this appendix. If a project is designed and constructed such that it meets the intent of core requirement, the County may detennine that strict adherence to a specific ESC requirement is unnecessary; an approved adjustment (see Section 1.4) from the SWDMis not required in these circumstances. Certain types of projects are particularly likely to warrant this greater level of flexibility; for instance, projects on relatively flat, well drained soils, projects that are constructed in closed depressions, or projects that only disturb a small percentage ofa forested site may meet the intent of this requirement with very rew ESC measures. D.4.3 ROADS AND UTILITIES COMPLIANCE Road and utility projects often pose difficult erosion control challenges because they frequently cross surface waters and because narrow right-of-way constrains .areas available to store and treat sediment- laden water. In most cases, the standards of this appendix may be applied to such linear projects without 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-69 SECTION DA ESC PERFORMANCE AND COMPLIANCE PROVISIONS modification. For instance, the ability to use perimeter control rather than a sediment retention facility for small drainage areas (see Section D.3.3) will apply to many of these projects. However, there may be some projects that cannot reasonably meet the standards of Core Requirement #5 and this appendix. In these cases, other measures may be proposed that will provide reasonable protection. An adjustment is not required for such projects, unless the County determines that measures proposed by the applicant fail to meet the intent of Core Requirement #5 and this appendix, and that significant adverse impacts to surface water may result. Examples of other measures that may be taken in lieu of the standards of this appendix are: I. Phasing the project so that the site is worked progressively from end to end, rather than clearing and grubbing the entire length of the project. This results in smaller exposed areas for shorter durations, thus reducing the erosion risk. It is recommended that there be no more than 500 feet of open trench during any phase of construction. 2. Placement of excavated materials from utility trenches on the upslope side of the excavation, to minimize transport of sediment outside of the project area. 3. Mulching and vegetating cut and fill slopes as soon as they are graded. Frequently, this is done at the end of construction when paving or utility installation is complete. Vegetating these areas at the start of the project stabilizes those areas most susceptible to erosion. 4. Protecting all catch basin inlets with catch basin inserts or other inlet protection when these do not drain to ponds or traps. This will not provide the same level of protection as a sediment pond or trap, but can remove most of the sand-sized material entrained in the runoff. 5. Phasing the project so that all clearing and grading in critical area buffers occurs in the dry season. This substantially reduces the chance of erosion and allows for rapid revegetation in the late SUmmer and early fall. 6. Using approved flocculent or other chemical treatment approved by King County to reduce the turbidity of water released from sediment ponds. 7. Hiring a private consultant with expertise in ESC to review and monitor the site. If alternatives are used, it may be appropriate to develop a monitoring program that would monitor compliance with the performance standard of Core Requirement #5 andlor impacts to nearby water resources. Of particular concern are impacts to salmonid spawning gravels. McNeil sampling is a possible method of sampling to determine impacts to spawning gravels (see Section D.5.3). D.4.4 ALTERNA TIVE AND EXPERIMENTAL MEASURES 1/24/2005 In general, the Surface Waler Design Manual only contains those BMPs that are standards of the local industry. There are a variety of other BMPs available that may also be used, even though they are not included in this appendix. Such alternatives may be approved without an adjustment if the alternative will produce a compensating or comparable result with the measures in this appendix. Variations on or modifications of the BMPs in this appendix may also be granted based on the same criteria. Technical support will be provided by WLRD when requested hy DDES. An adjustment is only required for those products or techniques that are so new and untested as to he experimental. If the County determines that a proposed alternative is experimental, then an experimental adjustment must be obtained (see Section 1.4.4 of the SWDMj. The intent of this requirement is not to discourage new techniques, but to insure that new techniques are monitored and documented for adequacy and possible inclusion in subsequent versions of the SWDM. An example ofa product that would have required an experimental adjustment prior to this version of the manual is the catch basin insert (see Section D.3.S.3) hecause it was not equivalent to any existing measure. 2005 Surface Water Design Manual-Appendix D D-70 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL D.S ESC IMPLEMENTATION REQUIREMENTS This section describes the ESC implementation requirements that are required at each construction site, The measures and practices correspond to the implementation requirements in Core Requirement #5. Three of the sections [the ESC report (Section D.5. J, below), ESC maintenance requirements (Section D.5.4, p. D· 73), and final site stabilization (Section D.5.5, p. D· 74)] are required of every project. The rest of the sections are special requirements that may apply to the project depending on site conditions and project type. The introductory paragraphs at the beginning of most sections present the purpose of the measures and when they should be applied to the site. Compliance with the implementation requirements (as appropriate for the site) ensures compliance with the ESC measures. Note, however, that additional measures shall be required by the County if the existing standards are insufficient to protect adjacent properties, drainage facilities, or water resources. D.S.1 ESC PLAN An ESC plan, showing the location and details of ESC measures, is required for all proposed projects and shall include an ESC report, which includes supporting infonnation for providing ESC measures and meeting ESC implementation requirements. A copy ofthe ESC plan with ESC report shall be kept at the project site throughout all phases of construction. All of the materials required for the ESC report are standard parts of engineering plan submittals for projects requiring drainage review. The simplest approach to preparing this report is to compile the pieces during preparation for submittal and include the report as a separate part of the ESC plan submittal package. The ESC report shall include the following: I. A detailed constrnction sequence, as proposed by the design engineer or erosion control specialist, identifYing required ESC measures and implementation requirements; 2. A technical information report (T1R) and ESC plan for King County review in accordance with Sections 2.3.1 and 2.3.3 oftbe Surface Water Design Manual. Incorporate any King County review comments as necessary to comply with Core Requirement #5 of the SWDM (Section 1.2.5) and the Erosion and Sediment Control Standards in this appendix; 3. Any calculations or information necessary to size ESC measures and demonstrate compliance with Core Requirement #5; 4. An inspection and maintenance program in accordance with Section D.5.4 (p. D· 73) that includes the designation of a certified ESC supervisor as point of contact; and 5. Anticipated changes or additions necessary during construction to ensure that ESC measures perform in accordance with Core Requirement #5 and Sections D.3 (p. D·7) and D.5 (p. D·7]). While the ESC plan focuses on the initial measures to be applied to the site, any changes or additions necessary during construction to ensure that ESC measures perfonn in accordance with Core Requirement #5 and Sections D.3 and D.5 must be identified in the ESC report. The County may require large, complex projects to phase construction and submit multiple ESC plans for different stages of construction. Development of new ESC plans is not required for changes that are necessary during construction. D.S.2 WET SEASON REQUIREMENTS Any site with exposed soils during the wet season (October 1 to April 30) shall be subject to the special provisions below. In addition to the ESC cover measures (see Section D.3.2, p. D·1 0), these provisions include covering any newly seeded areas with mulch and identifying and seeding as much disturbed area as possible prior to September 23 in order to provide grass cover for the wet season. 2005 Surface Water Design Manual ~ Appendix D 1/24/2005 D·7\ SECTION D.5 ESC IMPLEMENTATION REQUIREMENTS Wet Season Special Provisions All of the following provisions for wet season construction are detailed in the referenced sections. These requirements are listed here for the convenience of the designer and the reviewer. I. The allowed time that a disturbed area may remain unworked without cover measures is reduced to two consecutive working days, rather than seven (Section D.3.2). 2. Stockpiles and steep cut and fill slopes are to be protected ifunworked for more than 12 hours (Section D.3.2). 3. Cover materials sufficient to cover all disturbed areas shall be stockpiled on site (Section D.3.2). 4. All areas that are to be unworked during the wet season shall be seeded within one week of the beginning of the wet season (Section D.3.2.5). 5. Mulch is required to protect all seeded areas (Section D.3.2.1). 6. Fifty linear feet of silt fence (and the necessary stakes) per acre of disturbance must be stockpiled on site (Section D.3.3.1). 7. Construction road and parking lot stabilization are required for all sites unless the site is underlain by coarse-grained soil (Section D.3.4.2). 8. Sediment retention is required unless no offsite discharge is anticipated for the specified design flow (Section D.3.S). 9. Surface water controls are required unless no off site discharge is anticipated for the specified design flow (Section D.3.6). 10. Phasing and more conservative BMPs must be evaluated for construction activity near surface waters (Section D.5.3). 11. Any runoff generated by dewatering may be required to discharge to the sanitary sewer (with appropriate discharge authorization), portable sand filter systems, or holding tanks. 12. The frequency of maintenance review increases from monthly to weekly (Section D.S.4). D.5.3 CRITICAL AREAS RESTRICTIONS Any construction that will result in disturbed areas on or within a stream or associated buffer, a wetland or associated buffer, or within 50 feet of a lake shan be subject to the special provisions below. These provisions include, whenever possible, phasing the project so that construction in these areas is limited to the dry season. The County may require more conservative BMPs, including more stringent cover requirements, in order to protect surface water quality. Any project proposing work within 50 feet of a steep slope hazard area shan evaluate the need for diverting runoff that might flow over the top of the slope. Critical Areas Special Provisions Any project that disturbs areas on or within a stream or associated butfer, wetland or associated buffer, or within 50 feet of a lake has the potential to seriously damage water resources, even ifthe project is relatively small. While it is difficult to require specific measures for such projects because the ESC plan must be very site specific, the following recommendations shall be incorporated into the plan where appropriate: 1. Whenever possible, phase all or part of the project so that it occurs during the dry season. If this is impossible, November through February shall be avoided since this is the most likely period for large, high-intensity storms. 112412005 2005 Surface Water Design Manual -Appendix D 0-72 D.5.3 CRITICAL AREAS RESTRICTIONS 2. All projects shall be completed and stabilized as quickly as possible. Limiting the size and duration of a project is probably the most effective form of erosion control. 3. Where appropriate, sandbags or an equivalent barrier shall be constructed between the project area and the surface water in order to isolate the construction area from high water that might result due to precipitation. 4. Additional perimeter protection shall be considered to reduce the likelihood of sediment entering the surface waters. Such protection might include multiple silt fences, silt fences with a higher AOS, construction of a berm, or a thick layer of organic mulch upslope of a silt fence. 5. If work is to occur within the ordinary high water mark of a stream, most projects must isolate the work area from the stream by diverting the stream or constructing a cofferdam. Certain small projects that propose only a small amount of grading may not require isolation since diversions typically result in disturbance and the release of some sediment to the stream. For such small projects, the potential impacts from construction with and without a diversion must be weighed. 6. If a stream must be crossed, a temporary bridge shall be considered rather than allowing equipment to utilize the streambed for a crossing. For projects in or near a salmonid stream, it may be appropriate to monitor the composition of any spawning gravels within a quarter-mile of the site with a McNeil sampler or similar method approved by King County before, during, and after construction. The purpose of such monitoring would be to determine if the fine content of the gravels increases as a result of construction impacts. Monitoring results could be used to guide erosion control efforts during construction and as a threshold for replacing spawning gravels if the fine content rises significantly. D.S.4 MAINTENANCE REQUIREMENTS All ESC measures shall be maintained and reviewed on a regular basis as prescribed in the maintenance requirements for each BMP and in this section. For projects in Full or Large Project Drainage Review, the applicant must deSignate an ESC supervisor who shall be responsible for the performance, maintenance, and review of ESC measures and for compliance with all permit conditions relating to ESC as described in the ESC Standards. The ESC supervisor must be a Certified Professional in Erosion and Sediment Control (see www.cpesc.net for more infonnation) or a Certified Erosion and Sediment Control Lead whose certification is recognized by King County. King County recognition of certification means that the individual has taken a King County-approved third party training program and has passed the King County-approved test for that training program. Additionally, the applicant's selection of an ESC supervisor must be approved by King County. The ESC supervisor shall review the site at least twice a month during the dry season, weekly during the wet season, and within 24 hours of significant storms. The County may require that a written record of these reviews be kept on site with copies submitted to DOES within 48 hours. The County shall also require that the applicant designate an ESC supervisor with demonstrated experience in ESC to perform these reviews and to be responsible for ESC. ESC Supervisor The name, address, and phone number of the ESC supervisor shall be supplied to the County prior to the start of construction. A sign shall be posted at all primary entrances to the site identifying the ESC supervisor and his/her phone number. The requirement for an ESC supervisor does not relieve the applicant of ultimate responsibility for the project and compliance with King County Code. For highly sensitive sites, the County may require that the applicant designate a certified ESC supervisor with demonstrated expertise in erosion and sediment control. The qualifications of such a person shall include the successful completion of an approved erosion control class or program and several years of construction supervision or inspection and a background in geology, soil science, or agronomy. Typically, if a geotechnical consultant is already working on the project, the consultant may also be the 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-73 SECTION D.S ESC IMPLEMENTATION REQUIREMENTS designated ESC supervisor. The design engineer may also be qualified for this position. This requirement shall only be used for sensitive sites that pose an unusually high risk of impact to surface waters. At a minimum, the project site shall meet all of the following conditions in order to require the applicant to designate a certified ESC supervisor with demonstrated expertise in ESC: • Alderwood soils or other soils of Hydrologic Group C or D • Five acres of disturbance • Large areas (i.e .• two or more acres) with slopes in excess of 10 percent. Proximity to streams or wetlands or phosphorus-sensitive lakes, such as Lake Sammamish. shan also be a factor in determining if a site warrants an ESC specialist. However, proximity alone shall not be a determining factor because even projects that are a considerable distance from surface waters can result in significant impacts if there is a natural or constructed drainage system with direct connections to surface waters. IfDDES determines that the onsite ESC measures are inadequately installed, located, or maintained, DDES shall require the appointment of a certified ESC supervisor with expertise in erosion and sediment control. Documentation IfDDES requires that a written record be maintained, a standard ESC Maintenance Report, included in Section D.8.1 (p. D-89), may be used. A copy of all the required maintenance reports shall be kept on site throughout the duration of construction. Detailed maintenance requirements for each ESC measure are provided in Section D.3. Review Timing During the wet season, weekly reviews shall be carried out every 6 to 8 calendar days. During the dry season, monthly reviews shall be carried out within 3 days of the calendar day for the last inspection (e.g., if an inspection occurred on June 6, then the next inspection must occur between July 3 and July 9). Reviews shall also take place within 24 hours of significant storms. In general, a significant storm is one with more than 0.5 inches of rain in 24 hours or less. Other indications that a storm is "significant" are if the sediment ponds or traps are filled with water, or if gullies form as a result of the runoff. Note: The site is to be in compliance with the regulations of this appendix at all times. The requirement for periodic reviews does not remove the applicant's responsibility for having the site constantly in compliance with Core Requirement #5 and the requirements of this appendix. The reviews are a mechanism to ensure that all measures are thoroughly checked on a regular basis and that there is documentation of compliance. The requirementfor these reviews does not mean that ESC is to be ignored in between. D.S.S FINAL ST ABILIZA nON Prior to obtaining final construction approval, the site shall be stabilized, the structural ESC measures, such as silt fences and sediment traps, removed, and drainage facilities cleaned. The removal of ESC measures is not required for those projects, such as plats, that will be followed by additional construction under a different permit. In these circumstances, the need for removing or retaining the measures must be evaluated on a site-specific basis. To obtain final construction approval, the following conditions must be met: 1. All disturbed areas of the site shall be vegetated or otherwise permanently stabilized. At a minimum, disturbed areas shall be seeded and mulched (see Section D.3 .2.5) with a high likelihood that sufficient cover will develop shortly after final approval. Mulch without seeding is not adequate to allow final approval of the permit, except for small areas of mulch used for landscaping. The only exceptions to these requirements are lots within a plat that are to be developed under an approved 1/24/2005 2005 Surface Water Design Manual-Appendix D D-74 D.5.5 FINAL STABILIZATION residential pennit immediately following plat approval. In these cases, mulch and/or temporary seeding are adequate for cover. 2. Structural measures such as, but not limited to, silt fences, pipe slope drains, construction entrances, stonn drain inlet protection, and sediment traps and ponds shall be removed from the site. Measures that will quickly decompose, such as brush barriers and organic mulches, may be left in place. In the case of silt fences, it may be best to remove fences in conjunction with the seeding, since it may be necessary to bring machinery back in to remove them. This will result in disturbed soils that will again require protection. The DOES inspector must approve an applicant's proposal to remove fencing prior to the establishment of vegetation. In some cases, such as residential building following plat development, it shall be appropriate to leave some or all ESC measures for use during subsequent development. This shall be detennined on a site-specific basis. 3. All pennanent surface water facilities, including catch basins, manholes, pipes, ditches, channels, flow control facilities, and water quality facilities, shall be cleaned. Any offsite catch basin that required protection during construction (see Section 0.3.5.3) shall also be cleaned 4. If only the infrastructure of the site has been developed (e.g., subdivisions and short plats) with building construction to occur under a different pennit, then the critical area buffers, Critical Area Tracts, or Critical Area Setback Areas shall be clearly marked as described in Section 0.3.1 (p. D-8) in order to alert future buyers and builders. D.S.6 NPDES REQUIREMENTS As part of the implementation of the National Pollutant Discharge Elimination System (NPDES), projects that will disturb more than one acre for purposes of constructing or allowing for construction a development must apply for coverage under the Washington State Department of Ecology's Baseline General Pennit for Stonnwater. In general, the erosion control plan required by the Surface Waler DeSign Manual is equivalent to that required by the State through the Stormwater Management Manualfor Western Washington (DOE, 2001). The DOE stonnwater pennit application requires the filing of a Notice oflntent (NOI) at least 30 days prior to the start of construction. The only major requirement of the stonnwater pennit that is not included in the SWDM is a public notice requirement. Note that this public notice for Ecology's stonnwater pennit may be published concurrently with other public notices required for pennits or SEP A. Contact the Department of Ecology at (360) 407-7156 for complete infonnation on pennit thresholds, applications, and requirements. D.S.7 FOREST PRACTICE PERMIT REQUIREMENTS Projects that will clear more that two acres of forest or 5,000 board feet of timber must apply for a Class IV Special Forest Practice permit from the Washington State Department of Natural Resources (WSDNR). All such clearing is also subject to the State Environmental Policy Act (RCW 43.21 C) and will require SEPA review. King County assumes lead agency status for Class IV pennits and the application may be consolidated with the associated King County development pennit or approval. The pennit must be initiated with WSDNR, but will then be transferred over to King County to conduct the SEPA review and grant the permit. Contact the WSDNR for complete infonnation on permit thresholds, applications, and requirements. 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-75 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL D.6 EROSION AND SEDIMENT CONTROL PLANS This section details the specifications and contents for erosion and sediment control (ESC) plans. An ESC plan includes the plan's drawings plus an ESC report, which provides all supporting infonnation and any additional direction necessary for implementing ESC measures and meeting ESC implementation requirements. The ESC plan must be submitted to DDES as part of a complete engineering plan to facilitate proper drainage review. A copy of the approved ESC plan (with ESC report) must be kept on the project site (see Section D.S.I, p, D-71) at all times during the construction phase. ESC Plan General Specifications The site improvement plan shall be used as the base of the ESC plan, Certain detailed infonnation (e,g" pipe catch basin size, stub-out locations, etc.) that is not relevant may be omitted to make the ESC plan easier to comprehend, At a minimum, the ESC plan shall include all of the infonnation required for the base map of a site improvement plan (see Table 2.3, lA ofthe Surface Water Design Manual), as well as existing and proposed roads, driveways, parking areas, buildings and drainage facilities, utiliry corridors not associated with roadways, relevant critical areas' and associated buffers, and proposed final topography, A smaller scale may be used to provide better comprehension and understanding, The ESC plan shall generally be designed for proposed topography, not existing topography, since rough grading is usually the first step in site disturbance. The ESC plan shall address all phases of construction (e,g" clearing, grading, installation of utilities, surfacing, and final stabilization), The County may require large, complex projects to phase construction and submit multiple ESC plans for different stages of construction, The ESC plan outlines the minimum requirements for anticipated site conditions, During construction, ESC plans shall be revised as necessary by the ESC supervisor or as directed by King County to address changing site conditions, unexpected stonn events, or non-compliance with the ESC perfonnance criteria in Section DAI (p, D-69), The following list provides the basic infonnation requirements for the ESC plan, This infonnation shall be consistent with that in Section 8 of the technical infonnation report (TIR) required in the engineering plan submittal (see Section 2.3,1 of the SWDMj, Note that the ESC plan's drawings may be simplified by the use of the symbols and codes provided for each ESC measure in Section D.3, In general, the ESC plan's drawings shall be submitted as a separate plan sheet(s), However, there may be some relatively simple projects where providing a separate grading and ESC plan drawing is unnecessary. I, Identify areas with a high susceptibility to erosion, 2. Provide all details necessary to clearly illustrate the intent of the ESC design, 3. Include ESC measures for all on-and offsite utility construction included in the pennit. 4. Specify the construction sequence. The construction sequence shall be specifically written for the proposed project. An example construction sequence is provided in Section D,8.3 (p. D-93). S, Include standard ESC plan notes (see Section D,8,2, p, D-92) and specify the construction sequence. ESC Notes and a sample construction sequence are provided in the Reference Section, 6. Include an inspection and maintenance program for ESC measures, including designation of a certified ESC supervisor and identification of phone numbers for 24-hour contact. 7. Include the basis and calculations for selection and sizing of ESC measures, 8 Relevant critical areas, for the purposes of drainage review, include aquatic areas, wetlands, flood hazard areas, erosion hazard areas, landslide hazard areas, steep slope hazard areas, and critical aquifer recharge areas. 2005 Surface Water Design Manual-Appendix D 1124/2005 D-77 SECTION D.6 EROSION AND SEDlMENT CONTROL PLANS ESC Plan Measure-Specific Information The ESC plan must include the following information specific to applicable ESC measures and implementation requirements. As noted above, this information may need to be updated or revised during the life of the project by the ESC supervisor or as directed by King County. Clearing Limits I. Delineate clearing limits (areas to remain uncleared). 2. Provide details sufficient for installation of markings for maintenance of clearing limits. Cover Measures I. Specify the type and location of temporary cover measures to be used on site. 2. If more than one type of cover measure is to be used on site, indicate the areas where the different measures shall be used, including steep cut and fill slopes. 3. If the type of cover measures to be used will vary depending on the time of year, soil type, gradient, or some other factor, specify the conditions that control the use of the different measures. 4. Specify the nature and location of permanent cover measures. If a landscaping plan is prepared, this may not be necessary. 5. Specify the approximate amount of cover measures necessary to cover all disturbed areas. 6. If netting, blankets, or plastic sheeting are specified, provide typical details sufficient for installation and maintenance. 7. Specify the mulch types, seed mixes, fertilizers, and soil amendments to be used, as well as the application rate for each item. 8. For surface roughening, describe methods, equipment and areas where surface roughening will be use. 9. !fPAM is used on a site, show location(s) and describe application method. 10. When compost blankets are used, show site location, application rates, and the name of the supplier to document that compost meets WAC 173-350-22 standards and meets Grade A quality specifications. Perimeter Protection I. Specify the location and type of perimeter protection to be used. 2. Provide typical details sufficient for installation and maintenance of perimeter protection. 3. Ifa silt fence is to be used, specify the type offabric. 4. If compost berms or socks are used, documentation must be provide to assure the supplier meets the criteria under WAC 173-350-220 and compost meets Grade A quality standards. Traffic Area Stabilization I. Locate the construction entrance(s). 2. Provide typical details sufficient for installation and maintenance of the construction entrance. 3. Locate the construction roads and parking areas. 4. Specify the measure(s) that will be used to create stabilized construction roads and parking areas. Provide sufficient detail to install and maintain. 1/24/2005 2005 Surface Water Design Manual-Appendix D D-78 D.6 EROSION AND SEDIMENT CONTROL PLANS 5. If a wheel wash or tire bath system will be installed, provide location, typical details for installation and maintenance. 6. Provide a list of dust control products that will be used onsite and the location of potential application areas. Sediment Retention 1. Show the locations of all sedimentation ponds and traps. 2. Dimension pond berm widtbs and all inside and outside pond slopes. 3. Indicate the trap/pond storage required and the depth, length, and width dimensions. 4. Provide typical section views throughout the pond and outlet structure. 5. If chemical or electrocoagulation treatment of sediment-laden waters will be used, approval documentation from DOE must be included. 6. Provide details for disposal of contaminated or chemically treated waters (e.g., where Chitosan or C02 have been used). 7. Include appropriate approval documentation from local sewer districts if contaminated or chemically treated water will be discharged to the sanitary sewer. 8. Provide typical details of the control structure and dewatering mechanism. 9. Detail stabilization techniques for the outlet/inlet protection. 10. Provide details sufficient to install cell dividers. II. SpecifY mulch andlor recommended cover of berms and slopes. 12. Indicate the required depth gage with a prominent mark at I-foot depth for sediment removal. 13. Indicate catch basins that are to be protected. 14. Provide details of the catch basin protection sufficient to install and maintain. Surface Water Control 1. Locate all pipes, ditches, and interceptor ditches, dikes, and swales that will be used to convey stormwater. 2. Provide details sufficient to install and maintain all conveyances. 3. Indicate locations of outlet protection and provide detail of protections. 4. Indicate locations and outlets of any possible dewatering systems. Provide details of alternative discharge methods from dewatering systems if adequate infiltration rates cannot be achieved. 5. Indicate the location of any level spreaders and provide details sufficient to install and maintain. 6. Provide all temporary pipe inverts. 7. Provide location and specifications for the interception of runoff from disturbed areas and the conveyance of the runoff to a non-erosive discharge point. 8. Provide locations of rock check dams. 9. Provide details, including front and side sections, of typical rock check dams. Wet Season Requirements 1. Provide a list of all applicable wet season requirements. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-79 SECTION D.6 EROSION AND SEDIMENT CONTROL PLANS 2. Clearly identify that from October I" through April 30 th , no soils shall be exposed for more than two consecutive working days. Also note that this two-day requirement may be applied at other times of the year if storm events warrant more conservative measures. 3. Clearly identify that exposed soils shall be stabilized at the end of the workday prior to a weekend, holiday, or predicted rain event. Critical Areas Restrictions 1. Delineate and label tbe following critical areas, and any applicable buffers, that are on or adjacent to the project site: aquatic areas, wetlands, flood hazard areas, erosion hazard areas, landslide hazard areas, steep slope hazard areas, and critical aquifer recharge areas. 2. If construction creates disturbed areas within any of the above listed critical areas or associated buffers, specify the type, locations, and details of any measures or other provisions necessary to comply witb the critical area restrictions in Appendix D and protect surface waters and steep slopes. 1/24/2005 2005 Surface Water Design Manual-Appendix D D-80 KING COUNTY, WASHINGTON, ~URFACE WATER DESIGN MANUAL D.7 SMALL SITE ESC Smaller project sites have similar erosion and sediment control (ESC) needs, This section offers a simplified set of requirements for applying erosion and sediment controls to certain smaller project sites and guides the user through the preparation and submittal of a Small Site ESC Plan with the pennit application. D.7.1 INTRODUCTION TO SMALL SITE ESC What is ESC and Why is it Required for My Site? The basic erosion and sediment control requirement~that sediment shall be prevented to the maximum extent practicable from leaving the site~applies to all projects in King County. All projects, including those with small project sites, are required to use erosion and sediment control (ESC) measures. ESC measures prevent soil erosion during development of the site. The types of measures required for small sites are generally simple to construct and easy to maintain, and with few exceptions do not require engineering or fonnal design. Examples of such measures include phasing or minimizing clearing, terracing exposed slopes, routing water around exposed soils, and placing straw or other mulching materials and cover exposed soils. ESC is required because soils eroded from the site are always deposited downstream in pipes, streams, or lakes. Soils deposited in a pipe or channel reduce its capacity to convey flows and can increase the likelihood of flooding. Soils in streams can also clog the gravels that salmon use for spawning. Nutrients associated with soils that reach lakes can upset the chemical balance of the lake, causing excessive growth of algae and decreasing recreational uses such as swimming, boating, and fishing. Which Projects May Use Small Site Erosion and Sediment Control Requirements? All proposed projects that disturb soil on less than 3 acres and add less than 2,000 square feet of new impervious surface may use the Small Site ESC requirements contained in this section. These projects must apply erosion and sediment control per KCC 16.62 even though they may not be subject to drainage review under the Surface Waler Design Manual. In addition, all proposed projects subject to Small Project Drainage Review as determined in Section 1.1.2.1 of the Surface WaleI' Design Manual, and which disturb soil on less than 3 acres, may use the Small Site ESC requirements contained in this section. These same requirements are contained in Appendix C of the Surface Waler Design Manual, which details the drainage requirements for small agricultural and single family residential building or subdivision projects subject to Small Project Drainage Review. What Will I Be Required To Do? It is the responsibility of both the applicant and the contractor to minimize erosion and the transport of sediment to the greatest extent possible. Erosion and sediment control is a two step process that (I) minimizes the amount of sediment mobilized, and (2) traps any mobilized sediment before it leaves the site. Examples of erosion controls include use of mulches or other cover materials, marked/minimized clearing, and routing of water around exposed soils. Installation and maintenance of silt fencing is an example of sediment trapping. ESC techniques that are particularly suitable for small sites are described below (Section 0.7.2). 2005 Surface Water Design Manual-Appendix 0 1/24/2005 D-81 SECTION D.7 SMALL SITE ESC D.7.2 SMALL SITE ESC REQUIREMENTS The following measures will be required on small sites in order to minimize onsite erosion and prevent mobilized sediment from leaving the site: I. Stabilized construction entrance 2. Mulching or other cover methods 3. Minimized clearing 4. Silt fencing or other perimeter protection 5. Winter (or wet season) stabilization 6. Final stabilization. Typically, a combination of all of the above measures are required during construction, unless specific site conditions exist that make a particular measure unnecessary, as determined by DDES. Other measures may be allowed or required if these are inappropriate for the project or fail to contain sediment on the project site. A description of other measures that may be needed for successful ESC on some sites, and a more detailed description of those included here, can be found in Section D.3, "ESC Measures" (p. D-7). The placement and type of proposed ESC measures are shown on a small site ESC plan. Required features of this plan are outlined in Section D.7.3, "Submittal Requirements" (p. D-85). D.7.2.1 STABILIZED CONSTRUCTION ENTRANCE Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by motor vehicles or runoff by constructing a stabilized pad of quarry spalls at entrances to construction sites. Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling on paved roads or other paved areas within 1,000 feet of the site. See Section D.3.4.1 (p. D-39) for design and installation specifications and maintenance standards. D.7.2.2 MULCHING OR OTHER COVER MEASURES 1/24/2005 The cover measures described below are applicable to small sites. Mulching The purpose of mulching soils is to provide immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating soil temperatures. There is an enonnous variety of mulches that may be used. Only the most common types are discussed in this section. See Section D.3.2.2 (p. D-13) for conditions of use, design and installation specifications, and maintenance standards. Nets and Blankets Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turfto protect drainage ways during high flows. Nets are strands of material woven into an open, but high-tensile strength net (for example, jute matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. 2005 Surface Water Design Manual -Appendix D D-82 D.7.2 SMALL SITE ESC REQUIREMENTS See Section D.3.2.3 (p. D-I 5) for conditions of use, desii,'Il and installation specifications, and maintenance standards. Plastic Covering Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. See Section D.3.2.4 (p. D-I 7) for conditions of use, design and installation specifications, and maintenance standards. D.7.2.3 MARK CLEARING LIMITS I MINIMIZE CLEARING Minimizing clearing is the most effective method of erosion control. Undisturbed vegetation intercepts and slows rainwater. Plant roots hold soil in place, and dead vegetation on the ground acts as a mulch. Clearing limits shall be marked and clearing minimized on any site where significant areas of undisturbed vegetation will be retained. See Section D.3.l (p. D-8) for design and installation specifications and maintenance standards. D.7.2.4 SILT FENCING AND OTHER PERIMETER PROTECTION Perimeter protection to filter sediment from sheetwash shall be located downslope of all disturbed areas and shall be installed prior to upslope grading. The following perimeter protection measures are applicable to small sites. Silt Fence Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Silt fence may be used downslope of all disturbed areas. See Section DJ.3.1 (p. D-30) for design and installation specifications and maintenance standards. Vegetated Strip Vegetated strips reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Vegetated strips may be used downslope of all disturbed areas. See Section D.3.3.3 (p. D-34) for design and installation specifications and maintenance standards. Triangular Silt Dike (Geotextile Encased Check Dam) Triangular silt dikes (TSDs) may be used as check dams, for perimeter protection, for temporary soil stockpile protection, for drop inlet protection, or as a temporary interceptor dike. Silt dikes, if attached to impervious surfaces with tack or other adhesive agent may also be used as temporary wheel wash areas, or concrete washout collection areas. See Section D.3.3,4 (p. D-34) for conditions of use, design and installation specifications, and maintenance standards. D.7.2.5 WINTER STABILIZATION Purpose In order to minimize sediment-laden runoff, as much of the bare and disturbed portions of the site as possible should be covered during any period of precipitation. Once sediment is mobilized, it is much more difficult to effectively control. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-83 SECTION D.7 SMALL SITE ESC Application All sites require winter stabilization between October 1 and April 30 (the wet season). Design Specifications During lbe above time frame, slopes and stockpiles 3H: I V or steeper and with more than 10 feet of vertical rise shall be covered if they are to remain unworked for more than 12 hours. Other disturbed areas shall be covered or mulched according to D.3.2.2 (p. D-I3) if they are to remain unworked for more than two days. Cover material sufficient to cover all disturbed areas shall be stockpiled on site at the beginning of the wet season. Areas that are to be left unworked during the winter shall be seeded prior to September 23. Maintenance The site should be inspected weekly and immediately before, during, and after storms. Cover and other erosion control measures shall be repaired and enhanced as necessary to prevent or minimize sediment runoff and transport. D.7.2.6 FINAL STABILIZATION 1/24/2005 Purpose Final stabilization minimizes sediment-laden runoff from the site after construction has been completed. Application All sites require final stabilization prior to final construction approval. Design Specifications Prior to final construction approval, the site shall be stabilized to prevent sediment-laden water from leaving the site after project completion. All disturbed areas of the site shall be vegetated or otherwise permanently stabilized. At a minimum, disturbed areas must be seeded and mulched to ensure that sufficient cover will develop shortly after final approval. Mulch without seeding is adequate for small areas to be landscaped before October I. All permanent surface water facilities (including catch basins, manholes, pipes, ditches, channels, flow control facilities, and water quality facilities) impacted by sedimentation during construction must be cleaned. Maintenance Permanent erosion control is the responsibility of the owner. The site must be kept stabilized using landscaping, mulch, or olber measures to prevent sediment-laden water from leaving the site and to prevent sediment from being transported onto adjacent properties and roads. 2005 Surface Water Design Manual-Appendix D D-84 D.7.3 SUBMITTAL REQUIREMENTS D.7.3 SUBMITTAL REQUIREMENTS A Small Site ESC Plan must be submitted for all projects that are eligible to use the Small Site ESC requirements in this section. For projects in Small Project Drainage Review that disturb soil on less than 3 acres, this plan is part of the Small Project Drainage Plan described in the Small Project Drainage Requirements (Appendix C of the Surface Water Design ManuaT). For other projects, including those that may not be subject to drainage review, this plan would be submitted as directed by DOES. Directions for preparing a Small Site ESC Plan are provided below, and a sample plan is presented in Section 0.7.3.3 (p. 0-86). D.7.3.1 SMALL SITE ESC PLAN MAP The Small Site ESC Plan includes information that is routinely collected for a single family residence site plan or a short plat plot plan already required to be submitted with a permit application. One copy of the site plan or plot plan shall be used to show how ESC measures are to be applied to the site to comply with the Small Site ESC requirements. The approximate location and size of clearing limits, rock construction entrance, flow paths, silt fences, etc., should be indicated on the Small Site ESC Plan. Any plan must contain at a minimum the features listed in Section 0.7.3.2. Single family residential projects that qualify for Small Site ESC requirements should use the Residential Site Plan (see DOES Bulletin No.9, "Obtaining a Residential Building Permit") as the base map for the ESC plan. Proposed short plats that qualify for Small Project Drainage Review should use the Small Project Drainage Plan (see Small Project Drainage Requirements, detached Appendix C of the Surface Water Design ManuaT) as a base plan for the ESC plan. All projects subject to Small Project Drainage Review are required to submit these plans and a drainage assessment. If engineering plans are required for a short plat application, they may be used as a base plan for Small Site ESC plans. How the ESC measures are to be applied on the site are added directly to the base map. For more complicated sites, an erosion control professional should be readily able to add Small Site ESC BMPs to the base map with minimal additional effort or expense. The ESC plans for short plats usually apply only to the site development, since siting of homes on lots created by short plats is done after the short plat is approved (when the home applies for a residential building permit). It is the responsibility of the applicant for a proposed single family residence to show in detail how ESC requirements are met. The applicant is also responsible for Single family residential development is required to comply with the Stormwater Pollution Prevention Manual and KCC 9.12. D.7.3.2 FEATURES REQUIRED ON SMALL SITE ESC PLANS The Small Site ESC Plan should be drawn on 8-1/2" x II ",8-1/2" x 14", or II" x 17" paper (see the sample plan in Figure D.7.3.A, p. 0-88), and must include the following information. Identification I. Name, address, and phone number of the applicant 2. Scale-use a scale that clearly illustrates drainage features and flow controls (I "=20' is standard engineering scale; minimum acceptable scale is 1"=50') 3. Parcel number 4. North arrow 5. Dimension of all property lines, easements, and building setback lines 6. Street names and existing or proposed property address 2005 Surface Water Design Manual-Appendix D 112412005 D-85 SECTION D.? SMALL SITE ESC 7. Section, township, and range of proposal. Topography 1. Comer elevations 2. Benchmark (a permanent mark indicating elevation and serving as a reference in the topographic survey) 3. Datum (assumed datum is acceptable in many cases, i.e., fire hydrant base ~ 100'; datum for projects in or near FEMA floodplains should be NGVD 1929) 4. If over 15% slope: 5-foot contours, top of slope, toe of slope, and any erosion or landslide areas. Proposed ESC 1. Delineation of proposed clearing limits 2. Type and location of erosion control facilities 3. Location ofany significant offsite drainage features within 200 feet of the discharge point(s) for the lot, including streams, lakes, roadside ditches. TopographyfDrainage Features 1. Outline of any stream, wetland, lake, closed depression, or other water feature (including any required buffer width) 2. Location of all steep slopes, landslide hazard areas, and coal mine hazard areas (including buffers) 3. Location of all existing and proposed drainage easements, ditches, swales, pipes, etc. 4. Location of all critical areas as shown on any recorded critical areas notice on title. D.7.3.3 SAMPLE SMALL SITE ESC PLAN All sites are required to control erosion and contain sediment. The planning and use of ESC measures will be illustrated for a single family residence. Although the specifics of any lot will differ from those shown here, the process will be similar. The first step in the process is to determine whether the site is eligible to use the Small Site ESC requirements. This evaluation and the following materials are usually included in the drainage assessment that accompanies the Small Site ESC Plan. The proposed house is to be placed on an existing J.69-acre lot (see Figure D.7.3.A). Impervious surfaces are the roof, a driveway, and a parking area. The total proposed impervious surface is 6,950 square feet as determined from the residential site plan layout of residence and driveway (the site plan provides the base map for the Small Site ESC Plan). The amount exceeds 2,000 square feet but falls below the 10,000- square-foot limit for Small Project Drainage Review. Therefore, a Small Site ESC Plan is applicable. The proposal is not in a basin plan area or critical drainage area that might contain clearing limits. However, a portion of a wetland and an erosion hazard area have been identified on the site, and their approximate locations are shown in Figure D.7.3.A. While neither the wetland and its buffer, nor the erosion hazard area would be disturbed during construction, the locations of these critical areas must be verified. Approximately the southern 2/3 of the site will be cleared. Trees and other native vegetation will be left intact along the northern edge, near the street. Buffers will be maintained around the wetland and erosion hazard areas, respectively. The site slopes towards the street. In order to prevent erosion and to encourage sedimentation, the following BMPs are used: J. Clearing will be minimized to the extent possible, and clearing limits will be marked by fencing or other means on the ground. 1124/2005 2005 Surface Water Design Manual-Appendix D D-86 D.7.3 SUBMITTAL REQUIREMENTS 2. Water will be routed around the erosion hazard area and around the steep section of the driveway by constructing an interceptor dike or ditch that will intersect and direct water away to the east of the site. 3. Water will be filtered before it reaches the wetland. Silt fencing or other perimeter protection will be placed along slope contours at the limits of clearing in the vicinity of both the wetland and the erosion hazard area. 4. A rocked construction entrance will be placed at the end of the driveway. S. Mulch will be spread over all cleared areas of the site when they are not being worked. Mulch will consist of air-dried straw and chipped site vegetation. Other cover methods that prevent erosion may also be installed. The BMPs shown in Figure D.7.3.A must be installed as clearing progresses. For example, the rock construction entrance must be installed as soon as the path for the driveway has been cleared. Additional ESC measures must be installed if the ones proposed above prove insufficient. 2005 Surface Water Design Manual -Appendix D 1/24/2005 D-87 SECTION D.7 SMALL SITE ESC I 1/24/2005 FIGURE D.7.3.A SAMPLE SMALL SITE ESC PLAN ~. PROPERTi LINE ----- 5T. CENiERLINE ----- COH-rOUR HETLAND SlEEP SLOPE (40%+)~ OfFSITE DRAINAGE BENCHMARK, fiRE l-4YDRANT 400' AT BASEl \ - APPLICANT: Malene Mc.Resident. <bOO Nr: Z Street SornetoWfl, HA. ~H~··llI (20(,) 5SS-121;::- PROJECT PARCEL NO . ..: 322700 PROJECT ADDRESS-7SFI NE Q Street (prop=e:d) S~tOwn, NA. 98111 SECTIONITOW,NSI-iIP/RANGiE, .32-27-00 ELEV. 440' APPROX. AREA TO BE CLEARED. FLAG NET LAND EDGE t"il 5.AS.B. -rAPE ALL EXPOSED SOILS NILL 8£ MULCl-lED HHEN t·lDT BElhlG WORKED. MARK WEAIR "1(; v.l.1 S.A5.B. fErKf'-, SQ, FT. -------------CL NE Q ST~. ----------- I 2005 Surface Water Design Manual ~ Appendix D D-88 D.8 REFERENCE SECTION D.S REFERENCE SECTION This reference section provides materials useful in developing erosion and sediment control plans and for effectively implementing erosion control measures in the field. In order to make the Erosion and Sediment Control Standards a stand alone booklet, several key components relating to erosion and sediment control found in the Sur/ace Water Design Manual are repeated in this section. 1. ESC maintenance report 2. Standard ESC plan notes 3. Recommended construction sequence 4. References. D.8.1 ESC MAINTENANCE REPORT DDES may require a written record of all maintenance activities to be kept to demonstrate compliance with the Maintenance Requirements (Section D.S.4). A standard ESC Maintenance Report is provided on the next page. Copies of the ESC Maintenance Report must be kept on site throughout the duration of construction. 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-89 SECTION D.8 REFERENCE SECTION ESC MAINTENANCE REPORT Performed By: Date: Project Name: DOES Permit #: Clearing Limits Damage OK Problem Visible OK Problem Intrusions OK Problem Other OK Problem Mulch Rills/Gullies OK Problem Thickness OK Problem Other OK Problem Nets/Blankets Rills/Gullies OK Problem Ground Contact OK Problem Other OK Problem Plastic Tears/Gaps OK Problem Other OK Problem Seeding Percent Cover OK Problem Rills/Gullies OK Problem Mulch OK Problem Other OK Problem Sodding Grass Health OK Problem Rills/Gullies OK Problem Other OK Problem Perimeter Protection including Silt Fence Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Brush Barrier Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Vegetated Strip Damage OK Problem Sediment Build-up OK Problem Concentrated Flow OK Problem Other OK Problem Construction Entrance Dimensions OK Problem Sediment Tracking OK Problem Vehicle Avoidance OK Problem Other OK Problem Wheel Wash Dimensions OK Problem Sed build up or tracking OK .. Problem Other OK Problem Construction Road Stable Driving Surf. OK Problem Vehicle Avoidance OK Problem Other OK Problem Sediment Trap/Pond 1124/2005 2005 Surface Water Design Manual-Appendix D D-90 D.8.1 ESC MAINTENANCE REPORT Sed. Accumulation OK Problem Overtopping OK Problem InletJOutlet Erosion OK Problem Other OK Problem Catch Baslnflnlet Protection Sed. Accumulation OK Problem Damage OK Problem Clogged Filter OK Problem Other OK Problem Interceptor Dike/Swale Damage OK Problem Sed. Accumulation OK Problem Overtopping OK Problem Other OK Problem Pipe Slope Drain Damage OK Problem Inlet/Outlet OK Problem Secure Fittings OK Problem Other OK Problem Ditches Damage OK Problem Sed. Accumulation OK Problem Overtopping OK Problem Other OK Problem Outlet Protection Scour OK Problem other OK Problem Level Spreader Damage OK Problem Concentrated Flow OK Problem Rills/Gullies OK Problem Sed. Accumulation OK Problem Other OK Problem Dewatering Controls Sediment OK .. Problem Dust Control Palliative applied OK Problem Miscellaneous Wet Season Stockpile OK Problem Other OK Problem Comments: Actions Taken: Problems Unresolved: 2005 Surface Water Design Manual-Appendix D 1/24/2005 D-91 SECTION D.S REFERENCE SECTION D.8.2 ST ANDARD ESC PLAN NOTES 1/24/2005 The standard ESC plan notes must be included on all ESC plans. At the applicant's discretion, notes that in no way apply to the project may be omitted; however, the remaining notes must not be renumbered. For example, if ESC Note #3 were omitted, the remaining notes should be numbered 1, 2, 4, 5, 6, etc. I. Approval of this erosion and sedimentation control (ESC) plan does not constitute an approval of permanent road or drainage design (e.g., size and location of roads, pipes, restrictors, channels, retention facilities, utilities, etc.). 2. The implementation of these ESC plans and the construction, maintenance, replacement, and upgrading of these ESC facilities is the responsibility of the applicantlESC supervisor until all construction is approved. 3. The boundaries of the clearing limits shown on this plan shall be clearly flagged by survey tape or fencing, if required, prior to construction (SWDM Appendix D). During the construction period, no disturbance beyond the clearing limits shall be permitted. The clearing limits shall be maintained by the applicantlESC supervisor for the duration of construction. 4. Stabilized construction entrances shall be installed at the beginning of construction and maintained for the duration of the project. Additional measures, such as constructed wheel wash systems or wash pads, may be required t ensure that all paved areas are kept clean and track out to road right of way does not occur for the duration of the project. 5. The ESC facilities shown on this plan must be constructed prior to or in conjunction with all clearing and grading so as to ensure that the transport of sediment to surface waters, drainage systems, and adjacent properties is minimized. 6. The ESC facilities shown on this plan are the minimum requirements for anticipated site conditions. During the construction period, these ESC facilities shall be upgraded as needed for unexpected storm events and modified to account for changing site conditions (e.g. additional cover measures, additional sump pumps, relocation of ditches and silt fences, perimeter protection etc.) as directed by King County. 7. The ESC facilities shall be inspected daily by the applicant/ESC supervisor and maintained to ensure continued proper functioning. Written records shall be kept of weekly reviews of the ESC facilities. 8. Any areas of exposed soils, including roadway embankments, that will not be disturbed for two consecutive days during the wet season or seven days during the dry season shall be immediately stabilized with the approved ESC methods (e.g., seeding, mulching, plastic covering, etc.). 9. Any area needing ESC measures that do not require immediate attention shall be addressed within seven (7) days. 10. The ESC facilities on inactive sites shall be inspected and maintained a minimum of once a month during the dry season, bi-monthly during the wet season, or within twenty four (24) hours following a stonn event. 11. At no time shall more than one (1) foot of sediment be allowed to accumulate within a catch basin. All catch basins and conveyance lines shall be cleaned prior to paving. The cleaning operation shall not flush sediment-laden water into the downstream system. 12. Any permanent retention/detention facility used as a temporary settling basin shall be modified with the necessary erosion control measures and shall provide adequate storage capacity. If the facility is to function ultimately as an infiltration system, the temporary facility must be rough graded so that the bottom and sides are at least three feet above the final grade of the permanent facility. 13. Cover measures will be applied in conformance with Appendix D of the Surface Water Design ManuaL 2005 Surface Water Design Manual -Appendix D D-92 D.8.2 STANDARD ESC PLAN NOTES 14. Prior to the beginning of the wet season (Oct. I), all disturbed areas shall be reviewed to identify which ones can be seeded in preparation for the winter rains. Disturbed areas shall be seeded within one week of the beginning of the wet season. A sketch map of those areas to be seeded and those areas to remain uncovered shall be submitted to the DDES inspector. D.8.3 RECOMMENDED CONSTRUCTION SEQUENCE A detailed construction sequence is needed to ensure that erosion and sediment control measures are applied at the appropriate times. A recommended construction sequence is provided below: I. Hold the pre-construction meeting. 2. Post sign with name and phone number of ESC supervisor (may be consolidated with the required notice of construction sign). 3. Flag or fence clearing limits. 4. Install catch basin protection, if required. 5. Grade and install construction entrance(s). 6. Install perimeter protection (silt fence, brush barrier, etc.). 7. Construct sediment ponds and traps. 8. Grade and stabilize construction roads. 9. Construct surface water controls (interceptor dikes, pipe slope drains, etc.) simultaneously with clearing and grading for project development. 10. Maintain erosion control measures in accordance with King County standards and manufacturer's recommendations. II. Relocate erosion control measures, or install new measures so that as site conditions change, the erosion and sediment control is always in accordance with the King County Erosion and Sediment Control Standards. 12. Cover all areas that will be un worked for more than seven days during the dry season or two days during the wet season with straw, wood fiber mulch, compost, plastic sheeting, or equivalent. 13. Stabilize all areas within seven days of reaching final grade. 14. Seed, sad, stabilize, or cover any areas to remain unworked for more than 30 days. 15. Upon completion of the project, stabilize all disturbed areas and remove BMPs if appropriate. D.8.4 REFERENCES Goldman, S.l., Jackson, K., and Bursztynsky, T.A. 1986. Erosion and Sediment Control Handbook. McGraw-Hill Book Company, New York, New York. King County Dept. of Public Works. 1993. Guidelines for Bank StabilizationProjects. Surface Water Management Division, Seattle, Wash. Metropolitan Washington Council of Governments. 1990. Performance of Current Sediment Control Measures at Maryland Construction Sites. Washington, D.C. Prepared by T.R. Schueler and 1. Lugbill. Horner, R.R., Guedry, 1., and Kortenhof, M.H. 1990. Highway Construction Site Erosion and Pollution Control Manual. Washington State Transportation Center, Seattle, Wash. and Washington State Dept. of Transportation, Olympia, Wash. Report No. W A-RD 200.2. 2005 Surface Water Design Manual-Appendix D 1124/2005 D-93 GEOTECHNICAL ENGINEERING STUDY For JESSIE GLEN PRELIMINARY PLAT 116TH AVENUE SE & 120TH AVENUE SE RENTON, KING COUNTY, WASHINGTON Prepared For JPS HOLDING, LLC 18124 RNIERA PLACE SW SEATTLE, WA 98166 Prepared By Pacific Geo Engineering, LLC 831177THPLSW LYNNWOOD, WASHINGTON 98037 PGE PROJECT NUMBER 050996 September 19, 2005 September 19,2005 JPS HOLDING, LLC 18124 RIvIera Plaee SW Seattle, Washington 98166 Attn.: Mr. Joe Singh Re: Dear Mr. Singh: Geotechnical Engineering Study Proposed Jessie Glen Preliminary Plat 116th Avenue SE and 120th Avenue SE Renton, King County, Washington PGE Project No. 050996 As per the request of Laura Cociasu of ESM, Pacific Geo Engineering, LLC (PGE) has completed a geotechnical engineering study at the proposed development to be located at Renton. The purpose of this study was to determine the groundwater table, pond berm slope, and the pavement sections. This study was accomplished in general accordance with our proposal No. 58144, dated September 1,2005, and was granted to proceed by written authorization ofMr. Joe Singh, on September 8,200S. Site Location & Descriptions The general location of the site is shown on the Vicinity Map, Figure 1. The project site is located within a region dominated by residences. The site is currently vacant and covered with scattered to dense small to large trees, bushes, and sbrubs. Based on our visual observations, in general, the site is relatively level with minor undulations across the site. Field Investigation We explored the surface and subsurface conditions at the project site on September 8, 200S. SIX (6) test pits were excavated to depths of about 5 to 13 feet below the existing grades, three (3) of which were excavated at the proposed storm pond area to depths of about 13 feet below the existing grades. The test PIts were completed using a backhoe provlded by a subcontractor. The specific number, locations, and depths of the test pits were selected in relation to the existing and proposed site features, 831177th PL SW. Lynnwood. WA. 98037 (Tel) 425-918-1428. (Fax) 425-918-1401 Jessie Glen Preliminary Plat 116th & 120th Avenue SE Project No. 050996 September 19,2005 Page 2 of 8 Pacific Geo Engineering. LLC Geotechnical Engineering ConsultatIOn 8. Inspection accessibility, underground utility conflicts, purpose of evaluation, and budget considerations. The proposed locahons of the test pits were estimated by measuring from existing site features and should be considered accurate only to the degree implied by the method used. The approximate test pit locations are shown on the Site & Exploration Plan, Figure 2. A professional geotechnical engineer from our firm observed the excavations, continually logged the subsurface conditions in each test pit, collected representative bulk samples from different soil layers, and observed pertinent site features. Samples were designated according to the test pit number and depth, stored in watertight plastic containers. The samples that were not used for laboratory testing will be retained for 30 days from the date of submission of this report. Further storage or transfer of samples can be made at the client's expense upon written request. Results of the field investigation are presented on the test pit logs, which are presented on Pages A-I through A-3 of Appendix A. The final logs are modified based on the interpretation of our field logs, laboratory test results, and visual examination of the samples in the laboratory. Laboratory Testing The bulk samples were visually classified in the field and laboratory, and later on supplemented by grain size analysis to evaluate the general physical properties and engineering characteristics of the soils encountered. Sieve analysis was performed on one selected sample in accordance with the ASTM D-422 and D-2487 procedures. The result of the sieve analysis with the uses classifications of the soil is presented on the grain-size distribution graph (Figure B-ll enclosed in Appendix B. Engineering Evalnation The results from the field and laboratory tests were evaluated and engineering analyses were performed to provide pertinent information and recommendations on the following geotechnical aspects of the proposed site development: o Soil and groundwater condittons of the site. o Detention pond berm slope. o Asphalt pavement thickness. Jessie Glen Preliminary Plat I 16th & 120th Avenue SE Project No. 050996 September 19,2005 Page 3 of8 Soil & Grouudwater Conditions Pacific Geo Engineering, LLC Geotechnical Engineering Consultation & Inspection Based on the results of our field explorations, we believe that glacial till exists at shallow depths across the entire site with weathered silty sandy gravelly soils over it. The average thickness of the topsoil was found to be about 12 inches, which was composed of light brown silt with roots and organics. The topsoil was underlain by weathered brown silty sandy gravelly soils, which continued upto 2.5 feet below the existing grades. This deposit was then underlain by gray glacial tills consisted of silty sandy gravel. The till was occasionally cemented. This deposit was contmued up to the bottom of the test pits. In general, the weathered soils were medium dense and moist in condition, whereas the tills were very dense and slightly moist in condition. The preceding discussion on the subsurface conditions of the site is intended as a general review to highlight the major subsurface stratification features and material characteristics. For more complete and speCIfic information at individual test pit locations, please review the Test Pit Logs (Pages A-I through A-3) included in Appendix A. These logs include soil descriptions, stratification, and location of the samples and laboratory test data. It should be noted that the stratification lines shown on the individual logs represent the approximate boundaries between various soil strata; actual transitions may be more gradual or more severe. The subsurface conditions depicted in the logs are for the test pit locations indicated only, and it should not necessarily be expected that these conditions are representative at other locations of the site. Neither groundwater nor seepage or mottling was encountered in the test pits within their tennination depths. It is to be noted that seasonal fluctuations in the groundwater elevations and the presence of perched water in the upper weathered soils may be expected in the amount of rainfall, surface runoff, and other factors not apparent at the time of our exploration. Typically, the groundwater levels rise higher and the seepage flow rates increase during the wet winter months in the Puget Sound area. The possibility of groundwater level fluctuations and the presence of perched water mllst be considered when designing and developing the proposed pond at this site. Jessie Glen Preliminary Plat 116th & 120th Avenue SE Project No. 050996 September 19, 2005 Page 4 of8 Engineering Recommendations Pond Berm Slopes Pacific Geo Engineering, LLC Geotechnical Engineering Consultation & Inspection Based on the nature ofthe soils in this site the pond benns could be laid on 2H: I V slopes. Clearing and Grubbmg Initial site preparation for construction of paved areas should include stripping of vegetation and topsoils from the site. Based on the topsoil thickness encountered at our test pit locations, we anticipate topsoil stripping depths of about 12 inches, however, thicker layers of topsoil may be present in unexplored portions of the site. Stripped vegetation debris should be removed from the site. Stripped organic topsoils will not be suitable for use as structural fill but may be used for future landscaping purposes. Subgrade PreparatIOn After the site clearing and site stripping, cut and fill operations can be initiated to establish desired pavement grades. Any exposed subgrades that are intended to provide direct support for the pavement and/or require new fills should be adequately proofrolled to evaluate their conditIOns. Proofrolling should be done with a loaded dump truck or front-end loader under the supervision of a geotechnical engineer from PGE, and/or must be probed with aT-probe by the geotechnical engineer to identify the presence of any isolated soft and yielding areas and to verify that stable subgrades are achieved to support the pavements. If any sub grade area ruts and pumps excessively and cannot be stabilized in place by compaction, the affected soils should be over-excavated completely to finn and unYleldmg suitable bearing materials, and replaced with new structural fills to desired final subgrade levels. If the depth of overexcavation to remove unstable soils becomes excessive, a geotextile fabric, slleh as Mirafi SOOX or equivalent in conjunction with granular structural fills may be considered. Such decision should be made on-site by a geotechnical engineer from PGE during the actual construction of the proj ecL Reuse ofGn-Site Soils The on-site near surface weathered soils contain fines of approximately 12°/". Due to such fines content, this material IS considered moderately sensitive to changes in moisture content and therefore, may be adversely affected by wet weather conditions. A detailed discussion on this issue is provided latter on in thiS report. However, this soil may be considered suitable for use as structural fills dunng the dry weather penods. Jessie Glen Preliminary Plat 116th & 120th Avenue SE Project No. 050996 September 19,2005 Page 5 or8 Structural Fill Pacific Geo Engineering, LLC Geotechnical Engineering Consultation & Inspection Structural fill is defined as non-orgamc soil, free of deleterious materials, and well-graded and free-draining granular material, with a maximum of 5 percent passing the No. 200 sieve by weight, and not exceedmg 6 inches for any individual particle. A typical gradation for structural fill is presented in the followmg table. Structural Fill U.S. Standard Sieve Size Percent Passing by Dry Weight 3 inch 100 % inch 50 -100 No.4 25 -65 No. 10 10 -50 No. 40 0-20 No. 200 5 Maximum' Other materials may be suitable for use as structural fill provided these are approved by a geotechnical engineer from PGE. Such materials typically include clean, well-graded sand and gravel (pit-run); clean sand; various mixtures of gravel; crushed rock; controlled-density-fill (CDF); and lean- mix concrete. Recycled concrete derived from crushed parent material is also useful for structural fill provided tl1lS material is thoroughly crushed to a size deemed appropriate by the geotechnical engineer (usually less than 2 inches). The top 12 inches of compacted structural fill and all underlying fill should have a maximum 3-inch particle diameter unless specifically approved by a geotechnical engineer from PGE. fill Placement and Compaction Requirements Structural fills under the pavement subgrades should be placed in uniform loose lifts not exceedmg 12 inches in thickness, and compacted to a minimum of95% of the soil's laboratory maximum dry density as determined by ASTM Test Designation D-1557 (Modified Proctor) method, to produce a firm and unyielding surface. The fills should be moisture conditioned such that its final moisture content at the time of compaction should be within about 2 percent of its optimum moisture content, as determmed by thts ASTM method. If field density tests indicate that the last lift of compacted fills has not been achieved the required percent of compaction or the surface is pumping and weaving under loading, then the fills should be Jessie Glen Preliminary Plat I I 6th & 120th Avenue SE Project No. 050996 September 19,2005 Page 6 of8 Pacific Geo Engineering, LLC Geotechnical Engmeering Consultation & Inspection scarified, moisture-conditioned to near optimum moisture content, re-compacted, and re-tested prior to placing addittonal lifts. Wet Weather Construction Due to the moderate fines content in the near surface weathered soils this soil should be conSidered moisture sensitive when wet. During wet weather periods, typically between October and May, increases in the ma, sture content of this soil can cause significant reduction in the soils strength and support capabilities. In addition, this soil when become wet may be slow to dry and thus significantly retard the progress of grading and compaction activities. It will, therefore, be advantageous to perform the earthwork construction activities in this site during the dry season, typically between July and September, so that earthwork costs can be significantly reduced over wet weather construction. The earth contractor must use reasonable care during site preparation and excavation so that the subgrade soils are remain firm, unyielding, and stable, particularly during wet weather conditions. If the construction takes place during the wet weather, and should the near surface weathered soils become wet and disturbed, and cannot be adequately compacted it may be necessary to adopt some remedial measures to cnhance the sub grade conditions in this site. The contractor should include a contingency in the earthwork budget for this possibility. The appropriate remedial measure be best determined by PGE dunng the actual construction of the project. In the event earthwork takes place during the wet season, we recommend that special precautionary measurements should be adopted to minimize the impact of water and construction activities on the moisture sensitive soils. It is recommended that earthwork be progressed part by part in small sections to minimize the soil's exposure to wet weather. Traversing of construction equipment can cause considerable disturbance to the exposed subgrades, therefore, should be restricted within the specific drive areas. This will also prevent excessive widespread disturbance of the subgrades. Construction of a new working surface from an advancing working surface could be used to avoid trafficking the exposed sub grade soils. Any excavations or removal of unsuitable soils should be immediately followed by the placement of backfill or pavement. At the end of each day, no loose on-site soils and exposed sub grades be left uncompacted or properly tamped, which will help seal the subgrade and thereby to minImize the potential for moisture infiltration into the underlying layers of fills or sub grades. Pavement Thlckness All pavement subgrades be prepared as described above. Depending on the final grading plan, we assume that the pavement subgrades should either be comprised of adequately proofrolled competent undisturbed native soil, or be comprised of a minimum of one foot of granular structural fill that is compacted adequately. Jessie Glen Preliminary Plat 116th & 120lh Avenue SE Project No, 050996 September 19, 2005 Page 7 of 8 Pacific Geo Engineering, LLC Geotechnical Engineerino Consultation & Inspection We assumed that the traffic would mostly consist of passenger cars, which is typical for a residentlal community. Two types of pavement sections may be considered for such traffic, the minimum thickness of which are as follows: • 2 inches of Asphalt Concrete (AC) over 2 inches of Crushed Surface Top Course (CSTC) over a 6 inches of Granular Subbase, or • 2 inches of Asphalt Concrete (AC) over 4 inches of Asphalt Treated Base (A TB) material. The 1998 Standard Specifications for Washington State Department of Transportation (WSDOT) and American Public Works Association (APWA) should be applicable to our recommendations that aggregate for AC should meet the Class-B grading requirements as per WSDOT Standard Specifications 9-03.8(6). For the CSTC, we recommend using imported, clean, crushed rock, per WSDOT Standard Specifications 9-03.9(3). For the lmtreated base course (CRB), we recommend using Bank run per WSDOT Standard Specifications 9-03.19. For the ATB, the aggregate should be consistent with WSDOT Standard Specifications 9-03.6 (2). For the granular subbase course, we recommend using imported, clean, well-graded sand and gravcl, such as Ballast or Gravel Borrow per WSDOT Standard SpCClficatlons 9-03.9(1) and 9-03.14, respectively. Long-term performance of the pavement will depend on its surface drainage. A poorly-drained pavement section will deteriorate faster due to the infiltration of the surface water into the subgrade soils and thereby reducing their supporting capability. Therefore, we recommend that using a minimum surfacing drainage gradient of about 1% to minimize this problem and to enhance the pavement performance. Also, regular maintenance of the pavement be considered by sealing surface cracks that may occur during the life of the pavement. Report Limitations The recommendations submitted in this report are based on the information available from ESM, and the subsurface infonnation available from this study. If there are any revisions to the plans for this project or if traffic volume assumed for such development changes or if deviations from the subsurface conditions noted in this geotechnical report are encountered during constTuction, PGE should be notified immediately to determine if changes in the pavement recommendations are required. If PGE is not notified of such changes, PGE will not be responsible for the impact of those changes on the project. The geotechnical engineer warrants that the assumptions, recommendations, specifications, or professional advice contained herein have been made in accordance with the generally accepted professional geotechnical engineer practices in the local area. No other warranties are implied or expressed. Jessie Glen Preilininary Plat 1 1 6th & 120th Avenue SE Project No. 050996 September 19,2005 Page 8 of8 Pacific Geo Engineering, LLC GeDtechnical Engineering. ConsuitatJOn & Inspectian This report has been prepared for the exclusive use of JPS Holding, and their design consultants for the specific application to the proposed development in Renton, Washington. We appreciate the opportunity to perform this geotechnical study and look forward to continued participation during the design and construction phase of this project. If you have any questions pertainmg to this report, or if we may be of further service, please do not hesitate to call us at 425-918- 1428 or 425-218-9316. Respectfully submitted, Pacific Geo Engineering, LLC Santanu Mowar, MSCE, PE Principal Attachments: Figure I Figure 2 Appendix A Appendix B Vicinity Map Site & Exploration Plan Soil Test Pit Logs Laboratory Test Result D,\CiI::OTECI1N1CAL \2005-proj\050996Jessie Glen Rp! !EXPIRES 0/-01-Db Project No: 050996 Date: September 19, 2005 Drawn by: SM Client: JPS Holding, LLC VICINITY MAP Not to Scale PROJECT .J essie Glen Preliminary Plat 116th Ave SE & 120th Ave SE Renton, Pierce Co., Washington Pacific Geo Enqineerinq,LLc Geotechnical Engineering, Consufting & Inspection Figure No.1 SCALE:'· - 1"""1 I f1I-"~~"""" i I"l«'''' " WI. ROAC\D, " m"~.f' " ,/ lSI.IBAC~)' L~ 10"' '~'fj f>Z9~y j ~~,,'O IJ ~' ., .' ,0 O· .to ,. • SIGHT DISTANCE 1161H A'{f $F I ROAD A (MINOR NITERl&j PESIGH SI'EtD: 45 WPt! ~HG SICHf ~ SlOP'I"INC SIQfT DISlN!a:: R(0UftD: 620' REQUIR£l); 400' ~ )1!12()' PR(M)ll): >400" I l·lRtiH ~ I / 120IH A'tf Sf I BOOJ I>. (NEKiHROf!HOOQ CD!! ECTORI !lESICH SP£[Il:. 35 IFH E)fl(RI tIC SIGHT OIST NICE; :;JIJPf'lNG SIGHT tlIS1.'HCL ~~~~_L". ~~ .0 O' ./ «," REQUIl(D:. 490' REQUI!EIl:. 250' ~ >4!1O' f'RCI'I'l)(n)l5O' T =1 L,'Z A/W ~!'DOIro ","e",," r""'O ,~.M';, ,/ I ' ". ~ -.' h -------jlf-!j~ I " • , ~ 1 ~ v", ""-" ~ WI 0 A ,;~ ~ w' , ffi~o'" A: -.' >~ / , " " $0 .' " J Project No.: 050996 "'.... ""'''"~ 11fT ~~~Tro Date: September 19,2005 Drawn By: SM Client: JPS Holding, LLC ~~ SITE PLAN & EXPLORATION PLAN Not to Scale PROJECT Jessie Preliminary Plat 116th Ave SE & 120th Ave SE Renton, King Co., Washington Pacific Geo Enqineerinq,LLc Geotechnical Engineering, Consulting & Inspection Figure 2 ! , Pacific Geo Enqineerinq,LLC Jessie Glen Preliminary Plat Project No. 050996 Geotechnical Engineering Consultation & Inspection Sept 19, Z005 Page A-I SOIL TEST PIT LOGS TEST PIT -1 Date of Excavation: 09/08/05 Depth, Ft. USCS Soil Description Sample No.1 Moisture -#200 % Depth, Ft. Content % 0-1 Topsoil: 12" thk. Lt. Bm. Silt wi Roots and Organics I -2.5 GM Weathered Brown Silty Sandy Gravel SII2 10.5 12. I Moist, Med. Dense 2.5 -7 SP Gray Silty Sandy Gravel (Glacial Till) 8216 6.1 S1. Moist, Y. Dense V. Hard digging was encountered in this deposit Note: Test pit was tenninated at approximately 7 feet below the existing ground surfaces (bgs). No groundwater or seepage was encountered within the exploratory depth. No mottling was noticed within the exploration depth. No caving was noticed within the exploration depth TEST PIT -2 Date of Excavation: 09108/05 Depth, Ft. lJSCS Soil Description Sample No.1 Moisture -#200 % Depth, Ft. Content % 0-1 Topsoil: 12" thk. Lt. Brn. Silt wi Roots and Organics , I -2.5 GM Weathered Brown Silty Sandy Gravel Moist, Med. Dense 2.5 -5 SP Gray Silty Sandy Gravel (Glacial Till) SI. Moist. Y. Dense V. Hard digging was encountered in this deposit Note: Test pit was tenninated at approximately 5 feet below the existing ground surfaces (bgs). No groundwater or seepage was encountered within the exploratory depth. No mottling was noticed within the exploration depth. No caving was noticed within the exploration depth Jessie Glen Preliminary Plat Project No. 050996 Sept. 19, 2005 Page A-2 Pacific Geo Enqineerinq,LLC Geotechnical Engineering Consultation & lnspection 1---TEST PIT -3 Date of Excavation: 09/08/05 Depth, Ft. USCS Soil Description Sample No.1 Moisture -#200 % Depth, Ft. Content % 0-1 Topsoil: 12" thk. Lt. Bm. Silt wi Roots and Organics I -2.5 GM Weathered Brown Silty Sandy Gravel S1/2 9.8 Moist, Med. Dense 2.5 -13 SP Gray Silty Sandy Gravel (Glacial Till) S2110 4.2 SI. Moist, V. Dense V. Hard digging was encountered in this deposit Note: Test pit was terminated at approximately 13 feet below the existing ground surfaces (bgs). No groundwater or seepage was encountered within the exploratory depth. No mottling was noticed within the exploration depth. No caving was noticed within the exploration depth , I TEST PIT -4 Date of Excavation: 09/08/05 Depth, Ft, USCS Soil Description Sample No.! Moisture -#200 % Depth, Ft. Content % 0-I Topsoil: 12" thk. Lt. Bm. Silt wi Roots and Organics 1 -2.S GM Weathered Brown Silty Sandy Gravel Moist, Med, Dense 2.5 -12 SP Gray Silty Sandy Gravel (Glacial Till) SI. Moist, V. Dense V, Hard digging was encountered in this deposit Note: Test pit was terminated at approximately 12 feet below the existing ground surfaces (bgs). No groundwater or seepage was encountered within the exploratory depth, No mottling was noticed within the exploration depth, No caving was noticed within the exploration depth 1 Jessie Glen Preliminary Plat Project No. 050996 Sept. 19,2005 Page A-3 ! Depth, Ft. USCS 0-1 I -2.5 GM 2.5 -13 SP I -' Pacific Geo Engineering,LLC Geotechnical Engineering, Consultation & Inspection TEST PIT -5 Date of Excavation: 09/08/05 Soil Description Sample No.1 Moisture -#200 % Depth, Ft. Content '10 Topsoil: 12" thk. Lt. Bm. Silt w/ Roots and Organics Weathered Brown Silty Sandy Gravel Moist, Med. Dense Gray Silty Sandy Gravel (Glacial Till) SI. Moist, V. Dense V. Hard digging was encountered in this deposit Note: Test pit was terminated at approximately 13 feet below the existing ground surfaces (bgs). No ground\vater or seepage was encountered within the exploratory depth. No mottling was noticed within the exploration depth. No caving was noticed within the exploration depth [- TEST PIT -6 Date of Excavation: 09/08/05 Depth, Ft. USCS Soil Description Sample No.1 Moisture -#200 % Depth, Ft. Content % 0-1 Topsoil: 12" thk. Lt. Bm. Silt wi Roots and Organics I -2.5 GM Weathered Brown Silty Sandy Gravel Moist. Med. Dense 2.5 - 5 SP Gray Silty Sandy Gravel (Glacial Till) SI. Moist, V. Dense V. Hard digging was encountered in this deposit Note: Test pIt was terminated at approximately 5 feet below the existing ground surfaces (bgs). No groundwater or seepage was encountered within the exploratory depth. No mottling was noticed within the exploration depth. No caving was noticed within the exploration depth Particle Size Distribution Report < s , , , , , , ~ s ~ < ~ ~ 80 -l ___ ;----------, , 70 I i ! i , i , , ! n:: w 60f+-+-+~ T - ',I' ,---, , 1:1 , " , , , , , - -'1-' ; '"'i-I-, --+i-ri ,! ~ 40 1--1',--'" -"1\ II: : I ,I '\. --r---,:--+++11, H, rlc-,:: +-'~IC-, ~,-I'+,:I "1--, +-+--l+I+t-I,j"I,~ \,+-i--:i+8-H-I 30 * I ! I ! t ", , :: t ... 11 '-" II:, I " .. ~;-f II~' T+i+t' +10+ -i :,' J r '''';'--;-'1+8+++-I!-I--it+t-t++---I o 11 III I 'I J i I 500 100 10 1 0,1 0.01 0.001 % GRAVEL % COBBLES CRS, FINE 0,0 39.1 1-7 SIEVE PERCENT SPEC: SIZE FINER PERCENT 3.0 in. 100,0 2.5 ill. 88,5 2 in. 85,1 1.5 in. 70,1 I in. 66,8 3/4 In, 60.9 #4 53.2 #10 4% #40 39,7 #100 20,2 #200 12,1 (no specification provided) GRAIN SIZE -mm CRS, I 3,6 I PASS? (X:NO) % SAND % FINES MEDIUM FINE SILT I 9.9 I n6 12.1 Soil Description Silty gravel with sand USCS= GM Atterberg Limits LL= Coefficients D60-18,1 D15= 0,100 C c= Classification AASHTO= Remarks PI= CLAY Sample No.: S-I Location: Test Pit -! Source of Sample: Native Soil Date: 09-08-05 Elev./Depth: 2 feet Client: JPS Holding, LLC Pacific Geo Engineering, LLC Project: Jessie Glen Preliminary Plat GeotechnlclIl Engineering, Consultation & Inspection Project No: 050996 Plate B-1