HomeMy WebLinkAboutC11055-01 ■ ■ ■ COUGHLIN PORTER LUNDEEN ■ ■ ■ ■ ENGINEERING REPORT Preliminary Technical Information Report Maplewood Heights Elementary School Covered Play Structure March 28,2012 PREPARED FOR: Renton School District No. 403 7812 S 124`h Street Seattle,WA 98178 (425) 204-4479 Contact: Stuart Shusterman A�'+ PREPARED THROUGH: McGranahan Architects Sy' 21 1 1 Pacific Avenue #100 IC Q ®��A�p�p� �� Tacoma,WA 98402 Phone: (253) 383-3084 r �. . Contact: Kris Stamon PREPARED BY: SsIONAL E�G�� COUGHLINPORTERLUNDEEN �1-W 413 Pine Street, Suite 300 Seattle,Washington 98101 P: 206/343-0460 ENTON Contact: Keith Kruger CITY OF Fi 1=tECEiVED MAP, 2 9 2012 BUILDING DIVISION TECHNICAL INFORMATION REPORT AND HYDROLOGIC ANALYSIS Maplewood Heights Elementary School Covered Play Structure Coughlin Porter Lundeen Project No.C 1 10055-01 March 28,2012 TABLE OF CONTENTS Section Page I. PROJECT OVERVIEW................................................................................................................................................1 GENERALDESCRIPTION....................................................................................................................................................... 1 EXISTINGCONDITIONS....................................................................................................................................................... 1 PROPOSED DRAINAGE SYSTEM............................................................................................................................................. 1 II. CONDITION AND REQUIREMENTS SUMMARY....................................................................................2 TASK I -STUDY AREA DEFINITION AND MAPS....................................................................................................................2 KING COUNTY SURFACE WATER MANAGEMENT DESIGN MANUAL CORE REQUIREMENTS:.................................................2 SPECIAL REQUIREMENTS:......................................................................................................................................................2 PROJECT SPECIFIC REQUIREMENTS:.......................................................................................................................................2 III. OFF-SITE ANALYSIS.........................................................................................................................................3 TASK I —STUDY AREA DEFINITION AND MAPS....................................................................................................................3 TASK2-RESOURCE REVIEW................................................................................................................................................3 TASK3-FIELD INSPECTION.................................................................................................................................................3 TASK 4-DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS...........................................................................3 UPSTREAMANALYSIS...........................................................................................................................................................3 DOWNSTREAMANALYSIS....................................................................................................................................................3 TASK 5-MITIGATION OF EXISTING OR POTENTIAL PROBLEMS............................................................................................4 IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN.....................5 EXISTING SITE HYDROLOGY(PART A).................................................................................................................................5 DEVELOPED SITE HYDROLOGY PART B).............................................................................................................................5 PERFORMANCE STANDARDS AND FLOW CONTROL SYSTEM(PARTS C AND D)...................................................................5 WATERQUALITY SYSTEM PART E).....................................................................................................................................6 SPILLCONTROL...................................................................................................................................................................6 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN...............................................................................7 STANDARD REQUIREMENTS BASED ON KCSWDM AND SAO):.........................................................................................7 ON-SITE CONVEYANCE.......................................................................................................................................................7 VI. SPECIAL REPORTS AND STUDIES..............................................................................................................8 VII. OTHER PERMITS................................................................................................................................................9 Vill. CSWPP ANALYSIS AND DESIGN..............................................................................................................10 STANDARDREQUIREMENTS............................................................................................................................................... 10 IX. BOND QUANTITY, FACILITY SUMMARIES,AND DECLARATION OF COVENANT............11 X. OPERATION AND MAINTENANCE MANUAL.....................................................................................12 STANDARDMAINTENANCE............................................................................................................................................... 12 COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School i Renton,Washington LIST OF FIGURES Figure I —TIR Worksheet-Section I Figure 2—Vicinity Map-Section I Figure 3 —Soils Map-Section 3 Figure 4—Off-Site Analysis Map&Table-Section 3 Figure 5 — Existing Site Hydrology-Section 4 Figure 6— Developed Site Hydrology-Section 4 LIST OF TABLES Table 1: Existing Site Conditions Area Breakdown..............................................................................................................5 Table 2: Developed Site Conditions Area Breakdown........................................................................................................5 Table3: Peak Flow Rate Summary........................................................................................................................................6 Table4: Flow Control BMP Summary..................................................................................................................................6 COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School ii Renton,Washington SECTION I I. PROJECT OVERVIEW General Description The following Technical Information Report(TIR) provides the technical information and design analysis required for developing the Drainage and Temporary Erosion and Sedimentation Control Plan (TESC)for the Maplewood Heights Elementary school covered play structure project. The stormwater design for the project was based on the requirements set forth in the 2009 King County Surface Water Design Manual (KCSWDM) (See Figure I — Technical Information Report Worksheet). Maplewood Heights Elementary school is located at 130 Jericho Avenue SE in Renton,Washington. The site is bounded by NE I"Street to the north, SE 136`h Street to the south, Lyons Avenue NE to the east,and Jericho Avenue SE to the west. The site is relatively flat and slopes from north to south. Total site area is approximately 8.7 acres. (See Figure 2— Vicinity Map). The school building and parking areas are located in the north and west sides of the campus;the hard surface play areas are along the south and west sides of the school building and the fields are located in the southern portion of the campus. Total existing impervious surfaces are approximately 4.2 acres. A forested area is located along the eastern side of the site. Existing Conditions The play structure will be located east of the existing school building and north of the baseball field. The existing project area for the new play structure is covered with vegetation. Storm water runoff from the project area flows towards the south across the existing grass field. There is an existing sub-drainage system below the footprint of the new play structure. This system was installed during campus renovations which occurred in 1996 to dry out this portion of the existing play field. Proposed Drainage System The proposed project includes adding a covered play structure with 6,480 square feet of new roof area and 930 square feet of new paving. This structure will be located over an existing vegetated area. Storm water mitigation per City of Renton storm water standards will be required. BMP's will be installed to mitigate peak flows from the new development per the King County Surface Water Design Manual (KCSWDM) as amended by the City of Renton. Specifically,a gravel trench will be used for basic flow dispersion per Section C.2.4.4 as required by Section C.1.3.2 of the Surface Water Design Manual. COUGHLINPORTERLUNDEEN Maplewood Heights Elementary School 1 Renton,Washington KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND PROJECT ENGINEER DESCRIPTION Project Owner RE W M NI SENft L DWRIct- Project Name M,4P�ewaa� H�'jGk�S PCB► �f►rtu Phone (�/.2-5) o2e_/- -/'/7q DDES Permit# cJv� _ Address 7l/.2 .9. /.21V S77 Location Township ZSN K&Wl ok Gv-A q?/?8 Range S�E Project Engineer K,&7M KQU(rr72 Section (S' Company L'c9&(&N&/1y ?CWT`AW I-ONDE'W Site Address 130 7P_7p)C/JO AM SE Phone 20 3c -0 0 Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS ❑ Landuse Services ❑ DFW HPA ❑ Shoreline Subdivison / Short Subd. / UPD ❑ COE 404 Management ® Building Services ❑ DOE Dam Safety ❑ Structural M/F/Commerical / SFR Rockery/Vault/ ® Clearing and Grading ❑ FEMA Floodplain ❑ ESA Section 7 ❑ Right-of-Way Use ❑ COE Wetlands ❑ Other ❑ Other Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review Full / Targeted / Type (circle one): ull / Modified / (circle): Large Site mall Site Date (include revision 3/;ZP/o20/Z. Date (include revision 31.2dI-•20a dates): dates): Date of Final: Date of Final: Part 6 ADJUSTMENT APPROVALS Type (circle one): Standard / Complex / Preapplication / Experimental / Blanket Description: (include conditions in TIR Section 2) N/A Date of Approval: 2009 Surface Water Design Manual 1/9/2009 1 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes /0 Describe: Start Date: Completion Date: Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : N&AICA.tyt 6 Special District Overlays: Drainage Basin: L.OwZk 06*t)uw R I bh? Stormwater Requirements: Part 9 ONSITE AND ADJACENT SENSITIVE AREAS ❑ River/Stream ❑ Steep Slope ❑ Lake ❑ Erosion Hazard ❑ Wetlands ❑ Landslide Hazard ❑ Closed Depression ❑ Coal Mine Hazard ❑ Floodplain ❑ Seismic Hazard ❑ Other ❑ Habitat Protection Part 10 SOILS Soil Type Slopes Erosion Potential A a,C S" !tom 61 ❑ High Groundwater Table (within 5 feet) ❑ Sole Source Aquifer ❑ Other ❑ Seeps/Springs ❑ Additional Sheets Attached 2009 Surface Water Design Manual 2 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE LIMITATION /SITE CONSTRAINT ❑ Core 2—Offsite Analysis ❑ Sensitive/Critical Areas ❑ SEPA ❑ Other Ll ❑ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area Threshold Discharge Area: name or description) Core Requirements (all 8 apply) Discharge at Natural Location Number of atural Discharge Locations: Offsite Analysis Level: 1 2 / 3 dated: MC,t %,2VII Flow Control Level: 1 / 2 / 3 or Exemption Number 42 (coK-fekyw—w Incl. facility summary sheet Small Site BMPs 4b/_t N Conveyance System Spill containment located at: N Erosion and Sediment Control ESC Site Supervisor: Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private Public If Private, Maintenance Log Required: e / No Financial Guarantees and Provided: Yes / o Liability &'C L -lry Water Quality Type: Basic / Sens. Lake / Enhanced Basicm / Bog (include facility summary sheet) or Exemption No. _I Landscape Management Plan: Yes / o Special Requirements as applicable) Area Specific Drainage Type: CDA/SDO/ MDP/ BP/ LMP/Shared Fac. one Requirements Name: Floodplain/Floodway Delineation Type: Major / Minor / Exemption / one 100-year Base Flood Elevation (or range): Datum.- Flood Protection Facilities Describe: N Source Control Describe landuse: NIA (comm./industrial landuse) Describe any structural controls: N/A 2009 Surface Water Design Manual 1/9/2009 3 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Oil Control High-use Site: Yes o Treatment BMP: Maintenance Agreement: Yes No with whom? Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION ® Clearing Limits ® Stabilize Exposed Surfaces ® Cover Measures ® Remove and Restore Temporary ESC Facilities ® Perimeter Protection ® Clean and Remove All Silt and Debris, Ensure ❑ Traffic Area Stabilization Operation of Permanent Facilities ❑ Sediment Retention ❑ Flag Limits of SAO and open space preservation areas ❑ Surface Water Collection Other ❑ Dewatering Control Dust Control ❑ Flow Control Part 14 STORMWATER FACILITY DESCRIPTIONS Note: Include Facility Su mary and Sketch Flow Control Type/Description Water Quality Type/Description 1 ❑ Detention N�iq ❑ Biofiltration �1A ❑ Infiltration ❑ Wetpool ❑ Regional Facility ❑ Media Filtration ❑ Shared Facility ❑ Oil Control ❑ Flow Control ❑ Spill Control BMPs ❑ Flow Control BMPs ❑ Other ❑ Other 2009 Surface Water Design Manual 1/9/2009 4 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS ❑ Drainage Easement ❑ Cast in Place Vault ® Covenant ❑ Retaining Wall ❑ Native Growth Protection Covenant ® Rockery > 4' High ❑ Tract ❑ Structural on Steep Slope ❑ Other ❑ Other Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. 3/-2 71-20/2 Signed/Date 2009 Surface Water Design Manual 1/9/2009 5 COUGHLIN PORTER LUNDEEN STRUCTURAL CIVIL SEISMIC ENGINEERING z rT' NortwAet dth streat Nm1he&it 41h ebmt 7 P1W i1 14m -.. aw}1'QwTr a NE 3rd P1 R Shv.+'n&To4•v 'y T%L 3r1J Ct n „_ Mat Vatket C ' z r •aE 31d sr 'VI rn I-3rd SQ $ Cr 3�, = m Sx y in ,n NE 2hd St lb �+ - %-1 ct z ' z s& sa t:E 151.�i rn ,; ��' s 2►od St SE 2rd St sF ztie Ct Q t3E�5rrd PI ,, vL 1.�6tr ;� 5E 7tr�d Pt o 0.0 i'7Project it SE ., W r^ u, 1 PI ' 5 cn �3 P, S4- 13!A" P1 m } W CI+ W a z J K H K a J 0 u Figure 2 Vicinity Map V Project: Renton Elementary School Covered Play Area Designed By: - Date: 3/26/12 Project No: C 1 10055-03 Client: Checked By: - Sheet: I of I 413 PINE STREET • SUITE 300 SEATTLE,WA 98101 P.206/343-0460 F:206/343-5691 www.cplinc.com m n -i O Z II. CONDITION AND REQUIREMENTS SUMMARY Task I -Study Area Definition and Maps This section will address the requirements set forth by the Core and Special Requirements listed in Chapter I of the KCSWDM. King County Surface Water Management Design Manual Core Requirements: I. Discharge at the Natural Location (1.2.1): Existing drainage conditions will not be altered as a result of this project. Storm water runoff from the new play structure will be dispersed through gravel trenches and sheet flow across the existing play field towards the south. 2. Off-site Analysis(1.2.2):A Level I downstream analysis has been performed, see Section 3. 3. Flow Control(1.2.3):This project will not provide a flow control facility since the difference between the existing(forested) condition and the developed site is less than 0.1 cfs. See Section IV for more information. 4. Conveyance System (1.2.4): Refer to Section V. No new conveyance systems are proposed for this project. Runoff from the roof will be routed to a gravel trench designed for basic flow dispersion. 5. Erosion and Sedimentation Control(1.2.5): Refer to Section IX. Erosion and sedimentation control will include Construction Stormwater BMP's to meet the construction runoff standard equal to or greater than the Department of Ecology standard. 6. Maintenance and Operations(1.2.6): Refer to Section XI.The proposed storm drainage system will be owned,operated and maintained by the owner. 7. Financial Guarantees and Liability(1.2.7): The owner and contractor will obtain all necessary permits prior to the beginning of construction. The Renton School District,as a public agency, is not required to provide bonds. 8. Water Quality(1.2.8): Refer to Section IV.E.Water quality treatment is not required for this project since no new pollution generating surfaces are proposed. Special Requirements: Special Requirement#I. Other Adopted Area-Specific Requirements Section 1.3.1 • Critical Drainage Areas (CDAs): Not Applicable • Master Drainage Plans (MDPs): Not Applicable. • Basin Plans (BPs): Lower Cedar River • Lake Management Plans (LMPs): Not Applicable. • Shared Facility Drainage Plans (SFDPs): Not Applicable. Special Requirement#2. Flood Hazard Area Delineation,Section 1.3.2: Not Applicable Special Requirement#3. Flood Protection Facilities,Section 1.3.3: Not Applicable Special Requirement#4. Source Controls,Section 1.34: Not Applicable Special Requirement#5. Oil Control: Not Applicable Project Specific Requirements: There are no additional requirements for this portion of the project. Design and construction will abide by requirements set forth in these documents and King County as amended by the City of Renton. COUGHLINPORTERLUNDEEN Maplewood Heights Elementary School 2 Renton,Washington III. OFF-SITE ANALYSIS Task I -Study Area Definition and Maps The study area was mapped using the King County GIS iMAP tool. Task 2- Resource Review a) Adopted Basin Plans Lower Cedar River b) Floodplain/floodway(FEMA) Maps Not in 100-yr floodplain c) Off-site Analysis Reports None available d) Sensitive Areas Folio Not applicable e) Drainage Complaints and Studies See Below f) Road Drainage Problems Not available g) King County Soils Survey: See Figure 4 h) Wetland Inventory Maps: No Wetlands are indicated on iMap. i) DOE's Section 303d List of Polluted Waters Lake Washington j) KC Designated Water Quality Problems Not Available k) Critical Drainage Area Maps: Not in Critical Drainage Area. Soil Conditions On-site soils are classified as Alderwood Gravely Sandy Loam (AgC) per King County Soil Survey maps (See Figure 3). Task 3 - Field Inspection A Site visit was made to gather information including a Level I Downstream Analysis. This field visit took place October 4,2011. Refer to Task 4, Level I Downstream Analysis below for more information. Task 4 - Drainage System Description and Problem Descriptions Maplewood Heights elementary school site is fairly level,with a gentle slope from the north to the south at about I percent. The northern and western portions of the site are developed with the elementary school building and supporting infrastructure such as parking lots,fire access drives,and hard surface play areas. The southern and eastern portions are landscaped with native vegetation and play fields. Upstream Analysis The upstream area contributing to surface runoff is limited on the vegetated area immediately upstream of the project area. Downstream Analysis Storm water runoff from the project site flows towards the south where it is collected in a shallow ditch located at the southern edge of the field. This ditch flows from the east to the west to the southwest corner of the property and discharges to the storm conveyance system located in Jericho Avenue SE. A storm pipe conveys storm water across SE 136`h Street to the south east corner of the intersection of Jericho Avenue SE and SE 136`h Street towards the south and discharges to a ditch located on the east side of 144`h Avenue SE. Storm water flows along a vegetated ditch on the east side of 144`h Avenue SE for the remainder of the %, mile distance downstream of the project site.See Figure 4, Downstream Table and Map. COUGH LINPORTERLUND E EN Maplewood Heights Elementary School 3 Renton,Washington Task 5 - Mitigation of Existing or Potential Problems There are two recorded drainage complaints within '/< mile of the campus,both of which are closed. • Maplewood Heights: No.2004-0978,closed on 2/14/2005. • King County Park: No.2004-101 1,closed on 1 1/8/1996. COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School 4 Renton,Washington coil Map—King uunty ArCa, vJashiliywn (Maplewood Heights Soil Map) o m N N 564050 564100 564150 564200 564250 564300 564350 564400 564450 564500 47'29'0" r 0 47°29'0" N N ALAL N x 1, r O O Q d O � a N g. m k � r fn � h fn N Q +y'fa'S, R � • e O k • �`o � e +. i N N O � O Qf w u M N N eF 47°28'50" 47'28'50" 564050 564100 564150 564200 564250 564300 564350 564400 564450 564500 m Map Scale:12.240 it printed on A size(8.5"x 11")sheet. M m N N Meters N A 0 30 60 120 180 Feet 0 100 200 400 600 Natural Resources Web Soil Survey 3/27/2012 Conservation Service National Cooperative Soil Survey Page 1 of 3 Maplewood Heights 4' ti 1STC� i tZ NEISTCT 1 y� --r►EEIs7FI 4 s ;V.ELIAI t L k r R; y4 j - o „r- r.tg �.17h " � - -2 GT _ �; - - - 452.4 _- id, -� .283 acres V Qf Alai. ( �gT ST ( - - S: '1 { _ ;l•l 2008 King County COMMENTS:Downstream Map The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice.King County makes no representations or warranties,express or implied,as to accuracy,completeness,timeliness,or rights to the use of such information. This document is not intended for use as a survey product.King County shall not be liable for any general,special,indirect,incidental,or consequential I. damages including,but not limited to,lost revenues or lost profits resulting from the use or misuse of the information contained on this map.Any sale of R,2M King County this map or information on this map is prohibited except by written permission of King County. LIN Date:3/2 7120 1 2 Source:King County NAP-Property Information(http://www.metrokc.gov/GIS/iMAP) OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT#2 Basin: NAPlaume N,&(6NP'1' Subbasin Name: Subbasin Number: Symbol Drainage Drainage Slope Distance Existing Potential Observations of field l Component Type, Component from site Problems Problems inspector, resource Name, and Size Description discharge reviewer, or resident see map Type:sheet flow,swale, drainage basin,vegetation, % /<ml=1,320 ft. constrictions, under capacity, ponding, tributary area,likelihood of problem, stream,channel, pipe, cover,depth,type of sensitive overtopping,flooding,habitat or organism overflow pathways,potential impacts pond;Size:diameter, area,volume destruction,scouring, bank sloughing, surface area sedimentation, incision,other erosion SHen- �Gow l_awN l 3 3o FTC sm'(ccew AlWY 79 SJ Fl- L61c.44,ft A-r tDe,'nZ p�Pff �2",e��� 8ss FT ©PO4 rwrcH T1�cecc v o�� 2 1320 Fi DW&- v&Z;.&U e(v VCA �� 1 i9iz009 SECTION IV IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Existing Site Hydrology(Part A) The existing project site is approximately 0.22 acres,which is currently vegetated ground cover. (See Figure 5— Existing Site Hydrology Map).A summary of the existing site cover characteristics is shown below. Table 1:Existing Site Conditions Area Breakdown Development Areas Area(Ac) Forested Area 9,435 0.22 The site is located within the Lower Cedar River Drainage Basin,an area designated as a Conservation Flow Control Area and Basic Water Quality Area by King County code.There are no known designated landslide hazard zones or flood plains zones located onsite. Maplewood Heights elementary school site is fairly level,with a gentle slope from the north to the south at about I percent. The northern and western portions of the site are developed with the elementary school building and supporting infrastructure such as parking lots,fire access drives,and play areas. The southern and eastern portions are landscaped with native vegetation and play fields. The project site is located east of the hard surface play area and north of the baseball field along the eastern boundary. Existing land cover includes dense vegetation and lawn. Developed Site Hydrology(Part B) The project development will include a covered play structure with a footprint of 7,410 square feet. Roof downspouts will be routed to gravel trench designed for basic flow dispersion to mitigate the on-site storm water runoff per City of Renton standards. A summary of the developed project area is shown below. Table 2:Developed Site Conditions Area Breakdown Development Areas Area Ac Roof Area 6,480 0.15 Site Paving 930 0.02 Vegetated Area 2,025 0.05 Total 9,435 0.22 Performance Standards and Flow Control System (Parts C and D) Flow control will not be required for this project based on the peak flow exception#2 under Section 1.2.3.1(B)of the City of Renton Surface Water Design Manual. The 100-year peak flow rate of the developed site,with storm water mitigation BMP's (basic flow dispersion,as described in Flow Control and Discharge Requirements) implemented as required, is less than 0.1 cfs more than the existing(forested) peak flow rate at the 100-year design storm event. The existing(forested) peak flow rate is 0.02 cfs;the developed peak flow rate is 0.09 cfs. The increase in the 100-year peak flow rate is therefore 0.07 cfs. Table 3 summarizes the 100-year peak flow rates for the existing and developed site area. COUGHLINPORTERLUNDEEN Maplewood Heights Elementary School 5 Renton,Washington Table 3:Peak Flow Rate Summary Area Flow Control BMP Modeled Area 100-yr Peak Development Land Cover Ac BMP Credit Flow cfs Existing Vegetated 0.22 N/A N/A 0.22 Ac. Forest 0.02 0.15 Basic Flow 50% 0.075 Ac Imp. Roof Dispersion 0.075 Ac Perv. Developed Paving0.02 N/A N/A 0.02 Ac Imp. 0.09 Landscape 0.05 N/A N/A 0.05 Ac Perv. Flow Control and Discharge Requirements Total site area is approximately 8.70 acres,of which approximately 4.4 acres (or approximately 50%of the total site) will be impervious after the play structure is installed. Since the site is larger than 22,000 square feet,and the development will result in an impervious coverage of more than 45%,this site is considered a Large Lot, High Impervious Site,per Section 5.2.1.3.of the surface water design manual. Large lots with an impervious ratio between 45%and 65%must mitigate,at a minimum,surface water runoff from the lesser of the following areas: 1. 20%of the entire site (8.7 ac x 0.20) = 1.74 acres (75,790 square feet) 2. 40%of the target impervious surface((0.15+0.02)x 0.40) =0.07 acres (3,050 square feet) Flow mitigation is therefore required for at least 40%of the area from the play structure. A gravel trench designed for basic flow dispersion will be installed to mitigated roof runoff. Per C.2.4.4,a maximum of 3,500 square feet may be mitigated by a 50 LF gravel trench. The roof area is 6,480 square feet, requiring a minimum of(2)46 LF gravel trenches. Two 50 LF gravel trenches will be installed for the roof area. Table 4 summarizes the BMP's used to satisfy the flow mitigation requirements. (See Figure 6—Developed Site Hydrology Map) Table 4:Flow Control BMP Summary Target Surface Mitigated Areas BMP Length Min. Required Provided Required FProvided Roof Area 3,050 6,480 Gravel Trench (2)46 LF 1 (2) 50 LF Water Quality System (Part E) Standard Requirements The project will not add any pollution generating impervious surfaces. The roof area is constructed out of materials other than lead,copper,or zinc. There will be no new parking or driving surfaces created from this project. Spill Control Spill control is required for projects constructing or replacing onsite pipe systems that receive runoff from pollution- generating surfaces such as parking lots (1.2.4-G). Spill control measures are therefore not required for this project. COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School 6 Renton,Washington MGS FLOOD PROJECT REPORT Program Version: MGSFIood 4.12 Program License Number: 200610002 Run Date: 03/17/2012 8:06 AM Input File Name: Peak Flow Exemption.fld Project Name: Renton Elementary Schools- New Covered Play Areas Analysis Title: 100-year Peak Flow Exemption Comments: Maplewood Heights Elementary School PRECIPITATION INPUT Computational Time Step (Minutes): 60 Extended Precipitation Timeseries Selected Climatic Region Number: 14 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station 961044 Puget East 44 in MAP Evaporation Scale Factor 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User)*************** **********************WATERSHED DEFINITION *********************** ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Existing Forested Site ---------- -------Area(Acres) -------- Till Forest 0.220 Till Pasture 0.000 Till Grass 0.000 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 0.000 Impervious 0.000 ---------------------------------------------- Subbasin Total 0.220 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 3 ---------- Subbasin : Vegetation ---------- -------Area(Acres)-------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.050 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 0.000 Impervious 0.000 ---------------------------------------------- Subbasin Total 0.050 ---------- Subbasin : Mitigated Roof Area ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.075 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 0.000 Impervious 0.075 ---------------------------------------------- Subbasin Total 0.150 ---------- Subbasin : Site Paving ---------- -------Area(Acres)-------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.000 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 0.000 Impervious 0.023 ---------------------------------------------- Subbasin Total 0.023 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 3 Number of Links: 1 ***********Compliance Point Results************* Scenario Predeveloped Compliance Subbasin: Existing Forested Site Scenario Postdeveloped Compliance Link: Developed Project Site *** Point of Compliance Flow Frequency Data*** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr(Years) Discharge (cfs) Tr(Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 5.553E-03 2-Year 0.036 5-Year 9.087E-03 5-Year 0.048 10-Year 0.012 10-Year 0.058 25-Year 0.015 25-Year 0.075 50-Year 0.018 50-Year 0.081 100-Year 0.020 100-Year 0.085 / ° kI1FWY1 IIYF S 15 TWN 23N mewl Nu rzsa®r�rrrc - c r nc "\ �`-J crav os ME \ \ • O'�KYIN Ol4 R A Er!-�W Existing Forested Area r Maplewood ,. Elementary School Exiting CBEr r IX w ° "raw r cIfoV m c rY av(p.a Z / Ernc ax • • —vNP,BiOo .a PMw4T / I rar wlmwiee. ° Existing Sub-Drainage ° System n Existing flow 6B Path (TYP) Existing Play Field (pOQ]F III N OGL X' 1"= 50' Figure 5 ° Existing Site Hydrology Map COUGHLIN PORTERLUNDEEN EN09 " I N r- - s S 5 TWN 23N' k N O O EE ` 4 Jr am AM Er Existing Forested a E' Area Maplewood Elementary School I Paving Covered Play Structure r Exiting CB �. ol 50' Gravel Ir low Trench or ar i 50' Gravel °16 Trench 0 25' Catch Basin am , *Vegetated EFra. 'lf Flowpath / Existing flow Path (TYP) Existing Play Field110 �- 1"= 50' i Figure 6 0 Developed Site Hydrology Map COUGHLIN PORTERLUNDEEN o0 SECTION V V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN This section discusses the criteria that will be used to analyze and design the proposed storm conveyance system. Conveyance calculations will be provided with the full drainage submittal. Standard Requirements(based on KCSWDM and SAO): 1. Facilities must convey the 100-year flow without overtopping the crown of the roadway, flooding buildings, and if sheet flow occurs it must pass through a drainage easement. No new conveyance facilities will be installed for this project. 2. New pipe systems and culverts must convey the 2S-year flow with at least O.S feet of freeboard. (1.2.4-1). No new pipe systems will be installed as part of this project. 3. Bridges must convey the 100-year flow and provide a minimum of two feet, varying up to six feet, of clearance based on 25%of the mean channel width. (1.2.4-2)(4.3.5-6). NIA This project does not propose a bridge. 4. Drainage ditches must convey the 25-year flow with 0.5 feet of freeboard and the 100-year flow without overtopping. (1.2.4-2). No new drainage ditches are proposed as part of this proposed development. 5. Floodplain Crossings must not increase the base flood elevation by more than 0.01 feet[41(83.C)]and shall not reduce the flood storage volume[37(82.A)]. Piers shall not be constructed in the FEMA floodway. [41(83.F.1)]. There are no floodplain crossings associated with the construction of this project. 6. Stream Crossings shall require a bridge for class I streams that does not disturb or banks. For type 2 and type 3 steams, open bottom culverts or other method may be used that will not harm the stream or inhibit fish passage. [60(95.B)]. There are no stream crossings associated with the construction of this project. 7. Discharge at natural location is required and must produce no significant impacts to the downstream property(1.2.1-1). Runoff from the play structure will flow towards the field,which is the natural discharge location. On-site Conveyance Existing Conditions: Storm water runoff sheet flows across the play fields to the south to the southern edge of the property. Developed Storm system description: Storm water runoff will continue to sheet flow across the play fields to the south to the southern edge of the property. Outfalls No outfalls are proposed for this project. Energy dissipation will occur in the proposed flow dispersion trenches. COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School 7 Renton,Washington m A O Z VI. SPECIAL REPORTS AND STUDIES Maplewood Heights Elementary School Covered Play Area Subsurface Exploration, Geologic Hazards,and Preliminary Geotechnical Engineering Report Associated Earth Sciences, Inc. February 17,2012 COUGHLINPORTERLUNDEEN Maplewood Heights Elementary School 8 Renton,Washington VII. OTHER PERMITS The project will obtain a development permit from the City of Renton,at a minimum, prior to construction. COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School 9 Renton,Washington SECTION VIII r r r� r� r r� r r r it rr rr r ■� �r rr r r r� r r� Vill. CSWPP ANALYSIS AND DESIGN This section lists the requirements that will be used when designing the TESC plan for this site, not included at this time. Standard Requirements Erosion/Sedimentation Plan shall include the following: 1. Facilities required include:stabilized construction entrance,sedimentation pond, interceptor swales, filter fabric fencing. (1.2.5-1). Construction will occur during the summer months. Existing pavement will be used for the stabilized construction entrance,catch basin protection will be installed in adjacent structures,and a compost filter berm will be placed along the downstream edge of construction. A sediment pond and interceptor swales will not be installed since they will remove more natural vegetation than would otherwise be required, thereby increasing the risk of transporting sediment downstream. 2. Timing-For the period between November 1 through March 1 disturbed areas greater than 5,000 square feet left undisturbed for more than 12 hours must be covered with mulch,sodding, or plastic covering. A construction phasing plan shall be provided to ensure that erosion control measures are installed prior to clearing and grading. (1.2.5-1). Not applicable:Construction will occur between June and September. 3. Planning-Plan shall limit tributary drainage to an area to be cleared and graded. Delineate dimension, stake and flog clearing limits(1.2.5-1). The clearing limits have been indicated on the TESC plan. Notes addressing this item have been placed on the civil engineering plans. 4. Revegetation-Revegetate areas to be cleared as soon as practicable after grading. (1.2.5-1). Notes addressing this item have been placed on the civil engineering plans. COUGHLINPORTERLUNDEEN Maplewood Heights Elementary School 10 Renton,Washington SECTION IX IX. BOND QUANTITY, FACILITY SUMMARIES,AND DECLARATION OF COVENANT The Renton School District is a public agency and is therefore not required to post a bond for this development. Facilities Summary Sheet is included. Declaration of Covenant is included. COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School 11 Renton,Washington KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL STORMWATER FACILITY SUMMARY SHEET DDES Permit Number (provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Overview: Project Name MA?zewo04 /4&c d-y PLAY -r ?2uuvrer Date Downstream Drainage Basins Major Basin Name CaW 1r1keX/r ( kUL-MN Immediate Basin Name Lot,tt CZ3AA0e g/acX Flow Control: Flow Control Facility Name/Number WA Facility Location If none, Flow control provided in regional/shared facility(give location) No flow control required Exemption number 2 "Plow Flot.v4 General Facility Information: Type/Number of detention facilities: Type/Number of infiltration facilities: ponds ponds vaults tanks tanks trenches Control Structure Location Type of Control Structure Number of Orifices/Restrictions Size of Orifice/Restriction: No. 1 No. 2 No. 3 No. 4 Flow Control Performance Standard L Rle t Ir 2009 Surface Water Design Manual 1/9/2009 1 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Live Storage Volume Depth Volume Factor of Safety Number of Acres Served Number of Lots Dam Safety Regulations(Washington State Department of Ecology) Reservoir Volume above natural grade Depth of Reservoir above natural grade Facility Summary Sheet Sketch All detention, infiltration and water quality facilities must include a detailed sketch. (11"x 17" reduced size plan sheets may be used) 2009 Surface Water Design Manual 1/9/2009 2 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL Water Quality: NIA Type/Number of water quality facilities/BMPs: biofiltration swale sand filter(basic or large) (regular/wet/or continuous inflow) sand filter, linear(basic or large) combined detention/wetpond sand filter vault(basic or large) (wetpond portion basic or large) sand bed depth (inches) combined detention/wetvault stormwater wetland filter strip storm filter flow dispersion wetpond (basic or large) farm management plan wetvault landscape management plan Is facility Lined? oil/water separator If so, what marker is used above (baffle or coalescing plate) Liner? catch basin inserts: Manufacturer pre-settling pond pre-settling structure: Manufacturer high flow bypass structure (e.g., flow-splitter catch basin) source controls Design Information Water Quality design flow Water Quality treated volume (sandfilter) Water Quality storage volume (wetpool) Facility Summary Sheet Sketch 2009 Surface Water Design Manual 1/9/2009 3 S 15 TWN 23N' N ORE Rrrl®Yl MI E r-� EraP I' Ef• Y Pff E a6s \� 1.; ) Rua r r/E'aatam i �' Y .M aa.�•.�• ronaE gr r o� m r o Existing Forested 'Er �r Area � r �J Maplewood =a saw Elementary School Paving \; Covered + ` Play a o E}!r,p► Structure Exiting CB 50' Gravel ,ao Trench "` ; � o !IC A ar -- 50' Gravel OS � Trench 25' Catch Basin Vegetated rrra as Flowpath nra> n Existing flow Path (TYP) �., aua r taus rsr .r,R.or..•�.• maESQr w a�a Existing Play Field 1"= 50' , tr �. o �o RECORDING REQUESTED BY AND WHEN RECORDED MAIL TO: DECLARATION OF COVENANT FOR MAINTENANCE AND INSPECTION OF FLOW CONTROL BMPS Grantor: Grantee: King County Legal Description: Additional Legal(s)on: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved King County(check one of the following) ❑ residential building permit, ❑ commercial building permit, ❑ clearing and grading permit, ❑ subdivision permit,or ❑ short subdivision permit for Application No. relating to the real property ("Property") described above,the Grantor(s),the owner(s) in fee of that Property,hereby covenants(covenant)with King County,a political subdivision of the state of Washington,and its municipal successors in interest and assigns("King County" and"the County",or"its municipal successor"),that he/she(they)will observe,consent to,and abide by the conditions and obligations set forth and described in Paragraphs 1 through 8 below with regard to the Property. Grantor(s)hereby grants(grant),covenants(covenant),and agrees(agree)as follows: 1 1. Grantor(s) or his/her(their) successors in interest and assigns ("Owners") shall retain, uphold, and protect the stormwater management devices, features,pathways, limits, and restrictions,known as flow control best management practices ("BMPs"), shown on the approved Flow Control BMP Site Plan for the Property attached hereto and incorporated herein as Exhibit A. 2. The Owners shall at their own cost, operate, maintain, and keep in good repair, the Property's BMPs as described in the approved Design and Maintenance Details for each BMP attached hereto and incorporated herein as Exhibit B. 3. King County shall provide at least 30 days written notice to the Owners that entry on the Property is planned for the inspection of the BMPs. After the 30 days, the Owners shall allow King County to enter for the sole purpose of inspecting the BMPs. In lieu of inspection by the County, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the BMPs and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the Director of the Water and Land Resources Division or its municipal successor in interest("WLR")within fifteen days of receiving the County's notice of inspection. Within 30 days of giving this notice, the Owners, or the engineer on behalf of the Owners, shall provide the engineer's report to WLR. If the report is not provided in a timely manner as specified above,the County may inspect the BMPs without further notice. 4. If King County determines from its inspection,or from an engineer's report provided in accordance with Paragraph 3, that maintenance, repair, restoration, and/or mitigation work is required for the BMPs,WLR shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (Work) required under Title 9 of the King County Code ("KCC"). WLR shall also set a reasonable deadline for completing the Work or providing an engineer's report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the County access to re-inspect the BMPs unless an engineer's report has been provided verifying completion of the Work. If the work is not completed 2 properly within the time frame set by WLR, King County may initiate an enforcement action. Failure to properly maintain the BMPs is a violation of KCC Chapter 9.04 and may subject the Owners to enforcement under the KCC, including fines and penalties. 5. Apart from performing routine landscape maintenance, the Owners are hereby required to obtain written approval from WLR before performing any alterations or modifications to the BMPs. 6. Any notice or approval required to be given by one party to the other under the provisions of this Declaration of Covenant shall be effective upon personal delivery to the other party, or after three (3) days from the date that the notice or approval is mailed with delivery confirmation to the current address on record with each Party. The parties shall notify each other of any change to their addresses. 7. This Declaration of Covenant is intended to promote the efficient and effective management of surface water drainage on the Property, and it shall inure to the benefit of all the citizens of King County and its municipal successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest and assigns. 8. This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and King County that is recorded by King County in its real property records. 3 IN WITNESS WHEREOF,this Declaration of Covenant for the Maintenance and Inspection of Flow Control BMPs is executed this day of 220 GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: to me known to be the individual(s)described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed,for the uses and purposes therein stated. Given under my hand and official seal this day of , 20 Printed name Notary Public in and for the State of Washington, residing at My appointment expires 4 S 5 TWW23N' N 5 0 0 S Existing Forested Area ; r Paving � R Maplewood ti Elementary School Covered Play Exiting CB Q Structure r.r � oRRu i� Q ' 50' Gravel Catch Basin o Trench d� R4R 25' Vegetated 50' Gravel ° Trench Flowpath Existing flow Path (TYP) Existing Play Field Maplewood Drainage Basin Map COUGHLIN PORTERLUNDEEN = � o X. OPERATION AND MAINTENANCE MANUAL Standard Maintenance Per standards set forth in the King County Surface Water Design Manual,the owner will maintain facilities. Sections of the King County Storm Water Management Design Manual outlining the Operations and Maintenance of these facilities have been included in this section on the following pages. COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School 12 Renton,Washington MAINTENANCE STANDARDS FOR PRIVATE DRAINAGE FACILITIES AT MAPLEWOOD ELEMENTARY COVERED PLAY AREA NO. I -GROUNDS(LANDSCAPING) Maintenance Defect Conditions When Maintenance is Results Expected When Component Needed Maintenance is Performed General Weeds Weeds growing in more than 20%of the Weeds present in less than (Nonpoisonous) landscaped area(trees and shrubs only). 5%of the landscaped area. Safety Hazard Any presence of poison ivy or other No poisonous vegetation poisonous vegetation. present in landscaped area. Trash or Litter Paper,cans, bottles,totaling more than I Area clear of litter. cubic foot within a landscaped area(trees and shrubs only)of 1,000 square feet. Trees and Damaged Limbs or parts of trees or shrubs that are Trees and shrubs with less Shrubs split or broken which affect more than than 5%of total foliage 25%of the total foliage of the tree or with split or broken limbs. shrub. Trees or shrubs that have been blown Tree or shrub in place free down or knocked over. of injury. Trees or shrubs which are not adequately Tree or shrub in place and supported or are leaning over,causing adequately supported; exposure of the roots. remove any dead or diseased trees. COUGH LINPORTERLUNDEEN Maplewood Heights Elementary School 13 Renton,Washington A