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HomeMy WebLinkAboutSWP273025R-302.5 C.E.S. NW In c. Civil Engineering & Surveying STORM DRAINAGE AND EROSION CONTROL REPORT RENTON WINDERMERE OFFICE BUILDING PREPARED FOR: ABBEY ROAD GROUP, LLC PO BOX 207 PUYALLUP, WA 98371 PREPARED BY: ERIC OEHLER, PROJECT ENGINEER C.E.S. NW, INC. 5308 - 12TH STREET E., SUITE B FIFE, WA 98424 (253) 922-1532 41p / - V' STORM DRAINAGE AND EROSION CONTROL REPORT FOR Renton Windermere Office Building Renton, Washington March 2002 Prepared for: Abbey Road Group, LLC P.O. Box 207 Puyallup, WA 98371 Prepared by: Eric Oehler, Project Engineer Approved by: A Seabrook Schilt, PE, Principal 3444552 NAL REPORT #01202.1 lmr= 10 / 27 This analysis is based on data and records either supplied to, or obtained by, CES NW INC. These documents are referenced within the text of the analysis. This analysis has been prepared utilizing procedures and practices within the standard accepted practices of the industry. PAO1202.1 \STORM REPORT 01202.doc TABLE OF CONTENTS PAGE 1.0 PROJECT OVERVIEW...............................................................................................................................1 1.1 PURPOSE AND SCOPE....................................................................................................................................1 1.2 PRE -DEVELOPED CONDITIONS......................................................................................................................1 1.3 DEVELOPED CONDITIONS..............................................................................................................................2 Figure1, TIR Work -sheet .............................................................................:........................................................3 Figure2, Site Location Exhibit...................................................................:........................................................6 Figure3, Basin Exhibits.....................................................................................................................................7 Figure4, Soil Exhibit..................................................................................:...................................................... 12 2.0 CONDITIONS AND REQUIREMENTS SUMMARY............................................................................13 3.0 OFFSITE ANALYSIS.................................................................................................................................13 3.1 DOWNSTREAM............................................................................................................................................13 4.0 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS AND DESIGN ............................14 4.1 EXISTING SITE HYDROLOGY (PART A) ................................................. : ...................................................... 14 4.2 DEVELOPED SITE HYDROLOGY (PART B)...................................................................................................14 4.3 HYDROLOGIC ANALYSIS (PART C) ..............................................................................................................14 4.4 FLOW CONTROL SYSTEM (PART D).................................... :................ :...................................................... 15 4.5 WATER QUALITY SYSTEM (PART E)........................................................................................................... 15 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN...........................................................................15 6.0 SPECIAL REPORTS AND STUDIES.......................................................................................................15 7.0 OTHER PERMITS......................................................................................................................................15 8.0 TESC ANALYSIS AND DESIGN..............................................................................................................15 9.0 BOND QUANTITIES, FACILITY SUMMARIES & DECLARATI'ON OF COVENANT..................13 9.1 BOND QUANTITY SHEETS...........................................................................................................................13 9.2 FLOW CONTROL AND WATER QUALITY FACILITY SUMMARY SHEET AND SKETCH.....................................20 9.3 DECLARATION OF COVENANT.............................................................. :......... .............................................. 26 10.0 MAINTENANCE AND OPERATIONS MANUAL.................................................................................27 Appendix "A" Core Requirements Memo P:\01202.1\STORM REPORT 0 1 202.doc 1.0 PROJECT OVERVIEW 1.1 Purpose and Scope This report accompanies the civil construction documents for the proposed Renton Windermere Office Building project as submitted to the City of Renton. This document provides site information and the analysis used for the storm drainage design. The 1990 King County Surface Water Design Manual (Revised November 1995), and the City of Renton addendum to that document, as well as City of Renton design standards establish the methodology and design criteria used for this project. 1.2 Pre -Developed Conditions The existing site consists of a rectangular shaped parcel totaling approximately 0.76- acres. Currently, there is an existing building occupying the site. A majority of the site is currently existing asphalt pavement and gravel surfaces. The perimeter of the site consists of existing landscape areas having a combination of conifer and deciduous trees and other types of overgrown vegetation. The site also has 2 existing driveway approaches to Northeast 4th Street, existing cement concrete extruded curb, exterior overhead area lights, utility poles, monitoring wells, and a 25-ft. tall steel post for sign advertisement. All existing surfaces feature will be demolished and removed as a result of the proposed project. Currently, the site consists of 0.53-acres of existing impervious surfaces, which is a combination of building, asphalt pavement, and concrete surfaces. PAO 1202. 1 \STORM REPORT 0 1 202.doc The site is bordered to the south by Northeast 0 Street, to the west by an existing 30-ft. easement to a multi -family apartment complex, to the' north by an existing multi -family apartment complex, and to the east by a commercial 'property all within the City of Renton. See Figure 2. The property generally slopes at between 1-10 percent in a southwesterly direction. Topographically, the site is situated such that offsite' stormwater drainage contributes a negligible amount of runoff to the site. There are no known existing onsite drainage problems associated with this site. The average site elevation is approximately 388-ft. Currently, stormwater drainage from a majority of the existing site is collected by 2 existing catch basins located both in the southwest ana northwest corners of the property. A third existing catch basin centrally located along the east property line collects a small amount of stormwater drainage from the eastern portion of the site. Once collected by the existing onsite stormwater conveyance system, stormwater drainage is then conveyed to the existing stormwater conveyance system located withiik Northeast 4th Street. The U.S. Soil Conservation Service maps of King County, Washington, have identified the soils in the location of the proposed project as Alderwood gravelly sandy loam (AgC). See Figure 4. 1.3 Developed Conditions The proposed project consists of the construction of a new 6,618 sq. ft. commercial office building. The proposed project will be accessed from Northeast 4th Street by a new 24-ft. wide cement concrete commercial driveway approach. The 2 existing driveway approaches to the site will both be demolished and removed. One of the existing 2 PAO 1202.1 \Report\STORM REPORT 01202.doc driveway approaches will be replaced with new cement concrete curb, gutter, and sidewalk, while the other driveway approach will be replaced by a combination of the new cement concrete driveway approach and new curb, gutter, and sidewalk. The proposed project will include new asphalt pavement for general site access and parking requirements. The proposed project will be complete with both cement concrete extruded curb and poured in place curbing, cement concrete sidewalks, combination cement concrete sidewalk and curbing, and interior and perimeter site landscaping. Pedestrian access will be provided to the site by a portion of the onsite sidewalks that will connect to the existing sidewalk along Northeast 4th Street. Disabled parking and a curb ramp will be provided onsite as required. A new sign will be provided onsite just to the east of the proposed cement concrete driveway approach. A designated location within the proposed parking area has been provided for a proposed dumpster/recycle area. Stormwater drainage from the proposed asphalt pavement parking area will be collected by catch basins located along the west side of the parking area. After collection by the proposed catch basins, stormwater drainage will be tightlined to the existing catch basin located in the southwest corner of the site. Onsite stormwater drainage will then be conveyed to the existing stornwater drainage system located within Northeast 4th Street. A proposed tightline conveyance system will be provided to convey the proposed roof/footing drain systems and any required yard drains to the previously mentioned catch basins. Due to proposed onsite grading, a small amount of perimeter landscaping along the west and, north property lines will bypass the proposed stormwater conveyance system. However, these bypass areas are currently bypassing the existing stormwater conveyance system without any known impacts to the adjacent properties. 3 PA01202.1 \.STORM REPORT 01202.doc Stormwater drainage flow control for the proposed project will not be provided as a result of the proposed project reducing the amount of impervious surface area from what currently exists. As previously mentioned, the existing site consists of 0.53-acres of impervious surfaces while the proposed project will create 0.47-acres of impervious surfaces. Thus, the amount of net new impervious surfaces has been reduced by 0.06- acres over what currently exists. Therefore, no stormwater detention facilities are required since impacts to the existing downstream stormwater conveyance system have been reduced as a result of the reduction in total impervious surface areas. Stormwater quality treatment will not be provided due to the net reduction of new impervious surfaces subject to vehicle traffic. Currently, the existing site consists of approximately 0.49-acres of asphalt pavement surfaces and the proposed project will consist of approximately 0.26-acres of new asphalt pavement. Therefore, as a result of the net reduction of impervious surfaces subject to vehicular traffic being reduced by 0.23-acres, no water quality treatment will be provided. However, the proposed catch basins will provide a level of water quality treatment by trapping sediments in the sump portion of the catch basin structure. 4 P:\01202.1\Report\STORM REPORT 01202.doc Figure 1, TIR Worksheet PA01202.1\STORM REPORT 01202.doc Page 1 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Project Owned Rem`{ -'Lom> t_LG Address P.,o.. OoSL 207 . P� ra��-�F' u: a R 8 3•1r Phone (zss��35-3�4G Project Engineer Company V•£-c', �1="' s•,st" Address Phone `j30� tZN ST �`� "'� 5g4z4- F--J Subdivision 0 Short Subdivision 0 Grading ® Commercial = Other Community Drainage Basin River Stream Critical Stream Reach Depressions/,$wales Lake 0 Steep Slopes 0 Lakeside/Erosion Hazard Q-v--t4T 0".1 Soil Type Slopes Project Name2-;-` t ` Location � � Township Z 3 ^t Range `6 ICE Section Cl Project Size 3: 0 0-7 t-Ir AC o- 1 b t Upstream Drainage Basin Size AC — O DOF/G HPA 0 COE 404 DOE Dam Safety 0 FEMA Floodplain 0 COE Wetlands Floodplain Wetlands Seeps/Springs High Groundwater Table 0 Groundwater Recharge Other Shoreline Management 0 Rookery 0 Structural Vaults 0 Other HPA Erosion Potential Erosive Velocities 0 Additional Sheets Attatched 1/90 Page 2of2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET REFERENCE Ch. 4 - Downstream Analysis Additional Sheets Attatched LIMITATION/SITE CONSTRAINT MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION Sedimentation Facilities EK Stabilize Exposed Surface Stabilized Construction Entrance 0 Remove and Restore Temporary ESC Facilities Perimeter Runoff Control © Clean and Remove All Silt and Debris Clearing and Grading Restrictions ® Ensure Operation of Permanent Facilities Cover Practices Flag Limits of NGPES Construction Sequence 0 Other Other 'Grass Lined Channel Tank Infiltration ® Pipe System Vault Depression 0 Open Channel Energy Dissapator 0 Flow Dispersal Dry Pond 0 Wetland 0 Waiver Wet Pond 0 Stream 0 Regional Detention Method of Analysis Vie- Compensation/Mitigation of Eliminated Site Storage Brief Description of System Operation P-a-ope(- � t> —, �4HT �-� �Sc�tLv,�..sPT � r>0Ak"lt41r— Facility Related Site Limitations 0 Additional Sheets Attatched Reference Facility Limitation Cast in Place Vault Other Retaining Wall 0 Rockery > 4' High 0 Structural on Steep Slope 0 Drainage Easement Access Easement Native Growth Protection Easement Tract Other I or a civil engineer under my supervision have visited the site. Actual ' site conditions as observed were incorporated into this worksheet and the-, oz�/ '� attatchments. To the best of my knowledge the information provided r here is accurate. sigm-&Dare Figure 2, Site Location Exhibit PA01202. I \STORM REPORT 01202.doc C.E.S. NWinc. Renton Windermere Office Building Civil Engineering & Surveving Phone: (253) 922-1532 5308 12th Street East Fax: (253) 922-1954 Suite B ceservices@cesnwinc.com Vicinity Mali Fife, WA 98424 www.cesnwinc.com aw Map by Thomas Guide Maps 02000 Figure 3, Basin Exhibits P:\0202.1\STORM REPORT 0 1 202.doc i'�yi a 4r X -N I z g ,.. m Ala2 �A I� ca m C i'c � N Z mG) % a v ca i r / I r \ 1 I o �o m -i c7 z II M p r- G-) S Z D CD c7 m W rn aC _-- z II r t CD X II p cn C p cn cn C fT1 r p O Cn rn co w n cn m m Z cn w z c� A � F!� II ri II cn a 03 w Z mom II a II II 70 o � a cn + � � m CD CD rq cn z CD o co M 0 N n II 0:p, w C-) -' c0 m a a a' CO m CDnNly ��mo c,4 rr-I r#-; cn v, CA p II 70 C7 n Z a n00 m zz II c-) II r1cl- 00 oo C)cfl o kG :K% Y!t )tY9.D 3kY! AX#w v m w m ic m �v m O mn ca w0 yw CT� E CD oo Project:WINDERMERE OFFICE BUILDING z m 0 ° Z 0 o m a. a C.F.S. 1'VW INC. W EXISTING IMPERVIOUS SURFACES EXHIBIT CII1IL ENGINEERING S SURVEYING -i co C 0 N Client:ABBEY ROAD GROUP, LLC CD N o N„ oN N W N o Cn m m K z Z cn 0 0 P.O. BOX 207, PUYALLUP, WA 98371 (253) 435-3699 5308 12TH ST. E SUITE 8 Bus: 253 922-1532 FIFE, WA 98424 Fax: �253� 922-1954 m O ao CO) H ea Piro xt,; 3! ix n f?4; f =' M c a v, ca <- IC Z rn m` I Mid: rn'. O z 0° z z II o II c N O C)o Z �+ c O 0�0 iv m co 70 Rrn �o m m � D rrS z0 C-)-000m ODc� II o N orCm to atn ; c mz�N Cn r F+Q m —I n C D .Z�7 II II O - II D Q M OoMD W U) Cn rn Dm D z O D D p II � cNo rr*m m 11 N D n N N O v m n C-) D z cmi) Z IZI D rn II 00 to co C7 N °O °o 0) rm cn z u � Y3FA'e?n ISY))N1: A SiLL :p !i: I.tiYPiitb.4 TLL JYA agx M M a = " m u v N G) a m �a .y i z rN o � M v w 0 b Z v m w m m m m m O N rn a o° v m C°o 0 w v�///�y�, P�°;8°t: WIhIDERMERE OFFICE-BUILDIaG m • p CD `� N /%/��/T// y Wes:. DEVELOPED BASIN MAP CIVIL ENG/NEER/NG & SURVEY/NG N = o N � U N , N = N Cllent: ABBEY ROAD GROUP, LLC N p w N 0 K z Z v> 0 0 P.O. BOX 207, PUYALLUP, WA 98371 (253) 435-3699 5308 12TH ST. E SUITE 8 Bus: 253 922-1532 FIFE, WA 98424 Fax: 253; 922-1954 R5E W 1/2 R�Uce Dr aCL ' 1 Fir Dr .`4 VW ST - r- 9a- - - 0cAm Z O W m a Z y c) rnCy =ME �nz �o mAa M 0 M O CO) m v ca m m m m ic m m m 0 mn m 1 0 Orm a (oo Project: WINDERMERE OFFICE BUILDING � � � Z % a `° C., ►. Nr�INC. W o W .. a DOWNSTREAM ANALYSIS MAP C/I1/L ENG/NEE9/NG & SURVEYING � N Client: ABBEY ROAD GROUP LLC CD PI)N m rov 4t. oo j N 4 co 3 Z Z (n 0 0 P.O. BOX 207, PUYALLUP, VVA 98371 (253) 435-3699 5308 12TH ST. E SUITE 8 Bus: 253 922-1532 FIFE, WA 98424 Fax: f 2533 922-1954 Figure 4, Soil Exhibit 12 P:\01202.I\STORM REPORT 01202.doc C.E.S. NW Inc. Renton Windermere Office Building CPO Engineering & Surveying Phone: (253) 922-1532 53 48 12th Street East Fax: (253) 922-1954 Suite B ceservices@cesnwinc.com USDA Soil Conservation Service Soil Map Fife WA 98424 www.cesnwinc.com Site z ZIR Not to Scale >rr" c i m g #lt� Ak, Map by USDA Soil Conservation Service ©1976 C.E.,S. NWInc. Civil Engineering & Surveying 5308 12th Street East Suite B Phone: (253) 922-1532 Fax: (253) 922-1954 ceservices@cesnwinc.com www.cesnwinc.com Renton Windermere Office Building USDA Soil Conservation Service Soil Description Alderwood gravelly sandy loam, 6 to 15 percent slopes (AgQ This soil is rolling. Areas are irregular in shape and range from 10 to about 600 acres in size. Representative profile of Alderwood gravelly sandy loam, 6 to 15 percent slopes, in woodland, 450 feet east and 1,300 feet south of the north quarter corner of sec. 15, T. 24 N., R. 6 E.: Al 0 to 2 inches, very dark brown (IOYR 2/2) gravelly sandy loam, dark grayish brown (IOYR 4/2) dry; weak, fine, granular structure; slightly hard, friable, nonsticky, nonplastic; many roots; strongly acid; abrupt, wavy boundary. 1 to 3 inches thick. B2 2 to 12 inches, dark brown (IOYR 4/3) gravelly sandy loam, brown (IOYR 5/3) dry; moderate, me dium, subangular blocky structure; slightly hard, friable, nonsticky, nonplastic; many roots; strongly acid; clear, wavy boundary. 9 to 14 inches thick. B3 12 to 27 inches, grayish brown (2.5Y 5/2) gravelly sandy loam, light gray (2.5Y 7/2) dry; many; me dium, distinct mottles of light olive brown (2.5Y 5/6); hard, friable, nonsticky, nonplastic; many roots; medium acid; abrupt, wavy boundary. 12 to 23 inches thick. IIC 27 to 60 inches, grayish -brown (2.5Y 5/2), weakly to strongly consolidated till, light gray (2.5Y 7/2) dry; common, medium, distinct mottles of light olive brown and yellowish brown (2.5Y 5/6 and 10YR 5/6); massive; no roots; medium acid. Many feet thick. The A horizon ranges from very dark brown to dark brown. The B horizon is dark brown, grayish brown, and dark yellowish brown. The consolidated C horizon, at a depth of 24 to 40 inches, is mostly grayish brown mottled with yellowish brown. Some layers in the C horizon slake in water. In a few areas, there is a thin, gray or grayish -brown A2 horizon. In most areas, this horizon has been destroyed through logging operations. Soils included with this soil in mapping make up no more than 30 percent of the total acreage. Some areas are up to 3 percent the poorly drained Norma, Bellingham, Seattle, Tukwila, and Shalcar soils; some are up to 5 percent the very gravelly Everett and Neilton Soils; and some are up to 15 percent Alderwood soils that have slopes more gentle or steeper than 6 to 15 percent. Some areas in Newcastle Hills are 25 percent Beausite soils, some northeast of Duvall are as much as 25 percent Ovall soils, and some in the vicinity of Dash Point are 10 percent Indianola and Kitsap soils. Also included are small areas of Alderwood soils that have a gravelly loam surface layer and subsoil. I Permeability is moderately rapid in the surface layer and subsoil and very slow in the substratum. Roots penetrate easily to the consolidated substratum where they tend to mat on the surface. Some roots enter the substratum through cracks. Water moves on top of the substratum in winter. Available water capacity is low. Runoff is slow to medium, and the hazard of erosion is moderate. This soil is used for timber, pasture, berries, and row crops, and for urban development. Capability unit IVe-2; wood- land group 3d1. 2.0 CONDITIONS AND REQUIREMENTS SUMMARY Conditions and requirements for the proposed Renton Windermere Office Building project will be addressed once detennined by the site plan approval process. i 3.0 OFFSITE ANALYSIS Due to the topography and development of property surrounding the proposed site, offsite drainage has a minimal effect on the proposed project. In conversations with city of Renton public works officials, it was mentioned that the existing stormwater drainage conveyance system that the proposed project will connect to is currently not adequate to convey stormwater drainage collected by the existing drainage basin. As a result, flooding along a portion of Monroe Avenue NE just south of Northeast 41h Street occurs during larger storm events. However, as previously mentioned, the proposed project is reducing the amount of impervious surfaces that currently exist onsite and thereby will help to reduce the impacts of flooding along Monroe Avenue NE. 3.1 Downstream Stormwater drainage from the proposed project will be collected onsite by the proposed stormwater drainage conveyance system and then conveyed to the existing stormwater drainage conveyance system located within Northeast 41h Street. Onsite stormwater drainage will enter the existing stormwater drainage system within Northeast 4th Street at a catch basin located approximately 1000-ft. to the west of the Union Avenue NE pp Y within the existing stormwater drainage conveyance system located in centerline. Once wrt g g 13 PAO1202.1 \.STORM REPORT 01202.doc Northeast 4th Street, stormwater drainage is then conveyed to the west for approximately 1,650-ft. to Monroe Avenue NE. At Monroe Avenue NE, stormwater drainage is then conveyed to the south within the Monroe Avenue NE stormwater drainage conveyance system until it reaches NE 2nd Street. At NE 2nd Street, stormwater drainage is then conveyed to the east approximately 575-ft. where it is discharged into an existing underground infiltration system located south of NE 2nd Street (See Figure 3). 4.0 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.1 Existing Site Hydrology (Part A) Since stormwater' drainage flow control facilities are not required for the proposed project, an existing site basin map will not be provided. However, an exhibit showing the existing impervious surfaces and respective areas has been provided within figure 3. 4.2 Developed Site Hydrology (Part B) The developed basin map for the proposed project is located within figure 3. As previously mentioned, stormwater drainage from within the 0.76-acre developed site will be collected onsite and conveyed to the existing stormwater drainage system located within Northeast 4th Street. 4.3 Hydrologic Analysis (Part Q The Santa Barbara Urban Hydrograph (Type IA) computational method will be utilized ;. for the analysis and design of the proposed stormwater conveyance, system. Stormwater calculations will be provided with the final construction documents. 14 PA01 202. 1 \STORM REPORT 01202.doc 4.4 Flow Control System (Part D) As previously mentioned, as a result of the reduction of net new impervious surfaces, a stormwater drainage flow control system is not required. 4.5 Water Quality System (Part E) As previously mentioned, as a result of the reduction of impervious surface subject to vehicular traffic, water quality treatment will not be provided 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN rmwater cone stem will be designed to conveyance s All segments of the proposed sto y y adequately convey the 100-year, 24-hour storm event. 6.0 SPECIAL REPORTS AND STUDIES If necessary, additional reports or studies will be provided with submittal of the final construction documents. 7.0 OTHER PERMITS Not applicable at this time. 8.0 TESC ANALYSIS AND DESIGN As previously mentioned, soils on the site are Alderwood gravelly sandy loam and have a moderate erosion hazard. There will be cut, fill, and grading activities necessary to construct the proposed improvements. 15 P:\01202.1\STORM REPORT 0 1 202.doc As a result of the minimal area affected by the proposed construction limits and the short flow paths generated by grading activities, only minimal erosion and sedimentation control (TESC) measures will be required. Therefore, temporary erosion and sedimentation control measures will include a construction entrance and filter fabric fencing on the downhill side of grading activities as located on the proposed construction i documents. Other cover and control measures may be required if conditions make them necessary. 16 P:\01202.1\STORM REPORT 01202.doc 9.0 BOND QUANTITIES, FACILITY SUMMARIES & DECLARATION OF COVENANT 9.1 Bond Quantity Sheets Bond quantity sheets will be provided as necessary during the submittal of the final construction documents. P:\O1202.1\STORM REPORT 01202.doc 9.2 Flow Control and Water Quality Facility Summary Sheet and Sketch As previously mentioned, neither flow control or water quality facilities will be provided for the proposed project. See construction documents for the proposed stormwater drainage facilities. PA 1202. 1 \STORM REPORT 0 1 202.doe 9.3 Declaration of Covenant Not applicable at this time. PAO1202.1\STORM REPORT 01202.doe 10.0 MAINTENANCE AND OPERATIONS MANUAL Maintenance and Operation information for the above mentioned stormwater drainage facilities for the proposed Renton Windermere Office Building will be provided with the final construction documents. PA01202.1 \STORM REPORT 01202.doc APPENDIX A Core Requirements Memo Core requirement responses (1) The location to which existing downstream drainage flows has not been altered by this project. (2) The storm report includes a Level 1 analysis per core requirement #2. (3) As previously mentioned, a project specific detention and water quality system has not been provided for this development. See report description. (4) The proposed Conveyance system has capacity for the 100-year storm and will exceed the, requirements of this core requirement. (5) Construction plans require the contractor to provide appropriate erosion control measures. Special Requirements The proposed project does not meet the threshold requirements of any of the 12 special requirements as specified in Section 1.3 of the 1990 King County Surface Water Design Manual. PA01202.1 \STORM REPORT 01202.doc