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Home My WebLink About03462 - Technical Information Report TABLE OF CONTENTS 1.0 PROJECT OVERVIEW Figure 1 —Technical Information Report(TIR)Worksheet Figure 2—Vicinity Map Figure 3 —Drainage Basins, Subbasins, and Site Characteristics Figure 4—Soiis Map 2.0 CO\DITIONS AND REQUIREMENTS SUMMARY 2.1 Analysis of the Core Requirements 2.2 Analysis of the Special Requirements 2.3 Analysis of the Minimum Requirements 3.0 OFF-SITE AIVALYSIS 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN A. Existing Site Hydrology B. Developed Site Hydrology C. Performance Standards D. Flow Control System E. Water Quality System �.0 CONVEYANCE SYSTEM ANAL,YSIS AND DESIGN ' 6.0 SPECIAL REPORTS AND STUDIES i 7.0 OTHER PERMITS �3.0 CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN {CSWPPP) ANALYSIS AND DESIGN 9.0 BOND QUANTITIES, FACII.ITY SUMMARIES, AND DECLARATION OF COVENANT 10.0 OPERaTIONS AND NIAINTENANCE iV1ANUAL ��jYUFREN�Oti ��E��F� Mp,Y 12 20� g��o�N�arv�s�o�. i�zao.00a�o� � w H ��/ w w � 0 E"+ � W � O � a 0 � 1.0 PROJECT OVERVIEW The proposed Renton Walgreens is approximately 1.48 acres in size located within a portion of the Northwest quarter of Section 15, Township 23 North, Range 5 East, Willamette Meridian, City of Renton, King County, Washington. More particularly, the site is located on the southeast corner of Union Avenue N.E. and N.E. 4th Street. This site is a redevelopment project that will include the removal of an existing gas station and an existing Brown Bear Car Wash. A Les Schwab Tire Store forms the project site's southern boundary; portions of the Les Schwab site will be modified with this development. Under existing conditions, the entire site is almost entirely impervious surface, which will remain impervious after redevelopment on this project site. The same discharge location will be utilized after redevelopment on this project site. The project si[e's frontage on N.E. 4th Street slopes in an easterly direction at an approximate grade of 2.7 percent. The project site's frontage along Union Avenue N.E. also slopes at a fairly constant rate toward the north. There is an existing wetland immediately adjacent to and east of the project site to which the site drains. This wetland has a large upstream basin contributing to it and has been analyzed by this office in the past for a project lying on the east side of this existing wettand designed in April of 2005. Since this project is being designed under the auspices of the 2005 King County Surface Water Design Manual, Level 2 Flow Control is the required flow control standard to be followed for this project site. There is also a fairly large bypass area which will bypass detention on this site, creating a vault that is sized quite large for this development. Even through this is a redevelopment project and the entire site is impervious surface under existing conditions, the historic condition for land cover has to be used, which was a forested condition for the pre-developed site condition sizing the flow control facility for this project. The water quality features used for this development will include the Enhanced Basic Menu since this is a commercial site and a wet vault in combination with a storm filter are the proposed means for I providing water quality. There is no existing detention on this site; therefore, this development I should improve the flow control characteristics in the downstream drainage course over what I, exists cun•ently. I� I 3240.004.doc; FIGURE 1 TECHNICAL INFORMATION REPORT (TIR) WORKSHEET KING COUNTY, WASHINGTON, SURFACE WATER DESIGN VIANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND PROJECT ENGINEER DESCRIPTION Project Owner Walgreens Project Name Wal�reens#12497 Phone DDES Permit# Address Location Township 23N Range SE Project Engineer Ali Sadr Section 15 Company BarQhausen Consulting Engineers Site Address SEC—Union Avenue N.E. and Phone (425) 251-62?2 N.E. 4th Street Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS ❑ Landuse Services ❑ DFW HPA ❑ Shoreline Subdivision/ Short Subd. / UPD ❑ COE 404 Management � Building Services ❑ DOE Dam Safety � Structural M/F/Commercial / SFR RockeryNaulU � Clearing and Grading ❑ FEMA Floodplain � ESA Section 7 � Right-of-Way Use ❑ COE Wetlands ❑ Other ❑ Other Part 5 PLAN AND REPORT INFORMATION Technica! Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review Ful / Targeted / Type (circle one): Full / Modified / {circle): Large Site Small Site IDate (include revision Date (include revision � 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) Date of Approval: 2005 Surface VWater Design Manual 13?40.002.doc[8/3/O6j 1/1/OS 1 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Describe: Start Date: ' Completion Date: Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : Special District Overlays: Drainage Basin: Stormwater Requirements: Part 9 ONSITE AND ADJACENT SENSITIVE AREAS � River/Stream ❑ Steep Slope ❑ Lake ❑ Erosion Hazard � Wetlands ❑ Landslide Hazard ❑ Ciosed Depression ❑ Coal Mine Hazard ❑ Floodplain ❑ Seismic Hazard ❑ Other ❑ Habitat Protection ❑ Part 10 SOILS Soil Type Slopes Erosion Potential Alderwoad ❑ High Groundwater Table (within 5 feet) ❑ Sole Source Aquifer ❑ Other ❑ Seeps/Springs � ❑ Additional Sheets Attached i �OUJ Surtace Water Desicn Manual 132ao.0o2.doc[8/3/O6� 1/1/OS 2 KING COUNTY, W:�SHINGTON, SURFACE WATER DESIGN VIANU�L TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT ❑ Core 2—Offsite Analvsis ❑ Sensitive/Critical Areas ❑ SEPA ❑ Other ❑ ❑ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Cedar River Core Requirements(all 8 apply) i Dischar e at Natural Location Number of Natural Dischar e Locations: 1 Offsite Analysis Level: 1 / 2 / 3 dated: December 20, 2007 Flaw Control Level: 1 / / 3 or Exemption Number inci. facilit summar sheet Small Site BMPs Conveyance System Spill containment located at: Erosion and Sediment Control ESC Site Supervisor: Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private / Public If Private, Maintenance Lo Re uired: Yes /No � Financial Guarantees and Provided: Yes / No Liabilit Water Quality Type: Basic / Sens. Lake / Enhanced Basicm / Bog (include facility summary sheet) or Exemption No. Landsca e Mana ement Plan: Yes / No Special Requirements(as applicable) Area Specific Drainage Type: CDA/SDO/ MDP/BP/LMP/Shared Fac./None Re uirements Name: Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None 100-year Base Blood Elevation (or range): Datum: Flood Protection Facilities Describe: � Source Control Describe landuse: (comm.Tndustrial landuse) Describe any structural controls: 200� Surface Water Design Manual 13240.002.doc[8/3/OG] I/1/OS 3 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Oil Control High-use Site: Yes / No Treatment BMP: Maintenance Agreement: Yes / No with whom? Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL RE�UIREMENTS MINIMUM ESC REGIUIREMENTS 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 Control � Other � Dust Control � Construction Sequence ' Part 14 STORMWATER FACILITY DESCRIPTIONS Note: Include Facilit Summar and Sketch Flow Control T e/Descri tion Water Qualit T e/Descri tion � Detention Leve12 vault � Biofiltration ❑ Infiltration � Wetpool Wet vault � ❑ Regional Facility ❑ Media Filtration ❑ Shared Facility ❑ Oil Control ❑ Small Site BMPs ❑ Spill Control ❑ Other ❑ Small Site BMPs i � Other Stormfilter 2005 Surface�T�`ater Desi;n Manual 13240.002.dcx[8/3/O6� I/l/OS 4 KING COUNTY, WASHINGTON, SURFACE WATER DESIGIv MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS ❑ Drainage Easement � Cast in Place Vault ❑ Access Easement ❑ 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. 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FGng County Area, Washington (WA633} � Map Unit Symbol Map linit Name Acres in Percent of AOI AOI AgC Alderwood 315.4 76.1°�0 gravelly sandy loam, 6 to 15 percent slopes AmC Arents, 28.=� 4.�°�o il Alderwood material, 6 to II 15 percent ' slopes � An Arents, 57.0 13.79io I Evere tt ', material '� EvB Everett 23J 5.7°�0 gravetly sandy � loam, 0 to 5 I, percent slopes '� Totais for Area of Interest 414.6 IOO.OQ/o �� (AOI) i, GHAV Y� �IT��`S�� ' �Z- �' oils Ma ;, � � _ s� `�I V1 i� P (r,N�ENG�N�` Job No.13240 2.0 CONDITIONS AND REQUIREMENTS SUMMARY 2.0 CONDITIONS AND REQUIREMENTS SUMNIARY 2.1 Analysis of the Core Requirements Core Rec�uire�nent No. 1: Discharge at the Natural Location. Response: This project site will continue to discharge off the eastern property line in a 48-inch-diameter culvert> just as it does under existing conditions. However, flow control and water quality facilities will now be installed with this development, which were not there previously. Core Requirenaent No. 2: Off-Site Araalysis. Response: Please see Section 3.0 of this Technical Infoimation Report (TIR) for the off-site analysis prepared for this development. Core Ret�uir-e�nent No. 3: Flow Control. Response: The flow control feature provided with this development is Level 2 Flow Control, also known as Conservation Flow Control, which modeled the site as an historic condition for tl�e pre-deveIoped condition of till forest. This provides a large detention volume, especially since we are bypassing some of the flows to the project site. Core Requirement No. 4: Conveyurice Systern. Response: Since this site is less than 10 acres in size, the conveyance system will be sized based on the Modified Rational Method as delineated in the 2005 King County, Washington Surface Water Design Manual (KCSWDM) as adopted by the City of Renton. Initial time of concentration of 6.3 minutes with a Manning's "n" value of 0.014 will be used for this analysis with the 100-year precipitation in order to route all runoff generated on site into the wetldetention vault. Core Requirement No. 5: 2005: Erosion asul Sediment Control. Response: This project will concur with all erosion and sedimentation control requirements of the City of Renton as delineated in the 2005 KCSWDM for projects of this nature. Core Requiremerct No. 6: Maintenance arad O�erations. Response: A Maintenance and Operations Manual will be prepared with this development should the owner of the project site be personally responsible for maintenance on this development. Should the City accept maintenance responsibility, no report will be prepared. Core Reqt�irement No. 7: Financial Gaecer�cntees canrl Liabilih�. Response: This project will concur with all financial guarantees and liability requirements of the City of Renton for projects af this nature. i3zao.00a.d� Core Reqacirement No. 8: Water Quality. Response: Since this is a commercial development, the Enhanced Basic Water Quality Menu will be followed with this development as delineated in the 2005 KCSWDM. 2.2 Analysis of the Special Requirements Special Reqa:irement No. 1: Other Adopter�Area-Specific Re��uirements. Response: There are no known other adopted area-specific requirements required for this project site. S�ecial Reguirenaent No. 2: Floorl Hazard Area Delinecction. Response: This project abuts an area that has an existing stream coursing [hrough it and an analysis was performed in 2005 to determine the floodway elevation in the stream. That document could be provided to the City should they so require it; however, this site is much higher in elevation that the streambed below it. Therefore, it is not thought to be a problem. Special Requirernent No. 3: Flood Protection Facilities. Response: There are no flood protection facilities adjacent to this project site that will we will modify or construct. Speci�il Re��i�irement No. 4: Source Control. Response: Source controls will be applied to this project site in accordance with the King County Stoimwater Pollution Prevention Manual and all of the requirements of the City of Renton for projects of this nature. At the very least, the property owner will be , educated about the use of pesticides and the trash enclosures will also be covered and the II use of fertilizers will be kept to a minimum. I Special Requirernent No. S: Oil Control. I� Response: This project site is not considered a high use site; therefore, the requirements of Special Requirement No. 5 do not apply. , i 3zao.00�.do� � I��I � � � � � � W E-� � � � w w O 0 c�i LEVEL 'I OFF-SITE DRAINAGE ANALYSIS Proposed Walgreens No. 12497 SEC - Union Avenue N.E. and N.E. 4th Street Renton, Washington Prepared for: Thomas Thompson-AIA 29619 - 15th Avenue N.E. Stanwood, WA 98292 (360) 629-3985 December 20, 2007 Our Job No. 13240 f' IL�-0� + ��tY JACpe �� o�w�s,�s ,�w ��, a�' � " o � ^., .'h;� ,.� ,f+- ' � • , ��r `� ` '1�� ' �'GHaV �..�_ . ,_�D�--, � ��SZ CIVIL ENGINEERING, LAND PLANNING,SURVEYING, ENVIRONMENTAL SERVICES 18215 72ND AVENUE SOUTH KENT,WA 98032 (425)251-6222 (425)251-8782 FAx Z \ i BRANCH OFFICES ♦ OLYMPIA,WA ♦ TACOMA,WA ♦ SACRAMENTO,CA ♦ TEMECULA,CA , So� ��U�� Ph� www.barghausen.com , EE Nc ENG�N TABLE OF CONTENTS TASK 1 STL'DY AREA DEFINITION AND MAPS EXHIBIT A Vicinity Map EXHIBIT B Downstream Drainage Map EXHIBIT C Upstream Basin Map TASK 2 RESOURCE REVIEW EXHIBIT D FEMA Map EXHIBIT E Sensitive Areas Folios EXHIBIT F SCS Soils Map EXHIBIT G Assessor's Map EXHIBIT H Wetland Inventory Map EXHIBIT I Basin Reconnaissance Summary Report TASK � FIELD INSPECTION EXHIBIT J Off-Site Analysis Drainage System Table 3.1 Conveyance System Nuisance Probtems (Type 1) 3.2 Severe Erosion Problems (Type 2) 3.3 Severe Flooding Problems (Type 3) TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS I;?40.001.doc TASK 1 STUDY AREA DEFINITION AND MAPS TASK 1 STUDY AREA DEFINITION AND MAPS The proposed Renton Walgreens is approximately 1.48 acres in size located within a poition of the � Northwest quarter of Section 15,Township 23 North,Range 5 East,Willamette Meridian,City of Renton, King County, Washington. More particularly, the site is located on the southeast corner of Union Avenue N.E. and N.E. 4th Street. This site is a redevelopment project that will include the removal of an existing gas station and an existing Brown Bear Car Wash. A Les Schwab Tire Store forms the projcct site's southern boundary; portions of the Les Schwab site will be modified with this development. Under existing conditions, the entire site is almost entirely impervious surface, which will remain impervious after redevelopment on this project site. The same discharge location will be utilized after redevelopment on this project site. The project site's frontage on N.E. 4th Street slopes in an easterly direction at an approximate grade of 2.7 percent. The project site's frontage along Union Avenue N.E. also slopes at a fairly constant rate toward the north. There is an existing wetland immediately adjacent to and east of the project site to which the site drains. This wetland has a large upstream basin contributing to it and has been analyzed by this office in the past for a project lying on the east side of this existing wetland designed in April of 2005. UPSTREAM DRAINAGE ANALYSIS Based on our site visit and the topographic survey prepared for this project, it appears there is no upstream flow onto the site. There is upstream flow underneath the northeast corner of the project site from a large upstream basin on the north side of N.E. 4th Street, which is conveyed to the project site through 48-inch diameter pipe that this project will connect to piior to discharge from the site. This runoff will be routed through tl�e project site �vithout utilizine any of the detention and ��ater quality facilities. �;�ao.uoi ��,� EXHIBIT A Vicinity Map O � N M � W� O �� N� ' W W_]11R 11IM ' IY_ '"_M�U p.y � H. 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' EXHIBIT C Upstream Basin Map � w � � � N �/ � �i� � w � ��/ [..� w � 0 �/1 w � TASK 2 RESOURCE REVIEW • A�lopted Basin Plans: The site is par[of the Cedar River Basin. • Finalized Drainage Stculies: There was a Finalized Drainage Study prepared for the wetland and downstream drainage course for the project immediately east of this project site, known as Ribera Short Plat prepared by this office on April 29, 2005. Should that document be required for review by the City of Renton, it will be provided. • Basin Reconnaissance Summnry Report: Once again, the site is located in the lower Cedar River Basin. There are no projects proposed in Tributary 0302 to which this project site drains in the Cedar River Basin. • Critdcal Drainage Area Maps: According to the Water Quality Applications map in the 2005 King County, Washington Surface Water Design Manual (KCSWDM), Enhanced Basic Water Quality Treatment is required. According to the Flow Control Applications map, also in the 20d5 KCSWDM, the site is surrounded by Level 2 Flow Control areas, also known as Conservation Flow Control, which will be utilized for the design of the detention facility on this project site. • Floodplain and Floo�lway FEMA Maps: Please see the attached FEMA map in Exhibit D utilized for this analysis (Panel No. 981 of 1,725, Map No. 53033C0981 F, revised iVlay 16, 1995). As indicated by this map, the proposed project site dces not lie within a floodplain or floodway of a stream. • Otlaer Off-Site Analysis Reports: A review of Exhibit I - Basin Reconnaissance Summary Report, and a site investigation were conducted in preparation of this Level 1 Off-Site Drainage Analysis. The United States Department of Agriculture Soils Conservation Survey Soils map is also provided(see Exhibit F). • Sensitive Areas Folios: Based on a review of the King County Sensitive Areas Map folios, it was found the subject site does not lie within a sensitive area; however, it drains to a stream that appears on the Sensitive Areas Map folios. It is not known if this stream is salmon bearing. • Rocul Drainccge Problems: This is not applicable. • United States Departrnerat of Agricultt�re King County Soils Sccrvey: Based on our review of the Soils map for this area, the entire site lies within Alderwood type soils. • Wetlancl Invetztory Map: The Wetland Inventory map for this area is included herewith (see Exhibit H). There is no wetland listed for this site on that Inventory map; however, there is an existing wetland located immediately east of the project site on the development to the east. . Migrating River Stu�lies: This is not applicable. i�z-�o.00i.aa A � � � �� W W w �-- � � / �i�l � �—_ �� CORP(Y.f4TE UM1fY � �n.� 8 � �� I 8 `� I � \�. . _" . ."_... _ _..- .... . .1_ e:a�ic� i `- � � + � � u �� sw�n SITE , �— . ,� � � - � �� . � �z Z ; �y°°`° i g� ""� .ameurw n �_^ . 20W 71 I � 'I � n � �� I � I 7 NG/!e�Mt MR�t�10'I/I OM 11115 Mpl�tl 1OG/1D i MIIIM TOM7W1�7!NW1M RNF�f UqT. ��ss _ . �I ' a � u .cv�r � no nxt xM.wr u� 17 te �s„n` � � ��. � CIfY OP RFNfON �� '� . 33001t � i � n+" ro � � f �!jP. ' �. .___ . .i-� . -. . C�1'/ Nf ! � � � �++artaa . ^ ' . �__ i �+ �'++""� N" SPi°` AING COUKI'Y � UNINCORPORA7HD AREAS � ma■ � M��, 330071 a� ;an.cur ( — i` ---�x—9,�,,�,�„ 4 0 'v"+a��-.a . 1��7 � i L _` x 8 I %" � � j � � I � -----� --- i � - - d +� con>onaR uairs � � 'Mo °� � � 7 `/ :«u,u � �'�. . � GHAV � 1►I� F ''Z Z FEMA Ma � .o V ? sG ,,,� (T,NC E�G�H��pe Job No.13240� � �j :�J i� 1 i �1� � � y� � � �! � t° 1 i s � _� � ti i js� �;� ��3 �� j� , � } �� t � � �� t i� f�tf �� i � � ! - - + i t� ji a �f;l7 ; j a �i ��,�j �! ' } �6 �� t° ' � �;. �y�tR P. � � } � � � 9 j •} •it� ,�, r i f:r � � t �� .,3 �! , t. •t. c; �1 � p�� ; f�,� j, �� »� �i�i� 1 � f � � � �3313 �.};� � �� `i# � � �� S�•j�� y ' ; ,� e� `� _ z � j� „ � � ], 1,� ,t. � � � j a� j', 3 �t t, � • 3 t t - �o i W ! � � ,$' I i, : �u -� , �.� �:�i :!t �� !�� '_�1 �� t Ed` D � � fii�!!�l,�j 1 �:�� ;�� f � �L � ;�. �a , [ �� t• �. ��. : s 9 : s � 3, � � �� i � ��i;��!i j J tlti��j�i�� 31 1 �� s� .� � �� a � � ba �� i � 4 X3 � ; � �� , � 1 - �,�� , � , � �! �� '� ��t� I I '� � • � ��f,tl��= !;,�!��[�;��! (' �� i 9 � � � II � . � � r.�,�1.��la II�i�!��f�4��4 :�:t ' :e � � � � � � �� Y � � � � ' �, �� _ � � �� tl 8 �� a�; '� �i.C �3? �e �.. t�� q �L` __'_. .-- __. _-�� _+s _�{�i ��j+s:. a—��+ �-y--. �= �.. . ,� { �'`� Y'7L'•�' 4'154� _'��=�� _��s 'a�-� I EXHIBIT E Sensitive Areas Folios �. t�;a �S ,,� y� � � p...__ �� / � � � y � /� � �e _� ��r S"'� A p 31�� !��I� sew�.�w� � _ s �`_ .' �r f ,�, f. y 'r- � � / � N �, e�� vF� � � ��`s �� ; �� ,,� i �ninv��c'��,r"•;r,� ! y � / /, ,,� � � J��'�� y' ��,.� / � �l� {,'rfr� �u f; /�r� �/.i Z p� . , � �� > �'.;1 ✓� i;�� , �;; `/ . � ��#Iw��l��,�� ,� �� % ` �f ">>� ',.'� � BRL�.1£?TCN A'd£yP.�-+�++ .�, .� .� � � ��r _� Qy.' f / / / f �/ �_ u •., �,�� ' 1 ti,'I 11L 1\?�t.J"�{""'v" t��►�� i1��"'r" �\ r" � � .I;��P�� , x , � � f� . . , , . � .� � �. � � �� '�'�"`�� ■��I*�;^�r+'cy��4�# ��+, /'� �1.-�t r lr �: � `, y 1'�� x '� �;r� k�7�� u�!o- r f �. 3w�d�. �i � �M � �� ^�` �a^ „i- �,^--^'"'"' .. �� t, �vd�,��;.,,,,, �� _ , ��" ��,�u�^ r � b n"«:.Ul� j �1 N a •,,� .�f, t�.� .. . {Q r "� �� q'� :. � �+•LI Y�"ri 71��,k" i�..'� i �I �. ..,��. � _ � rR:utl�� `/ r T� � - .� . ��Y. ��h f � ♦t�� r�� lT �� ,�' .�i'�f�~�• ,� � ��e`�. ��,, , � y, �3� 1 j.� .�*`� ,1^s c�'�",, ' ��z � f'" �'� t1��,�F'�� t� � � '; a °"' p,�,-�„'�+�� W «t�e � �' .. . -� , . .4ri., f ...-.�.sr.L':.�i' i`� L r.s h�by�llkl/le.' r�� .�2' . �� ''��z �� ► ��. a 3 ;.a r ��y;, , , �� k� � � � y,� � =M fl < �6 i'�r'�4. 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UVIJ'J•r,V� Vt� iJ � � � �, ��.,.,�s s . .:"�...... � �m�� :' �a� , .�a �� . .�� .� �1�� ,�e _ � � � �,� .�:��.,,� �� «W�a�r..s�.no,..w � � .� ,�� '"�d .. � ;-�`� �� 1 �.��_.� � }M,�tYd►W07'Vl � � t � ,�,,, � �,,,.. � � �d � �"� � .� `�, ��..,.+'a�0'��i �iE�p .�j . .'._ a (� ��;�� ,�f�� '��^�(,�i��i14� ��W �� t.:: � � �'o .�� i��ii��.j x ,� �. � � � � , � . ----- y� � �� , ' � ��a�� . � � � � � , � w r p�q k � �� ,.. �� W ��:�t` s^!��'��`,��5 ' � �Yaw,p� .. �',! �..� ��Y.^. � � ��a��dli�P 1JiEh�p��s ' �} � FS� �4.��'� ,y�i , �'_.. . ��'� �tlli�y�, .��. f ra � ,.�.k�� , �. � �� .�� "''w�i�;' . ` `�� ;a ��ifyeCAEl7 �}'idQy[:lltiiy T �.p,.4 �'."�n�5�,ta.t`3'a ��f!.� � � � � Y �S�y� dY�t � 4�• rvf � �+ . ' ♦ ��IL � �M!�f P 7 � �...�,�e� y .;y x , r . .»�.. ,�,C�� ,�� U��r�7�� .�$M � , ��,� �x �� .��'�r��ar� � � ,� a��;�_: � , ;�; �` � �� •�.� ,, +� �MW� 3n�nv n�ro M _"_" .'-" '��..: ._.. .. �N �N, ', �_ �r� �I��ia � � s ,y °' � � ��e � .��1�1�� .� � ► l�',. � _ W � �!�P � � �,'�� cu • �� i � �� . � �^ � b._ oHs'V Sensitive Areas BCE # 13240 �egend � Highlighted Feature � Lakes and Large Rivers � Hyn �_I �MY �►�rY fr�� Streams CAO Basin Co�dition x Mountain Peaks � ��aY � Hqn CAO 5hareline Cor►ciitlon � 1D0 Year Floodplain � y�;,A, `� �;��, Channel NGgration Hazard � �,,, l� Areas �*` �Iadium Shaded Relief , Low 'mm A18DERATC Hlghways �a t, S[v[RE � Incorperated Area � Sale Saurce Aquifer Streets .\ SAO WeUand �.. ��'�"""�' � 5A0 Landslide A`�O"� ,� SAO Coal Mine Lonl � 5A0 Seismic Parcels 5A0 Ervsion Wildlite Network � Chinoak Distribution 5A0 SVsam ■ Sensitive Area Noti�e on TiUe � �� ' Drainage Complairtts � CLtss 2 Paronn at . Areas Susceptable to � c►ass2sa�x� Groundwater Contaminati�n :�•f c�� , UnttassT� ,i� La� � _� d i Madium (C Oflt� TTre Inbnnalan induded on C�is map has bean compiled by IGng Couny sWB hom a variely d sources and is subjeG b change wi0�ou1 no6ce.Kng County makes ra representa5m�a vrerranUes,express a impied.as W auuracy,cortpleteness,4meiness.a rigl�b b tl�e use ol sud�intmna6on. This do��rnent b nol inbnded(or uae as a wrvey produG.FGnp Caxdy aAaN nol be fable la anY 8eneral.special,incfiired,ncidenfal,a cortsequenGd � damegee induding,Eul not tlmited b,lo�t rev�ues a bst proGa reaulh�g hom Ihe uae a miwse o!Ihe i�ortnation conlained o�Ihis mep.Mp sefe d K ing County Ihia map a nfortna6on on this map i�pro�ibiled except by wrkta�pertnission ot King Co�nty. Oafe:1 2/1 82 00 7 Source:King County iMAP-Ser�aitive Mea�(http/fwww.mebokc.gov/GISliMAP) EXHIBIT F SCS Soils Map Ir � tJ -'p — ' •.{ � "�.'�' . � �[��f��'�,t. `1��'� 1��` �.. _ a �" °.��• d 7" '.,'' - � � ' r '� ,'.�'� : -« �t' �.�.?. R F4 ,•� �� • : t � 4 +.r r� s � `lt � �� +{`� •� y,. �� . , 1� •�'�'? � � =. � �' �V. s� �� i � '� - �. � �R� - ' 1 . �'� ��. �. � r — ,�� ' • ♦ 14.i� .1i �i � f' �� :l� •��.Li `�� .�..e�� e s" .4 ( � i.9��'�� .`:. '�►� � �� ' „r r- � , _ ., � � ,�, . " � .� t�^. .d�,�- �. • �� .ILR P a 1-�E�t •!''' �G�� '°�T � .;.� i ..� ,�j,r�r ._� -�� •�:'�, 1 �+• {� � -S- . . t.. l 'f•• � �r � �e•� .. 1 ,n��" t �', ' • < � s. � i � ��.�,1., � � � {. � ..�� ♦;r'��. � I�: t � ��t+Y14 ��'�'�+� 1 . . � a�i�� {+� ` � .s_ 1- f... , y•,`�:.�".� .�� i...«r� •. " ��X ! ,� �R.:T ' .{ H�'r„ 1 .. 1 .. '�l C,.'� ••i�_ 1� ,. i *f L �4 { � � C. .�``1 t�t� . �� '..- � 4:��' , ��.�+Zi� SSY� � 'fr � :�` c-�� r� c '�y�� 4�"�• i f ,t a ��- � � . j '�` •,' t� f�� a. -"� � k . , ,�� l' ��1► yx��„i� � sC'i ��' ,:�'f ( ' IM1'� I _ � 'j�� _� � � "•�� y � �•�� . •�� , x� . , - � , ' ✓.� . * • C/. l� —� � _ ��. '.4� ¢ � . � j � �.� � �a.�� J� S � - ^� . � ' � ' T ' ,��a: :'� �` ► �►'- �- ,r,, � ' 'T•` s t,'� G,� t. �; ' ��._ . � , � � -- t ,.- i h .. �.• s . ; , a � .;�I� '�D""'. . ao� ''� � •t . �' !#��'�,{� �• � ,.�.. " ` .+•_ - � ,�,,; '�. IGng County Area, Washington (WA633) � Map Unit Symbol Map Unit Name Acres in Percent of AOI AOI AgC Alderwood 315.4 76.1% gravelly sandy loam, 6 to 15 percent slopes AmC Arents, 18.4 4.4% Alderwood material, 6 to 15 percent slopes An Arents, 57.0 13.7% Everett materiai EvB Everett 23.7 5.7°10 gravelly sandy loam, 0 to 5 percent slopes Totals for Area of Interest 414.6 100.0% (AOI) GHA� � �I,s� t- z OIIS �a V i ? �� `j U► Pb. �'�C EHG�M�� Job No.13240 EXHIBIT G Assessor's Map � ��- � • _ . . , � _ ;: _ j i t � � � n �' s �, w�� WI� � nt�, � �� 4 �.}y�� s.f � � � � �' ... ...�'' �.;., ..... . ..�..� ti.. •. 1 9 � u ! � ' � �'_._�.___�.�. .�.�).V.U.' .____._'_ � .• _ . .. w�w �• s t,-�---i _"_'_..__J.S�1 .........�w....�.. • ... �. .�r.v _.'._,ucK.d}'✓....... ', �,: .'-_--�--�-- �—__ra � . ��. "� . • a ... Jlp�wl� l i Vl��:.4�_..(l�t�. �Y •Ml1�Y"�'�_. _� . J �+� ...�w iH IIIf __�_' _ '� '� � SITE ...� � ; �'�.,: ,.., '�"• '��' "� ��,I _ � .'� " ^ ^��• . � 2 S p� ^,• �: r w i. �� j �. �.. � ,�w. .c�� - f asa� , ` 4$ 1 � - � .� `'�' s;r" _i y! s ,� } `., „L� �+ . � ��; ' ..-,...,: .°' _ � 5 ��! n��. ��F.. � ;� ' ' + _.�.s .r ,'"`fii'� n �!� ��, F� ,n� � � ,��:, :�v::; n��e:� ..w,.�....' • �.• ":« . ,/ ... u�sum.,,i;:c:,�.. �i . ::��,.�•y K� . I � i , i � � . - � � : i:j � 'i„: : + j � INiN ) '" T , � ;,y �� " 1 . •��i i�i y, : F..«.0�wy.. � iti " ,� �,``�� •;MARTW'S. E �;," �: m»��y� � > j: :1 �'y ��7 ..v,.. • � �.i .,.. .. �;�'M - , f ;a'r •r.' .c�< - 4.; ex1•"�' ' 1 " TRACTS UNREC. , 'o,w ! � �~.•r r� i .,. �l �•!➢' ' ;..n � ; ,�.� , � .,�. � . ;. �T;/ 4� .. s" � n` h„ }t ;a T r:.3,�w�ir r.� ' �y '' Jt .n" .''i _..... �� '!� K7 '�Y �J iv" ,,. `6 �� . . , _ F �� ; y :s-�a � M� � r i i . ��'� ' "�:7 � l ; 1:� 1fY�ON1�OY lM!�a[A Y MI M tl fG�:� � 'J „ '•_ i ,l �. � :._..__rrv�n_r,�._ , -.9.Msl._ _ k`J �i �.,l� � I ;'..cf��,.. +`!' .. ., ., , .:� �wa1�Y.Q�l..�'�:. T� _ • " Y��,v.. I �..:'� ..,Ae,.� ' �• '. - .a, . t , .w� _� �•i ✓ �. .�..w . _ �: � !. „ cn �f �i� t "►.� w. «Xui ��r:� ':ie� ! ,itv'v"�' � f .'' ' , _ : 7�i: wt.,�•� ,t� :� �e Y 'u�' �n� � Sp.'t• �9 a. _ a _:w �, .�Y.7 �.i "�V� i.� j � �'iy'•a iS5 g.� ;r ; �J!i%'iy � r.u. n� `'rJ , . �. A_ ._ __ _ _ '!Y.?" _ _ � '�}_«n ,'��aRf� li1� Il�i /f�T� �.y�.,.�.r. ,� 111��7k.-. F � ,� .L�{�c.5 M �rY' ,'f .�aw. `., �N 1if` s��[ i� f t r ^ _ _ i .x' .7. �.. , a � � � tc ��. � Q'��..8 Y�"i t�� ra! � va S �, s w �� '' ' ., �. � ' � 'K"M��:, •'i�,Fn .YL�, ':� '°�2,.y' �*r'f'S � '�. �� L x, a i _ �a � ;' r _ .t.�, � 'R..i�- , » m�i e�iir_. "'� .• ,'�.„ '_� ^.a � , ,� a ?� � m �.i' �...r-3.. � wi. ,_�ii._..t��..la�.7:`�_•�-„ ' Ci � H v �.o,� �.. .,.. �. .r5� "7� ° � .^.;+ •. ..:-.. �.� .4. �.�� „ .� �s_ � � �`.�"' :.. � .P� .yj� � , ::'a .. .v. � . � x '-�lw,.�,�YaRMK�._ r .� . ;� A A s n �f � 't 1 Y JM � � �.w "" 4� ,. - • _ .__ ..._ �_'� •�� .�F•� � F+i ii oC ioir '�b 'i.ii�w '.�.. ;u WR'+,;2 Ci7 ,qCy u a� s' x _s_ ...x v �a .r �• i w . w v ^• �.v�en.�ir: v .t� p .* . .� `,;�+ _ ti.__tt.iri.t�.�.•�n.. _..�. ��.i+ v v � �a +�.•�� 'x �. w ��" �• � , hl ... • . �.u... ... .. . .�. .. .W�f.� V�r�. '�Y .. iU t jj�Y� . E I\ 1!' u � - .. . T .� � ��,r�av �►I st� �= z ssessor's Ma o =� j� :� v„�► ,. (r LP Job No.13240 4 �G ENG�N EXHIBIT H Wetland Inventory Map �;.:�..;: >:. . - Seattle::; ..•--.. . ..J . ::: �: ---� :J --- :4 � �4 � � .� ' g+y Vr �\ . 8�8C�.�VC! .:� 4��n �� jAII(� a• 1: � ... �Bas� _ . - : East:Lake.:: ' � �� Was oa —�_� �.��' 20 : :Rentorr :: : Sooe Creek�..�4 v 2 2 3 �� :� �a� �ys Zs 63 S i�y � 25 �� •� � � May Creek �,� �� 16 g � Q �15 � 1 40�.� Oj4 41 28 � Jenklns Creek 42 29 h �v °� � � 32 3013 `� 76 74 31 12 61 Covingtoa �9� 5554 44 34 ' - Creek ,S, ��3 36 33 , Black.: � � �9 58\ 4� /' Diamond:� � 77� 73 60 88 9� 5.� ; �-_::._j 80,68 90 72 62 50 91 ��' 8� 66 7071 Iesaqaah Creek 92 �! 83 s� 93 o g4 82 64 94��5 Lower 4j'�g� Middle 87 (�edSl• �� Green g �VCI $ � Rtver yf yJ s �, . ��t ` 'O � �g��_ u �Up�`r U � Green pPper Ced,ar R3ver � Rtver � O� � Mile N o � � � � Lower Cedaz River Cedar River Basin EXHIBIT I Basin Reconnaissance Summary Report � � � � RECONNAISSANCE REPORT NO. 13 LOWER CEDAR CREEK BASIN � JUNE 1987 Natural Resources and Parks Division and Surface Water Manapement Division Kin; County, Washington King Couoty Executiv�e Tim �iiU King County Council Audrey Gruger, District 1 Cynthia Sullivan, District 2 Bill Reams, District 3 L,ois North, District 4 Ron Sims, District 5 Bruce L.aing, District 6 Paul Barden. District 7 Bob Grieve, District 8 Gary Grant, District 9 Department o[ Public Works �ark.�, Plannin� and Resources Don LaQelle, Director Jce Naget, Director Surface Water Maoagemeot Division Natucal Resoun�es and Parks Divisioo Joseph J. Simmler, Division Manaber Russ Cahill, Division Mana�er Jim Kramer, Assistant Division Manaoer Bill Jolly, Acting Division Manaaer Dave Clark, Manaber, River R Water Derek Poon, Chief, Resources Plannina Sertion Resource Section Bill Eckel, Mana�er, Basin Planninb Probram Lany Gihbons, Manager, Project Mana�ement and Desibn Section Contributing Staff Coottt�buting Staff Doug Chin, Sr. Engineer Ray Heller, Project Mana�er S Team Leader Randall Parsons, Sr. Enbineer Matthew Clark, Project Manaber Andy Levesque, Sr. Engineer Robert R. Fuerstenberg, Biolobist � Team Leader Bruce Barker, Engineer Matthew J. Bruengo, Geologist Arny Stonkus, Engineer Lee Benda, Geologist Ray Stei�er, Engineer Derek Booth, Geoloaist Pete Rin�en. Enbineer Dyanne Sheldon, Wetlands Biolooist Cindy Baker, Earth Scientist Di Johnson, Plannino Support Technician Robert Radek, Planninb Support Technician Randat &�ys, Planninb Support Technician Fred Bentler, Plannina Support Technician Consulting Sta[f Mark Hudson, Plannino Support Technician Sharon Ctausen, Plannin� Support Technician Don Spencer, Associate Geolobist, Earth David Truax, Planning Support Technician Consultants, Inc. Brian Vanderbur�, Planning Support Technician Johrt Bethel, Soif Scientist, Earth Carolyn M. Byerly, Technical Writer Consultants, Inc. Susanna Hornio, Technical Writer Vir�nia Newman, Graphic Artist Marcia McNulty, Type.setter Mildred MiIler, Typesetter Jaki Reed, Typesetter Lela Lira, Office Technician Martv Co�. Office Technician P:CR TABLE OF CONTENTS I. SUMMARY 1 II. INTRODUC'TION 1 [II. FINDINGS IN LOWER CEDAR RIVER BASIN 2 A. Overview of Basin 2 B. Effects of Urbanization 4 C. Specific Problems 5 1. Drainabe and flooding problems 5 2. Damaoe to property 6 3. Destruction of habitat 6 [V. RECOMMENDATIONS FOR ACTION 7 A. Reduce landslide hazards 7 B. Reciuce erosion and flooding 7 C. Prevent future erosion and fiooding with appropriate analysis, 3 planning, and policy development D. Stop present (and prevent future) damage to habitat 3 by addressing specific problems in stream systems V. MAP il APPL-:NDICES: APPENDIX A: Estimated Costs A-1 APPENDIX B: Capital improvement Project Rankinb B-1 APPEDDIX C: Detailed Findinps and Recommendations G1 I. SUMMARY The L.ower Cedar River Basin, in southwest King County, is unique in its development pat- terns and the associated environmental problems that appear throughout the basin. Except for the city of Renton and areas on the Cedar River VaNey floor, most of the development in the basin has occurred on the upland plateaus. Most of this development is recent and primarily residential. In addition, the plateau is the site of numerous sand and gravel mining operations and, in the southern uplands, an abandoned coal mine. Peat is also being mined north of Otter Lake. In some areas livestock are being raised on small farms; there are no major crop-re(ated agricultural activities in the basin. The effects of development are most apparent where storm drainage is routed over the valley walls. Impeivious surfaces on t6e plateau have increa.sed the tate and volume of � storm ruaoff, c+esulting in substantial erosioq siltation, and flooding belvw. In addi- tion, erosion aad siitation have damaged or destroyed habitat in many tributaries, threatening the survival of fish. Habitat and water quality throughout the basin are also threatened by the filling of wetlands and the presence of large amounts of domestic trash in some streams. The reconnaissance team noted that the Peterson Creek system has so far remained in its natural, nearty pristine condition. Maintaining this quality should be a hioh priority in future basin planning capital project programs. Recommendations in the Low•er Cedar River Basin include l) designing and constructing appropriately si7�ed R/D and other drainape facilities; 2) establishing stricter land use poGcies regarding floodplains, wetlands, and gravel mining; 3) eonducting more detailed and mmpreheasive hydrauGc/hydrolo�c analyses of proposed deveEopments; and 4) preventing damage to the aatura! drainage system. The field team also recommends � restoring the habitat of severat tributaries {e.g., cleaning gravels, revebetating stream banks, and diversifying streambeds for spawning and rearing) as well as 6) prntecting the nearly pristine quality of Peterson Ct+eek. II. Qd"1'RODUCITON: History and Goals of t6e Pivgram In 1935 the King County Council approved funding for the Planninb Division (now called the IVatural Resources and Parks Division), in coordination with the Surface Water Management Division, to conduct a reconnaissance of 29 major drainage basins located in Kina County. The effort began with an initial investigation of three basins -- Evans, Soos, and Hylebos Creeks -- in order to determine existina and potential surface water problems and to recommend action to mitigate and prevent these problems. These initial invesiiga- tions used available data and new field observations to examine geoloby, hydrology, and habitat conditions in each basin. Findings from these three basins led the King County Council to adopt Resolution 6013 in April 1986, calling for reconnaissance to be completed on the remainin� ?6 basins. The Basin Reconnaissance Program, w�hich was subsequently established, is now an important ele- ment of surface water management. The goals of the program are to provide useful data ��ith regard to 1) critical problems needing immediate solutions, 2) basin characteristics for use in the preparation of detailed basin management ptans, and 3) capital costs associated with the early resolution of draina;e and problems. The reconnaissance reports are intended to provide an evaluation of present draina;e con- ditions in the County in order to transmit information to policymakers to aid them in developin� more detailed regulatory measures and specific capital improvement plans. They are not intendcd to ascribe in any conclusive manner the causes of draina�e or erosion P:I.0 1 Lower Cedar River Basin (continued) problems; instead, they are to be used as initial sun�eys from which choices for subsequent - detailed engineerinb and other professional environmental analyses may be made. Due to the limited amount of timc available for the field work in each basin, the reports must be viewed as descriptive environmental narratives rather than as final engineerinb conclusions. Recommendations contained in each report provide a description of potential mitigative measures for each particuiar basin; these measures might provide maximum environmentai protection throubh capital project construction or developmcnt approval conditions. The appropriate extent of such measures wilt be decided on a case-by-ca.se basis Uy County offi- cials responsible for reviewing applications for pennit approvals and for choosing among competino projects for public construction. Nothing in the reporEs is intended to substitute for a more thorouol� environmental and engineerinb analysis possii�le on a siEe-specific basis for any proposal. �_ E'INDINGS IN LOWER CEDAR RIVCR BASQY The field reconnaissance of Lower Cedar River Basin was conducted in Januarv 1937 bv Robert R. Fuerstenber�, bioloDist: Bruce L. Barker, enoineer; and Lee Benda, �eolobist. Ti�eir findinbs and recommendations are presented here. A. Overvicw of I.owe;r Cc;dar River I3asin 'I�I�e lower Cedar River Basin is located in southw�est King County and is 27 square miles in area. [t extends southeast from the moutl� of the Cedar River on C.ake Washin�ton �o approaimately river mile 1-3.0. The boundarv to the northeast is marked by a ridgetop connectin� the citv of Renton to Wel�ster and Franklin Lakes; the boundary to the southw•est runs alona Yetrovitsky Road to L,ake Younbs. Renton is the only incorporatcd area in the basin. Other population centers include Fairw�ood, Maplewood Heiahts, and Mapie Valley_ Except for the ciry of Renton, most of the residential concentrations are la-ated on the upland plateaus overlookinb the C�dar River Valfey. These upland developn�ents are recent compared to the smaller established commt�nities on the valley floor. The basin lies w-ithin portions of tliree Kin� Cowitv plannina areas: Newcastfe in the northeast (which includes Renton), `I'ahoma-Raven Heibhts in the east, and Soos Creek (the larbest of the three) in the w est. Rural areas e�ist on the va(lev ffoor on both sides of the Lower Cedar River, from approximately river mile 5.50 to li.00. These are limited to pastureland for hoi:sc;s, cows, and some shcep and several small "u-pick" fn�it and ve�eta�ile farms. Similar areas are located on the southern uplands abo��e the reach from river mile 5.50 to 7.00 and in the Lake Desire-Otter Lake area. The plateau is also the site of sand and �ravel mininb operations and, in the southern uptands, of the abandoned Fire Kino Coal Mine. Peat deposits exist west of L.�ke Desice and nortlt and south of Otter L,ake, and peat mininb is beinb carried out north of Otter I�ike. Present zoninr al[ows for urban and suburban densities throu,hout much of the basin, particulariy on the upland plateaus and in the Cedar River Valley from its mouth to appo�imately river mile 6.50. Population projections for the vear 2000 in the three plannicn arcas containin� the Lower Cedar E3asin are over �11,004 an increase of 47 P:I.0 � Lower Cedar River E3asin (continued) percent from the present. Most of this growth w�ill occur in the Soos Creek Plannina Area. Dominant geolo�cal and geomorphic features. The beology of the Lower Cedar River Basin is diverse. Geological formations exposed along the valley include sedimentaiy rocks, undifferentiated older glacial drift, eatensive ground moraine deposits, recent alluvium along thc Cedar River, and landslide deposits along the river and its tribu- taries. The sedimentary rocks, composed of moderately dipping sandstones, con- �lomerates, mudsrones, and shales, are exposed locally along the cliffs of the Cedar River Vallev near the mouth of the Cedar River. In addition. tlie Renton formation. composed of sandstones, mudstones, and shales with periodic deposits of coal, is also exposed alonb the lower portion of the Lower Cedar River Valley. Undifferentiated glacial deposits found here are composed of three or more till sheets, glacio-fluvial s��nd and gravel, glario-lacustrine clay, and sand, and non-glaciai s��nd, clay and thin peat. These lie over the sedimentary rock fonnations and are best exposed in cro.ss-section alonb the cliE'fs of the main valley and major tributaries. Tlse morpholob of the Lower Cedar River Basin is dominated by the valley formed by the Cedar River. Valley walls are steep cliffs formed by landsiides in glacial sedi- ments. A once extensive and meandering River, which created a wide valley ftoor as it cut its way w-estward, the Cedar today is diked for most of its lenp h throu�h the low�er valley. A narrow but extensive band of landslide deposits exists alon� the steep ctiffs of the main river and its major trii�utaries. The landslide deposits consist of deformed bfocks of glacial sediments and colluvium derived from slides or mass flowa�e, such as landslides and debris flows. Recent alluvial deposits fill the vallev and major tributaries. Small, composite, alluvial del�ris fans esist at the mouths of the largest tributaries. Closed depressions, principally in the uplands, have lacustrine and pcat deposits. ' The Lower Cedar River Valley has a high potential for erosion due ro stecp stopes and the existenre of a clay layer that promotes soil failures. In addition. the confined nature of trii�utaiy channels betu,een steep hilfslopes promotes bank erosion durinp hibh flo�vs. Numerous recent [andslides are evident alonb cliffs of many of the steep tributaries and alona the main stem of the Cedar River. These have been accelerated by tlie removal of �-ebetation and the routinb of concentrated storm flows over steep slopes in areas w•here development has occurred. Hydrologic and hydraulic characteristics. The Cedar River Basin is composed of a romplex drainace netuork consistino of the Cedar River and 17 h•ibutaries. The largcr tributaries becin in lakes or wetlands on the bluffs and flow� throu�h relativelv flat, stable channels to the ed�e of the Cedar River Vallev, then plun�e down to the valley floor tltt'ou�h steep, erodible ravines. Tributaries of this type such as Tributarv 0�04 (with headw�aters at Wetland 3111) and Tributary 0323 (which be;ins at Lake Desire}, are found on the south side of the Cedar River. Another tvpc of tributary collects surface n�noff from urbanized areas, pastureland, and wooded areas. Tributaries 0302, 0307, and 0312 are eaamples of this type of tributarv. "I'iic�� are intermittent (depending on rainfall). shorter in lenbth, flow through shallower rhanncls that are steeper at the bluffs and transport more materia! durinr ti��es of P:I.0 ; L,ower Cedar River &isin ' (continued) high flows. Some of the worst pmblems located during field investigation (see Appendix C for a full listing) occur on this type of tributary. Catchments 5, 6, and 12 have very infiltrative soils. Urban developments hvae utilized R/D poinds to effectively infittrate all urban runoff before it reaches the valley hillslopes. The infiltrated runoff then reappears as sprinb. Two farge lakes (Desire and Otter}, together with four smaller ones (Shady, Peterson, Webster, and Francis) lie in the southeast third of the basin. Numerous larbe wettand areas eaist in this section as well. The field team identified 10 potential wetland sites that had not been previous(y identified in the Sensitive Areas Map Folio (SAMF). The system of lakes and wetlands in this area eEfectively buffers the hi�h flows draining to these tributaries. Habitat characterisiics. With few exceptions, usable fish habitat exists only in peren- nial streams (i.e., Trib. 0302, 0304, 0305, 0323, and possibly 0303). In other streams (e.g., Trib. Q303 and 0310), steep gradients preclude fish use. Steep gradients also reduce fish use in the perennial systems (except for 1'rib. 0323}. Habitat is in various stages of deoradation in these systems; pools are being filled and bravets and dehris shift reb larly. In Tributary 0328 (Peterson Creek}, however, habitat divenity is eatensive, and the channe! is not seriously degraded. At this location the field team observed at least three species of salmonoids. In oeneral, the most diverse and least disturbed habitat in a tributary system occurs in the large wetland areas in the southeast third of the basin. Us��ble habitat for I anadromous fish is found in the low-gradient portions of streams w•here channels cross the Cedar River Valley floor. In these reaches, however. only spawning habitat is likely ro be available, as the pools and woaiy debris necessary for successful rearinc either do not exist or are quite limited. Facellent spawninc and rearinr areas exist where pools and riffles are extensive, instream cover and bank vegetation are intact, and divenity of habitat types is abundant. B. Cffects of Utbanization in the Basin Floaiing, erosion, and the degradation of haUitat associated with development in the Low�er Cedar River Basin are most apparent where development has eliminated vege- tation alon, the edbes of the valley and where stormwater has heert routed down channels and sw�ales. The removal of ve�etation, such as trees, above and below the ed�es of valley walls, as we11 as the dis�:haroina of stormwater over the valley watl, has resulted in tension cracks and landslides that are endangerinc some houses. The sedi- ments from these failures are depositinc in streams and on valley floors and damacino fish habitat and private praperty. Discharbin� stormwater from incre�sed impervious areas into steep tributary channels and swales is seriously destabilizino channels and valley walls; this in turn results in channel downcutting, bank erosion, and landslides. The sediments from these problems often debrade fish habitat and settle out on pri- vate property alonb the valley floor. Two serious instances of development-related erosion occurred durina the November 193G storm: 1) culverts rerouting the stream were plu�ed, causinb the formation of a new channel tllat destroyed portions of roads on Tributary 031�; and 2) new�, uncom- P:LC 4 L,ower Cedar River Basin (continued) pacted fi11 adjacent to new residences near coliection point 5 was washed partly away durinb the storm, causing landsliding and b llying. Future problems will be similar io these, as commercial and residential developments increase ftow rates and volumes by decreasing natural storage and infiltration. This is expected to occur if wetlands on the upper plateau are encroached upon or lost (e.o., on Trib. 0304 at RM 2.30 and on Trib. 0304A at Rm 1.60). The preservation of wetlands and streambank vegetation and the attenuation of storm flows are essential in this basin. C. Spccific Problems Ideotified The steep valley sideslopes tl�rouph wliich streams pass and the often dense upland development result in a number of similar problems that repeat themselves throubhout the Lower Cedar River Basin. The most significant of these are outlined and discus.sed below•. 1. Drainage aod [looding problems are often the t+csult oE severat cooditions: a. Uadersv�ed cuhrerts and inadequate entranoe structuc+es. The most notable area is on Tributarv 0306 at river mile .�0, where a culvert here was blocked by debris carried downstream by the stream and caused erosion and floaiinb of Fai�w�ood Golf Course. The block<ice was compounded bv tl�e fact that the culvert was undersized; the problem will worsen as flows increase from upstream development. b. Serious instream emsion and subsequent dawnstream sedimentation. These have been caused by thrce main factors: 1) runoff from residential developments on the bluffs above the valley, ?) compacted pastureland due to livestock, and 3) runoff from impervious areas oripinatino at gravet pits. These problems will continue and worsen until mitigative measures are taken. (See Appendix C for specific examptes.) c. Uodersr�.ed rechannelized streams. Tributaries on the vallev floor are too small ro carry the increased flows oribinatino in developed residential areas alono the top of the hluffs. For e�ample. Tributary 0�02 at river mile .?5, the channel alonb Maplewood Ciolf Course, overtops and [loods durinb storms. d. (:onstruction in wetiand aad t7oodplain areas, Many of the wetlands on the south side of the Cedar River are peat bo�s, and roads huilt throu�h them continue to settle each year, increasing the amount of floodinc on the road. For example, the road crossinb with Tributary 0,?SB north of L.ake Desire will esperience more severe floodinb as the road settles. e. Discharging of stormwatcr at the top of steep banks. At river mile 2.20 on the Cedar River, a trailer park (constructed on the ed�e of the clif[) disc�llarbes its drainace down the valley wall. Increased flows erode the steep valley, depositin� sediments on the valiev floor, blockina channels and causing floodin�. These problems w�ill eventually stabilize, but only after a larce quantity of soil has been eroded. P:LC S Lower Cedar River Basin (continued) 2. Damage to property is being caused by thrce factors: a. IandSlicies and poteotial landsiides. Landslides are accelerated by the removal of vebetation on steep slopes in preparation for residential constn,ction and/or by the routing of storm flows over hilislopes. For example, a large landslide has already occurred in the front yard of a resi- dence on the Cedar River at river mile 7.30. b. Sedimentation (from landslides). Sedimentation and channel and hank ero- sion are damaging private property alon� the vailey floor (Tril�. 0299 and 0310). c. Ilooding during storms. Flooding has been brought on by the effects of development and associated changes to the natura[ draina�e systems in the basin. (See "B" above.) 3. De.struction of habitat is being caused by four conditions: a. Sedimeatation of pools and riffles aod ecmeoting of gravels. These problems, the result of severe erosion and Uie transport of bedload material, have been caused by upland developments in the basin and the presence of associated impervious surfaces, which increase the rate and quantity of surface runoff. Sedimentation and cementing of gravels in streambeds destroy natural spaw�nin� and rearinb habitat. On Tributarv 0307 at river mile .40 and Tributary 0305 at river miles .9$, 1.20, and 1J0, recent hi�h flows have eroded the streambed at least one foot, contrihutina to a serious siltation problem downstream. Heaw bedload h•anspori is evi- dent in all systems of the basin except Trihutary 0�?3. [n Tributary 0�03 at river mite ?5, fine sediments are accwnulatin� in gravels that may be used by resident fish. In Tributary 0304 betw•een river miles .95 and 1.30, pools are being filled by sands and gravels and rearing habitat is beinp rapidty lost. b. Channelization oE stream beds. Loss of habitat throu�h channelization has occurred in all the major streams of the basin. but most noticeably in those reac:hes that cross the vallev floor. These reaches lark habitat diversitv. reduc:in� fish use for spawninb and rearino. Channetization has damaoed or destroved habitat in several reaches that were once heavilv used bv fish: these include Tributary 0302 betw�een river mile .30 and -30, Tributary 030�3 i�eh.�een river miles .OS and .14. Tributarv 0305 hetw•een river mile .20 and .75, and Tributarv 0.23 from river mile 1.10 to 1.-�0. The.se svstems cannot afford a further reduction of habitat and still remain viable fislierv resour- ces. c. The accumulation of tzash in stream bed.s. This problem occuis in close proximity to residential areas. Trash degrades water quality and is visuall�� unpleas�nt. Tires, appliances, furniture, and other trash have l�een thrown inro Tributarv 0�03 at river miles 1.00 and 1.10 and in Tributarv 0�03 ac river mile .i5. P:LC 6 Lower Cedar River Basin (continued) d Wetland enc�oachment. Encroachment destrovs habitat and eli►ninates natural wa[er filtration and storabe for surface runoff. Cxamples of this problem were observed on Tributary 0304 at river mile 3.�0, Tribut<lry 0�03 at .30, and Tributary 0304A at river mile 1.30. Many w�etiands have already been completely lost throurh filling, for example on Tributarv 0306A at river mile .55. Suspected violations were foiwarded to Buildinr and I..and Development for enforcement. IV. RECOMIuu�NDATIONS FOR ACI'ION The priman+ recommendations for action in the Low•er Cedar River Qasin addresses current severe problems related to erosion, habitat destruction, and floodinb. Prevention of these problems will be accomplished by control(inp tocations and densities of new development and providing adequate R/D facilities for stormwater. A. Rcduce landslide hazar�ds by: L Including seasitive areas not pneviously mapped on t6e Sensitive Areas Map Folio (SAMF). See Appendia C for a full lisiinb of sensitive areas. 2. Establishiag building setbacks along cliffs and native prow�th protection easements along steep ravines. 3. Discouraging or e(iminatiag the routing of stormwater aver cliffs, unles.s adequate tightline svstems can be const►�c1ed to convey flow�s in a safe, nonerosive manncr to the bottom of rliffs. 4. Decreasing pcak flaws by constn�cting larber R/D facilities ro le.s.sen tlie landslide and erosion occurrence alono tributary slopes. I3. Reduce emsion and [Iooding in the basin by impmving surface water managemcnt: 1. Dinect ihe I�acilities Management Section of the Surface Water Management Divisioo to evaluate existing storm�etention and oonveyance facilities to deter- mine whether they are properly sized to meet current standards. Evaluation should bebin with all sin�le-orifice R/D facilities� 2. Coosider ac+eas other than wetlands as regional storm�detention facilitics. Tributary 0300 at river mile .�2 is the site for a proposed dam, for example. 3. Utilize ezisting lower quaGty wetlands (tho6e rated other than #1) as regiooal storm-dctention facilities. Wetlands 3IO2 and 3142 could provide more live stora�e, for example. 4. Review channe( and cutvert capacity for mnveying existing and fu/ure runoff, and establish floodplain areas in re�ions of sli�ht bradient for existinb and Future ninoff conditions. 5. Promote the infiltratioo o[ surfacc water t6rough t6e use of retention facilitics and opcn channels instead of pipes where the soil and slope conditions permit. Collection points S, 6. and 13 on plateaus have such soil conditions. P:f,C 7 Lower Cedar Riv�r Basin (continued) C. Prevent future problems of erosion and floodiag wit6 appropriate anatysi.� plaanin� and policy cicvelopment c+elated to surface water maaagement: 1. Conduct a detailed, oomprehenSive hydrauGc/6ydrologic aoalysis of any proposed devetopments to determine impacts on the drainage courses downstream. This is especially critical for areas on the upper bluffs and plateau, which drain over steep, sensitive banks above the Cedar River. 2. Conduct a study of t6e impact of locating inf'iltration ponds utitized near the ed�c of the bluffs to determine their effect on seepape faces on the low•er face of the bluffs. This might be accontplished with a computer-hased numerical model of the broundw�ater ftow�. 3. Require the tightlining of storm drainage dawn steep or seasitive stopes when they cannot be direcied away from the slopes. This is done by pipinc the flow down the slope and discharoing it at the bottom with adequate ener�� dissipation. Many of the intermittent tributaries flowing do�an the l�anks should be ti�htlined as urban development increases flow to them. 4. Coostruct new R/D ponds wit6 filter berms to improve water quality and reduce fine sedimeot loads. New R/D ponds should have two cells with pravel-berm filters and vegetated swales at the inlet and outlet. Consider Tributaries 0�0-�, 0304A, 0302, and 030� as sites for this type of facility in order enhanre w�ater quality. 5. Maintaio natural vegetation oo strcambanks and (7oodplains. This is esperiallv important for relatively flat channels flowinb on the plateau before Y�IeV I'eilCll ihe steep bluffs because these channels and their floociplains will attenuate flows durin� times of heavy runoff. 6. Maintain bufEer areas amund wetlands. Manv of the tributaries on the south side of the Cedar River headw�ater a[ wetlands. 'I'hese wetlanJs act as natural storace areas durinr storms. 7. Rcevaluate King County policy regarding permitting for grave! mining on steep, sensitive slopes. 8_ Include t6e city of Rention in future intcrlocal agreements for plannin� and capi- tal improvement projects where city and countv interests overlap. D. Eliminate present damage to 6abitat and prevent tuture damage by addressing spccific problcros in the stream systems. The followinp activities should be coor�iinated amon� Kinc County, the Muckleshoot Indian Tril�e, and State Departn�ents of Fisheries and Game: 1. Reduc� damaging storm flows with breater detention volume and lower release rates at upstrean� developments. 2. Implement restoration pnojects on Tril�utaries 0:0�3 (river mile .00-.?0), "I'ributary 0305 {iiver mile .20-.30), Tributarv 0303 (river mile .35-.;5). and Tributarv 0�2�5 (river mile 1.10 -1.40): P:LC 4 Lower Cedar River Basin (continued} a. On Tributary 0304: Clean streambed gravels, add habitat and bed-control weirs, and plant bank vegetation for shade. b. On Tributary 0305: Construct a new channel and move stream from road- side channe! to its new location on adjacent lands. Implement a full restoration project to provide channel meanders, habitat structures, pool/riffle enhancement, streambed gravel replacement, and revegetation. c. On Tributary 03t)3: Move stream from present channei to a location further north, away from the roadside. If relocation is not possible, these minimum steps should be taken: Add habitat structure to existing channel with root masses, deflectors, boulder clusters, and other features; revegetate channel banks with shrubs and small trees; enhance stream crossings with battomless pipe arches. d. On Tributary 0328 (Peterson Creek): Add habitat struciure by replacing the straight, shortened channel with a more natural, meandering one; place habitat structures (such as root masses, def7ectors, cover loas, and boulder clusters) throughout the channel; and revegetate banks with shrubs common to adjacent riparian zones (salmonberry, ninebark, or dod ood, for example). 3_ Pr�tert the Peterson Creek system (Trib. 0328) in its present, near-pristine statc. I This will include not onty the restoration outlined in section A above, but also i the adoption of land use management rea lations to prevent future habitat destruction: a. Protect all e�osting wetia�ds within the subcatchments of Petersoa Creek. Employ wetland buffers at least 100 feet wide without exception. b. Restrict development in the critical beadwater area (drainage, habitat, water quality) bounded by Lake Desire, Otter Iake, and Petersoo Lake to rural densities. c. Desig�ate and protect streamside management zoaes of at least 100 feet from the ordinary hibh-water mark (OHWM) along the main stem of the creek. Use 25 feet from the OHWM on tributaries. d_ Prese�ve floodplains and their forests for dynamic retention of sediments and w�ater. e. Restrict vegetation eemoval in streamside/wetland management zones. [. Size R/D facilities to store the 100-year storm at a two-to-five-year release rate. Use t6e two-cetl type of po� with a forebay, a gravel filter, and a vegetated swale outftow where feasible. g. Regulate more closely all septic tanlc and dcain-6eld installations, as wcll as maintenance schedules, particularly in the Lake Desire, Otter [ake, and Peterson Lake drainage areas. P:LC 9 L.ower Cedar River Basin (continued) h. Work with t6e Statc Department of Emlogy to establis6 minimum stream- Oow requiremeats for Peterson Creek and Lake Desire tributary. 4. Devebp and pinmote public education and involvement proarams for basin awareness. Work with schools. environmental groups, and the civic and business communities to conduct educational and restoration probrams. ,J Y:L.0 10 ., i �, I �i ... � ,..�-.... :. ''.. . .,i �' I µ i I `�\ .-......' i�. 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'. i . _ j y � , - � 3`y . _ '� c� � Q 1 t 9'9 �`"'k i ��:�;. � `, p3� �j'j , ,,r; 1 �,�� `, � ; �� ., , ;+�. �.1i__.,.._ .�a„y .'; ,"' +' .�a .. \ ('..�. � . . , \ �. � `°'�,. �° ' ,� . � . . � ri� r� ., . . . . . . ._. .... . .. ... :.... _._. ..._ \ y . - � � � �, '��, o �: � � „ �4a � ,.�� ,a,,� .��`� `� �� ,�3'•'��.3115 '�, � , , � �,.,. , j .. . � '^"� �, ,..�� yti� ,� ,. ' i.__��; ,T---• �� -, o ',__. ,. 3`` 1 , , ,.. ,.... .,� ; O— ry��. � 3 c, �oc scnrne wnrensn �i $9C `�� d ryj ..-��z : � ' � 3 „ ; ,.v. , . , : �.. � _,� . __. _ _ _. ....._ ._._._ . __ . _. _._ :. ._� __... I I 1 '+� � �112 . < 11' ,:� `�.`'.,.. � �...,0 . �� r • ,.� � - i .. �-� , � '. � � . c' i , I � �� ,�, , . i ; .�� ,�. i , • �,..'�� % t �� r .. � . � . . ..1 .�� ,',� s �'� �, r*, t MaPIa Vall¢Y � . .. � . . �•� .. �"r . .S.-._ ,.mG / � ._..._..... .. ,I .. �e:q;X�r. , , ,,., ( . :�: s� . � � , .. I � . .�, ' ' i 1-., � _ =F x� \s� , I ,. I.,.,. . r, .i ,I tI „I�., S� _ tf .�� r� f ' � , � :.I .. ,. .. . j �l'� I - � �. ., ��, i ' � i . ., _,.I ..: . . .. .._�...._ ..- .. ....-- ----__. .. .----- -. --'__._ - ' -� 4 ��i... . .:. � ' ��.,,, ��.i � � : . _`• �... . ��, .�_., � . _ �,'r'��T. .�!;r \ j�t�� .. \ APPENDIX A . ES"I'IMATEU CUSTS: PROI'OSEU CAP[TAL 1MPROVEMENT PROJECTS LOWLR CEUAR CRELK BAS[N " Indicates project was identified by Sur(ace Water Management o(fice prior to reconnaissance. NOTE: All projects are located on map included in this report. Projeet Collect. Estimated Costs Numhcr Point Projcct Ues�ription Problem Addres.sed and Comment5 3105" lU L-'nh�ncc 220U' of Trih. 0305 from Mitigates floodinr of King $115,000 Cedar River to Elliot Brid�e. County park land. (NOTE: This project was proposed by SurCace Watcr Management, is in the design phase, and will be constructed I�y 1989.) 3109" 10 Secure e�se;ments to wetland loc��ted I3etter utilizcs wetl�nd's storage $13G,000 in Cascade Park and ronstrurt a berm c�pacity to address peak flows from �u the outlet. Rcplace existing surroundin� url�an area. catch hasins with rontrol stn►ctures. Pcoject should hc justiCicci hy a , hasin studv. Wetland rated #?. ('I'his wetland will requin: furthcr biolo�ical cvaluation l�cfore R/U dCSI�^,t1 and construction.) t�:[_c.nrn �-1 P�nject Collect. Estimated Costs Numl�er Point Projcct Uesc:ription Prohlem l�ciJcc�.sc:d and Comme;nts 3111 Secure e�isements to outlet to Francis Will provide additional storage $175,000 (WeUand Lake and 11U0' of channel from lake to mitigatc anticipate�i future 313G) to SE 1;S4th St. Construct a weir to increaseci Clows. raisc lake Icvcl 1', and cnhance 1100' of '1'rih. 0:�17. Should he .justificd hy a basin plan. Wctland r��tcd #1. (This wctlan�i w•ill rcyuirc ftirthcr hiolo�iral evaluation hcfore R/D �icsign an� const�vction.) 3112 19 Sccurc cascmcnt for oiitict to wetlan�i Will providc adciitional storage $117,000 (Wctlund anci replacc existinp wcir with a for anticiparod future peak flows. 314�) concrctc-slottcd wuir. Should he justified hy a b�sin plan. Wetland r�ued #2. ('I'his w�etland will requirc further hiological evaluation heCore R/D desi�n and �onstruction. 3114" Sccurc casemunt to Wctland 3L5U an�i Addresses anticipated inrrea.ses in $134,000 (Wetland constn�ct a containment l�erm and flow causeJ hy dcvclopmcnt. 3150) control struc:ture at the outict. I'roject should Ue justificd by a hatiin plan. Wetland rated #3, ("I'his wetland will require furlher hioloric:il cvaluation hcforc: R/D deSi<<*.,r1 and constniciton.) 3115 14 Install dctcntion pond and 1,(?00' Mitigatcs scvcrc �rosion and $311,000 of tightlinc. Projcct is indcpcn- floodino durinb times of hirh dcnUy .justifiablc. flow:s. 1':l.C.APA t�-2 Projcct Colicct. Estimatcd Costs Nwnher Point Projc�t Dcu;ription Prohlcm �lddresscd and Commcn�s :�IIC, ?1 Raise existing road emhankment Miti�ates seasonal flooding of I.��ke $73,000 2-4'. Project should be indcpen- Desire Ur. SL caused by road bed dently .justifiahle. (Refer to settling in the peat bog. Roads Uivision.) 3117 16 Install 1,400' of ti�htline, a Miticates sevc;re erosion, sediments $SO1,000 scdimcnt trap, and 700' of channcl depositcd on County roads, and from Joncs Rd. to CcJar River. flooding during times of high Projcct is indcpcndcntly justi- flows. fiablc. 3118 10 Install 300' of :�(�" culvcrt, a new Will preveni hlorka�e of culvert �37,000 inlet smicture, m��nhole, and catch and the arcompanyin� floodino and hasin. Yrojcct is independently erosion of Ijai�wood Golf Course and justifiablc;. m�bile home park below. 3119 4 Construrt a detention dam �nd I'roject loc:ation is ideal because $159,000 control structure in a deep it addres.Se;s flow:s from a laroe channelized sc:ction of '1'ril�. resi�ential area bcfore they reach 03(�. Pro.jc:ct is independently the Steep, sc:nsitive ��na neat to justifiahle. the Cedar River. 3120 15 Consti-uct �� x:Jimcntation pon�i anJ Mitigatcs Cloo�iinr of resi�icncc and $1G3,000 1,000' of channcl from Joncs Itd. to sediment deposition on Jones Itd. Ccciar Rivcr. I'rojcct is indepen- �i�ntly justifiablc. P:LC.nPA A-3 Project Collect. Estimatcd Cos�s Nunthcr Point I'i•ojcct Dcscription Prohlem Addre�.sed and Comm�nis 31?I 7 Sccure easement to wetland and con- Addresses inrrcased flows in Trib. $371,U00 (Wctland struct a containmcnt hcrm and �oncrete 0304 anci 030-1/� from residcntial 31U2) wcir at outlet. 1'roject should be dcvelopmcnts. justified by a basin plan. Wetlan� CIlICc� #�. I31010�IC8I a�.sessment is nccded to assurc tl�at this projcrt does not decrcase habitat values. 3122 11 I'urcha�: existing ponds on Faitkoo�i Mitiratcs floodin�, and crosion $342,000 Golf Coursc; and expand ro provi�le downstream. grca�cr flow �ietention. 1'roject is in�ependently justifiahle. P:I_C.AI'A A-4 APPENDIX B CAPITAL IMPROVENIENT PROJECT RANK[NG LOWER CEDAR RIVER E3ASIN Prior to the Lower Cedar River Basin field reconnaissanre, 1? projects had been identified and - rated usinb the CIP selection criteria developed by the Surface Water Mana�ement {SWM) and Natural Resources and Parks Divisions. Following the reconnaissance, i3 projects remain pmposed for this area. They include eight new, previously unidentified and unrated projects. These displace seven previously selected projects, which were eliminated based on the consensus of the recon- naissance team. Projects were eliminated for several reasons: two sites w�ere annexed by the city of Renton, tv��o projects were found to be unnecessary, two sites were categorized as #1 wetlands (and are ineli�ihle), and one project was determined to be infeasible. The previous SWM capital improvement project list for the Lower Cedar River Basin had an esti- mated cost of $2,710,000, while the revised list increases to an estimated cost of S2,7'�4,000. This 3 percent increlse in estimated capital costs is due to the addition of projects after the reconnaissance. The follow�ing table summarizes the scores and costs for the CIPs proposed for the Lower Cedar River Basin. The.se projects were rated according to previously established SWM Program Citizen Advisory Committee criteria. The projects ranked Ueiow are those for which the first rating question, ELEMENT 1: "GO/NO GO," could be answered affirmatively. Projects with xores of 100 or hi�her can be considered now for merDinb into the "live" CIP list. RANK PROJ�('T NO. SCORE COS"1' 1 3122 103 $342.000 2 3113 90 87.000 � 31?0 7S I63.000 -t �109" 67 136.000 5 31?1 65 371.000 G 3117 60 SO1.000 7 3115 60 361.000 3 3116 55 73.000 9 3114° 23 134.000 10 3111" 25 175,000 11 3112' 17 117.000 12 3119" 15 1$9,ppp 13 3105 1? 115,000 TOTAL $?.73=1,000 ' Projects proposed prior to the Reconnaissance Pro�ram P:LC.APE3 B-1 APPENDIX C DETAILED FINUINGS AND RECOMMENDATIONS LOWER CCDAR RIVER I3ASIN � ° All items listed here are located on final display maps in the offices of Su�tace Water Management, Building and Land Development, and Basin Planning. Trib. & Collect. Existing Antiripated Item° River Mile Point Cate�;or.y Prop. Proi. Conditions and Prohlems Conditions and Problcros Recommendations 1 -- 5 Geolody Gullying and landslides in Continued crosion. Recompact fill, revegetate, uncompacted fill in new and drain adequately. development ncar edge of steep hillslope. 2 -- 13 Geology Small landslide has formed None (natural failure). None. debris flow (11/86). Sedimentation in yard of residence. 3 0299 4 Geology Landslides in sedimentary Natural failure. None. RM 2.G rock in cutbanks adjacent to railroad. 4 0299 IG Geology Drainage from residential Increasing erosion. Provide adequate R/D to RM 9.65 area is resulting in attenuate flows. gullying in swale. P: LC.APC G1 Trib. K Collect. Existing Anticipated Item River Mile Point Cate�ory Pro . Proj. Conditions and Problems Conditions and Problems Recommendations 5 0299 13 Geolog}+ Horse farm in uplands has Continued high erosion and Develop R/D at horse f<irm RM 12.1 created extensive imper- sedimcntation. to attenuate pcak flows. vious surfaces, resulting See Project 3115. in channel scour, bank erosion, landslides, and st:dimentation at mouth of basin. Residence overcome with sediment. 6 -- 13 Geology I.2ndslide terrain for s��le Site of future mass erosion. Prohibit development here. I by realtois. High risk for Notify Building and Land landslidcs, floodin� (from Development. Add area to springs). SAMF. 7 -- 7 Geoloby L.arge-scale landsides Natural process. None. adjarent to Cedar River due to springs and cutting of tceslopes by streams. , Appears to be natural. g -- 2 Geology Gullying in valley wall, Unknown. None. possibly from natural springs. 9 -- 14 Geology Landslide debris flow from Existing tension cracks Revegetate hillslope with residence on SE 147th PI., indicate future instability. trees and shrubs. Renton. P: LC.APC G2 Trib. & Collect. Existing Anticipated Item River Mile Point Cate�ory Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 10 0299.1A 21 Hydrolo�+ 3116 Frequent flooding of Road located on top of peat Elevate the road 3-4' by RM .08 county road caused by low bog and will continue to filling on top of the road embankment. settle, a�ravating flooding present road embankment. problem. Also stabilize embankment. 11 0300 4 Geoloby Extensive channel and Problems will continue. Provide adequate R/D in RM .00-.40 bank erosion and numerous uplands. (See Project landslides due to 3119.) development-related stormwater. 12 0300 4 Hydrology 3119 Development-related peak Increased erosion on Construct detention dam in flows have caused sig- hillslopes below. deep, channelized reach of nificant bank erosion. Trib. 0300. 13 0300 4 Hydroloby 3109 Collection point 4 has Degradation of Trib. 0300 Construct berm and standard RM 1.40 been nearty completely from RM .42 downstream. This control structure at outtet urbanized. section is very�steep and to Wetland 3120 in Cascade � susceptible to erosion. Park. 14 0302 6 Geology Channel downcutting and Will continue at same level Control storm flows from RM .50 bank erosion. or increase. uplands. 15 0302 G Geology Bank erosion (medium den- Increasing erosion with Provide adequate R/D in RM .30-1.00 sity) at meanders and increasing flow from deve!- uplands as area develops. - obstructions. opments. P: I_C.APC C-3 Trib. & Collect. Existing Anticipated Item River Mile Point Cate�ory Prop. Proi. Conditions and Prohlems Conditions and Problems Recommendations 1G 0:�02 6 Geolofiy Gully erosion from broken None. Culvert has been None. culverts. repaired. 17 0302 6 Geology Severe wlly erosion Continued erosion. Tightline flows to i RM .60-.40 creating small valleys main stem. from daylight culverts. I 14 0302 b Iial�it��t Stream channeled �long While fish now use this Add habitat diversity RM35 golf course road. No reach, lack of habitat wilt (e.g., structures, overhead overhead cover. No habi- eventually reduce popula- vcoetation). Gain tat diversity. tions. easement ro restore mean- ders, if possible. 19 0302 6 I�ydrologV Tributary drains down Problem will worsen as Construct detention dam IZM .45 steep Uluffs on noi•th development upstream upstream of golf course. side of Cedar River, continues. carrying debris and flooding Maplewood Golf Cou rse. 20 0303 6 Habitat Water supply dam. Full As impoundment fill.s, storm- Dredge pond and maintain RM .50 barier to upstre�m water will flood over bank. it as sediment catch. migration. Impoundment Stn�cture may fail. is filling with sediment. ?1 0302 6 Habitat Severe gullying from right Will continue to erode until - Tightline downslope. RM .90 bank corre�ated metal reaches till layer. - Add velocity attenuator at pipe. Heavy sediment stream. delivery to stream. P: LC.nPC G4 i Trib. & Coilect. Existing Anticipated Item River Mile Point Categorv Prop. Proi. Conditions and Prohlcros Conditions and Problems Recommendations 23 0302 6 Habitat Tr►sh in stream (auto, Area adjacent to corridor, - Remove trash. RM 1.0� tires, appli�nces). will continue to collect - Distribute educational trash and debris. Further materials to streamside worsenin� of water quality, residents. sedimentation, erosion. - Cite violators, if problem persists. 23 0302 6 liabitat Trash in stream. Water Area adjacent to corridor, - Remove trash. RM 1.10 qullity problem, will continue to collect - Distribute educational unsightly. trash and debris. Further materials to streamside worseninr of water quality. residents. - Cite violators, if problem persists. ?-� 0303 6 Gcology Extensivc bank crosion in Nonc. Increa.se R/D volumes, slow relcasc: upper portions of tribu- rate to nonerosive levels. tary. 2S 0�03 6 Eiabitat H�bitat suitable for resi- Scdimcnts will eventually - Control stormwater volumes RM .2S dent fish. Sediment accu- cover gravels. Etabitat and discharge rates from mulating. will become unsuitable for developments. fish use. - Manually clean gravels when necessary. 26 O:t03 G Habitat Trash and litter in Further dccreascs in water - Rcmove trash and litter. RM .35 channet affecting water quality. - Distribute educational materials quality, causing erosion. to streamside residents. - Cite violators, if problem persists. P: LC.APC GS Trib. R Colle�t. E�isting Anticipated Item River Mile Point Cflte�orv Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 27 O:iO4 7 H�bitat I��ndslides contributino Sediment will continue to Maintain riparian corridor RM .40 sc;diment to channel. Heavy enter system until landslide with setbacks at least 50' deposition in pools, at stabilizes. from tops of banks. obstructions, even in riffles. 2� O�iO4 3 Habitat Florses have acce�.s to Further dccreases in water - Encourage residents to fencc RM 2.10 stream, causino some bank quality, hank erosion likely. channel back 15' from ordinary deterioration and possibly high-water mark. affecting w�ter quality. - I_imit access to livestock to one or two points along stream. 29 0304 3 �iydroloby Flooding c�used by failinp Problem will continue until - Problem refened to Main- RM 2.30 R/D at 17Gth St. �C 146th outlet structure is tenance section of Surface Ave SE. modified. Water Managcment Division. 30 0304 3 Habitat Encroachment occurrino Wetland likely to be - Require encroaching fills ItM ?.40 along all boundaries of reduced slowly until it is to be removed. this headwater wetland. completely destroyed. Loss - Establish specific buffer of storage, filtration, around this wetland. organic production, and - Enforce sensitive areas wildlife habitat. ordinances and regula- tions. 31 Q304 7 Geolobry Several gullies due to Problem will continue. - Tightline drainage. RM .30 d�ylight culverts; a few have recent landslides. P: L,C.APC C-6 Trib. �C Collect. Existine Anticipated Ilem Rivcr Mile Point Catenoiy Prop. Proj. Conditions and Prohlems Conditions and Problems Recommendations 3? 0304 7 Iiahitat Extensive riffle (to RM Gravels risk becoming - Enhance habitat by ad�1i- RM .00 .15. Crcek channeled. No cemented. Few resting areas tion of woody debris in woody debris, little bank for upstream migrating fish. stream. vebetation. Steelhead, - Revegetate bank. colio spawners here. - Enhance pool/riffle raeio. 33 030� 7 �Iahitat Debris jam may he a Debris will continue to - Selectively remove dehris RM .20 partial migration harrier. accumulate. C;hannel will to allow Fish pas.s�lge. likely divert or jam will - Stabilize large woody fail, releasing accumulated debris. scdimcnt. 34 0304 7 Habitat Debris jam. Bed drops 3' Debris will continue to - Selectively remove debris RM .62 over jam and sediment, accumulate. Channel will to atlow fish passage. [orming anadromous likely divert or jam will - Stabilize large woociy barrier. fail, releasing accumulated debris. sediment. 36 0304 7 I-iabitat Water turbid; oily sheen Water quality will continue - Educate residents about RM .SO and odor present. Storm to dec;line as runoff and how to maintain water quality. drains empty directly into waste enter stream. - Mark storm drains with stream. "Dump no oil" signs. - Emphasize recyclinb of oil. 37 0304A 7 I�ydrology 3102 Existing forested wctland Additionnl storage could be Construct a proportional weir RM 1.30 providcs detention for utilized by constructing and berm at wetland outlet. Trib. 0304A and 0304 in berm and weir at outlet. Project could be used instead heavily developed area. This could be done to atten- of Project 3107 to rpeserve the uate increlsed peak flows #1 rated wetland (where project as upstream area develops. would be built). P: LC.APC C-7 'I'rih. �C Collect. Existino Anticiplted Item River Mile Point Cate�ory Prop. Proj. Conditions and Prohlems Conditions and Problems Recommendations �`� U3U4A 14 I�lydroloby 3115 Runoff generated on top of Flooding will continue as - Construct detention pond RM .40 bluffs on southwest side lon� as land use remains the at top of bluffs. of Cedar River is causing same on top of bluffs or - Tightline drainage down severe bank erosion, until miti�ating measures bluffs, then channeli�e it floaiing and dehris flows are taken. Runoff origin- to an existing ditch onto several residc;nccs ates from hi�hly compacted alongside SR 169. of valley floor. p�stureland on uplands. - Prevent similar prohlems elsewhere with land use regulations, including provisions for preservation of vegetation buffers ncar tops of cliffs. 39 0305 10 Geology Extensive bank erosion, Susceptible to increases Attenuate high flows. ' partly due to subsurface with increasing storm flow. clay layer and landslide topography. 40 0305 10 Geology Local severe bank Problem will continue. Existing rock-filled RM 1.10 erosion. gabions are deflecting f low. 4] O�t05 10 Gcology Extcnsive channel down- Continued erosion. Attenuate high flows with RM 3.10- cutting and bank erosion. adequate R/D. (R/D 1.75 currently exists.) 42 0305 10 Geolo� Several a Ilies and as.so- Erosion will continue. Tightline culverts. RM 2.15- ciated landslides due to 1.75 daylight culverts on steep slopes adjacent to chan- nels. I': LC.APC C-3 Trih. �� Collcct. Existing Anticipated Item Itivcr Mile Point Cate�orv Prop. Proi. Conditions and Problems Conditions and Problems Recommendations 43 0305 10 Ilabitat Madsen Creek in ditcl� alonb Potential for fuel entry in- Acquire 30' easement away RM .20 S� Jones Rd. Hcavy silt; to creek. I'urther decreases from roadside. Construct road runoff; water yuality in water quality can be ex- new stream channel. adversely affected. pected. 44 0305 10 IIabitat Creek in ditch along south Further decreases in water Acquire 30' easement away RM .35 side of SR 169. I ieavy quality can be expected. from roadside. Construct inputs of oils, anti- Potential for autos to enter new stream channel. freezes, heavy mctals, channel. L,ack of habitat. orpanic pollutants likely. Sand, silt From roadside (of SR 169) enters also. 4S 0305 1ZM .OU- 10 1�ydrolopy 3105 Scction of Trib. 0305, Flooding will continue. Construct and enhance 2200' of .40 RM .00-.40 is eapericncing (See Appendix A, Project channel through undeveloped eatensive flooding. 3105.) King County Park Land. 4G 0�05 10 H�bitat Channclized alona dri- rurther siltation, water Acquire easement; move RM .SO veway; lacks habitat quality dcgradation can be creek from driveway diversity. Driveway scdi- anticipated. Lack of habitat 10-15'. Add meanders and ments enter channel, and precludes optimum salmonid habitat structures to oil, placed on driveway use. increase diversity. enters stream. 47 0305 10 IIabitat Channelized tributary Little s��lmonid use Add structures to increasc IZM .fiS lacks hahitat diversity, anticipated. Spawnino and diversity in stream. cover for s��lmonids. rearing success limited Manually clean gravels by Gravels compacted. (unless reach is restored). churning them. P: I.C.APC C-9 TriU. �C Collect. Ezisting Anticipated Item River Mile Point Cate�orv Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 44 0305 10 Habitat Good splwnina rifflcs occur Increased flows may cause Control flows into system I2M .�� here. '/a-3" gravels, few gravcl l�ar movement. from devcloped areas fines, not compact. Hioh Suitable gr►vels may be upstream. If necessary, flows are moving materiai, transported downstream to add bed controts to hoiJ I�owever. unus��l,le are��s for spawning gravels or "vee" struc- salmonids. tures to recruit them. 49 0305 10 Habitat Severe bank cutting and Further erosion/scouring can Control high flows by RM .95 erosion occurs hcre. Bed be expected. Channel increasing upper basin R/D scouring evident. Reach deterioration will continue. facilities, lowering sul�ject to hiph, rapid Flows appear to be gener�ted disch�rge rates to stream. flows. at developments. SO O305 10 Ilabitat Much woody debris Debris jams will occur with Control upstream flows RM 1.30 movement and numerous �reater Creyuency as flows with greater R/D volume, ' dcbris jams. Reach is incrcase. Sediments will lower discharge rates. subject to hioh, rapid build up and channel will Sclectively remove debris. flows. divert. S 1 O:i05 10 Hahitat Channel erosion, bank Further channel deteriora- - increase R/D capacity. RM 1.70 failures, downcuttino oc- tion may be expected. Silt, - Decrease discharge rates. currino. Reach subject to sand transport to mainstem high, rapid flows. will increase. S? 03p6 10 Gcology f�ilure of manhole during Not applicahle. Repair manhole. RM .40 11/3( storm has resulted in gully crosion. P: I.GAPC C-10 'I'rih. R Collect. Existing Anticipated Item River Mile Point Cate�ory Prop. Proj. Conditions and Prohlems Conditions and Prohlems Recommendations 53 0�06 10 Geology Channel downcuttinb, bank Erosion will inerease. Clay Further increase in runoff I2M .20 erosion and sc:vcral layer in valley makes area should be attenuated; this landslides, due both from sensitive to landslidcs. is a sensitive channel. increased storm flows and development along e:dge. 54 0306 10 Geology Undeisized culvert in arti- Possible fill failure: Lake Enlarge the corregated RM .30 ficial fill in golf course ponded behind culvert in metal pipe and/or threatens to build lake and in 1931 and threatened construct adequate trash possibly overtop bank. the fill. rack. Brcach flood possiblc. .5S 030�i 11 IIabitat Channel subject to I�igh, Further channel damage can Increase R/D capacity, RM .25 damabino flows. Erosion be eapected. Sediment decrease discharge rate. evident. transport downstream will continue. SG 030�i 10 Cieoloay Downcutting, bank erosion Will continue or increa.se in Attenuate storm flows. 1tM .30-.45 �nd landslides. future. _57 030C� I�Iydrolopy 311�g Trib. 0306 conncets with Problem will worsen as - Replace existing pipes RM .30 large tributary at manhole development upstream with 1lrger diameter pipes here. Debris from 030G continues. (if downstream analysis clobs this manholc, causinp �Ilows for increased flows). severe erosion of Painvood - Install new inlet struc- IGolf Course. tures with trash racks. $8 030GA 11 I-Iydrology 3122 Existing small ponds on Area upstream is developing - Acquire easements for ponds I2M 1.30 0306A are overtopped and quickly, thus worsening the and additional area around ponds receive considerable silt problem. and construct detention pond. during high flows. The - L,ocation is ideal for addressomg ponds are located on peak flows before they reach I�ainvood Golf Course. the sensitive Cedar Reiver bluffs. P: LC.APC C-11 '1'rib. �� Collert. Existin; Anti�ipateci [tem River Mile Point Cate�oiv Prop. Proj. Conditions and Problems Conditions and Probiems Recommendations 59 030GA 11 1-labitat Some usable habitat exists Further habitat deterioration - Increase R/D capacities. RM .25 for residcnt salmonids. likely. Channcl erosion will - Uecrease discharge rat�s. Water quality is poor. increase. - Encourage use of 2-celt Channel subject to high detention ponds, swales. flows. - Prohibit filling of existing wetlands, ponds in upper basin. GO 0307 12 Geology Extensive bank erosion at Increased erosion will - Mitigate development- RM .10-.40 all meanders and obstruc- result with increased flows. related hi�h flows. tions (trees, cars) due - Provide adequate R/D. to increased fiows from development. 61 0307 12 Geolo�y Stream erodin; toes of Increasing erosion with - Mitigate development RM .10-.60 slopes resulting in increasing flows. related high flows. landslide f�i(ures. - Provide adequate R/D. 62 0�07 12 Ilabitat Stream channel pushed ro Erosion will worsen as - Incrcase R/D capacity at RM .30 one side of ravine for stream flows increase. all delivery points. roadway. Hiah encrey May threaten road bank at - Reduce release rate bclow system. Much bank cuttinr, tce of slope. channel scour levet. s�;dimcnt transport, dcbris movement. �i:i 0307 13 Hydrology Area on top of hluFfs near Infiltration sites should Construct retention faci- ItM .60 Trib. 0307 has excellent be used whenever possible. lities for new develop- infiltrative capacity. These would provide pround- ments in area at these sites. watcr rech��rge. P: LC.APC C-12 'I'rib. �C Collect. Existing Anticipated Itcm River Mile Point Cate�ory Prop. Proj. Conditions and Prohlems Conditions and Problems Recommendations G� 0309 15 Habitat Subject to heavy, rapid Erosion, deposition will - Control storm flows RM .10 flows. Channel erosion, increase. Scdiments will upstream. deposition bars mi�ration. micrate downstream, creating - Control volume and discharge a water quatity problem. rates. GS 0310 15 Geoloay Sedimentation upstream from Continued sedimentation. - See "Hydrologic and hydraulic IZM .60 culvert due to debris and characteristics" section in undenized culvert. New this report. corregated metal pipe con- tinues to pass water throuol�. 6G 0310 1S Gcology Severe erosion below Continued erosion and - Insta(I energy dissipator RM .OS culvert, severe sedimcn- se;dimcntatio�. below corregated metal pipe. tation in residence yard. - Excavate channel through yard where original channel was located. 67 0310 1S Gcology Road drainage forming gully Continucd erosion. Reroute drainage. Refer probtem RM 1.5p adjacent to road; road bed to Roads Maintenance. in danger. G� 0�10 1S I Iabitat 3120 Corre�ated met11 pipe is Probtem will continue. Reinstall corregated metal RM .2S anadromous barricr. pipe at or below bed level. I': LC.APC G13 i Trih. � Collect. Cxisting Anticipatcd Item Rivcr Milc Point Catehorv Prop. Prol• Conditions and Prohlems Conditions and Problems Recommendations 69 0310 1S I�ydrolo�ry 3120 L'xistina channel draininb Freyuency and severity of Construct detention pond RM .40 off bluffs on north side problem will worsen as on upstream sidc oE Joncs of Cedar River, causing development on bluffs Rd. to trap sediments, <ind flooding of residcnces and increases. enhance 1,0()0' of creek debris flows onto Jones Rd. from Jones Rd. to Cedar during peak flows. River. 70 0310 15 Habitat Corregated metal pipe Problems will continue and Remove new and old pipes; RM .60 outlet approximately worsen as outfall velocities replace at lower level ' 9' �bove bed levcl. will scour bed and banks. with oversized pipe with Complete b�rrier to fisli. Upstrelm has recent (I1/36) trash rack. Old culverts at bcd level deposition up to 4' deep. are plu�;ed. 71 0311 13 Geolooy Gully erosion in drainare Continued accelerated ero- If possible, enlarge R/D � RM 1.70 swale due to outflow of sion. prior to its outlet in the wetland that partly seems wetland. to act as an R/D facility. 72 0314A 1G liydrolo�y 3117 Severe erosion, flooding, Problem will be a�ravated - Tightline drainage between RM .20 damagc to County and as area above develops. detention ponds in gravel pit. private roads from - Constn,ct detention pond increased runoff from neat to Jones Rd. to trap gravel pit operations on sediments. hillside. - Constn�ct channel from Jones Rd. to Cedar River. 7; 0314A/ 16 C;eoloby Inadequate R/D, pluooed Not applicable. See hydrology comment 0314B culvert caused by exten- above. RM .10-.40 sive channel and bank erosion and landslides. Water has cut a new channel. P: LC.APC G14 Trih. �C Collect. Existin� Anticipated Itcm River Mile Point Caterory Prop. Proj. Conditions and Prohlems Conditions and Problems Recommendations 74 0317 Hydrology 3111 Francis I.ake is only Trib. 0317 flows through - Construrt proportional RM L�iO hydraulic control for steep �rea cfownstream of weir at outlet. Trib. 0317. lake. if area around Francis - Enhance 1,100' from L,ake develops, increased Francis L.ake to SL 1��4th St. peak Clows could cause severe dama�c to Trib. 031� in the steep rerion. 75 0320 Hydrolopy 3114 Existing forested wetland if surrounding area urban- Construct containment b�rm RM 2.40 witl� l:�rbe amotint of un- izes, this would be a good and control structure at utilize�i storage. Wctland site to attenuate peak outlet of wetland (if bio- currently detains flows on flows. logicai an<ilysis permits). "Trib. 0320. 7G 031;� 19 I�abitat Salmonid parr in many Decrease in water quality Establish and maintain ItM .10 pools. L.arge pools up to with increasing develop- adequ�te buffen, 100' 1.'75' deep. Some deposi- ment. Loss of habitat. from ordinary high-water tion in pools, bchind Decrease in fish use. mark or 25' from top fo ol�stnictions. . slope break, whichever is greater. 77 O:t�2 19 I-�abitat Salmonid use apparcnt from System is mostly in natural - Maintain adequate stream RM .�5 carcasses. Sockeyc, condition. As development corridor buffen. Chinook spawners. Some incre�ses, hiaher flows and - Reduce discharge rates ro sedimentation occurring. worse water quality can be pre-development levels. eapected. Prevent clearing, grading within buffets. P: LC.nPC C-1S Trih. �C Collect. Existino Anticipated Item River Mile Point Catehory Prop. Proj. Conditions and Prohlems Conditions and Problems Recommendations 7�4 0324 19 Geology Medium-density landslides None. Limit development in thc RM .SO and hioh-density b�mk hasin. erosion occurring duc to natural causes. This indi- cates channel and valley se;nsitive to effects of development. (Sensitivity due to clay layer. Basin hosts some of best fish habit�t in upper reaches.) '79 0324 19 I[aUitat SigniCicant salmonid use Sedimentation from upstream Maintain leave strips RM .70 chroughout. Sockeye reach possible. Adjacent adjacent to stream at spawners, carcasses pre.sent. development will likely least 100' from ordinary Coho, steelhead parr in reduce diversity and quality high-water mark. Restrict pools. Excellent habitat of habitat. use/development within this for spawning an�i rearinp streamside management zone. (a redd site). Much diversity -- most eaemplary in basin. Channelized reach. Uniform May cause thermal problems Restore stream habitat �t0 0324 19 Hahitat channel, no habitat diver- as w�ter temperatures rise. throughout: add structure, RM 1.10 sity. I-ieavy sand de�osition. No useful habitat. diversity, bank vegetation, 1.40 I.ittle overhead canopy or and canopy. Cost should be bank vegctation. borne by party(ies) who channelized this reach. gl 032g 19 Ilydrolooy 3112 L,ake Peterson is smalt, Lake provides good peak flow Replace weir at outlet Rti4 1.40 open-water wetlan�i with a attenuation and will become with a higher weir in wcir at outlet. morc important as upstream order to gain additional tribiitarv arca devclops. stonge. P: I.C.�1PC C-16 TASK 3 FIELD INSPECTION EXHIBIT J Off-Site Analysis Drainage System Table OFF-SITE ANALYSIS : �INAGE SYSTEM TABL� Surface Water Design Manual, Core Requirement #Z Basin: Cedar River Subbasin Name: Tributary 0302 Subbasin Number. Distance Observatiuns of Field Inspector, Urainagc Component Drainage Component from Site Existing Potential Resource Reviewer,or Symbol Type,Name,and Size Description Slope Discharge Problems ProblenLs Resident Consvictions,under capacity,pondino, Typc: sheet(luw,swalc,stream, overtopping,floocJing,habitat or organism channel,pipe,pond;sir.e, Drainage basin,ve�etation,cover, destruction,scouring,bank sloughing, Tributary area,likclihood of prohlem, See Map diameter,surface area depth,rype of sensitive arca,volumc % Ft. sedimeniauon,incision,other erosion overflow pathways,potcntial impacu �Q 48-inch CMP Discharges from site to wetland 1.85 0-20 None Noted None Noted Qz Channcl 2:1 side slopes with thick Fairly 20-1,250 None Noted None Noted vegetation, 10-feet-wide and flat 5-feet-deep Q3 Swale Lined wilh gravel and dirt, 1± 1,250-1,600 None Noted None Noted lU-feet-wide and 1-foot-deep 4Q Drainage field Lined with grass and gravel, Varies 1,600-2,200 None Noted None Noted Acts as a delention pond 400-feet-long by 80-feet-wide QS 12-inch pipe with trash Under Bremerton Place N.E. — 2,200-2,300 None Noted None Noted rack combined with an overflow structure 6Q Ueep ravine to Maplewood Thickly vegetated V�u-ies 2,300-5,000 None Noted None Noted Uolf Course i��ao au i ,iu� TASK 3 FIELD INSPECTION There were no problems observed during the resource review and based on our site visit. Since there is no drainage complaint review required by the City of Renton, this project site lies �vithin the City of Renton. This project assumes that Level 2 Flow Control, also known as Conservation Flow Control and Enhanced Basic Water Quality should be sufficient. 3.1 Conveyance System Nuisance Problems (Type 1) Conveyance system nuisance problems are minor but chronic flooding or erosion problems that result from the oveiflow of a constructed conveyance system that is substandard or has become too small as a result of upstream development. Such prablems warrant additional attention because of their chronic nature and because they result from the failure of a conveyance system to provide a minimum acceptable level of protection. There were no conveyance system nuisance pi-oblems no[ed any�vhere in dle downstream drainage course. 3.3 Severe Erosion Problems(Type 2) Severe erosion problems can be caused by conveyance system overtlo�vs or the concentration of runoff into erosion-sensitive open drainage features. Severe erosion problems warrant additional attention because they pose a significant threat either to health and safety or to public or private property. The downstream drainage course is fairly fla[until approximately 2,200 feet from the project site, where runoff enters a deep ravine that has been severely eroded in the past to create the ravine. This ravine is thickly vegetated and Level 2 Flow Control should provide a level of safety for this project site's development to minimize erosion caused by the project, and also since it is a redevelopment project and there is no flow control facilities on the project site under existing conditions. 3.3 Severe Flooding Problems (Type 3) Severe flooding problems can be caused by conveyance system overflows or the elevated water surfaces of ponds, lakes, wetlands, or closed depressions. Severe flooding problems warrant additional attention because they pose a significant threat either to health and safety or to public or private property. The downstream drainage course was analyzed for ability to convey the flows fi�om an upstream basin over 300 acres in size that contributes to it. The upstream basin is mostly built out and was modeled with conservative estimates. The project to the east of this development had to perform the modeling for their downstream detention pond in order to ensure that it was not located below the floodwater elevations in the streambeds lying on that project site. This project site is considerably higher in elevation than the existing project site to the east and, since this project is proposing Level 2 Flow Control, flooding problems should be mitigated downstream due to the fact that there is no detention on this project under existing conditions. l 3240.001.doc TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS , TASK 4 DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS Runoff leaves the project site in one location, which is at approximately the central portion of the eastern property line of the site through a 20 foot, 48-inch diameter CMP culvert discharging from a manhole on the project site. Runoff then courses down through a wetland and a channeled area with a 10-foot-wide channel appraximately 5-feet-deep for approximately 1,230 feet until entering a swale that is 10-feet-wide and 1-foot-deep for another 350 feet. Runoff then enters a large drainage pond, which the downstream analysis noted as a drainage field that is lined with grass and gravel approximately 400-feet-long and 8Q-feet-wide. This acts as a detention pond prior to runoff being discharged in the downstream drainage course underneath Bremerton Place N.E. and into the deep ravine toward Maplewood Gold Course much further downstream, over 1 mile from the project site. There were no problems noted in the downstream drainage course. The downstream drainage course was walked in September of 2000, and verified in 2003 and 2005 by the Ribera Short Plat report prepared for the downstream drainage course analysis. 1;240.00I.doc 4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN 4.0 I'LOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN A. Existing Site Hydrology linder existing conditions, the site is almost entirely impervious surface and consists of 1.4 acres of development, which has a gas station and an existing Brown Bear Car Wash. A Les Schwab Tire Center forms the project site's southern boundary and portions of the , Les Schwab site will be modified with this development. For the purpose of sizing flow '' control features on this project site, the existing condition has to be modeled as an historic condition, which is a forested condition. This is a conservative methodology since no flow control facilities are provided with the existing development. B. Developed Site Hydrology Under developed conditions, 1.27 acres of the site will be considered impervious surface with 0.05 acre of till grass landscaping. There will also be a bypass area which consists of 0.09 acres of impervious surface and 0.01 acre of landscape, totaling 0.10 acre of bypass. Portions of the existing N.E. 4th Street as well as the new road improvement to occur on N.E. 4th Street will be routed to the on-site detention vault to minimize the amount of area bypass utilized on this project site. Level 2 Flow Con[rol is the required flow control standard, also known as Conservation Flow Control, and the proposed wet/detention vault will be located between the Walgreens building and the Les Schwab building in the southein portion of the project site. C. Performance Standards The applicable flow control standard for this project site is Level 2 Flow Control, also known as conservation flow control. The applicable water quality menu followed for this project site since it is a redevelopment commercial project site is the Enhanced Basic Water Quality Menu utilizing a two-train U�eatment system. The required conveyance capacity standard is the Modified Rational Method using the 100-year precipitation rate. D. Flow Coutrol System Please see the illustrated sketch on the following pages of this report for the flow control system proposed for this development. The calculations to size the Level 2 flow conti-ol vault are also included on the following pages of this report. E. Water Quality System As mentioned previously, the Enhanced Basic Water Qualiry i�lenu is followed and the calculations to size these facilities are included on the following pages of this report. There are two water quality features for this development since a treatment train is required, a wet vault located below the live storage and a wet/detention vault combined with a storm filter located downstream of the detention prior to discharge to the downstream conveyance system. Calculations are included on the following pages of this report. i��ao.00a�� ; � GRADING AND STORM DRAINAGE PLAN �� N�' =�� '�"U WALGREENS `` "f-` NORTHWEST Y, NORTHWEST�, SECTIOn 15, TOWNSHIP 23 NORTH, RANGE SE., W.M. =-=�_ � RENTON, WASHINGTON � 1"-30' o ,s ao so � _ . �i �i O � _ .. .., � ,, „ ,, , �, � � -„-, ;� � � � / cA tS � � � ° ;i �' , Z Z : r:�, ;i �� ,, 3_ � u i'� � ;� � W L= Q '� � � _ ," -- ,y i� ,' < „e:. _. s �< < r(rv,tusr ea+ro r+Ew cruo� � c w -s�'` � i��, • = :� L �( �d'Q �� 7 ��t \` . _ -;.� - .`Z' - . ., . .... .. . . ,9ry��. �w 3 � �� ,��a�-��- - �` �,� na�-�--- -; - - S Q Z C � � "�s. _._..n az-�c�_e. _ ..!L \� . �_ � '� - ._ q u � � v�'--ir--a�sqs'.:es'�..,.-�.-��-- ---=�,�-�__ ! 3�� - ,`' ? _ �,, -_ ---__�==�r� __ _ ,, � ,` � Q ,.� .� ,:' it WZ NOTE ' �. _ _ �� t� ::: Q � = - � -� � ,.. -� _: n � ' - -- �t�- �'+� 8a�s'(�oF eEwwc) �. �r� srte uTa.m corrtwterat ro coar�rHTe wm+ ,;,s -: 1 ��, -:> __. _ __ ' �-. - `` �=---1, _� -- _ -_ _____.._ ___ . _ .� , _ y BULDWC CONfR/CfOR TO 7K;Hi IJNE AEl ROOF .. -, -��..-.�.._-'- -.C , � � 'H�ROW� -_ . . . ._ _ -. . ___._ .. ..___ .-.-..__ _ .� . _. _. ___.. ._ _ G WMNSPOUT TO TNE PROPOSE�ROOF DRNN .-__� ' -_; � "``--` . .0�(NG �,~. . ..f�.... _ STUB PIPE. -� ' -- i.r -- � . �� _- '_____ .. . 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O ; v �\�r►ry y � � . . � t Z , ' . !,I = � W K I � � . � � O I � V � � I T� ..._ � I_.e..� �! � � 1 � J I � DeM W I, z� �d'8 ;��o"� U _ � m ftc�P�`.7:'.N.��Cn,il-SO\e•;q�r' �,��'.i'>n�-;1�:wq Uet�,�,n•e�5:'�/:•;'�E 2.`,_ . .c...e - � �NEFFrt:'f :vct. . ^'il-sb+.n, �:�Si4C-I,•a]. • ._v rcntr�.�..irry, usi.ta-� II DETENTION SIZING CRITERIA Detention Sizing Criteria Pre-cieveloped (historic condition) = 1.42 ac. Till Forest I Developed: '' Impervious = 1.27 ac. Till Grass = 0.05 ac. , Bypass: Impervious = 0.09 ac. Till Grass = 0.01 ac. I� 13240,(N33.doc �' j �-"r LJ �e� � ��.�1 '� �n�a� � xcx'rs_commana LGt/ ! � �G. `J/ �J CREATE a new Time Series �,,�a M ,�vG� ------------------------ !,' Oi,1�5 Production of Runoff Time Series Project Location : Sea-Tac �,_ ' _ O� Computing Series : 13240pre.tsf Regional Scale Factor : 1.00 Data Type : Reduced Creating Hourly Time Series File Loading Time Series F'ile:C: \KC_SWDM\KC_DATA\STTF60R.rnf . Till Forest 1 .42 acres Total Area : 1.42 acres Peak Discharge: 0.115 CFS at 9:00 on Jan 9 in Year 8 Storing Time Series File:13240pre. tsf . Time eries m S Co puted KCRTS Command Enter the Analysis TOOLS Module ------------------------------- Analysis Tools Command ---------------------- Compute PEAKS and Flow Frequencies ---------------------------------- Loading Stage/Discharge curve:13240pre. tsf . Flow Frequency Analysis -------------------------------------------------------- `Pime Seri�s File:13240pre.tsf project LocaLion:Sea-Tac Frequencies & Peaks saved to File:13240pre.pks . Analysis Tools Command ---------------------- RETURN to Previous Menu ----------------------- KCRTS Command CREATE a new Time Series ------------------------ Production of Runoff Time Series Project Location : Sea-Tac Computing Series : 13240dev.tsf Regional Scale Factor : 1.00 Data Type : Reduced Creating Hourly Time Series File Loading Time Series File:C:\KC_SWDM\KC_DATA\STTG60R.rnf . Till Grass 0.05 acres Loading Time Series File:C:\KC_SWDM\KC_DATA\STEI60R.rnf . I Impervious 1 .27 acres � -------------- Total Area : 1. 32 acres Peak Discharge: 0. 611 CFS at 6:00 on Jan 9 in Year 8 Storing Time Series File: 13240dev. tsf . Time Series Computed KCRTS Command Enter the Analysis TOOLS McdL,ie ------------------------ - Analysis Tools Comma -------------------- Compute PEAKS and Flow Fre_ _ ------------------------------ Loading Stage/Discharge �ui-vc: ��ua�v . t5i . Flow Frequency Analysis -------------------------------------------------------- Time Series File:13240dev.tsf Project Location:Sea-Tac Frequencies & Peaks saved to File:13240dev.pks . Analysis Tools Command ---------------------- RETURN to Previous Menu ----------------------- KCRTS Command CREATE a new Time Series ------------------------ Production of Runoff Time Series Project Location : Sea-Tac Computing Series : 13240bypass.tsf Regional Scale Factor : 1.00 Data Type : Reduced Creating Hourly Time Series File Loading Time Series File:C: \KC_SWDM\KC_DATA\STTG60R.rnf . Till Grass 0.01 acres Loading Time Series File:C: \KC_SWDM\KC_DATA\STEI60R.rnf . Impervious 0.09 acres -------------- Total Area : 0.10 acres Peak Discharge: 0.045 CFS at 6:00 on Jan 9 in Year 8 Storing Time Series File:13240bypass. tsf . Time Series Computed KCRTS Command Enter the Analysis TOOLS Module ------------------------------- Analysis Tools Command ---------------------- Flow Frequency Analysis Time Series File:1324Qpre.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0 .090 2 2/09/01 18:00 0. 115 1 100. 00 0.990 0 .024 7 1/Q6/02 3:00 0.090 2 25 . 00 0. 960 Q.066 4 2/28/03 3 :00 0.069 3 10 . 00 0.900 0.003 8 3/24/04 20:00 0 .066 4 5 . 00 0.800 0 .040 6 1/05/Q5 8:00 0.058 5 3 . 00 0.667 0 .069 3 1/18/06 21:00 0.040 b 2 .00 0.5Q0 0 . 058 5 11/24/06 4:00 0.024 7 1. 30 0.231 0 .115 1 1/09/08 9:00 0.003 8 1. 10 0 .091 Computed Peaks 0.106 50.00 0 .980 clow Frequency Analysis Time Series File:13240de��. tsf Project Location:Sea-Tac ---Annual Peak Flow Rates—- -----Flow F'requency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS} (CFS) Period 0.312 7 2/09/01 2 :00 0 . 611 1 100.00 0. 990 0.274 8 1/05/02 16:00 0 . 462 2 25. 00 0.960 0. 380 3 12/08/02 18:00 0. 380 3 10 . 00 0. 9GG 0.317 b 8/26/04 2:00 0.377 4 5 . 00 0.800 0 . 377 4 10/28/04 16:00 0.334 5 3 . 00 0. 667 � 0 .334 5 1/18/06 16:00 0. 317 6 2 .00 0.500 0 .462 2 10/26/06 0:00 0.312 7 1.30 0.231 0 . 611 1 1/Q9/08 6:00 0.274 8 1.10 0.091 Computed Peaks 0 . 561 56.00 0. 980 Flow Frequency Analysis Time Series File:13240bypass.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob iCFS) {CFS) Period 0 . 023 6 2/09/01 2 : 00 0. 044 1 100.�0 0.990 0 . 020 8 1/OS/02 26: 00 0. 033 2 25 .00 0 .960 0 . 027 3 12/08l02 18:60 0. 027 3 10 .00 0 . 900 C . 022 7 8/26/04 2 : 00 0 . 027 4 5 .00 d.800 � . 027 4 10/28/04 16:60 0 . 024 5 3 .00 0. 667 � . 024 S 1/18/06 16:00 O .a23 6 2 .00 0. 500 0 . 033 2 10/26/06 a: ao 0 .�22 7 1 .30 0.231 �� . 044 1 1/09/08 6:00 O.a20 8 1 .10 0.091 Computed Peaks 0 . 041 50 .00 0 . 980 Flow Frequency Analysis Time Series File:13240rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0 .071 1 2/09/01 20:00 0. 071 5 .72 1 100.00 0.990 0.015 6 1/07/02 4:00 0.063 5. 32 2 25.00 0.960 0.063 2 3/06/03 22 :00 0.060 5.21 3 10.00 0.900 0.012 8 8/26/04 8:00 0.042 4 .62 4 5.00 0.800 0.015 5 1/08/OS 6:00 0 . 015 3 . 60 5 3 . OQ 0. 667 0. 015 7 1/19/06 1:00 0.015 3 .60 6 2 .00 0 . 500 0. 042 4 11/24/06 8:00 0.015 3.55 7 1.30 0.231 0.060 3 1/09/08 16:00 0.012 2.21 8 1.10 0.091 Computed Peaks 0. 069 5. 59 50.00 0. 980 , �� Flow Frequency Analysis Time Series File:13240dsout.tsf Project Location:Sea-Tac --Annual Peak Flow Rates-- ----Flow Fr.equency Analysis----— F'lo�,v Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS} Period 0 .083 1 2/09/01 18:00 0 . 083 1 10Q. 00 0.990 0 . 033 7 1/Q5/02 16:00 0 .082 2 25.00 0. 960 0 .075 3 3/06/03 19: 00 0.075 3 14.00 0.9�0 0 .033 6 8/26/04 2 : 00 0.050 4 5. 00 0.800 0 .033 8 10/28/04 16: 00 0.037 5 3 . 00 0.667 0.037 5 1/18/06 16: 00 0.033 6 2 . 00 0.5�0 0.050 4 11/24/06 6: 00 0.033 7 1.30 0.231 0.082 2 1/09/08 9: 00 0. 033 8 1.10 0.091 Computed Peaks 0.083 50. 00 0.980 Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 126. 00 ft'� Facility Width: 40. 00 ft� Facility Area: 5Q40. sq. ft Effective Storage Depth: 5.75 fti/ Stage 0 Elevation: 390.25 ft Storage Volume: 28980. cu. ft✓ Riser Head: 5.75 ft Riser Diameter: 12 .00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0. 54 '� 0.019 � 2 4.30 1 .27 ✓ 0.053 4 .0 3qy S- 3 9�l,S = �.d Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (f t) (ft) (cu. ft? (ac-ft) (cfs) (cfs} 0. 00 390.25 0. 0.000 0.000 0.00 0. 01 390 .26 50. 0.001 0.001 0.00 0 . 02 390 .27 101. 0.062 0.001 0.00 0. 03 390.28 151. 0. 003 0. 001 0. 00 0. 04 390.29 202 . 0 . 005 0.002 0. 00 O.a5 390.30 252 . 0 .006 0 .002 0. 00 0 . 15 390 .40 756. 0 .017 0 .003 0. 00 0 .25 390.50 1260. 0 .029 0 .004 0.00 0 .35 390.b0 1764. 0 . 040 0.005 Q. 00 0.45 390.70 2268. 0. 052 0.005 0. 00 0.55 390.80 2772 . 0.064 0.006 0.00 0. 65 390.90 3276. 0 .075 0.006 0.00 0.75 391 .00 3780 . 0 .087 0.007 0.00 Q. 85 391 .10 4284 . 0 .098 0.007 0.00 0.95 391 .20 4788 . 0 .110 O .Q08 0. 00 1 . 05 391 .30 5292 . 0.121 0.008 0. 00 1 . 15 391.40 5796. �. 133 0.009 0.00 1 .25 391 .50 6300. 0.145 0.009 0.00 1 . 35 391.60 6804 . 0 .156 0.009 0.00 1 .45 391.70 7308 . 0 .168 0.010 0.00 1. 55 391.80 7812 . 0.179 0.010 0. 00 1 . 65 391.90 8316 . 0.191 0.010 0.00 1 .75 392 .00 8820. 0.202 0.011 0.00 1 . 85 392 .10 9324. 0 .214 0.011 0.00 1 . 95 392 .20 9828. 0 .226 0.011 0.00 2 . 05 392 . 30 10332 . 0.237 0.011 0. 00 2 . 15 392 .40 10836 . 0.249 0.012 0. 00 2 .25 392 . 50 11340 . 0.260 0.012 0. 00 2 . 35 392 . 60 11844 . 0 .272 0.012 0. 00 2 .45 392 .70 12348. 0.283 4.013 0.00 2 .55 392 .80 12852 . 0 .295 0.013 0.00 2 .65 392 .90 13356. 0.307 0 .013 0.00 2 .75 393 .00 13860. 0.318 0.013 0.00 2 .85 393 .10 14364. 0.330 0.014 0.00 2 .95 393 .20 14868. 0.341 0.014 0.00 3 .05 393 .30 15372 . 0 . 353 0.014 0.00 3 . 15 393 .40 15876. 0 . 364 0.014 0. 00 3.25 393 . 50 1638a. 0. 376 0.014 0.0� 3 . 35 393 . 60 16884 . 0 . 388 0. 015 0.00 3 .45 393 .70 1"7388 . 0. 399 �.015 0 .00 3 . 55 393 . 80 17892. 0 .412 0.015 0.00 3 . 65 393 .90 18396. 0.422 0.015 0. 00 3 .75 394 .00 18900. 0.434 0.016 0.00 3 . 85 394.10 19404. 0 .445 0.016 0.00 3.95 394.20 19908. 0.457 0.016 0.00 4. 05 394.30 20412. 0.469 0.016 O .QO 4. 15 394.4Q 20916. 0.480 0.016 0.00 4.25 394. 50 21420. 0.492 0.017 0.00 4 . 30 394.55 21672. 0.498 0.017 0.00 4. 31 394 .56 21722 . 0 .499 0.017 0.00 4.33 394.58 21823 . 0. 501 0.018 0. 00 4 . 34 394 .59 21874. 0.502 0.020 0 .00 4. 35 394.60 21924 . 0.503 0.022 0.00 4. 37 394. 62 22025. 0.506 0.025 0.00 4.38 394.63 22075. 0.507 0.029 0.00 4. 39 394 .64 22126. 0 .508 0.030 0.00 4 .41 394 . 66 22226. 0. 510 0.031 0.00 4 . 51 394.76 22730. 0. 522 0.037 0.00 4 . 61 394.86 23234. 0.533 0. 042 0.00 4.71 394. 96 23738. 0 .545 0. 046 0.00 4. 81 395.06 24242 . 0.557 0 .049 0. 00 4.91 395.16 24746. 0 .568 O.Q52 0.00 5. 01 395.26 25250. 0. 580 0.055 0.00 5. 11 395.36 25754 . 0 . 591 0 .058 0. 00 5.21 395.46 26258 . 0. 603 0 .060 0.00 5. 31 395. 56 26762 . 0 .614 0.063 0.00 5 .41 395 .66 27266. 0. 626 0.065 0.00 5.51 395.76 27770. 0. 638 0.067 0.00 5. 61 395.86 28274 . Q. 649 0.069 0.00 5.71 395.96 28778 . 0. 661 0. 071 0.00 5 .75 396.00 28980. 0. 665 0 .072 0.00 5. 85 396.10 29484. 0. 677 0 .382 0. 00 5 .95 396 .20 29988. 0. 688 0.947 0.00 6. 05 396.30 30492 . 0.700 1 .680 0. 00 6 .15 396.40 30996 . 0.712 2.470 0.00 6.25 396.50 31500. 0.723 2 .760 0.00 6 . 35 396. 60 32004 . 0 .735 3 .010 0.00 6 .45 396.70 32508. 0.746 3 .250 0.00 6.55 396.80 33012 . 0.758 3 .470 0.00 6. 65 396.90 33516. 0.769 3 . 680 0.00 6.75 397 .00 34020 . 0 .781 3 .870 0.00 6. 85 397 .10 34524 . 0 .793 4 .060 0.00 6 . 95 397 .20 35028 . 0 . 8fl4 n .240 0 . 00 7 . 05 397 .30 35532 . 0. 816 4 .410 0. 00 7 .15 397.40 36036. 0.827 4.570 0.00 � 7 .25 397 .50 36540. 0.839 4 .730 0. 00 7 . 35 397 .60 37044 . 0. 850 4 .880 0. 00 7 .45 397 .70 37548. 0. 862 5 .030 0. 00 7 .55 397 . 80 38052 . 0. 874 5 .180 0.00 7 . 65 397 .90 38556. Q. 885 5.320 0.00 7 .75 398.00 39060. 0. 897 5 .450 0 .00 Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 0.31 Q.07 5.72 395.97 28831. 0 .662 2 0 . 61 0.06 5.21 395.46 26240. 0.602 3 0.38 0.06 5.32 395. 57 26831. 0.616 4 0.46 0.04 4. 62 394. 87 23296. 0.535 � 5 0 .33 0.01 3 .55 393 .80 17867. 0.410 6 0.27 0.01 3 .60 393 . 85 18122 . 0.416 7 0 . 32 0 . 01 2 .21 392 . 46 11158. 0.256 8 0.38 0.01 3 . 60 393 . 85 18125. 0.416 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.07 0.02 ******** ******* 0.08 2 0.06 0.04 ******** 0.09 0.08 3 0 .06 0.03 ******** ******* 0.07 4 0.04 0.03 ******** ******* 0.05 5 0.01 0.02 ******** ******* 0.04 6 0.01 0.02 ******** ******* 0.03 7 0.01 0.02 ******** ******* 0 .03 8 0. 01 0.03 ******** ******* 0.03 ---------------------------------- Route Time Series through Facility Inflow Time Series File:13240dev.tsf Outflow Time Series File:13240rdout POC Time Series File:13240dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.611 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 4.071 CFS at 20:00 on Feb 9 in Year 1 Peak Reservoir Stage: 5.72 Ft � Peak Reservoir Elev: 395.97 Ft Peak Reservoir Storage: 2883� . Cu-Ft . 0. 662 Ac-Ft Add Time Series: 13240bypass.tsf Peak Summed Discharge: 0.083 CFS at 18:00 on Feb 9 in Year 1 Point of Compliance File:13240dsout.tsf Flow Frequency Analysis Time Series File:13240rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0 .071 1 2/09/O1 20: 00 0.071 5.72 1 100.00 0.990 0 .015 6 1/07/02 4 : 00 0.063 5.32 2 25.00 0.960 0.063 2 3/06/03 22 :00 0.060 5.21 3 10.00 0.900 0 .012 8 8/26/04 8: 00 Q. 042 4. 62 4 5.00 0.80Q 0 .015 5 1/08/05 6: 00 0. 015 3. 60 5 3 .00 0. 667 0.015 7 1/19/06 1:00 0.015 3. 60 6 2 .00 0.5d0 0 .042 4 11/24/06 8:00 0 . 015 3.55 7 1 .30 0.231 0 .060 3 1/09/08 16:00 0 .012 2 .21 8 1. 10 0.091 Computed Peaks 0. 069 5.59 5Q. 00 0.980 Flow Frequency Analysis Time Series File:13240dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob {CFS} (CFS) Period 0 .083 1 2/09/01 18 :00 0.083 1 100.00 0.990 0 .033 7 1/05/02 16:00 0.082 2 25.00 0.960 0 .075 3 3/06/03 19:00 0.075 3 10.00 0.900 0.033 6 8/26/04 2 :00 0.050 4 5.00 0.800 a.033 8 10/28/04 16:00 0.037 5 3 . 00 0.667 0 . 037 5 1/18/06 16:00 0.033 6 2 .00 0.500 0 . 050 4 11/24/06 6: 00 0. 033 7 1 .30 0 .231 0.082 2 1i09/08 9 : 00 0. 033 8 1.10 0.091 Computed Peaks 0. 083 50.00 0.980 Flow Duration from Time Series File:13240rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS $ � � 0 .001 21913 35.735 35.735 64 .2b5 0.643E+p0 0 .003 6946 11.327 47 .063 52 .937 0.529E+00 0 .005 7793 12 .709 59 .772 40.228 0.402E+00 0 . 007 6819 11 .120 70 . 892 29 .108 0.291E+00 0 . 009 6798 11 .086 81 . 978 18 .022 0.180E+00 0 .011 5108 8 .330 90. 308 9 .692 0.969E-01 0 .013 1806 2 .945 93 .253 6.747 0. 675E-01 O .a15 2846 4 . 641 97 .895 2 .105 0.211E-01 Q .017 1047 1 .707 99.602 0.398 Q.398E-02 Q .019 62 0 .101 99.703 0.297 0.297E-02 0 .021 4 0 .007 99.710 0.290 0.290E-02 0 . 023 3 0.005 99 .715 d.285 0.285E-02 0 . 025 5 Q.008 99.723 0.277 0.277E-02 0 . 027 5 Q.008 99.731 0.269 0.269E-02 0 . 029 0 0.000 99 .731 0.269 0.269E-02 0 . �31 10 0.016 99 .747 0.253 0.253E-02 0 . 033 17 0.028 99 .775 0.225 0.225E-02 0 . 035 13 0 .021 99 .746 0.204 0.204E-02 0 . 037 10 0.016 99 . 872 0.188 0. 1$8E-02 � . 039 10 0.016 99 . 829 0. 171 0. 171E-02 0 . 041 7 0.011 99 . 840 0.160 0. 160E-02 O . 043 10 0.016 99 . 856 0 .144 0. 144E-02 r'� . 045 3 0.005 99 . 861 0 .139 0.139E-02 0 . 047 4 O .OJ7 99 . 868 0 . 132 G . 132�'-02 0 . 049 10 0.016 99. 884 0.116 0 . 116E-02 II 0 .051 6 0.010 99.894 0.106 0.106E-02 0 .052 9 0.015 99 .909 0.091 0.913E-03 0.054 3 0.005 99 .914 0.086 0.864E-03 0 .056 6 0.010 99 .923 0.077 0.766E-03 0 .058 9 0.015 99 .938 0. 062 �. 620E-03 O.Q60 13 0.021 99.959 0.041 0.408E-03 , 0 .062 5 O.OQ8 99.967 0 .033 0. 326E-03 � 0 .064 6 0.010 99 .977 0 .023 0.228E-03 0.066 3 0.005 99 .982 0 .018 0.179E-03 ! 0 .068 3 0.005 99 .987 O.Q13 0.130E-03 � 0 .070 4 0.007 99.993 0.007 0. 652E-04 '' Flow Duration from Time Series File: 13240dsout. tsf II Cutoff Count Frequency CDF Exceedence_Probability CFS � � � � 0.001 21646 35.300 35 .300 64 .700 0. 647E+00 0.003 8132 13.262 48.562 51 .438 0.514E+00 0.006 7606 12 .404 60.965 39 .035 0.390E+00 0.008 7546 12 .306 73 .271 26 .729 0.267E+0� ', 0.010 6679 10.892 84.163 15. 837 0. 158E+00 j 0. 013 4204 6.856 91.019 8.981 0.898E-01 'i 0. 015 3377 5.507 96.526 3 .474 0. 347E-01 '�I 0. 017 1280 2 .087 98 . 614 1 .386 0.139E-01 � 0 .020 310 0.506 99 .119 0.881 0.881E-02 0 .022 181 a.295 99.415 0.585 0.585E-02 0 .024 60 0.098 99.512 0.488 0.488E-02 0 .027 54 0 .088 99.600 0.400 0.400E-02 0 . 029 34 0 .055 99.656 0.344 0.344E-02 0 .031 19 0.031 99 . 687 0.313 0 .313E-02 0 .034 28 0.046 99.733 0.267 0.267E-02 0 .036 21 0.034 99 .767 0.233 0.233E-02 0.038 24 0.039 99.806 0.194 0.194E-02 0 .041 10 0.016 99 .822 0.178 0. 178E-02 0 .043 8 0.013 99 . 835 0.165 0.165E-d2 0 .045 9 0.015 99 . 850 0.150 0 .150E-02 0 .048 7 0.011 99 .861 0.139 0.139E-02 0 .050 7 0.011 99. 873 0.127 0. 127E-02 0 .052 9 0 .015 99 .887 0 .113 0.113E-02 0 .055 4 0 .007 99 .894 0.106 0.106E-02 0. 057 7 0.011 99 .905 0.095 0.946E-03 0 .059 9 0.015 99 .920 0.080 0 .799E-03 0 .062 10 0.016 99 .936 0.064 0. 636E-03 � .064 7 0.011 99 .948 0.052 0.522E-03 0 . 066 6 0.010 99 .958 0.042 0.424E-03 0 .068 8 0.013 99 .971 0.029 0.294E-03 0 .071 5 0.008 99 .979 0. 021 0.212E-03 0 . 073 3 0.005 99 .984 0.016 0.163E-03 0 . 075 3 0.005 99 .989 0.011 0.114E-03 0 . 078 2 O.OQ3 99 .992 O.OQ8 0. 815E-04 0 .080 2 0.003 99 .995 0.005 0.489E-04 0 . 082 2 0.003 99 .998 0. 002 0.163E-04 vuration Comparison Anaylsis Base File: 13�4Gpre. tsf New Fi1e: 13240rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New �Change Probability Base New �Change 0 . 020 � 0. 92E-02 0.30E-02 -67 .7 � 0. 92E-02 0.020 0.016 -19 .9 0. 025 � 0. 63E-02 0.28E-02 -56.0 � 0.63E-02 0. 025 0.016 -36 .5 ' 0 .a31 � 0.49E-02 0.25E-02 -48.2 � 0 .49E-02 0. 031 0 .016 -46 .4 0.036 � 0.36E-02 0.19E-02 -47 .1 � 0 .36E-02 0.036 0.017 -52 .8 0.041 � 0.28E-02 0.16E-02 -44 .5 � 0.28E-02 0.041 0.023 -43 .7 0.047 � 0.22E-02 0.13E-02 -40.4 � 0.22E-02 0.047 0.033 -28.5 0.052 � 0.15E-02 0.98E-03 -32 . 6 � 0.15E-02 0.052 0.042 -18.3 0.057 � 0.99E-03 0.70E-03 -29 .5 � 0.99E-03 �.057 0.052 -9 .5 0 .063 � 0. 60E-03 0.33E-03 -45 .9 � 0. 60E-03 0.063 0.059 -6 . 5 , 0 .068 � 0. 34E-03 0.13E-�3 -61.9 � 0. 34E-03 0.068 0.062 -8 .9 i 0 .073 � 0 .21E-03 O.OQE+00 -100.0 � 0.21E-03 0.073 0.066 -10.5 0. 0%9 � 0.16E-03 O.00E+00 -100. 0 � 0.16E-03 0.079 0.067 -14 .6 0 .084 � 0.11E-03 O.00E+00 -100.0 ( 0 .11E-03 0.084 0.069 -18 .5 0 .090 � 0. 26E-04 O. QOE+00 -100 . 0 � 0 .16E-04 0.090 0 . 071 -20 . 6 There is no positive excursion Maximum negative excursion = 0.�22 cfs (-55.9�) , occurring at 0.039 cfs on the Base Data:13240pre.tsf , and at 0.017 cfs on the New Data:13240rdout.tsf F1ow Duration from Time Series File: 13240pre.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS � � � 0.020 60756 99 .080 99 .080 0.920 0.920E-02 0 . 022 109 0.178 99 .258 0.742 0.742E-Q2 0 . 025 71 0.116 99 .374 0. 626 0. 626E-02 0 . 027 39 0.064 99 .437 0.563 0.563E-02 6 . 030 37 0.060 99 .498 0.502 0. 502E-02 0 . 032 39 0.064 99.561 0.439 0.439E-02 0 . 035 30 0.049 99.610 0 .390 0.390E-02 0 . 038 34 0.055 99.b66 0 .334 0.334E-02 0 . 040 22 0.036 99.702 0.298 0.298E-02 0 .043 18 0.029 99 .731 0.269 0.269E-02 0 . 045 20 0.033 99.764 0.236 0.236E-02 � . 048 19 �.031 99.795 0.205 0.205E-02 0 . 050 20 4. 033 99.827 0.173 0.173E-02 0 . 053 17 0.028 99.855 0.145 0.145E-02 � 0 . 055 15 0 .024 99.879 0 .121 0 .121E-02 0 .058 13 0 .021 99 .901 0.099 0.995E-03 0 .060 13 0.021 99 .922 0.078 0.783E-03 0 .063 10 0.016 99.938 0.062 0. 620E-03 �� .065 10 0.016 99.954 0 .046 0.457E-03 0 . 068 6 0.010 99.964 0 .036 0.359E-03 0 . 070 4 0 .007 99.971 0.029 0.294E-03 0 . 073 2 0.003 99 .974 0 . 026 0.261E-03 O 075 4 0 .007 99 .980 0. 020 Q. 196E-03 '; . 078 2 O . a03 99. 984 0.016 0. 163E-03 �i . 080 1 0.002 99 . 987 0 .015 0. 147E-03 u . 082 1 0.002 99. 987 0 .013 0 . 130E-03 I G . 085 3 0.005 99.992 0.008 0 . 815E-04 � . 087 3 0.005 99.997 0.003 0.326E-04 0 . 090 2 0.003 100.000 0.000 O.O00E+00 0 . 092 0 0. 000 100.000 0.000 O.O00E+00 0 . 095 0 0.000 100.000 0.000 O. O00E+00 0 . 097 0 0.000 100.000 0.000 O .O00E+00 Q .100 0 0.000 100.000 0.000 O.O00E+00 0 .102 0 0.060 1Q0 .000 0.000 O.O00E+00 �� .105 0 0 . 000 100 .000 O. 00Q O . O�0E+00 0 . �.0� 0 � . 000 'C0 . 0�0 �. 0�0 O . OG�E��O Flow Duration from Time Series File:13240rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS � � � 0.001 21913 35.735 35.735 64 .265 0. 643E+00 0.003 6946 11 .327 47 .063 52 .937 0.529E+00 0.005 7793 12 .709 59 .772 40.228 0.402E+00 0. 007 6819 11.120 70.892 29 .108 0.291E+00 0.009 6798 11.086 81 .978 18 .022 0.180E+00 0 .011 5108 8.330 90.308 9 .692 0. 969E-01 0.013 1806 2 .945 93 .253 6.'747 0. 675E-01 0.015 2846 4.641 97 .895 2 .I05 0.211E-U1 O .Q17 1047 1 .707 99 . 602 0 . 398 0. 398E-02 0.019 62 0.101 99 .703 0.297 0.297E-02 0.021 4 0.007 99 .710 0 .290 0.290E-02 0.023 3 0.005 99 .715 0.285 0.285E-02 0 .025 5 0 .008 99 .723 0.277 0.277E-02 0.027 5 0.008 99.731 0.269 0.269E-02 0.029 0 0.000 99 .731 0.269 0 .269E-02 0.031 10 0.016 99 .747 0.253 0.253E-02 0.033 17 0.028 99 .775 0.225 0.225E-02 0.035 13 0 .021 99.796 0.204 0.204E-02 0.037 10 0.016 99 .812 0 .188 0.188E�-02 0.039 10 0.016 99 .829 0.171 0.171E-02 0. 041 7 0.011 99 .840 0.160 0.160E-02 0.043 10 0.016 99 .856 0.144 0.144E-02 0 .045 3 0 .005 99 .861 0 .139 0. 139E-02 0.047 4 0.007 99 .868 0.132 0.132E-02 ' 0.049 10 0.016 99 . 884 0.116 0. 116E-02 0.051 6 0. 010 99 .894 0.106 0. 106E-02 0.052 9 O.Q15 99.909 0.091 0 .913E-03 0.054 3 0.005 99 . 914 0.086 �.864E-03 0.056 6 0.010 99.923 0.077 0.766E-03 0 . 058 9 0 .015 99 .938 0.062 0. 620E-03 0 .a60 13 0.021 99 .959 0. 04� 0.408E-03 0. 062 5 0 .008 99.967 0.033 0. 326E-03 0.064 6 0.010 99 .977 0 .023 0.228E-03 0 .066 3 O.QOS 99 .982 0.018 0.179E-03 0.068 3 0.005 99.987 0.013 0. 130E-03 0 .070 4 0.007 99 . 993 0.00� 0. 652E-Q4 Flow Duration from Time Series File:13240dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS � � � 0 .001 21646 35.300 35.300 64 .700 0.647E+00 0.003 8132 13 .262 48.562 51 .438 0.514E+00 0 . 006 7606 12 .404 60.965 39.035 0.390E+00 0 . 008 7546 12 .306 73 .271 26.729 0.267E+00 0. 010 6679 10. 892 84.163 15 . 837 0. 158E+00 0.013 4204 6.856 91 .019 8.981 0. 898E-01 0. 015 3377 5 .507 96 .526 3 .474 0.347E-01 0 .017 1280 2 .087 98.614 1 .386 0.139E-01 0 .020 310 0 .506 99 .119 0 .881 0. 881E-02 0 .022 181 0.295 99 .41� 0. 585 0. 585E-02 0 .024 60 0.098 99 .512 0.488 0.488E-02 0 .027 54 0.088 99 .600 0.400 0 .400E-02 0 .029 34 0.055 99 .656 0 .344 0.344E-02 0 .031 19 0.031 99.687 0.313 0.313E-02 0 .034 28 0.046 99.733 0.267 0.267E-02 0 .036 21 0.034 99 .767 0.233 0.233E-02 0 . 038 24 0 .039 99 .806 0 . 194 0.194E-02 0 .041 10 0 .016 99.822 0.178 0 .178E-02 0 .043 8 0.013 99.835 0.165 0.165E-02 0 . 045 9 0.015 99.850 0. 150 0.150E-02 0.048 7 0.011 99 .861 0.139 0. 139E-02 O.Q50 7 0.011 99 .873 0 .127 0. 127E-02 0 .052 9 0 .015 99 .887 0 .113 0.113E-02 0 .055 4 0 .007 99.894 0. 106 0.106E-02 I 0 .057 7 0.011 99 .905 0.095 0.946E-03 � 0 .059 9 0.015 99.920 0. 080 0.799E-03 I 0 .062 10 0.016 99.936 0.064 0.636E-03 �� 0.064 7 0.011 99 .948 0.052 0 .522E-03 0.066 6 0.010 99.958 0.042 0.424E-03 0 . 068 8 0.013 99.971 0. 029 0.294E-03 0 .071 5 0 .008 99 .979 0 .021 0.212E-03 0 .073 3 0. 005 99 .984 0 .016 0. 163E-03 0.075 3 0.005 99 .989 0 .011 0.114E-03 0 . 078 2 0 .003 99 .992 0 .008 0. 815E-04 0.080 2 0 .003 99.995 0.005 0.489E-04 0 .082 2 0.003 99 . 998 0.0�2 0.163E-04 Duration Comparison Anaylsis Base File: 13240pre.tsf New File: 13240rdout. tsf Cutoff Units : Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New �Change Probability Base New �Change 0 . 020 � 0.92E-02 0 .30E-02 -b7 .7 � 0 .92E-02 0. 020 0.016 -19 . 9 0 . 025 � 0. 63E-02 0.28E-02 -56 .0 � 0.63E-�2 0. 025 0. 016 -36 .5 0 . 031 � 0. 49E-a2 0.25E-02 -48 .2 � 0.49E-02 0.031 0 .016 -46 .4 0 .036 � a. 36E-02 0.19E-02 -47 .1 � 0.36E-02 0.036 0 .017 -52 . 8 0 .041 � 0.28E-02 0.16E-02 -44.5 ( 0 .28E-02 0.041 0 .023 -43 .7 0 .047 � 0.22E-02 0.13E-a2 -40.4 � 0 .22E-02 0.047 0.033 -28 . 5 0.052 � 0.15E-02 0.98E-03 -32 .6 � 0.15E-02 �.052 0.042 -18 .3 0.057 � 0.99E-03 0.70E-03 -29 .5 � 0 .99E-03 0. 057 0.052 -9 .5 0.063 � Q.60E-03 0.33E-03 -45 .9 � 0 .60E-03 0.063 0.059 -6 .5 0.068 � 0. 34E-03 0.13E-03 -61 .9 � 0.34E-03 0 .068 0 .062 -8 .9 0.073 � 0.21E-03 O.OdE+00 -100.0 � � .21E-03 0.073 0 .06b -10. 5 0.079 � 0.16E-03 O.00E+00 -100.0 � 0 .16E-03 0 .079 0.067 -14 . 6 0 .084 � 0. 11E-03 O.00E+00 -100 .0 � 0.11E-03 0.084 0.069 -18 . 5 0 .090 � 0.16E-04 �.00E+00 -100 . 0 � 0 . 16E-04 a . o9a �. Q?1 -20 . 6 There is no positive excursion Maximum negative excursion = 0 .022 cfs (-55 . 9�) occurring at 0 .039 cfs on the Base Data: 13240�re. tsf and at 0 . �17 c�s on �:�e PJe.v Data: 13340rdout . tsF SIZE THE BASIC WET VAULT ; Size the Basic Wet Vault V� _ (0.9A; +0.25A,$) (R) V� _ [(09)(1.27)+ (025)(0.05)](0.039)(43,560j V,. = 1,963 CF V� = 3(V�j Vv = 3(1,963) V� = 5,889 CF 13240.003.doc w��%�ITCAL!'' "��i►�'■� i �� . . STORMWATER Size and Cost Estimate SOLUTlONS iNc. Prepared by Kathryn Thomason on December 18, 2007 Walgreens — Stormwater Treatment System Renton, WA Information provided: • Total contributing area = 1.32 acre • Impervious area = 1.27 acre � • Detention release rate, Q��eat = E3.015 Cf5� • Presiding agency = City of Renton, WA Assumptions: • Media = ZPG cartridges • Cartridge height = 12" • Per cartridge flow rate = 5.0 gpm • Drop required from inlet to outlet = 1.8' minimum Size and cost estimates: The StormFilter is a flow-based system, and therefore, is sized by calculating the peak water quality flow rate associated with the design storm. However, when the StormFilter is placed downstream of detention the flow rate generated at the water quality storm is not always representative of the total volume of water that will go through the system or type of pollutant-loading the system may experience in one year. For this site, CONTECH Stormwater Solutions Inc. recommends using a 72" Manhole StormFilter with 5 cartridges (see attached detail). The estimated cost of this system is 20 500, complete and delivered to the job site. This estimate assumes that the vault is 6 feet deep. The final system cost will depend on the actual depth of the unit and whether extras like doors rather than castings are specified. The contractor is responsible for setting the StormFilter and all extemal plumbing. Typically, precast manhole StormFilters have internal bypass capacities of 1.5 cfs. If the peak discharge off the site is expected to exceed this rate, we recommend placing a high-flow bypass upstream of the StarmFilter system. CONTECH Stormwater Solutions could provide our high-flow bypass,the StormGate, which provides a combination , weir-0rifice contro! structure to limit the flow to the StormFilter. The estimated cost of this structure is $4,000. The � final cost would depend on the actual depth and size of the unit. ' .�.-- - �� -- - -- - ��,��..�_.�,�.�.vv�_„�. ----- �...�:� 02006 CONTECH Stormwater Solutions 12021-B NE Airport Way,Portland OR 9722U Page 1 of 1 contechstormwater.com Toll-free:800.548.4667 Fax:800.561.1271 TS-P022 7��%- .�' ' ' � `� Determining Number of �%►�:�• : :.�� STORMWATER Cartridges for Systems �- so�uriorus�N�. Downstream of Detention CONTECH Stormwater Solutions Inc. Engineer: KET Blue Cells= Input Date 12/18/2007 Black Cells= Calculation Site Information Project Name Walgreens Project State Washington Project Location Renton Drainage Area,Ad 1.32 ac Impervious Area, Ai 1.27 ac Pervious Area, Ap 0.05 % Impervious 96% Runoff Coefficient, Rc 0.92 Upstream Detention System Peak release rate from detention,Qrelease peak 0.07 cfs Treatment release rate from detention, Qrelease Ueat 0.02 cfs Detention pretreatment credit 60% (from removal effciency calcs) AAass loading calculations Mean Annual Rainfall, P 38 in Agency required % removal 80% Percent Runoff Capture 90°/a Mean Annual Runoff,V, 150,093 ft' Event Mean Concentration of Pollutant, EMC 60 mgfl Annual Mass Load, Mtota� 561.86 IbS Filter System Filtration brand StormFilter Cartridge height 12 in Specific Flow Rate 1.0 gpm/ft2 Number of cartridges - mass loading Mass removed by pretreatment system, MPfe 33T.11 Ibs Mass load to filters after pretreatment, MPass� 224.74 Ibs Estimate the required filter e�ciency, Efne� 0.50 Mass to be captured by filters, Mt�ter 112.37 Ibs Allowable Cartridge Flow rate, Q�a� 5.00 Mass load per cartridge, M��(Ibs) 24.00 Ibs Number of Cartridges required, Nmazs 5 Treatment Capacity 0.06 cfs Determine Critical Sizing Value Number of Cartridges using Qrelease aeat� Nn� 2 Method to Use: MASS-LOADING SUMMARY Treatment Flow Rate, cfs 0.06 Cartridge Flow Rate, gpm 5.0 Number of Cartridges 5 1 of 1 5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN 5.0 CONVEYANCE SYSTE�41 ANALYSIS AND DESIGN The conveyance system for this project was sized based on the 2005 KCSWDM for sites less than 10 acres in size such that a 100-year precipitation was uti(ized with an initial time of concentration of 6.3 minutes and a Manning's "n" value of 0.014 for all the conveyance piping on the project site. All pipes were sized to convey the 100-year storm without overtopping or surcharging any catch basins which they have achieved. All pipes on this project site were sized to be 12-inch diameter and the calculations and basin map are enclosed on the follawing pages of this report. �3�aaou�d�� PIPE CONVEYANCE CALCULATIONS UU%�� BARGHAUSGN CONSULTING GNGWEERS-PIPE FI.OW CALCUTATUR using the Rational Me�hod 8 Manning Fortnula KING COUNTY DESIGN FOR 100 YEAR STORM .lU(�i�AMF WALGRFFNS NOTE:ENTER DEFAULTS AND STORM DATA BEFORE BEGINNING JOBt� 13140 DEFAULTS C= 0.9 n= 0.014 F it.E NO.13240-t00.XLS d= 12 Tc= 6.3 n=Contribu6ng Area(Ac) Qd=Design Flow(cfs) COEFFIGENTS FOR THE RATIONAL METHOD"Ir"-EQUAiION C�Runofl CoeKcienl Qf=Full Capacity Flow(cis) STORM Ar Br Tc Time of Concentration(min) Vd=Velociry at Design Flow(ips) 2YR 1.58 0.58 I=IMensity at Tc(iNhr) Vt=Velocity al Full Flow(fps) tOYR 2.44 0.64 PRECIP= 3.95 d��-Uiamnter of Pipe(in) s=Sbpe of pipe(%) 25YR 2.66 0.65 Ar- 2.61 L-Length of Pipe(fQ n=Manning Roughness Coefficient 50YR 2J5 0.65 Br- 0.63 D-Water Dep�h at Qd(in) Tt=Travel Time al Vd(min) t00YR 2.61 0.63 �-ROM TO A s L tl Tc n C SUM A A'C SUM A'C I Qd Qf Qdlqf D/d D V( VJ Tt ----- ------ - -- ----------- --'---0 ______ ______ _ =___._. ______ ______ __=_- ------ - -'- __--- - '--- ------ ---- - _-_=_' _______`_____= � -= ------ ----- ------ - -� CBS CB4 0.36 0.50 21 12 6.3 0.014 0.9 0.38 0.32 0.32 323 1.05 2.34 0.448 0.470 5.64 2.98 2.92 0 i� C84 C63 0.17 0.50 184 12 8.4 0.014 0.9 0.53 0.15 0.48 320 1.52 2.34 0.652 0.592 7.10 2.98 3.16 O.ri� C63 C82 0.0fi 0.50 94 12 7.3 0.014 0.9 0.59 OA5 0.53 2.95 1.57 2.34 0.670 0.598 7.18 2.98 3.79 0 ag C81 C62 0.17 1.84 70 12 6.3 0.014 0.9 017 D.15 0.75 323 0.49 4.49 0.�10 0.225 2.70 5.72 373 u's� C62 VAULT 0.67 10.50 46 12 7.8 0.010 0.9 0.67 0.60 1.29 2.83 3.65 1072 0.340 0.403 4.84 i3.66 i2.ap o or�, Page 1 PIPE CONVEYANCE BASIN MAP 0 � GRADING AND ST4RM DRAINAGE PLAN � . 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'�. � � N N � ._T s. . . . __ ._ . __'� � . . � �� d� ' . . �' ' "=a=c- �" I °o Y�v cZi q .'�____'_ � � i � � I � _ --__, � � ! � N . i G� ' �Mi. T � � , ! � �V�, �b� I : . : . , � � � i � Q `�,� sW a �. I ;• • • ' ..' �'t.�... � �, o.�s m ' � � i ° .� �• , ~_ + � � °S : �� j p �� f C�NgJ I I 4 � U 2 m 6.0 SPECIAL REPORTS AND STUDIES i i I 1 The Riley Group Inc. � I GEOT�CHNTCAL ENGINEERING REPORT Proposed Walgreens Drugstore � 4105 & 4111 NE 4rh Street j Renton, WA 98059 ' I Project No. 2007-254 Prepared By: The Riley Group, Inc. , 17522 Bothell Way NE Bothell, WA 98011 Prepared for: Mr. Robert Sherry � Phillips Edison & Company ', 175 �as� 400 South, Suite 402 ' Sait Lalce City, U�ah 84111 ` � i �, . I I November 14, 2007 ! � Servin�the Pacific Northwest Main Office: 17522 Bothell Way 1V�,Bothell,WA 98011 � Tel(425)415-0551 . Fax(425)415-0311 ! i �r "I'I7e Riley Groarp Inc. November 14, 2007 1VIr. Robert Sherry Phillips Edison 8c Company 175 East 400 South, Suite 402 S�lt Lalce City> Utah 841 l 1 Subject: Geotechnical Lngineering Report Proposed Walgrcens Drugstorc 4105 &4111 N� 4t�' Street Renton,WA)8059 Project No. 2007-2_S4 Dea.r Mr. Sherry: As c•equested, "The Riley Group, Inc. (Riley) has performed a geotechnical engineering study for the above referenced site. �The attached report presents our findings and r•ecommendations for the geotechnical aspects of the project design and construction. Our field exploration indicates that the site is generally underlain by 5 to 10 feet of fill overlying medium dense to very dense silty SAND with gravel. The fill consists of loose to dense sandy GRAVEL to silty SAND with some gravel and trace �vood debris. Groundwater seepage was not encountered during the field exploration. Based on the subsurface soil condition, the fill seems to be placed during the site grading and utilities for the gas station and car wash before. The loose fill underlain the site is not suitable for directly supporting the proposed building foundations and floor slab. If the loose fill is encountered below the proposed footing subgrade, it should be compacted. If the organic soil encountered, it shouid be over-excavated and replaced with structural fill. The subgrade condition should be veriFed by a geotechnical engineer during construction. Riley recommends that the proposed retail building be supported on conventional spread footing foundations beaxing on medium dense native soil or 2 feet of properly compacted native fill. The building floar slab and pavement can be similarly supportcd. This report provides our geotechnical findings and recommendations for the project. 'I�hese recommendations should be incu�poi•ated into the project desig» and construcCion. Scrviut tl�e Pacific Northwest Main Of'fice: 17522 Bothetl Way N�,Botl�cll,WA 98011 Tcl(425)415-OSS1 • Fax(425) 415-0311 ! � Geotechnical Engineering Reporl ii November 19, 20D7 Proposed Walgreens Drugs•tore, Renton, WA Project#2007-254 We trust the inforination presented is sufficient for your currcnt needs. If you have any I questions or require additional uiformation,please call. � Sincerely yours, I TxL Rft.r�:v c�iour,►Nc. � � _ t"(1V C U�F.�aF w,�sy,ticTo� y ,� ,r '� R 4��.o � r �S�ONAL�''� I I��/�7 EXt'�RES SEPT. 12, .?�� ' Cllien-Lin(Johnny) Chen,P.E. Ricky R. Wang, Ph.D.,P.E. Project Engineer Principal Engineer .IC/RW The Riley Group, Inc. i � TABL� OF CONTENTS I � � 1.0 PRO.7ECT D�SCRIPTION..................................................................................... 1 � 3 2.0 SCOPE OF WORK................................................................................................... 1 { 7 3.0 S1TE CONDITIONS.................................................................................................2 3.1 SURFACE..................................................................................................................... 2 3.2 SotLs ..........................................................................................................................2 3.3 GROiJ1VDWATER..........................................................................................................2 3.4 SEISMIC CONSIDERATIONS..........................................................................................2 f 4.0 llISCUSSION ANll RI;COMM�NllATIONS.......................................................3 4.1 GENERAL .................................................................................................................... 3 4.2 S[TF..PREPARATION AND GItADiIVG.............................................................................. 3 �.3 FOUNDATIONS.............................................................................................................4 4,4 SLAB-ON-GIZADE CONSTRUCTION...............................................................................4 4.5 RETA]NING WALLS ..................................................................................................... 5 4.6 DRAfNAGE AND STORMWATER FAC[LITY.................................................................... 5 � 4.7 UTiLITiES.................................................................................................................... 6 4.8 PAV�MENTS................................................................................................................ 6 5.0 ADDITIONAL SI:RVICES......................................................................................� � G.0 LIMITATIONS.........................................................................................................� i LIST OF FIGURCS I Figur�e 1....................................................................................................................Site Vicinity Map ' Figure 2..............................................................................................Geotechnical�xploration Plan Figure 3............................................................................................Retaining Wall Drainuge Detail I'i,�trre 4 ............................ ...................................................................Typical Footing Df�airr Detail Lisr or A��;n�i�ic�:s �� lp��endix fi....................................................................... Field L:rplorntion and I.afinratorv 7esting The Riley Group, Inc. , Geotechnical Engineering Report 1 November 14, 2007 Proposed Walgreens Drugstore, Renton, WA Project#2007-254 � � I 1.0 PROJEC'I'D�SCRIl''1'ION ; The project site is located at 4105 �uld 4111 N� 4�h Street in Renton, Washington. The ; approximate location of the site is shown on the Site Vicinity Map, Fi�ure l. The site is cuirentiy occupied by an abandoned Union 76 gas station and the Brown Bear car wash � with asphalt-paved parlcing lots aro�.u�d the buildings. Riley understands that the existing buildings will be demolished and a Walgreens ' drugstore building, approximately 14,800 square feet, will be constructed in the middle portion of the site. Our understanding of the project is based on a preliminary site plan prepared by Thomas Thompson, AIA dated October 8, 2007. At the time of preparing this report, site grading and building plans were not available for us to review. Based on our experience with similar consh�uction, we anticipate that thc proposed Walgreens building will be a single-story structure supported on perimeter walls with a bearing load of 1 to 2 lcips per linear foot, and a series of columns with a maximum load up to 75 kips. The recommendations in the following sections of this report are based upon our i.ulderstanding of the above design features, lf actual features vary or changes are made, we should review them in order to modify our recommendations as required. In addition, , Riley requests to review final design drawings and specifications to verify that our project I tmderstanding is correct and that our reconunendations have been properly inteipreted and �, incorporated into project design and construction. 2.0 SCOl'I: OI+ WORK On October 24, 2007, Riley drilled a total of seven test borings to a maximum depth of 20.5 Peet below ground surface (bgs). Test borings were drilled with a truck-mounted, hollow-stem auger drili rig. Test horings B-1, B-2 and TB-7 were drilled in the proposed parking and driveway areas. Test borings B-3 throu�h II-6 were drilled in the proposed building footprint area. The approximate test boriiig locations are shown on Figttre 2. Using the information obtained from our subsui-face exploration, we perforined analyses to develop geotechnical recommendations for project design and construction on the following: ➢ Soil and groundwater conditions y Retaiiung Walls > Seismic considerations ➢ Drainage and stormwater ➢ Site preparation and grading � Utilities ➢ Poundation support ➢ Pavemcnts � Slab-on-gradc support The Riley Group, Inc. Geotechnica!Engineerrng Report 2 November 14, 2Q07 � Proposed Walgreens Drugstore, Renton, WA Project#2007-254 � � i 3.0 S1TE CONDITIONS 3.1 Surface The site is an L-shaped parcel of land approximately 1.14 acres in size. The site is bounded to the north by NE 4��' Street, to the east by an undeveloped property, to the south by a Les Schwab Tire Store and parking, and to the west by Union Avenue NE. � The site is currently occupied by an abandoned Union 76 gas station (#4105) on the � western portion of the site. The eastern of the site is occupied by the Brown Bear car wash (#4111). 1'he rest of the areas are asphalt-paved parking lots and driveways. The site gently slopes down to the east with an overall elevation difference of 7 feet approximately. 3.2 Soils "I'he soils encountered in the test borings are relatively consistent across the site. The soil profile includes 5 to 10 feet of fill overlying medium dense to very dense silty SAND with gravel. The fill consists of loose to dense sandy GRAVEL to silty SAND with some gravel and trace wood debris. '1'he native soil is dense to very dense glacial till which consists of � silty sand with gravel. I I Review of the Geologic �t�Iap of King County, Washington, by Vaughn E. Livingston Jr. ' (1970) indicates that the soil in the project vicinity is mapped as Vashon till (Qt), which is a hard blue-gray concrete-lil<e mixture of clay, silt, sand, and gravel. These descriptions are similar to the native soil encountered during our field explaration. � Ylore detailed descriptions of the subsurface conditions encountered are presented on the Test Boring Log, Figures A-2 tl�rough A-8 in Appendix �1. ' 3.3 Grrouudwatcr Groundwater seepage was not encountered in any test borings reaching a maximum depth of 2U.5 feet bgs. '1'he groundwater level seems to be deeper than the bottom of the test boring termination depth. Rased on the soil condition, minor perched groundwater inay be expected over the dense layer during wet season. Fluctuations in groundwater level should be expected on a scasonal and annual basis. The level will be highest during the extended periods of heavy seepage in the wet winter months. 3.4 Scismic Considerations Based on 2003 International Building Code (IBC), the site soil is Class D from Table 1615.1.1. The earthquake spectral response acceleration at short periods (SS) is 131%g and at 1-second period(Si} is 46% g. Liquefaclion is a phenomenon where there is a reduction or compiete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are below the groundwatcr table. Soils of this nature derive their strength from intergranular The Riley Group, Inc. i � � � Geotechnical L'ngir►eeriJag Repnrt 3 November 14, 2007 l Propo,sc:d Walgreens Drugstore, Renton, WA Project#2007-254 � � I friction. The generated water pressure or pore pressure essentially separates the soil grains � and eliminates this ultergranular friction, thus reducing or eliminating the soil's strength. ' � We reviewed the soil conditions encountered during field exploration and assessed the potential for liquefaction of the site's soil during an earthquake. Since the soil below the groundwater level is dense to very dense silty sand, Rilcy believes that the potential of soil liquefaction durin�an earthquake event is Iow. i ; 4.0 DISCUSSION AND RECOMMENDATIONS I 4.1 General Based on our study, the site is suitable for the proposed constructiou from a geotechnical standpoint. The loose fill underlain the site is not suitable for directly supporting the proposed buildinb f'oundations and flooi• slab. If the loose till is encountered belo�� the proposed footing subgrade, it should bc properly coinpacted as structural fill. If the organic soil encountered, it should be over-excavated and replaced with structural fill. The proposed retail building can be supported on conventional spread footing foundations bearing on at least medium dense native soil or 2 feet of properly compacted native fill. The building floor slab and pavement can be similarly supported. Detailed recommendations regarding the above issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 4.2 Site Preparation and Gr�din� To prepare the site for construction, the existing buildings and pavements should be demolished and stripped. Surface stripping depths of up to 6 inches should be expected to remove the asphalt surface. All remriants related to previous constiuction, which occupied the site, should also be cleared and removed fiom the site. Once clearing and other preparing oper•ations are complete, cuts and fills can be rnade to establish desired parking grades. Prior to placing fill, we recommend proofrolling all exposed surfaces to determine if any isolated loose and yielding areas are present, Proofroliing should also be performed in cut areas that will provide direct support for new construction. The on-site excavated soils without oi•ganics are generally suitable for use as structural till if the moisture can be properly coi�trolled. If the on-site soil or native fill will be used as structural fill, it can be compacted onsite. The compaction should meet the general structural fill coinpaction requirement. If the site gradin� requires additional structural fill, we recommend importing a material that meets the grading requirements listed in Table I. Prior to use, a geotechnical engineer should examine and test all materials impoc-ted to the site for use as sh•uctural fill. Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted io a minimum of 95 percent of the soil's The Riley Group, Inc. Geotechnica!Engineering Report 4 November 14, 2007 ' Prnposed Walgreens D��ugstore, Ren(on, W�t Project#2007-254 � � maximum density, as determined by ASTM 'I'est Designation D-1557 (Modified Proctor). i The moisture content of the soil at the time of co�npaction should be within about two � percent of its optimum, as determined by this ASTM method. i Table 1. Structural rill U.S.Sieve Size Percent Passin ' 3inches 100 ercent i No.4 sieve 0 to 75 ercent � No.200 sieve 0 to 5 ercent* � I *Based on minus 3/4 inch fraction. �!, 4.3 Foundations Following the site preparation and grading, Riley recommends that the proposed building , foundations can be supported on conventional spread footings beaxing on medium dense native soil or 2 feet of compacted native fiIl. Perimeter foundations exposed to the weather i should be at a minimum depth of 18 inches below final exterior grades. Interior foundations can be constiucted at any convenient depth below the fioor slab. ; We recommend designing foundations for a net allowable bearing capacity of 2,500 �I pounds per square foot(ps�. I'or shart-term loads, such as wind and seismic, a 1/3 increase I in this allowable capacity can be used. � Por designing foundations to resist lateral loads, a base friction coefficient of 0.25 can be used. Passive earth pressures acting on the side of the footing and buried portion of the foundation stem wall can also be considered for resisting lateral loads. We recornmend � calculating this lateral resistance using an equivalent fluid weight of 250 pounds per cubic i foot(pe�. At perimeter locations, we recommend not including the upper 12 inches of soil � in this coinputation because they can be affected by weather or disturbed by future grading i activity. This value assumes the foundation will be const�ucted neat against competent till soil or backfilled with structural fill as described in the Site Preparation and Grading ; section. The recominended fiiction a�id passive resistance values include a safety factor of ' 1.5. With spread footing foundations as recoirunended, you should expect maximum total and I � differential post-construction settlements of 1-inch and '/2-inch, respectively. 4.4 Slab-on-Grade Construction i Wiih site preparation completed as described in the Site Preparation and Grading section, suitable support for slab-on-brade construction should Ue pi•ovided. Riley recommends that slab-on-grade construction be supported on firm native soil or on 12 inches of compacted native fill. Immediately below the floor slab, we recommend placiiig a four-inch thick ' capillary break layer of clean, free-draining sand or gravel that has less tlian S% passing The Riley Group, Inc. � � � i November 14 20 7 Geotechmca!Gngrneerrng Report S 0 Proposed Walgreens Drugstore, Rentofr, WA Projec[#2007-254 the No. 200 sieve. This material will reduce the potential for upward capillary movement ; of water through the underlying soil and subsequent wetting of the floor slab. I Typically, an eight to ten-mil thick plastic membrane is placed on the capillary break to I avoid moisture by vapor transmission. The membrane should be covered with one to two inches of clean, moist sand to guard against damage during construction and to aid in i curing of the concrete. For the anticipated floor slab loading, we estimate post-construction floor settlements of'/4 i to '/z inch. For thicicness design of the slab subjected to point loading froin storage racks , and fork lift vehicie traffic, we recommend using a subgrade modulus (Ks) of l00 pounds per square inch per inch of deflection (pci}. i 4.5 Ret�inin� Walls ' At the tiine of preparation of this report, Riley is not awa�•e of any new retaining walls ' proposed for thc site. If retaining walls will be needed, they should be designed based on � the soil parameters provided below. , Riley recommends designing w�restrained walls for an active earth pressure imposed by an equivalent fluid weighing 35 pcf. For restrained walls, an earth pressure imposed by an � equivalent fluid weighing 55 pcf should bc used for design. For seismic design, an addition uniform load of 5 to 7 H (H is wall height) should be applied to the wall surface. These ! values assume a horizontal backfill condition without building or traffic surcharge loading I� on the wall. i 'The walls mu5t also be provided with adequate drainage and should be waterproofed. A typical retainin� wall drainage detail is shown on Fibure 3. I I 4.6 Draina�e and Stormwater I'acility I Surface Final exterior grades should promote free and positive drainage away from building. Water � must not pond or collecl adjacent to foundations or within the immediate building area. We recommend providing a minimum drainage gradient of 3% for a minimum distance of ten feet from thc building perimeter, except in paved locations. In paved locations, a minimum gradient of 1% should be provided unless provisions are included for collection and • disposal of surface water adjacent tl�e structure. j Subsurface � We recommend installing perimeter foundation drains. A typical recommended drain detail is shown on rigure 4. The foundation drains and roof downspouts should be tightlined � separately to an approved discharge facility. Subsurface drains rnust be laid with a gradient � sufficient to promote positive flow to a controlIed point of approved discharge. The Riley Group, Inc. I i I i Geotechnicul Engineering Reporl 6 1VovemGer 1 a�, 2007 � Proposed Walgreens DruKstore, Renton, WA Project#2007-254 � 4.7 Utilities Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) specifications. For site utilities located within the City of Renton right-of-ways, bedding and backfill should be completed in accordance with City of IZenton specifications. As a minimum, trench backfill should be placed and compacted as structural fill, as descrihed in the Site Preparation and Grading section. Where utilities occur below unimproved areas, the degree of compaction can be reduced to a miiumum of 90 percent of the soil's maximum density as detei7nined by the referenced � ASTM standard. As noted, soils excavated on-sile will be suitable for use as backfill � material if t6e soiPs moisture can be properly controlled. The backfiIl material should satisfy the structwal fill requirements listed in the Site Preparation and Grading section. 4.8 Yavements Yavement subgrades should be prepared as described in the Site Preparation and Grading section of this report and as discussed below. Regardless of the relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade should consist of�rm native soil or properly compacted native fill. The condition should be verified by a geotechnical engineer during consti�uction. With the pavement subgrade prepared as described above, we recommend that d�e general � parking area be paved with flexible pavement surface. The following pavement sections ' are recommended: ! ➢ For heavy trucic traf�c areas: 4 inches of asphalt concrete (AC) over 6 inches of crushed rock base (CRB) over 18 inches of compacted native fill; and ➢ For general parking areas: 3 inches of AC over 4 inches of CRB over 12 inches of compacted native fill. The asphalt paving materials used should conform to the Washingt�n State Department of Transportation(WSDOT) specifications for Class B asphalt concrete and CRB surfacing. � Long-term pavement performance will depend on surface drainage. A poorly-drained � pavement section will be subject to pi•emature failure as a result of surface water � in[iltrating into the subgrade soils and redt�cing their supporting capability. For optimum pavement performance, surface drainage gradients of no less than two percent are recommended. Also, some degree of longitudinal a.nd Ixansverse cracking of the pavement surface should be expected over time. Regular maintenance should be planned to seal cracics when they occur. i The Riley Group, Inc. I Geotechnical Engineering Report 7 November J4, 2007 Proposed Walgreens Drugstore,Rentvn, WR Projecf#2007-254 5.0 ADDITTONAL S�RVICES Riley is available to provide iurther geotechnical consultation as the project design develops. Riley shoutd review the final design and specifcations in �rder to verify that earthworlc and foundation recommendations have been properly interpreted and incorporated into project design and construction. Riley is also available to provide geotechnical engineering and monitoring services during ` construction. The integrity of the foundation depends on proper site preparation and ' construction procedures. In addition, engineering decisions may have to be made in the I'zeld in the event that vai7ations in subsui-face conditions become apparent. Construction �nonitoring services are not part of this scope of work. If these services are desired, please let us know and we will prepare a cost proposal. G.0 LIMITATIONS Tl:is re ort is the ro ert �f Thc Rile Grou Inc. and Philli s Edison & Com an and � P p P Y Y R P P Y, was prepared in accordance with generally accepted geotechnical engineering practices. I,his report is infended for specific application to the Proposed Walgreens Drugstore at 4105 and 4111 NE street in Renton, Washington, and for the exclusive use of Phillips f�dison & Company and its authorized representatives. No other warranty, expressed or :inplied, is made. � "1'he analyses and recommendations presented in this report are based upon data obtaiiied � from the test borings drilled on-site. Variations in s�il conditions can occur, the nature and extent of which may not become evident until construction. 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'- i i � � � I I � NE 4th STREET � o ' _ ___ _ _ ___ _ _ O ---------- --1 � Z .? j ,� _� c� — - - - - • � � I —o ---� �, - ---��— --- X I + — oo w � i 8 ST�P� ' ---- -------- --------- f� � �o��,,, ""`:'`��^ � --- --- - ---`- -- --Z--------------- � £?:.?<�'��`w'!i1!'�lt'1'4��:'65a_. e��qm��,,�'�,,,'ilSilU � i ~ � �� n �� I 40 0 �; � . B-CJ � I w � I 30'��N WAIL B'3! O I I N ,o p � Y , a - a j , B-2 1 14'X 130' I � � Z I( � 1 �� 14,8 Os.f.GROSS I ' � -- � 1 1 12,0�0 s.f. net @0.4/10 I ! I O ' � " � max�parking =48 � , z W ( I � = I � � � perk ng provided=45 � ; �I �-�< � � � � � � '�► B-1;z Q 1 1 � ! . .� � — B-4 � B-6 ��I i 8 � o ° � [�5� �A� —r unQp �,` /1 g_7 . � --* - - lc a t �� R OC T r - � �--- E TIN � --► • ' ; CE S I 6 j t � �! i 4 � � 21 � � ~ I RECONFIGURE EXISTING PARKIN� �: , � ' 8 8 I � � � I Z I � I � EXISTING LES SCHWAB TIRE STORE � v ' a I I � � ' i � w ' � a � � � - - --- F- _— _ _— _ _— � I � _ --.__ - - - - - �.�J � � i i Reference: Figure modified from site plan prepared by Thomas Thompson,AIA dated October 6, 2007. N , Geotechnical test bo�ing location drilled by The Riley Group, DRAWING NOT TO SCALE I g� Inc.on October 24, 2007. Proposed Walgreens Drugstore � The Riley G�oup, Inc. , [7522 BOTHELL WAYNE Geotechnical Explor-ation Plan Figure 2 BOTHELL,WASHINGTON 98011 I Site Address:4105 &4111 NE 4th Street,Reuton,Wlshington ; f I I i � 12" MINIMUM WIDE FREE—DRAINING GRAVEL i S�OPE TO DRAIN � ' . . �. . � - . . _ � � . . .: � . � . ,� , � .. .� � : �o� 12" MIN. o .. . . . .. . - 0 o� 00 . , �. � • � �� o . : . . . . . . I - � ,, . .. � ,�,. . . . . . o�� i, o°° . . � � . o . a$° :. � ' � � - :. � .. .. -� _ FILTER FABRIC MATERIAL °ao � �• � � � - �a � . � � � . � �. EXCAVATED SLOPE ' �° � � � � (SEE REPORT FOR °o ' � � � . � �.� � ' APPROPRIATE �° • ' . . , � INCLINATIONS) ' : o; r! COMPACTED STRUGTURAL a°ao - - BACKFILL (NATIVE OR �o � IMPORT) oo�, , �°°oaoa o08° °°o°o�o °V�oaootJ VotiopU po�a � ./i /. /.. /. /\ .\ ♦ \ ; ; .�, a ,_,. _._ o. a0�� . . . . . . . . . . . . . . . . . . �� , �� • �% �� , � 12" OVER THE PIPE �� 3° BELOW THE PIPE 4 DIAMETER PVC PERFORATED PIPE NOT TO SCA�E `� The Riley Group, Inc. Proposed Walgreens Drugstore , 17522 BOTHELL WAY NE Retazning Wall Drainage Detail Figure 3 BOTHELL,WASHINGTON 9801 l Site Address: 4105 &4111 NE 4th Street,Rentov,Washington i i �� I � i BUILDING SLAB ' da� � e i a e . .. a e .s . � � _� a. e '�\/\//\//\/� � /� /� /� /� / a a �'� . �� I � � ,O'' ��I.�MPAI.l i'iL� \�\ I ` • � . �'STRUCTURAIl; % I,I � � . . , ::BACKFILL:�;:::.�`;:::��'.;:/ \ � ^. � FILTER I \ � . - � i FABRIC /\/ \/ \ . � �a a� . .0.�..;O'. ..0.� 'j .s _ ,. a ... .-a � , '� � � � . \ / .� ` ,a � ..,� . ` � . a • O /� d o'. a a' a . d�. � O \\ \ o o a o o � a \ /� /� /� /� /� /� /� /\ / �/ 4" PERFORATLll PII'B 3/4" WASHED ROCK OR PEA GRAVEL NOT TO SCALE Proposed Walgreens Drugstore r~ The Riley Group, Inc. , 17522 BOTI-IELL WAY N� Typical Footing Drain Detail Figure 4 BOTHELL,WASHINGTON 98011 Site Address:4105 &411 I NE 4th Street,Renton,Washington � � Geotechnical Engineering Report November 14, 2007 Proposet!Walgreen.r Drugstore, Renton, WA Pt-oject#2007-254 APP�NDIX A � Y+'IELD�XPLORATION AND LABORATORY TESTING Proposed Walgreens Diugstore 4105 &4111 NE 4th Street Renton, WA 98059 On Octobec• 24, 2007, we performed our field exploration using a truck-mounted drill rig. We explared subsuriace soil conditions at the site by advancing seven test barings to a i maximum depth of 20.5 feet below existing �rade. The test boring locations are shown on � I'igttre 2. Thc; Cest boring locations were approximately determined by measurements from existing property lines and paved roads, "1 he Test Boring Logs are presented on Pigures A- 2 through A-9. A �eologist/engineer froin our oftiee conducted the field exploration and classified the soil conditions encountered, maintained a log of each test boring, obtained representative soil samples, and observed pertinent site features. All soil sainples were visually classified in � accordance with the Unified Soii Classification System(USCS)described on Figure A-1. Representative soil samples obtained from thc test borings were placed in closed containers and talcen to our laboratory for further examination and testing. The moistt�re contenf of typical sainple was measured and is repoi�ted on the Test Boring Logs. I i � ' I !, ; ' � � I � � � The Riley Group, Inc. � f � MAJOR DIVISIONS LETTER TYPICAL DESCRIPTION ' SYMBOL � CLEAN e -gra e grave s, grave-san mix ures, i e s GRAVELS G� or no fines. ...r GRAVELS Poorly-graded gravels, gravel-sand mixtures, � � More than 50% <�% fines GP little or no fines. I z � of coarse Silty gravels, gravel-sand-silt mixtures, Q � � fraction is larger GRAVELS GM non- lasticfines. � J � .N than No. 4 sieve with fines GC Clayey grave1s, gravel-sand-clay mixtures, i lastic fines. W � � N SANDS CLEAN SW Well-graded sands, gravelly sands, little or no � {n � fines. � Z Mare than 50% SANDS Poorly-graded sands or gravelly sands, little or � Q � o f coarse �5% fines SP no fines. ! � -� fraction is SM Silty sands, sand-silt mixtures, non-plastic fines. U �' smaller than No. SANDS o with fines Cla e sands, sand-cla mixtures, lastic fines. � 4 sieve SC Y Y Y P � norganic si s, roc our, c ayey si s wi s�g � � ML plasticity. p �� SILTS AND CLAYS norganic c ays o ow o me ium p as ici y, ean W � o Liquid limits CL clay). Z (n o "' less than 50% � J o z �L Organic silts and organic clays of low plasticity. — o U � � � MH Inorganic silts, elastic. w � � SILTS AND CLAYS z � � Liquid limits greater CH Inorganic clays of high plasticity, (fat clays). �. — � g � than 50% N QH Organic clays of high plasticity. HIGHLY ORGANIC SOILS PT Peat. DEFINITION OF TERMS AND SYMBOLS L � Density SPT (Blows/Foot) 2�� Outside diameter split spoon o W Very loose 0-4 I sampler p � Loase 4-10 Z Q Medium dense 10-30 2.4" Inside diameter ring sampler or Q � Dense 30-50 � Shelby tube � � Very dense >50 � Water level (date) Consistency SPT(Blows/Foot) Tr Torvane reading, tsf ` Very soft 0-2 pp Penetrometer reading, tsf o �-- Soft 2-4 pp Dry density, pcf J Q Medium stiff 4-8 LL Liquid limit, percent � U Stiff 8-15 p� Plasticity index Very stiff 15-30 N Standard penetration, blows per foot Hard >30 Proposed Walgreens Dr-r,sgstore /� The Riley Group, Inc. , 17522 BOTH�LL WAY NE Unified Soil Classif cation System FiguYe A-1 BOTHELL,WASHINGTON 98011 Site Address:4105&4111 N�4th Street,Renton,Washington I i 1 � Boring No. B-1 ' � �� Logged by : PL I Date: 10/24/07 Approximate Elev.: N/A : �, j I Consistency/ Q (N} Moisture ; � Soil Description Relative Depth � g�ows Content � Density (feet) � �ft �o�o� Surface: Asphalt - 3". _ � i CRB down to 3.8'. Medium -- � (Crushed Rock Base) Dense -- � 12 3.1 - 5 I Brown silty SAND with some _ � 4 10.5 � gravel, dry to damp, loose, Loose __ I (Fill). T -- 1 4 9.8 Mottled Brownish gray silty Medium -- 10 SAND with gravel, damp, Dense - I 21 10.1 � � medium dense, (SM}. -- ' Terminated at 11.5'. No groundwater seepage encountered. -- 15 � - 2p '�� The Riley G�oup, Inc. 1'�'oposed YYalgreens Drugstore , i�sz2 aoTxELL wAv tv� Test Boring Log B-1 Figure A-2 BOTHF.LL,,WASHINGTON 9801 I Site Address:4105&4111 N�4th Street,Renton,Washtngton i I Boring No. B-2 I i Logged by : PL Date: 10/24/07 Approximate Elev.: N/A Consistency/ � (N) Moisture Soi! Description Relative Depth � g�ows Content Density (feet} � /ft (%) Surface: AsphaEt - 1.5". __ � Brown sandy GRAVEL with cobbles, trace silt, damp, Dense -- dense, (Filf). -- ' 5 Mottled Grayish brown silty Very Dense -- I 89�9�� 5.0 SAND with gravel, damp, very dense, (SM). Terminated at 6.5' at refusal. Na groundwater seepage - 10 encountered. -- -- 15 - 20 ' Tlze Riley G�oup, Itzc. Proposed Walgreens Drugstore 17522 BOTHELL WAY N� 7est Boring Log B-2 Figure A-3 BOTHELL,WASHINGTON 98011 Site Address: 4105&4111 NE 4th Street,Renton,Washington � ; i i Boring No. B-3 Logged by : PL Date: 10/24/O7 Approximate Elev.: N1A Consistency/ Q (N) Moisture Soil Description Relative Depth � g�ows Content Density (feet) � /f� �a/a� ,� Surface: Asphalt - 1.5". __ �', Brown silty SAND with gravel, __ trace silt, turning black at tip, damp, loose, (Fill). Loose _- 5 T 1 6 7.2 Black silty SAND with wood debris(charred), damp, loose, -- (Fill). Loose _ 10 T _ 1 fi 34.7 Mottled reddish brown silty Loose SAND with gravel, damp, fo -- Ioose to dense, (SM). Dense -- - 15 -- � 50/3" 8.7 Gray silty SAND with gravel, Very Dense damp, very dense, (SM). _ 2� 1 50/3" 10.0 Terminated at 20.5'. No groundwater seepage encountered. - '"^ The Riley G�oup, ji2C. P�'oposed Walg��eens Drugstore 17522 BOTH�LL WAY NE Test Boring Log B-3 Figure A-4 BOTH�LL,WASHINGTON 98011 Site Address;4105&4i 11 NE 4th Street,Renton,Washington i i � ; ; i Boring No. B-4 Logged by : PL i Date: 10/24/07 Approximate Elev.: N/A i Consistency/ Q (N} Moisture � Soil Description Relative Depth � Blows Content � Density (feet} � �ft /a ' �° ) � Surface: Asphalt - 1.5". � Light brown silty SAND with Loose - � gravel, damp, loose to medium to __ dense, (Fill). Medium Dense__ - 5 _ � 50/4" 5.9 Gray silty SAND with gravel, �ery Dense damp, very dense, (SM). � 50/3" 7.5 - 10 Terminated at 9.0' at refusal. No groundwater seepage encountered. -- 15 -- 20 I "�� The Riley Group, Inc. Proposed Walgreens� Drugstore 17522 BOTI-IELI.,wAY N� Test 13oring Log B-4 Figure A-5 BO"T'H�LL,WASHINGTON 9801 f Site Address:41fl5 &4111 NE 4th Slreet,Renton,Washington ! Boring No. B-5 Logged by : PL Date: 10/24/07 Approxima#e Elev.: N/A ' i � Consistency/ Q (N) Moisture � Soil Description Relative Depth � Blows Content Density (feet) � �ft ��o� � i Surface: Asphalt - 2.0". Brown silty SAND with gravel, damp, loose, (�ill). Loose - 5 Loose � g 15.2 Gray silty SAND with trace to - some gravel, damp, loose to to -- medium dense, (Fill�. - Medium Dense i - 10 T _ 1 11 15.4 ; Brown silty SAND with gravel, -- � damp, very dense, (SM). Very Dense -- � �0/4" 8.0 Terminated at 14.0' at refusal. -- �� No groundwater seepage - encountered. i i _ � � -- � � - 20 _ � 7'�"r The Riley Group, Inc'. Proposed Walgreens Drugsto�e 17522 BOTI-IBLL WAY NE Test Boring Log B-S Ffgure A-6 ' BOTH�LL,WASHINGTON 48011 Sitc Address:4105&4I 11 NE 4th Street,Renton,Washington i i � i Boring No. B-6 � � Logged by : PL Date: 10/24/07 Approximate Elev.: N/A Consistency/ � (N) Moisture Soil Description Relative Depth E Blows Content Density (feet) � �ft �%� , Surface: Asphalt - 2.0". Brown silty SAND with gravel, ; damp, loose, (Fill). Loose -- 5 Loose _ � g 8.1 Grayish brown SAND with some gravel, some silt, damp, to loose, (Fill). Medium _ Dense 1 a T _ 1 10 11.0 Gray silty SAND with gravel, damp, dense, (SM). Dense -- 15 T _ 1 36 7.8 Terminated at 16.5'. No groundwater seepage encountered. -- -- 20 �r The Riley G�oup, �nC. �'�"oposed Walgreens Drugstore , 17522 BOTHELL WAY NE Test Boring Log B-6 Figure A-7 BOTHELL,WASHINGTON 48011 Site Address:4105&4111 NE 4th Street,Renton,Washington � Boring No. B-7 � I Logged by : PL � Date: 10/24/07 Approximate Efev.: N/A Consistency/ � (N} Moisture Soil Description Relative Depth � g�ows Content ' Density (feet) � /ft (%} Surface: Asphalt - 3.5". ' - � Gray silty SAND with gravel, i damp, dense, (Fill). Dense - � 27 g g ; i _ 5 ' Brown to gray silty SAND with - I 11 12.2 some gravel, damp, medium Medium '� dense, (SM). Dense ,I� I 14 9.5 Terminated at 9.0'. - 10 No groundwater seepage encountered. - 15 -" i i -- 20 i I � � , 7"r The Riley G�ou�n, Ine. P�"oposed Walgreens Df�ugstore E 17522 BO'I'HEI,L WAY N� Test Boring Log B-7 Figure A-8 BOTHELL,WASHING'i'ON 9801 I , Site Addretis: 4105 &41 l 1 1_VE 4th Strcct,Renton,Washington i , � � i � � M� �N w � a x w � � 0 0 � 7.0 OTH�R PERMITS Other permits for this project site include: • Water Connection Permit • Sanitary Sewer Side Sewer Permit • NPDES Permit • Clear and Grade Permit from the City of Renton • Site Development Permit fi-om the City of Renton • Building Permit from the City of Renton • Ribht-of-Way Use Permit from the Ciry of Renton i;�ao.noa�� 8.0 CSWPPP ANALYSIS AND DESIGN S.0 CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN (CSWPPP) ANALYSIS AND DESIGN As part of the NPDES Permit, this section of the report will be prepa�•ed with a Surface Water Pollution Prevention Plan, otherwise known as a SWPPP for the Department of Ecology since this site is over 1 acre in size. That replaces the King County CSWPPP which could be prepared as well, and the only portion of this section of the report that applies then is the sizing of the erosion control pond. A sediment trap has been sized for this site since this site is less than 3 acres in size and the calculations are on the following pages of this report. The sizing is based on 2,080 x 2-year flow rate during graded condition, otherwise known as erosion controI condition on the site, creating a surface area in the pond of 583 square feet. In addition to the sediment trap, temporary V-ditches with rock checkdams witl be installed on this project site to ►•oute all surface water runoff toward the sediment trap; silt fences will be installed along the downstream perimeter; clearing limits will be specified; a rock construction entrance will be installed; and cover measures will be instituted on this project site to prevent sediment transport off the project site. The entire site is almost all impervious surface and the site is totally developed under existing conditions. �.,�ao.00a.do� EROSION CONTROL CALCULATIONS ! � _� • - ., s^ .d ' i � Appcndcd on: 0$:38:33 Tucsday, April O1, 2008 13240esc l:vent Summary � Evcnt Pcak Q (cfs) Pcak"T (hrs) ,Eiyd Vol (acft) ,Arca (ac)jlVlcthod jRaintypc - _---• ----- , �6 month j 0.0)18 j 8.00 j 0.0460 I 1.4200 ( SBUH ITYPEIA i -- --- - - -- I 2 year U.2786 8.00 I 0.1072 1.4200 SBUH TYPEIA i 10 year I 0.5568 8.00 0.1955 1.4200 SBUH TYPE 1 A � 25 year � 0.7218 8.00 0.2476 1.4200 SBUH TYPE 1 A i 100 year�908 � 8.00 ( 0.3012 1.4200 SBUH �YPE 1 A i Rccord Id: 13240csc �Design Method � S13UH �Rainfall type i TYPEIA (Hyd Intv v� 10.00 min IPeaking Factor �484.00 �` �--� �Abstraction Coeff �0.20 �Pcrvious Arca � 1.42 ac DCIA � 0.00 ac ;- - --- - - --- -------- - - ------ - - ----- ------ -- �Pervious CN , 87.00 �DC CN � 0.00 � Pervious 'I'C 5.00 min DC "I'C � 0.00 min - ___ Pcrvious CN Calc ________ ; _ I, I ; �•' Description , SubArca A( Sub cn ;; _._ . _- - - ---- - �� :i Dirt roads & Parkinb I.ots j 1.42 ac 87.Q0 � ;� - - - -- --- --- -- _ _ --------- ------ �� _ Pervious Composited CN (AMC 2)__ �87.00� � Pervious TC Calc , � Type � Description �Length � Slope ` Coeff Misc TT Fixed � �- 5.00 min � ' Pervious TC 5.00 min I, �� ,. Licctiscd to: [3arghausen Engineers �Go��,��rV" '`��o S,�.r �,�� ,�-��t = Si9. = ZflXO C , _ �i r�:�0)�r�. 1_�� - �� , 9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATIONS OF COVENANT 10.0 OPERATIONS AND MAINTENANCE MANUAL APPENDIX A MAINTENANC�REQUIREMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACIL[TIES NO. 3-DETENTION TANKS AND VAULTS Maintenance Defect or Problem Conditions When Mai�tenance is Needed Results Expected When Component Maintenance is Perfortned Storage Area Plugged Air Vents One-hal(of the cross section of a vent is blocked Vents free of debris and sediment at any point wiih debris and sediment. Oebris and Sediment Accumulated sediment depth exceeds 10%of All sediment and debris removed the diameter of the storage area for Y:length of from siorage area. storage vault or any poi�t depth exceeds 15%of diameter. Example:72-inch storage tank would require cfeaning when sediment reaches depth of 7 inches for more than%:length of tank. Joints Between Any crack allowing material to be transported into All joint between tank/pipe secUons Tank/Pipe Section facility. are sealed Tank Pipe Bent Out of Any part of tank/pipe is bent out of shape more Tank/pipe repaired or replaced to Shape than 10%of its design shape. design. Vault Structure Damage to Wall, Cracks wider than Y�-inch and any evidence of Vault replaced or repaired to design Frame, Bottom, sal particfes entering the structure through the specifications. and/or Top Slab cracks,or maintenance inspection personnel determines that the vault is noi stn.�cturally sound. Damaged Pipe Jants Cracks wider than Yrinch at the joint of any No cracks more than Y.-inch wide at inleUoutlet pipe or any evidence of sal particles the joint of the inleUoutlet pipe. entering the vault through the walls. Manhole Cover Not in Place Cover is missing or only partially in place.Any Manhole is closed. ope�manhole requires maintenance. Locking Mechanism Mechanism cannot be opened by one Mechanism opens with proper tools. Not Working maintenance person with proper tools.Bolts into frame have less than Y�inch of thread(may not app{y to self-locking lids.) Cover Difficult to Qne maintenance person cannot remove lid after Cover can be removed and Remove applying 801bs of lift. Intent is to keep cover from reinstalled by one maintenance sealing off access to maintenance. person. Ladder Rungs Unsafe King County Safety O�ce and/or maintenance Ladder meets design standards. person judges that ladder is unsafe due to Allows maintenance perso�safe missing rungs,misalignment,rust,or cracks. access. Large access Gaps,Doesn't Cover Large access doors not Flat and/or access hole Doors closes flat and covers access doors/plate Completely not completely covered. NOTE however that hole completely. grated doors a�e acceptable. Lifting Rings Missing. Lifting rings not capable of lifting weight of door Lifting rings su�cient to remove lid. Rusted or lid. lr"24l�00_5 300� SurYacc Water Dcsign Manual-:1pPcndix A A-4 APPENDIX A MAINTENANC�REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITICS NO. 4-CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is Performed Generai Trash and Debris Distance between debris build-up a�d bottom of Ali trash and debris removed. (Includes Sediment) orifice plate is less than 1.5 feet. Structural Damage Structure is not securely attached to manhole Structure securely attached to wall wall and outlet pipe structure should support at and outlet pipe. least 1,000 Ibs of up or down p�essure. Structure is not in upright position(allow up to Structure in correct position. 10%from plumb). Connections to outlet pipe are not watertight and Connections to outlet pipe are water sFaw signs of rust. tight;structure repaired or replaced and works as designed. Any holes—other than designed holes—+n the Structure has no holes other than structure. designed holes. Cleanout Gate Damaged or Missing Cteanout gate is not watertight or is missing. Gate is watertight and works as designed. , Gate cannot be moved up and down by one Gate moves up and down easily and maintenance person. is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Gate is rusted over 50%of its surface area. Gate is repaired or replaced to meet design standards. Orifice Plate Damaged or Missing Control device is not worlcing properly due to Plate is in piace and works as missing,out of place,or bent orifice plate. designed. Obstruc6ons Any trash,debris,sediment,or vegetation Plate is free of all obstructions and blocking the plate. works as designed. Overflow Pipe Obstructio�s Any trash or debris blocking(or having the Pipe is free of all obstructions and potential of blocking)the overflow pipe. works as designed. Manhole See"Detention Tanks See"Oetention Tanks and Vaults"Table No.3 See"Detention Tanks and Vaults" and Vaults" Table No. 3 2005 Surface Water Design Manual -Appendix A V24i2005 A-5 APPENDIX A MAMTENANCE REQU[REMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 5-CATCH BASINS Maintenance Defect or Problem Conditio�s When Maintenance is Needed Results Expected When Component Maintenance is performed General Trash 8 Debris Trash or debris of more than%:cubic foot which No Trash or debris located (Includes Sediment) is located immediately in front of the catch basin immediately in front of catch basin opening or is blocking capacity of tfie basin by opening. more than 10%. Trash or debns(in the basin}that exceeds'/3 the No trash or debris in the catch depth from the bottom of basin to invert the basin. lowest pipe into or out of the basin. Trash or debris in any inlet or outlet pipe blocking Inlet and outlet pipes free of trash or more than�/3 of its height. debns. Dead animafs or vegetation that could generate No dead animals or vegeta6on odors that could cause complaints or dangerous present within the catch basin. gases(e.g.,methane). Deposits of garbage exceeding 1 cubic foot in No condition present which would volume. attract or support the breeding of insects or rodents. Structure Damage to Comer of frame excends more than'/.inch past Frame is even with curb. Frame and/or Top curb face into the street(If applicable). Slab Top slab has holes targer than 2 square inches Top slab is free of holes and cracks. w cracks wider than'/.inch(intent is to make sure all material is running into basin). Frame not sitting flush on top slab,i.e., Frame is sitting flush on top slab. separation of more than'/.inch of the frame from the top slab. Cracks in Basin Cracks wider than%:inch and longer than 3 feet, Basin replaced or repaired to design Walls/Bottom any evidence of sal partiGes entering catch standards. basin through cracks,or maintenance person judges that structure is unsound. Gacks wider than Yz inch and longer than 1 foot No crack$more than'!e inch wide at at the joint of any inleUoutlet pipe or any the joiRt oi inleUoutlet pipe. evidence of soil particles entering catch basin through cradcs_ SettlemenU Basin has settled more than 1 inch or has rotated Basin replaced or repaired to design Misalignment more than 2 inches out of alignment. standards. Fire Hazard Presence of chemicals such as natural gas,oil No flammable chemicals present. and gasoline. Vegetation Vegetation growing across and blocking more No vegetation blocking opening to than 10%of the basin opening. basin. Vegetation growing in inleUouUet pipe jants that No vegetation or root growth is more than 6 inches tall and less than 6 inches present. apart. Pollution Nonflammable chemicals of more than Y�cubic No pollution present other than foot per three feet of basin length. surface film. Catch Basin Cover Cover Not in Place Cover is missing or only partiaily in place.Any Catch basin cover is closed open catch basin requires maintenance. Locking Mechanism Mechanism cannot be opened by on Mechanism opens with proper tools. Not Working maintenance person with proper tools.Bolts into frame have less than YZ inch of thread. Cover Difficult to One maintenance person cannot remove lid after Cover can be removed by one Remove applying 80 Ibs.of lift:intent is keep cover from maintenance pe�son. sealing off access to maintenance. Ladder Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, Ladder meets design standards and misalignment,rust,cracks,or sharp edges. allows maintenance person safe access. 1/24/2005 2005 Surface Water Design Manual—Appendix A A-6 APPENDIX A MAINTENANCE RLQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 5-CATCH BASINS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Mainte�ance is performed Metal Grates Unsafe Grate Grate with opening wider than 7!e inch. Grate opening meets design (If Applicable) Opening standards. Trash and Debris Trash and debris that is blocicing more than 20°/a Grate free of trash a�d debris. of grate surface. Damaged or Missing. Grate missing or broken member(s)of the grate. G�ate is in place and meets design standards. NO. 6- DEBRIS BARRIERS(E.G.,TRASH RACKS) Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When Component Maintenance is PerFormed. General Trash and Debris Trash or debris that is piugging more than 20% Barrier clear to receive capacity of Yhe openings in the baRier. flow. Metal Damaged/Missfng Bars are bent out of shape more than 3 inches. Ba�s in place wifh no bends more Bars. than'/.inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars are loose and rust is causing 50°/a Repair or replace barrier to design deterioration to any part of barrier. standards. i NO. 7-ENERGY DISSfPATERS Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed. ExternaL• Rock Pad Missing or Moved Only one layer of rock exists above native soil in Replace rocks to design standards. Rock area five square feet or larger,or any exposure ' of nafive sal. Dispersion Trench Pipe Plugged with Accumulated sediment that exceeds 20%of the Pipe cleaned/flushed so that it Sediment design depth. matches design. Not Discharging Visual evidence of water discharging at Trench must be redesigned or Water Properly concentrated points along trench(normal rebuilt to standards. condition is a"sheet flow"of water along trench). Intent is to prevent erosion damage. Perforations Plugged. Over'/:of perforations in pipe are plugged with Clean or replace perforated pipe. debris and sediment. Water Flows Out Top Maintenance person observes water flowing oui Facility must be rebuilt or of"Distributor"Catch during any storm less than the design storm or redesigned to standards. Basin. its causing or appears likely to cause damage. Receiving Area Over- Water in receiving area is causing or has No danger of landslides. Saturated potential of causing landslide p�oblems. Intemal: Manhole/Chamber Wom or Oamaged Structure dissipating Flow deteriorates to%:or Replace structure to design Post.Baffles,Side of original size or any co�centrated wom spot standards. Chamber exceeding one square foot which would make structure unsound. 2005 Surface Water Design Manual—Appendix A I/24/2005 A-7 APP�NDIX A MAINTENANC�REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 10-CONVEYANCE PIPES AND DITCHES � Maintenance Oefect or Problem Conditions When Maintenance is Needed Results Expected When Component Maintenance is Performed Pipes Sediment&Debris Accumulated sediment that exceeds 20%of the Pipe Geaned of all sediment and diameter of the pipe. debris. Vegetation Vegetation that reduces free movemertt oi water All vegetation removed so water through pipes. Flows freely through pipes. Damaged Protective coating is damaged;rust is causing Pipe repaired or replaced. more than 50%deterioration to any part of pipe. Any dent that decreases the cross section area Pipe repaired or replaced. of pipe by more than 20%. Open Ditches Trash&Debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from square feet of ditch and slopes. ditches. Sediment Accumulated sediment that exceeds 20°/a of the Ditch cleaned/flushed of all design depth. sediment and debris so that it matches design. Vegetation Vegetation that reduces free movement of water Water flows freely through ditches. through ditches. Erosion Damage to See"Detention Portds"Tabte No. 1 See"Detention Ponds"Table No. 1 Slopes Rock Lining Out of Maintenance person can see native soil beneath Replace rocks to design standards. I Place or Missing(If the rock lining. I ApPlicable). ' h N0. 11 -GROUNDS (LANDSCAPING) Maintenance Defect or Problem Conditions Whe�Maintenance is Needed Results Expected When Component Maintenance is Pertormed General Weeds Weeds growing in more than 20%of the Weeds present in less than 5%of (No�poisonous,not landscaped area(trees and shrubs only). the landscaped area. noxious) � Safety Hazard My presence of pason iry or other poisonous No poisonous vegetation present in �egetation. landscaped area. Trash or Litter Paper,cans,bottles,totating more than 1 cubic Area clear of litter. foot within a landscaped area(trees and shrubs only)of 1,000 square feet. Trees and Shrubs Damaged Limbs or parts of trees or shrubs that are split or Trees and shrubs with less than 5% broken which affect more than 25%of the total of total foliage with split or broken fofiage of the tree or shrub. limbs. Trees or shrubs that have been blown down or Tree or shrub i�place free of injury. knocked over. Trees or shn�bs which are not adequately Tree or shrub in place and supported or are leaning over,causing exposure adequately supported;remove any of the roots. dead or diseased trees. ' ,' 2005 Surfacc Water Design Manual-Appendix A 1i24/2005 A-9 APP�NDIX A MAINTENANCE REQUIRE1�tENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILIT[ES NO. 17-WENAULT Maintenanoe Defect or P�oblem Condition When Maintenance is Needed Recommended Maintenance to Component Correct Problem Vault Area Trash/Debris Trash and debris accumulated in vault(includes Remove trash and debris. Accumulation floatables and non-floatables). Sediment Sediment accumulation in vault bottom exceeds Remove sediment from vault. Accumulation the depth of the sedime�t zona plus 6 inches. Ven6lation Ventilation area blocked or plugged Remove or clear blocking material from ventilation area. A specified% of the vault surface area must provide ventilation to the vault inieriw(see p.6-82 for required%). Vault Structure Damage to WaII, Cracks wider than'h-inch and any evidence of Vault replaced or repaired to design I Frame,Bottom, soil particles entering the structure through the specificalions. and/or Top Slab cracks,or maintenance inspection personnel determines that the vault is not structuraQy sound. Damaged Pipe Jants Cracks wider than Yz-i�ch at the joint of any No cracks more than%-inch wide at inleUoutlet pipe or any evidence of soi!parGcles the joint of the inleUoutlet pipe. entering the vault through the walls. Baffles Damaged/Defective BaFfles corroding,cracking,warping and/or Repair or replace bafffes to �I showing signs of failure as determined by specifications. mainte�ancelinspection staff. InIeUOutlet Damaged Pipes lnletloutlet piping damaged or broken and in Pipe repaired and/or replaced. need of repair. Trash/Debris Trash and debns accumulated in pipe or Remove trash and debris. ' Accumulation inleUoutlet(includes floatables and non- floatables). , Access Cover Damaged/Not Cover cannot be opened or removed,especially Pipe repaired or replaced to proper Working by one person. working specifications. Access Ladder Damaged Ladder is corroded or deter+orated,not Ladder replaced or repaired to functioning properly,missing rungs,has cracks specifications,and is safe to use as and/or misaligned. Confined space warning sign determined by inspection personnel. missing. Replace sign warning of confined space entry requirements. 1/24/2005 2005 Surface Water Design Manual--Appendix A A-14 APPENDIX A MAINTLNANCG REQUIREMGNTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES NO. 20-STORMFILTER° * Mai�tenance Defect or Problem Condition When Maintenance is Needed Recommended Maintenance to Component Correct Problem Media Section Sediment Sediment depth exceeds 0.25 inches. No sediment deposits that would Accumulation on impede permeability of the compost Media. media. Trash/Debris Trash and debris accumulated on compost filter Trash and debris removed from the Accumulation bed. compost filter bed. First Chamber Sediment Sediment depth exceeds 6 inches in first No sediment deposits in vauft Aca�mulation chamber. bottom of first chamber. Drain Pipes Clean- Sediment When drain pipes,clean-outs,become full with Remove the accumulated material Outs Accumulation sedime�t and/or debris. from the facilities. NO. 21 -STORMFILTER�(CARTRIDGE TYPE) Maintenance Defect or Problem Condition When Maintenance is Needed Recomme�ded Maintenance to Component Correct Problem Compost Media Plugged Drawdown of water through the media takes Replace media cartridges. longer than 1 hour,and/or overflow occurs frequently. Short Circui6ng Flows do not properly enter filter cartridges. Replace filter cartridges. Pipes Damaged Any paK of the pipes that are crushed,damaged Pipe repaired and/or replaced. due to corrosion and/or settlement. Access Cover Damaged/Mot Cover cannot be opened,one person cannot Cover repaired to proper working Wo+icing open the cover,corrosioNdefortnation of cover. specifications or replaced. i Vault Structure Damage to Wall, Cracks wider than Yz-inch and any evidence of Vault replaced or repaired to design Frame, Bottom, soil particles entering the structure through the specifications. and/or Top Slab cracks,or maintenance/inspection personnel determines that the vault is not structurally sound. ! Damaged Pipe Joints Cracks wider than Y=-inch at the joint of any No cracks more than Y.-inch wide at inleVoutlet pipe or any evidence of soil particles the joint of the inleVoudet pipe. entering the vautt through the walls. BafFles Damaged Baffles corroding,cracking warping,andlor Repair or replace baffles to showing signs of failure as determined by specification. maintenance/inspection person. Access Ladder Damaged Ladder is coRoded or deteriorated,not Ladder replaced or repaired and functioning properly,missing rungs,cracks,and meets specifications,and is safe to misaligned. use as determined by inspection personnel. 2005 Surface Water Design Manual—Appendix A U24/2005 A-l7