The URL can be used to link to this page

Home My WebLink About02869 - Technical Information Report - Preliminary _' �r �� v� �� PRELIMINARY DRAINAGE REPORT City of Renton, Washington ��F��/E� �� - 200y � Prepared for: (�'TIL��RE��ron, I Treece & Company, Inc. � ST�Ms Engineering and Development Consultants 320 Second Ave. South, Suite 200 Kirkland, WA 98033 I Prepared By: Nicole E. McWhirter 1:��,, Reviewed By: `-'�`Y�FRF�;r,, , Barton G. Treece, Jr., P.E. � �U� �� 'qa � %;- --��5�'�� ,`� �' r`� �� T'f �� ..��WA��' ! e �,. „O t � ETERSON �: ��,w � , C4NSULTING ; ��` � � �� S;� c� z`' F� . � � .�� 27505 �y �c�� l'S, GfsTE�' G*.� 320 SECOND AVENUE SOUTH `�jorar��.�r �'�� KIRKLAND, WASHINGTON 98033 � �FFICE(425)827-5874 FAX(4251822-721b �FiR S �t2� July 20, 1999 PCE Job No. TREC-0019 Page 1 of 2 �L King County Bullding and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET - . . � - . . . . . � � . Project Owner ot��u. -- �R��tA Pr�ject Name ��Git=i C;� (7uU= ►'��Rt�4�G�3..`� Address Location a� Phone Township Project Engineer � �"�fv'��=�E Range `-�� Company TtZE�� C:�MP+AN� , �c=• �tion �� Project Size `7�� AC Address Phone �'a �C��5• K+r�KUaN� Upstream Drainage Basin Size AC 5 3�- `77 " � • • • � Subdivision � DOF/G HPA � Shoreline Management 0 Sho�t Subdivision � COE 404 � Rodcery � Grading � DOE Dam Safety � Structu�al Vaults � Commercial � FEMA Floodplain 0 Other � Other � COE Wetlands � HPA • � � - � Community ,I.iC:O�'►�0�� (�1�`l Oi– �'�~+�El�� Drainage Basin $t,�W �v��Z S�3��-S ti�� C��N `��v�� U:�s��J � River � Floodplain � Stream � Wetlands � Critical Stream Reach � Seeps/Springs � Depressions/Swales � High GroundwaterTable � Lake — 0 Groundwater Recharge � S;eep Slopes � Other _ � Lakeside/Erosion Hazard • ' Soil Type Slopesp Erosio.n Potentiai Erosive Velocities �." � �� --- ----__Lol-c,3 ---- -- I [_� Additional Sheets Attatched i/90 r " Peg920i2 _� K[ng County Buitding and Land Development Divislon TECHNICAL INFORMATION REPORT (TIR) WORKSHEET � . . REFERENCE LIMITATION/SITE CONSTRAINT � Ch.4-Downstream Analysis a 0 a 0 0 � Additional Sheets Attatched � MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURiNG CONSTRUCTION FOLLOWING CONSTRUCTION 0 Sedimentation Facilities 7� Stabilize Exposed Surfaoe � Stabilized Construction Entrance � Remove and Restore Temporary ESC Facilities � Perimeter Runoff Control � Clean and Remove All Silt and Debris � Clearing and Grading Restrictions � Ensure Operation of Permanent Faalities � Cover Practices 0 Flag Limits of NGPES � Construction Sequence 0 Other � Other �I , i � Grass Lined Channel 0 Tank � Infiltration Nlethod of Analysis � � Pipe System � Vault 0 Depression "�J�i�,N 0 Open Channel 0 Energy Dissapator � Flow Dispersal CompensatioNMitigaGon � Dry Pond 0 Wetland 0 Waiver of Eliminated Site Storage � Wet Pond 0 Stream � Regional Detention Brief Descriptio�of System Operation �Ciqh�line. Yl�.f10 '� 'tU QragS SlJ�3�.s �t? e'�txl�Yic�n �aC,�\�k�l_ . Facility Related Site Limitations � Additional Sheets Attatched Reference Facility Limitation • . , - � � Drainage Easement 0 Cast in Place Vault � Other � Access Easement 0 Retaining Wall 0 Native Growth Protection Easement � Rockery>4'High Q Tract 0 Structural on Steep Slope � Other • -. • I or a civil engineer undef my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the i attatchments. To the best oi my knowledge the iniormation provided here is accurate. �r • 1/'90 r— _y TABLE OF CONTENTS I. PROPOSED SITE CONSTRUCTIO�'.....................................:........................................................1 II. EXISTING CONDITI01'S...............................................................................................................2 III. DEVELOPED CONDITIONS.........................................................................................................2 N. CORE REQUIREMENTS..............................................................................................................7 A. CORE REQLTREr-1ENT#1: DISCH.aRGE AT THE NATLjR.1L,LUCATION.....................................................7 B. CORE REQLTREb[ENT#2: OFF-SITE�':�.Ll SIS....................................................................................7 C. CORE REQLiIRE�-IE\T#3: RLNQFF CONTROL.........................................�--..........................................7 D. CORE REQLIIREhSEN"I'#�: COVVEYANCE SYSTE\-1...............................................................................7 E. CORE REQL'IREA-IE\T#�: TEMPOR.�R1-EROSIQti:�I�1D SEDThiE\T CO\TROL PL_4\................................7 V. SPECIAL REQUIREMEI�TS........................................................................................................S A. SPECIAI.REQL'IREn4EN�I'#1: CRITIC?L DR.AINAGE AREAS....................................................................8 B. SPECIAL.REQLnREMENT#2: C0:�4PLIANCE WITH�E.l"ISTING MASTER DR�INAGE PL.AN.......................R C. SPECIAI.REQi.RRE:�4E\T#3: CONDITIONS REQi'IRINU A M.�.STER DR.-�IN�GE PLA1V................................8 D. SPECL4L REQLIIRE:�3E�T#�: ADOPTED B:1SIN OR COI�-1'��IL�ITl"PLA.\S..................................................$ E. SPECI4I.REQUIREMENT#j: SPECI,aL WATER QL1,�,IT1"CONTROIS......................................................8 F. SPECI.�L.REQiIIREMENT#1 I: GEOTECHI�ICAL AN.ALYSIS:�ND REPORT.................................................9 �'i. SPECI.AL.REQi IIRE\4E'.VT#12: SOILS f�\AL.YSIS:�ND REPORT.................................................................) VI. DETENTION..................................................................................................................................9 VII. WATER QUALITY..................................................................................................................... 10 VIILOFF-SITE ANALYSIS............................................................................................................... 10 IX. CONCLUSION............................................................................................................................... 11 APPENDIX A—HYDROLOGIC PARAMETERS & DETENTI01�' CALCULATIONS SCS Curve Numbers Table Wc�terWorks Data Output 2, 10 and 100-Year Isopluvials Black River Sub-Basin Map & Summary APPENDIX B—OFF-SITE BACKWATER ANALYSIS SYormCcrc�Data Output Peter.san (.'onsa�ltin�En�ir�eer.e Paoe i ' — Prelinriraan.�Drainage Report.for Pacific Gul f b�'arel�ouse Julv?0, 1999 _� I. PROPOSED SITE CONSTRLTCTION The proposed project is the construction of a 106,752 SF warehouse and office facility with associated parking and landscaping on approximately 7.39 acres. The site is located within the City of Renton at the 3900 block of Lind Avenue SW, south of SW 34th Street (see Vicinity Map below). More specifically, the site is located within Section 30, Township 23 North, Ran�e 5 East, W.M in King County, Washington. Existing development adjacent to the site includes railroad tracks and U.S. Rentals, bounding the site to the north; Home Base retail store and a wetland and detention berm bounding the site to the east; undeveloped land to the south; and Lind Avenue bounding the site to the west. Based on the results of an onsite detailed soil content analysis completed by Terra Associates, the site contains alluvium soils (Qaw). This soil type contains several layers of silty sand fill, and displays characteristics of moderately high runofF potential. The soil qualities closely resemble those_defined as hydrologic soil class C per the King County Surface Water Design Manual (SWDI�. SW�ADy WAY OS SW 16TN 3 ST , y W � J J) 1.5 ¢ � 3 2 = �U J (^ _ W SW?77H S7 167 I SW 347H ST sirE CARR RD SW 43RD 5T VICINI T Y MAP (NOT TO SCALE) Pctei•.�on (.'nn.ccrlting Er�gineers Prrgc> 1 Prelimincn•v Draii�age Report for PnciTc Gulf 6Y'arelTouse Ju/v?0, 1999 II. EXISTING CONDITIONS The e�sting site contains sparse grasslands and relatively no vegetation. There are several small shrubs along the western boundary of the site. A portion of the site, approximately 1.25 Acres, contains an e�sting wetland buffer and will not be disturbed as part of this project and excluded in the detention calculations. There are also portions of the site which are detained for in the e�sting condition and are not included in detention calculations. The onsite drainage patterns generally sheet flow from the east to the west at relatively flat slopes (1% to 3%). The existin� basin area, 5.57 Acres, used in the Water•Works analysis has been delineated on the Ezisting Conditions Map on Pa;e 3. The hydrologic parameters are summarized below and the e�sting peak flows for the 2, 10 and 100-year, 24-hour storm events are summarized in Table 1 on Page 6. The existing conditions area was modeled using an existing S.C.S. curve number (CN = 90) for grass cover on 50% to 75% of the area. Please refer to Appendix A for the ; Curve Numbers table and WcrterWorks data output. Total Area= 5.57 Ac Pervious Area= 5.57 Ac @ CN=90 (grass cover 50-75%) Time of Concentration= 18.28 min. Reach 1: 160' Sheet Flow @. 2.00%; `n' = 0.40 (jrass) III. DEVELOPED CONDITIOI�S The proposed site will consist of a 2.45-Acre warehouse and office facility with parking/paved areas and landscaping. The onsite drainage will be divided into two hydrolojic basins (See Developed Conditions Map on Page 4}. The southern portion of the site will comprise onsite Basin `A'. Runoff jenerated within Basin `A' will be routed to approximately the midpoint of the southern boundary of the site, into a combination detention/wet pond, via �rass swales and a ti�htline system. The northern portion of the Peter.eon ('onscrltii�g E�tgi��eer.c Page 2 � �� '�� y . - 100' 0 100' SCALE: 1" = i 00' i� _ 1' I �J �� _ I � � _-�-_ �� ,� �:, P �s c !� /��/ -�� R .�\\. IP �� _ `-- ' U� � � "� � � �� i �s-q _ •A _� J —r� L—� —c-�,-- --a„Z,— I� � �b•t�i r �'�� `'�� _ 's � ,� — --- I�I � �l` � �� ; ` � _ —,——�- — �.--_— _ — — ' � I' ' `` � j '" -� 'c•w � ..� � I "` 5 o- I — .5 l � � , \ _ _ �� , _" ,s-_ � l `� � i � --y � y — �--- i � i J� � `t �,� ,.,J ,� �_.._ �_ _ _ � � - _ i �� ; �, � � _^ i �� ( _ , � � � � , � I �\ / _ i �� I "'� � ' ( � ,� � - - - , , � 'i I ro FaR wEsr y i� � i'' �,,� — — — � � �� 1�' ''� S TEEL DETEN TION ' i / � � i � � � � � _ _ _ _ � —„— il I'�� '' �FACILITY I � � - , } 1 i / ;� '�,� � ! I � / � EXISTlNG BASI� ^ � i � '!,, fIAREA=0.42 AC , � � � � � / �0 EXISTING TIGHTLINE � ARE�=�57 ,4C TIME OF CONCENTRATION � I ! r ,,�,,!t� ��I � � ` / / — � / � � TC=18.28 MINU TES 1 � � h i I I �\�`•f\'•� � / SYSTEM IN LIND A 1/E. �1! ' I 1(; � -� � � AREA=O. 13 AC i � 1 � ��,- � / I ;� , �,'�!�'`•,, �,, � � �I, l \. // �\ / � �� / /i\ L � � � I , � I�; � �-�,=�-�— � � � � � � � � 1 � � I �� I(� I; _ � � � � / �.. � I _ - � - - � + � � � `' � / � ,� ( �_�.� � �, I� I�(�\�`\ -�` ��`�' \ ' / � �' �\��, \`• "�� "-b � 160' SH�E-T"�F-L�7W� i! \ ; � � ��\ I I ' l � - - - - - � I� �� \� � �i '�� 5: I �� ` � i ',q��Il; -1� ' I�I�, \ � —'—� _ _"_ _ _ - _ —�—_ � 2.oo�-- � �� \�� . � ii l,,�► 1r�1� � L \ �\, ' . � i _ - 1�ifETL;�ND"B' FER, — � — � — — — —J —" � �\\� \ii . _,. (� _�,,� 1�.' , ��-�`� � � �I H!I� I I��lI� �� . �_ ' �,'�= � _ _ -, _ � „_ .�i�"� �� ` , _ , ,. , AREA 1 2��-A'Cy ,I ,,.,, -:--� ,�__1_ _ - � �' , � _ —— — — — ,� �i �, -r n,� , . `__—,, / _ � -� - � �r —�' _� rr� a—`—+` � 7 1 , �� / _ �`� 1' —_—� � 1� � � � � �� ' ' _ �;� �11 �, ; � i ;�� =,� , , I � �•, , � � �� `'� � . � ��\\ i 1,� _ ; � � , , � � , ` � TREECE COMPANY ENGINEERING AND DEVELOPMENT CONSULTANTS 3E0:rN�n.Sou��.SUX�300 KiPFIAf:D.K�ISNIW-On 9Bp55 P40ME(�25)d2I-ISfl l411(a75)L22-!'S! - CITY OF RENTON � ` DEPARTMENT OF PUHLIC WORKS - PACIFIC GULF WAREHOUSE EXISTING = CONDITIONS MAP , � 06�GMFD: BGT. ' �,� �/p�99 �µWE�C/IIREI9 - � DRAWN: R.SC : ' CIiECKEO: dC.T. X�: f'a f00. f-,_•»_ _.� � �o. R�,,S�, , B, ,�PR. aa� ,�r�ro�ro- ._PAGE 3 r i � ,,I II I, I j � J i � � � , �; �'i _ � � �� I ! / I �;.��—� � �, � f 1 P1 �, i�`I ��.� N 'l �\ I I �, \ 1� `, _ _ " �� - ___ � , r � I � ",,, � _ ` �_ � J , \ ;�� : T PROPOScD DETENTlON � _.� i —�=�- �.._ �ULT K� I: � � � � -`'_T"'- -�--�_- _ � x , ,„�. 10 d' 0 10 0' ` � — —�—�-i Mq�-�-- }� � ,s— { ° ._ �i ^1 i ��t-�` � ' �'^' � �-/ � — -- — � ---- — —��y�I _ I SCALE: 1' _ �OC, � I �I� � \ /q �, - � _ � � ^..�� I I c � \ `✓ , � 1 r - �T iY . ..� . �, / � �� c �f-:_� TO EXlS Tl '�! H TL�(NE '�� -�� ' - � (= -� �_ �--'= �µJ� � i SYSTEM I N dt I/E. SW. �" --�� ` - �' {� °� � /�� AREA=D�1� AC� � >,:�r " �` _ � ,� �,�� ` .'',� � ' ! I �_ � �, �'`��' � ; _ r /' � , � - ;� � �` •� 1 ' n �%` ,z� �f{ \ ;; l, ` 5 � zs 5, ,�: �r.� I �, TD FAR WEST � - ;al, � �� • �� f � a ' �-�-�;._:: ��' S TEEL DE TEN TION ,: i ��` � � �� , �` > i , � /� � - - �.� � '�,, �FACIUTY I ��'� , �� - -. �`� , '�� %AREA=0.42 AC � � � �i - i_ � � j r- ' '� ' �,� '( � � ; � II__ = _ BA$IN A � /� ( I �� \�, �I ' � ! ' � /�°'' �I�- � � � ARE,4�2.88 AC � � � f BASIN B 'i � , ,�� ,. /�/ � i.. �_ i � ( AREA=2.69 AC � -� � � � : �i' �� '�,, � 1 I � - / I ,�� i �/ I � � ,-- � / I �� ' � �. ' l �'r� '%� \ '�_- � c� �� 1 �� -' I �� I � � �`,�.�, �� ' , I '�� : �' � � � � � - �1 �� ,� ___ , � � I � , ��, II( � �" �- _ , � � � " , _ 1 . i �; -� �� - \ _� -' '' � / � � : � _ -� - _ _ � � � � �� 1f\� � �= ��' �� /-__ � `� � �_ r� _ � �= � � �� _ _ � � �� i � ��\�� N�'� ��, i� _�� _ � � �`` � � ��` -z �i�� `. , , � I — — _ : �� I�: .� '') �� - - � — ._ _ _ — �� — � —� - - - - -_ _ i �; ;�� \�� _, �� 1 �I I�rll� ��I�' \ \/ _�--�� ,l�JET�ArJ �'(J;�FcR - � - _ - - - - ` ,_ •�\\�j � 1'- � PRGPOSED � �l � /. c � �� \ � a� . ,� l IiII �IliiCli lll� DEiENTION/WETPON\ �_ T_�� I AREA=1 2��'� --� �,, i _ _ _ _ _ .— �F; '�� ,G , � �`�— • �` „ — � _ _� ,�, I.�"y.),� i 1 =� ` , `_ il �� —� - •�.- - --�� 1� _ I , � ,'�',,, � � � I� ,'; I ,i ,y` ;I� `1\ �� , , l ' �'� � ,�I � ��`, .,� � I ,,� _ �, i ry ,' l � I . � � TREECE COMPANY � ENGINEERINC AND DEVEIAPMENT CONSULTANTS i20 3d Arw So�rh,SuN�?OC KRY.UND.N'ASNINGiM 99033 iYONE <zs)e:7-zsn fAY(335��2]-B]58 � CITY OF RENTON _ DEPARTMENT OF PUBLIC WORKS - PACIFIC GULF WAREHOUSE � DEVELOPED � CONDITIONS MAP DES.C/+CD.' dC.T. pq7F 7/10/99 F/LE NM/£Mf1AFi9 � ORAWN: R.S.0 CHEL'KPD: B.GT. SGfE.' f'- ]00' r__.. - � PAGE 4 ', rl�. AEY15T'JN � BY ,IPAR. A<7E AAPROVFO: S__.. . Prelinrincrrv Drcrir�age Report.for Pacr fic Gulr l�'arehouse Julv?0, 19>9 ' �� I site comprises hydrologic Basin `B'. Runoffgenerated within Basin `B' will be conveyed I via a grass swale and tightline system to a combination detention/wet vault. An onsite hydrologic analysis was completed for both of the onsite basins utilizing the WaterWorks software to determine the 2, 10 and 100-year, 24-hour peak flows generated by the developed conditions, see output in Appendig A. The hydrolo�c parameters are summarized below for Basin A and B and peak flows presented in Table 1 on Paje 6. Basin `A' Area = 2.88 Ac Pervious Area= 025 Ac @ CN=86 (landscapin�) Impervious Area=2.63 Ac �r CN=98 (pavement & roofs) Time of Concentration= 5.00 minutes (minimum) Basin `B' Area= 2.69 Ac Pervious Area= 0.25 Ac rr CN=86 (landscaping) Impervious Area=2.44 Ac @ CN=98 (pavement & roofs) Time of Concentration = 5.00 minutes (minimum) Both the northerly and the southerly detention basins w�ill discharse into an existing 60- inch storm drain within Lind Road via two existing storm drain stubs coming in to the proposed site. A detailed discussion of the proposed storm drain system is discussed in the section within this report entitled "offsite analvsis." Two on-site storm detention facilities will be provided, as discussed in the previous section, to limit the on-site runoff to quantities defined by the existin� drainage condition hydrolo�ic analysis. Pc terso�7 C'o��.��arlling Er�oirzeer.r Pcr,oe � P�•eliminnrv Drail�a�e Repnrt for Paci�c Gul/'F�arel�nu.ce Julv?D. 1999 .` Precipitation Site runoff and water quality treatment rates were calculated usin; WaterWorl�� software with the SBUH KC24HR, 24-hour storm event. Precipitation was determined from the Kin� County SWD:VI Manual Isopluvial Maps for the 2, 10 and 100-year, 24-hour storm events, see Appendix A. Precipitation rates are: • Water Quality Desijn Storm: 0.65 inches • 2 Year, 24 Hour Storm: 1.95 inches • 10 Year, 24 Hour Storm: 2.85 inches • 100 Year, 24 Hour Storm: 3.90 inches _._ .__. __. _ T�BLE 1 __. _ . _._. .__...__ �0�'�]3 ` Pc:tk�tm} Preci��it:itFon ��fints�ih�:ti►z�� Resultin� �r�cque�e� �rca Zrolt�mc (cf�� {in) > (�creti} �acre-t'tl � ' � � Existin�13r�.�i,z 2-vear 1.�1 19> >S7 0.�3� 10-�-ear 2.26 2.�� 5.i 7 0.8C 100-�-ear �.�� ;.90 5.i7 1.;1 ,' Developerl Basin `A' 2-��ear 1.;4 1.)� 2.£8 0.39 1�-vear 2.04 2.8� 2.88 0.61 1 c)l)-vear 2.86 �.90 2.b8 0.8� Water Qualit�� 0.3� 0.6� 2.88 0.10 Developed Busin `B` 2-vear 1.2i L9� 2.<9 0.;7 10-year 190 2.8� 2.69 0.�6 100-year 2.66 3.9U 2.69 0.8O Water Qualitt- 0.;2 0.6� 2.69 0.09 Pcler.so�a (,on.cultino En�>ineers Page 6 Pre/imiJ�arvDrninngeReportT�rP�rcificGulflT'urel�ouse Julv30, 1999 "� IV. CORE REQUIREMENTS A. Core Requiren:ent#1: Disch�crge at tlte Natur�cl Loc�ction The proposed onsite conditions and patterns emulate those of the existing site conditions. The developed onsite runoff will be routed via surface flow within the onsite street/parking section, stored within two onsite detention facilities and discharged to the west into an e�sting storm drain within Lind Avenue. The development runoff will be discharged at two locations to approximate the e�sting sheet flow conditions. B. Core Requirement#2: Off-site Analysis An existing 60-inch storm sewer system is located within Lind Avenue. An outfall storm drain system will be constructed for each of the onsite detention facilities that will serve to connect to two e�cisting storm drain stubs adjacent to the site (see detailed discussion within Section VIII, entitled "offsite analysis"). C. Core Requiren:ent#3: Runoff Co�itrol Runoff control will be provided for the warehouse and office facility by constructing two onsite detention facilities capable of capturing the developed peak flows and releasing them at the existing condition peak runoff rates for the 2, 10 and 100-year, 24-hour storm events. A detailed discussion of the design and calculations for the volume of the detention basin is included in the ne� section. D. Core Requiremefit#4: Com�eyance.Systenz The proposed onsite conveyance system, grass swales and tightline system, will route runoff to a detention�water quality facility prior to being released from the site. E. Core Reyuirentent#�: Temporary Erosion anrl Secliment Control Plrtn An erosion and sediment control plan, which will serve to minimize soil erosion/sedimentation durin�the proposed site construction, will be prepared for the Peterson Consultin�Engrneers Page 7 • Prelimnur�•v Drainage ReportT�r Pacific Gulf Lb'arehouse Jttiv?0, 1999 II _- final submittal of the warehouse and office facility improvement plans. Temporary erosion and sediment control Best Management Practices (BMP's) will be implemented during the project construction phase. BMP's will include perimeter protection silt fencin� (where necessary), temporary sediment ponds, stabilized construction entrances, catch basin protection, and permanent cover protection (landscapin;). V. SPECIAL REQUIREMENTS A. .S`pecial Requirement#1: Critical Drainage Areas The site is located within the Black River Sub-Basin, Green River Basin (See Black River Basin Map and Summary in Appendix A). This basin is not defined as a critical drainage area in the '92 King County Surface Water Design Manual. B. .Special Requirement#2: Compliance with an Existing Master Drainage Plc�n Not applicable to the Pacific Gulf Warehouse site. C. .Specinl Requirement#3: Conrlitions Requiring n Master Drainnge Plan Not applicable to the Pacific Gulf Warehouse site. D. Special Requirement#4:Adopted Basin or Community Plans The site is located within the Black River Sub-Basin, Green River Basin (See Black River Basin Map and Summary in Appendix A). E. .Special Requirement#�: Special Water Quality Control.s The proposed project will create approximately 111,500 SF of new impervious area subject to vehicular traffic. A wet pond and wet vault have been desijned to meet this special requirement. Special Require��zents #6-#10 are not�ipplicable to this site. Peter.��on C,on.culting En�il�eer.c Pa,�e f� �-- _� Prelinrincrrv Drainage Report fi�r Pncifrc Gcrlf GT rn•ehncr.�e Julv?0, 1999 F. .Special Requirement#11: Geotechnical Ancclysis and Report Terra Associates, Inc., have prepared a Geotechnical Study dated June 9, 1999, copies have been submitted to the City of Renton as part of the SEPA submittal. G. .Special Recluirement#12: .Soils Analysis and Report Terra Associates, Inc., have prepared a Geotechnical Study dated Jun.e 9, 1999, copies have been submitted to the City of Renton as part of the SEPA submittal. VI. DETENTION A hydrologic analysis of the site was completed in order to determine the required on-site detention necessary to eliminate negative downstream impacts due to development. An analysis was completed utilizing the WaterWorks software to determine the existin� and developed runoff rates for the 2, 10 and 100 year, 24-hour storm events. The runoff rates were then used to determine the corresponding Basin A and Basin B required detention to �enerate release rates equivalent to those produced by the existing conditions, see Table 2 on pa�e 10. Additionally, the Wate�•Work,s-software was utilized to determine the required detention storage volume, as well as the required dimensions of the discharge facility. The WcrterWorks output is included within Appendig A and indicates that the required on-site detention volume is approximately 3,988 cubic feet and 3,575 cubic feet for the Basin A and Basin B detention facilities, respectively. Basin A detention facility will be approximately 45 feet long by 45 feet wide pond at the ma�imum water surface, providing 22,000 cubic feet. This detention facility is desi�ned to detain runoff as delineated on the Developed Conditions Map on page 4. The proposed detention outfall system will he a 12-inch storm drainpipe, which will connect to the e�isting 15-inch storm drain stub which outlets to the existing 60-inch storm drain on the West Side of Lind Avenue. Peterson (,nt�strltiii�E��it7eer•.� Page 9 L"1'�::771;i1[il"'��U/"[ili1Lltiri;L':(.'��U]"i j�il"C'!lCi�/C i�LllJ ll Cil"cliUii�� i Basin B detention facility will be approximately a 40� providing 3,600 cubic-feet. This detention facility is designed to detain runoff as delineated on the Devetoped Conditions Map on pa;e 4. The proposed detention will outfall via a 12-inch pipe connecting to an existing 12-inch storm drain stub (from the 60- inch pipe) crossing Lind Avenue. TABLE 2: RELEASE R�TES ,.J > ,, ; ' ' , �o�b�ed ; ; �Il�w�bt� � Basi� ��' � Basir� �.; ��s�a�� ' ; > ��ea�+e �te I �� Reie��s� iZ�� Ze�eas� R�t� : ��e;�s� R�te � ��,��,� j ':�� '�� I �C�'�� - ; � .: �� ; : 2-Year 121 � 0.63 0.58 1.21 10-Year 2.26 1.16 1.10 2.26 100-Year 3.54 1.80 1.73 3.53 VII. WATER QUALITY The water quality volume was calculated based on the water quality design storm per City of Renton Standards. This volume of runoff is determined from the tributary sub-basin proposed developed conditions usin� a water quality design storm event having a precipitation equal to one-third of the two-year, 24-hour precipitation. Basin A Required Dead Storage Volume = 4,405 CF Dead storage will be- provided under the live storaye depth in the combination detentionlwet pond. Basin B Required Dead Storage Volume = 4,091 CF Dead stora�e will be provided under the live storage depth in the combination detention/��et vault. VIIL OFF-SITE ANALYSIS As shown in Figure 3, an existing 60-inch storm pipe is located within the north half of Lind Avenue. Two existin� storm pipe stubs e�tend from the existing 60-inch storm pipe adjacent to the site; one 24-inch stub at the southwest corner of the site, and one 15-inch Peterso�� C'a�sarlting Er��h�eei�.c Page 10 i - � Prelinrinnrv Druinage Report fc�r Pacific Gulf[�'arehouse Jcrlv?0, 1999 j � II going in to a 12-inch stub located at the midpoint of the western boundary. The outfall 'i � pipe from the southerly detention facility will consist of approximately 40 LF and will �� connect to the 24-inch lateral stub. The northerly detention facility will discharge into a �I 12-inch pipe and will be extended approximately 270 LF to the southwest to the 12-inch I�, lateral stub. Both of the stubs will contribute flows to the existin� 60-inch pipe. ' The report entitled "Drainage Calculations for li.S. Rentals," completed by Concept ' En�ineering, indicates that the City of Renton recognizes a tailwater condition in the 60- inch diameter pipe within Lind Avenue. According to information within the report, development projects within the area are required to base their conveyance analyses on a 2-year tailwater elevation of 14.6 (I�TAVD 88). Converted to the vertical datum used for the warehouse and office facility, the tailwater elevation is approximately 11.26 feet. This tailwater was adjusted for our site location by usinj the 60-inch �radient and the distance from the U.S. Rentals site. The StormCcrd program by Haestad was utilized to determine the hydraulic �rade lines of the two storm drainpipes dischargin� 2-year developed site flows. The.Sto��n7Cc�d output is included in Appendiz B. IX. COI�CLUSION Based on the information contained wli�llll this Freliminary Draina�e Report, the construction of the proposed warehouse and office facility is not expected to create a negative impact on the existing adjacent areas. Pe�erso�� (,on.carlti�zg Ei7,�i7�eer.s Pa,oe 11 APPENDIX A HYDROLOGIC PARAMETERS & DETENTION CALCULATIONS I� _ _ � KING COUNTY, WASHINGTON, SURFACE WATER DESIGN I�'fANUAL TABLE 3.5.2I3 SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS i �I SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) �, Runoff curv� numbers for selected agricultural, suburban and urban land use for Type 1A rainfall distribution, 24-hour sform duration. CURVE NUMBERS BY HYDROLOGIC S GROUP LAND USE DESCRIPTION A B +C D Cultivated land(1): winter cond'rtion 86 91 94 95 Mountain open areas: (ow growing brush and grassiands 74 82 89 92 , Meadow or pasture: 65 78 85 89 Wood or forest land: undisturbed or older second growth 42 64 76 8t Wood or forest land: young second growth or brush 55 72 8t 86 • Orchard: with cover crop 81 88 92 94 Open spaces, lawns, parks, goif courses, cemeteries, landscaping. good condition: grass cover.on 75°,G or more of the area 68 80 � 90 fair condition: grass cover on 50°�G to 75°,G of the area 77 85 O 9� Gravel ro�ds and parking lois 76 85 89 91 Dirt roads and parking lots 72 82 87 89 Impervious surfaces, pavement, roofs, etc. 9A 98 Q8 98 Open water bodies: lakes, wetlands, ponds, etc. 100 100 100 100 Single Family Residential (2) Dwelling Unit/Gross Acre °�6 Impervious {3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected 2.0 DU/GA 25 For pervious and 2.5 DU/GA 30 impervious portion 3.0 DU/GA 34 of the site or basin 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DUJGA 50 6.0 DU/GA 52 � 6.5 DU/GA 54 � 7.0 DU/GA 56 Planned unit deve�opments, °� impervious condominiums, apartments, must be computed commercial business and industrial areas. (�) For a more detaiied description of agricultural land use curve numbers refer to National Engineering Handbook, Seciion 4, Hydrology, Chapier 9, August 1972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. �� 3.5.2-3 11/92 � -^ 7/21/99 4 :22 :36 pm Peterson Engineering Consulting page 1 BASIN A - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: A1 NAMfi: 2 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5 .57 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 1 . 95 inches AREA. . : 5 . 57 Acres 0 . 00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 90 . 00 0 . 00 TC. . . . . 18 . 28 min 0 . 00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 160 . 00 ns : 0 . 1500 p2yr: 1 . 95 s: 0 . 0200 PEAK RATE: 1.21 cfs VOL: 0 .49 Ac-ft TIME : 480 min BASIN ID: A2 NAME: 10 YEAR EXISTING SBUH METHODOLOGY TOTAL AREA. . . . . . . : 5 . 57 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 . 85 inches AREA. . : 5 . 57 Acres 0 . 00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 90 . 00 0 . 00 TC. . . . . 18 .28 min 0 . 00 min ABSTRACTION COEFF: 0 .20 PEAK R.ATE: 2 .26 cfs VOL: 0 . 86 Ac-ft TIM£: 480 min BASIN ID: A3 NAME: 100 YEAR EXISTING SBUH METHODOLOGY T�TAL AREA. . . . . . . : 5 .57 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPF. . . . : KC24HR PERV IMP PRECIPITATION_ . . . : 3 .90 inches AREA. . : 5 . 57 Acres' 0 . 00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 90 . 00 0 . 00 TC. . . . . 18 .28 min 0 . 00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 3 .54 cfs VOL: 1 .31 Ac-ft TIME: 480 min BASIN ID: Bl NAME: BASIN A - 2 YEAR DEVFLOPED SBUH MFTHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 1.95 inches AREA. . : 0 . 25 Acres 2 . 63 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 .20 PEAK R.ATE: 1 .34 cfs VOL: 0 . 39 Ac-ft TIME : 470 min -, 7/21/99 4 :22 :36 pm Peterson Engineering Consulting page 2 BASIN A - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS � BASIN SUMMARY BASIN ID: B2 NAME: BASIN A - 10 YEAR DEVELOPED � SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 . 85 inches AREA. . : 0 .25 Acres 2 . 63 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 ' TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 2 . 04 cfs VOL: 0 . 61 Ac-ft TIME: 470 min BASIN ID: B3 NAME: BASIN A - 100 YEAR DEVELOPED i SBUH METHODOLOGY TOTAL AREP,. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 .25 Acres 2 .63 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 ' TC. . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 .20 PEAK RATE: 2 . 86 cfs VOL: 0 . 85 Ac-ft TIME: 470 min BASIN ID: B4 NAME: BASIN A - WATER QUALITY SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 88 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 0 . 65 inches AREA. . : 0 . 25 Acres 2 .63 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . OQ min 5 . 00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0 . 34 cfs VOL: 0 . 10 AC-ft TIME: 470 min .� 7/21/99 4 : 19 :48 pm Peterson Engineering Consulting page 4 BASIN A - PACIFIC GULF WAREH�USE PRELIMINARY DETENTION CALCULATIONS HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF �F Contrib NUM RATE PEAK HYDRO Area cfs min. cf\AcFt Acres ' --------------------------------------------- --------------------------------------------- 1 1 .212 480 21261 Cf 5 .57 2 2 .262 480 37342 Cf 5 .57 3 3 .544 480 57108 Cf 5 . 57 4 1 .340 470 17203 Cf 2 . 88 5 2 . 040 470 26395 Cf 2 .88 6 2 .856 470 37221 cf 2 .88 7 0 .340 470 4405 Cf 2 . 88 8 1 .245 470 16013 Cf 2 . 69 9 1 .899 470 24589 cf 2 . 69 10 2 . 662 470 34693 cf 2 . 69 11 0 .386 470 3996 cf 2 . 69 14 0 . 630 500 17203 cf 2 . 88 15 1 . 160 500 26395 cf 2 . 88 16 1 . 801 500 37221 Cf 2 . 88 17 0 . 602 500 16013 cf 2 .69 � 18 1 . 100 500 24589 Cf 2 .69 -� 7/21/99 4 : 19 :49 pm Peterson Engineering Consulting page 5 BASIN A - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS STAGE STORAGE TABLE TR.APEZOIDAL BASIN ID No. BASINA Description: PRELIMINARY DETENTION POND Length: 45 . 00 ft. Width: 45 . 00 ft . Side Slope 1 : 3 Side Slope 3 : 3 Side Slope 2 : 3 Side Slope 4 : 3 Infiltration Rate: 0 . 00 min/inch STAGB �----STORAC&----> STAGS <----STORAG$----> STAGB <----STORAGB----> STAGB r---3TORAGS----> (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- 10.50 0.0000 0.0000 11.90 3397 0.0780 13.30 8050 0.1848 14.70 14157 0.3z50 iD.60 205.21 0.0047 12.00 3686 0.0846 13.40 8436 0.1937 14.60 14654 0.3364 10.70 415.90 0.0095 12.10 3980 0.0914 13.50 8829 0.2027 14.90 15159 D.3480 10.80 632.12 0.0145 12.20 4282 0.0983 13.60 9230 0.2119 15.00 15674 0.3599 10.90 853.97 0.0196 12.30 4590 0.1054 13.70 9638 0.2213 15.10 16196 0.3712 11.D0 1082 0.0248 12.40 4905 0.1126 13.80 10054 0.2308 15.20 16726 0.364� 11.10 1315 0.0302 12.50 5226 0.1200 13.90 10478 0.2405 15.30 17268 0.39F� 11.20 1554 0.0357 12.60 5554 0.1275 14.00 10910 0.2504 15.4D 1781� 0.409 11.30 1799 0.0413 12.70 5690 0.1352 14.10 11349 0.2605 15.50 18375 0.42'_�. 11.40 2050 0.0471 12.80 6232 0.1431 14.20 11797 0.2708 15.60 18942 0.434�: 11.50 2307 0.0530 12.90 6581 0.1511 14.30 12252 0.2813 15.70 19518 0.44E: 11.60 2570 0.0590 13.00 6938 0.1593 14.40 12716 0.2919 15.80 20103 0.461�. 11.70 2840 Q.0652 13.10 73D1 0.1676 14.50 13168 0.3028 15.90 20698 D.475:. ---60 --5 .,..,-�_ _=.�0 -_-� �._ cl --.-_ --=E3 =.�1.i2 __._.. ..__..� ...zcyC � _ ;/�i/9� =� : 1� : =�9 p:�1 reterscr Ei:g�neeri:�g �or.su��r.g p�ce 6 BASIN A - PACIFIC GULF WARFH�USE � PRELIMINARY DETENTION CALCULATIONS STAGE DISCHARGE TABLE MULTIPLE ORIFICE ID No. BASINA Description: CONTROL STRUCTURE Outlet Elev: 10 .50 Elev: 8 .50 ft Orifice Diameter: 5 . 1445 in. Elev: 11 .40 ft Orifice 2 Diameter: 4 . 9805 in. Elev: 11 . 80 ft Orifice 3 Diameter: 4 . 6875 in. � STAGB <--DZSCHARGH---> STAGE <--DISCHARGE---> STAGB r-DISCHARGS---> STRGS r-DISCHRRGB---> �I (ft) ---cfe-- ------- (ft) ---cfe-- ------- (ft) ---cfa-- ------- (ft) ---cfs-- ------- li 10.50 0.0000 11.90 1.5143 13.30 2.8599 14.70 3.�101 10.60 0.2271 12.00 1.6677 13.40 2.9293 14.80 3.7633 10.70 0.3212 12.10 1.7983 13.50 2.9969 14.90 3.8157 10.80 0.3934 12.20 1.9156 13.6D 3.0629 15.00 3.8674 10.90 0.4542 12.30 2.0238 13.70 3.1275 15.10 3.9184 I'i 11.00 0.5079 12.40 2.1250 13.8D 3.1908 15.20 3.9687 I� 11.10 D.5563 12.50 2.2206 13.90 3.2527 15.30 4.0184 I� 11.20 0.60D9 12.60 2.3115 14.00 3.3135 15.40 4.0675 I 11.30 0.6424 12.70 2.3984 14.10 .� 3.3731 15.SD 4.1159 11.40 0.6814 12.80 2.4820 14.26� 3.4316 15.60 4.1636 11.50 0.9311 12.90 2.5624 14.30 3.4892 15.70 4.2112 �, 11.60 1.0543 13.00 2.6402 14.40 3.5457 15.80 4.2580 ' 11.70 1.1555 13.10 2.7156 14.50 3.6014 15.90 4.3043 ��, 11.80 1.2446 13.20 2.7688 14.60 3.6562 16.00 4.3501 � r 7/21/99 4 : 19 :49 pm Peterson Engineering Consulting page 7 BASIN A - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS --------------------------------------------------------------------- --------------------------------------------------------------------- LEVEL POOL TABLE SiJMMARY MATCH INPLOW -STO- -DIS- <-PfiAK-> STORAG& <--------DBSCRSPTSON---------> (cfe) {cfs) --id- --id- <-STAGS> id VOL (cf) A-MATCH 2 YBAR ............... 0.63 1.3.4 HASINA BASZNA 11.27 14 1728.36 cf A-MATCH 10 YHAR .............. 1.16 2.04 BASINA BASI2iA 11.7D 15 2853.05 cf A-MATCH 100 YEAR ............. 1.60 2.86 BASINA BA3INA 12.10 16 3988.45 cf - . 7/21/99 4 :31 :37 pm Peterson Engineering Consulting page 1 BASIN B - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY I BASIN ID: C1 NAMfi: BASIN B - 2 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 .69 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 1. 95 inches AREA. . : 0 .25 Acres 2 .44 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 . 20 PEAK RATE: 1 .25 cfs VOL: 0 .37 Ac-ft TIME: 470 min BASIN ID: C2 NAME: BASIN B - 10 YEAR. DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 .69 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 2 .85 inches AREA. . : 0 .25 Acres 2 .44 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 .20 PEAK R.ATE: 1 . 90 cfs VOL: 0 .56 Ac-ft TIME: 47a min BASIN ID: C3 NAME: BASIN B - 100 YEAR DEVELOPED SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 .69 ACres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PER�F IMP PRECIPITATION. . . . : 3 .90 inches AREA. . : 0 .25 Acres 2 .44 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0.20 PEAK RATE: 2 .66 cfs VOL: 0 . 80 Ac-ft TIME : 470 min BASIN ID: C4 NAME: BASIN B - WATER QUALITY SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 69 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 0. 65 inches AREA. . : 0 .25 Acres 2 .44 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0.20 PEAK RATE: 0 .32 cfs VOL: 0 . 09 Ac-ft TIME : 470 min - . 7/21/99 4 :31 :37 pm Peterson Engineering Consulting page 2 BASIN B - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM R.ATE PEAK HYDRO Area cfs min. cf\AcFt Acres --------------------------------------------- --------------------------------------------- 1 1 .212 480 21261 cf 5 .57 2 2 . 262 480 37342 Cf 5 .57 3 3 .544 480 57108 Cf 5 .57 4 1 .340 470 17203 Cf 2 . 88 5 2 . 040 470 26395 Cf 2 . 88 6 2 . 856 470 37221 cf 2 . 88 7 0 .340 470 4405 Cf 2 . 88 8 1 .246 470 16013 cf 2 . 69 9 1 . 899 470 24589 cf 2 . 69 10 2 . 662 470 34693 cf 2 .69 11 0 .315 470 4091 cf 2 . 69 14 0 . 630 500 17203 cf 2 . 88 15 1 . 160 500 26395 cf 2 . 88 16 1 . 801 500 37221 Cf 2 . 88 17 0 . 580 500 16013 cf 2 . 69 � 18 1 . 101 500 24589 cf 2 . 69 19 1 .729 500 34693 cf 2 . 69 ' - . 7/21/99 4 :23 :27 pm Peterson Engineering Consulting page 3 BASIN B - PACIFIC GULF WAR.EHOUSE PRELIMINARY DETENTION CALCULATIONS STAGE STORAGE TABLE RECTANGULAR VAULT ID No. BASINB Description: PRELIMINARY DETENTION VAULT Length: 40 . 00 ft. Width: 15 . 00 ft . voids : 1 . 000 STAGB <----STORAG$----> STAGfi <----STORAG$----> STAGB <----STORAGB----> STAGS r---STORAGS----> �, (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Pt- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- -----------====�a=====_____�_____________=====s=====_________�___________________�_ ==a::.:______________ __________ 10.50 0.0000 0.0000 12.60 1260 0.0289 14.70 252D 0.0579 16.80 3780 0.0868 �'� � 10.60 60.000 0.0014 12.70 1320 0.0303 14.80 2580 0.0592 16.90 3840 0.0882 10.70 120.00 D.0028 12.BD 1360 0.0317 14.90 2640 0.0606 17.00 3900 0.0895 10.80 180.00 0.0041 12.90 1440 0.0331 15.00 2700 0.0620 17.10 3960 0.0909 10.90 240.00 0.0055 13.00 1500 0.0344 15.10 2760 0.0634 1�.20 4020 0.0923 11.00 300.00 0.0069 13.10 1560 0.0358 15.20 2820 0.0647 17.30 4080 0.0937 11.10 360.00 0.0083 13.20 1620 0.0372 15.30 2880 0.0661 17.40 4140 0.0950 11.20 420.00 0.0096 13.30 1680 D.0386 15.40 2940 0.0675 17.50 4200 0.0964 11.30 480.00 0.0110 13.40 1740 O.D399 15.50 3000 0.0689 17.60 4260 0.0976 11.40 540.00 0.0129 13.50 1800 0.0413 15.60 3060 0.0702 17.70 9320 0.0992 11.50 600.00 0.0138 13.60 1860 D.0427 15.70 3120 0.0716 17.80 4380 0.1006 11.60 660.00 0.0152 13.70 1920 0.0441 15.80 3180 0.0730 17.90 4440 0.1019 I, 11.70 720.00 0.0165 13.80 1980 0.0455 15.90 3240 0.0744 18.00 4500 0.1033 � 11.80 780.00 0.0179 13.90 2040 0.0468 16.00 3300 0.0756 18.10 4560 0.1047 11.90 840.00 0.0193 14.00 2100 0.0482 16.10 3360 0.0771 18.20 4620 0.1061 12.00 900.00 0.0207 14.10 2160 0.0496 16.20 3420 0.0765 18.30 4680 0.1074 12.I0 960.00 0.0220 14.20 2220 0.0510 16.30 3480 0.0799 18.40 4740 0.1088 12.20 1020 0.0234 14.30 2260 0.0523 16.40 3540 0.0813 18.50 4800 0.1102 12.30 1080 0.0248 14.40 2340 0.0537 16.50 3600 0.0826 12.40 1140 0.0262 14.50 2400 0.0551 16.60 3660 0.0840 12.50 1200 0.0275 14.60 2460 Q.0565 16.70 3720 0.0854 - . 7/21/99 4 :23 :27 pm Peterson Engineering Consulting page 4 BASIN B - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS --------------------------------------------------------------------- --------------------------------------------------------------------- STAGE DISCHARGE TABLE MULTIPLB ORIFICE ID N�. BASINB Description: CONTROL STRUCTURE Outlet Elev: 10 .50 Elev: 9 .50 ft Orifice Diameter: 3 .5801 in. Elev: 13 .40 ft Orifice 2 Diameter: 3 . 3633 in. Elev: 15 . 00 ft Orifice 3 Diameter: 3 .2344 in. � STAGB c--DISCHARGB---> STAGB <--DZSCHARG$---> STAGB <--DISCHARGB---> STAGS <--DISCHAFtGS---> �� ' (ft) ---cfa-- ------- (ft) ---cfe-- ------- (ft) ---cfa-- ------- (ft) ---cfa-- ------- 10.50 0.0000 12.10 0.4400 13.70 0.7903 15.30 1.3406 � 10.60 0.1100 12.20 0.4535 13.80 0.8260 15.40 1.3836 � 10.T0 0.1555 12.30 D.4666 13.90 0.8584 15.50 1.4233 10.80 0.1905 12.40 0.4794 14.00 0.8885 15.60 1.4607 � 10.90 0.2200 12.59 0.4919 14.10 0.9168 15.70 1.4962 '' 11.00 0.2459 12.60 0.5040 14.20 0.9436 15.80 1.5302 I 11.10 0.2694 12.70 0.5159 14.30 0.9692 15.90 1.5629 ��i 11.20 0.2910 12.80 0.5275 14.40 0.9938 16.00 1.5945 I 11.30 0.3111 12.90 0..5388 14.50 1.0176 16.10 1.6252 I' 11.40 0.3300 13.00 0.5499 14.60 1.0405 16.20 1.6550 11.50 0.3476 13.10 0.5608 14.70 1.0628 16.30 1.6841 11.60 0.3648 13.20 0.5715 14.80 1.0644 16.40 1.7124 11.70 0.3810 13.30 0.5820 14.90 1.1055 16.50 1.7401 11.80 0.3966 13.40 0.5923 15.00 1.1261 11.90 D.4115 13.50 0.6995 15.10 1.2360 12.00 D.4260 13.60 0.7497 15.20 1.2928 - . 7/21/99 4 : 23 :28 pm Peterson Engineering Consulting page 5 BASIN B - PACIFIC GULF WAREHOUSE PRELIMINARY DETENTION CALCULATIONS --------------------------------------------------------------------- --------------------------------------------------------------------- LEVEL POOL TABLE SUMMARY MATCH ZNFLOTV -STO- -DIS- <-PSAK-> STORAGS <--------DBSCRIPTION---------> (cfs) (cfs) --id- --id- c-STAGB> id VOL (cf) ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- 8-MATCH 2 Y&AR ............... 0.58 1.25 BASINB BASINB 13.28 17 1667.77 cf B-MATCH 10 YBAR .............. 1.10 1.90 BASINB BASINB 14.88 18 2625.69 cf B-MATCH 100 YfiAR ............. 1.73 2.66 BASINB BASINB 16.46 19 3575.19 cf � � � . � . � . . � . ► �i��1�' $� �� s � �f��`"�!!'f � � �r ' -�� `"'"� -� �;. ,r . - � �1�� ;�� -� - �,,• �� ..�, E � � ��- � . �.s - ��"�'�� r/.'�►�r ^�1 -- �� O e�� .� ��, �..... �,�' ' „ . —��..�.... � � - ,��■.�-;, �I� � �. _�l�i� � � 1�'�t�- � •w ��_ �� '� ��A,•�'� '''�,► ,�1��:�1�' ,� ��;�� I �.��p_',-'-. � `�t�,,� �' �� _ � . � �� wc - / �� ,I� P � -- d �� W �r� � .+I� � � � .,.�,.._ � � (, \ � i i"' �� a�� `��i �i��s ��• . �-��.i'�,; ' '�::, �� r �..; `�� - ��, � �,`w� �. � ,, ��" Ca�l�/�_. •. �� \\�� _ �/��''pr�'��i�i��,�� i � �� y'��,w�+•.a.•��I�I`'i �� '. � ��:I�!"��'��e��I�- d�'�►- �r , 1 '�`�_ ��.�, _=�i►�, ��l�� :�,. � : � _ . .- `IA �► ��, � . `F � 1 �� R I�� \\'. � ' '�` � � �'�.�� '► ' � �`�,;, �"�� =��, .�. �,•�� - �t�rr ,i�� _�.Z.� V ' ` � � � �� . -,. '�. � . -- � �'�i�',��%'��_��-�i►�� ,. _ � IN (��'1 ��} ��.f�` l �;��61��, �. � �:�,,, � '� �a, � ':'�'� �ij ��liit�' ��`' .��.�� ', �� ; '�,,� ,�✓ 1�.�.�A ',�r,wu�'� � � �► M � �� n� �� V.��, .� ti'I �, � � '�; � ; �� . ;_�� ,_ � �, �� J,�� , _ ��, , � ,� �. ��'�. - � - �.-�- � �s ,.. i �� i, ... �►��'� � � � z. - ---� ��ww�w� )�� -- - � _► ; . _ ��!� �'iir.�� - �� ,.�.,�� z, �- , �`�1 �r �L� — �i► :�! �\ � • +9� ,�� , _�� ,��; . � ` ��- �� , � ,� • � r � '' �� s � � � ' ... . �� ■� �I�� , . , � . . . • . • '��,�, ,� . ,_�wic � ��' I/� • - . � - . . ' ,, _ - � .. ,., " �� • • � i � � � � ,�cm,:�ll��r.- � r ` �, �., _ �i�:�,`1�� ..:,��./_ .j� � �,� ��'� �i• •�� .�� .� , i�. . ��, � �� ,� � . _ � � ��.. �� , � . . ��`�� ,.,In!� ,�; ,��., . ,_ a�_.��`'� r' �� f �� , e �'��I !�. � � �' I ;;��- �i�- ...�►,��i� �;��..� �� : — ,NI►�ia��'' �.� ��..r.� � � �� ` ' .�r'� \ , ,� �� '� Ir � � , 1 . � .�� _ _ - �. ��.�� ,�� , ,:��-� :��1� ��- r .. �t �. � ,(� ._m---.�� , � � �� `• �i�" �+�� !i � � .��--- �E{a�M..��ti ' � �'�'� � � � � - � '�::,�a-. ��i�� h�rwf��' ''•�� '�` � ~(�, �r'��► , � �J�,� �� `i { �t •' 'I� � � l �� o �, �I � •��_, �� :� � ' �� %�'a.i� � ��3t •��. �� . : „ �� .�.. �, ;�� .� � _ � � '�'�_� � -�� ,, � R .�� _* � _ ��►�� , � � �' �� 1'��.\ I►` �� ` �:-,�► 1�� . :-�►• 1' �� — `�' '7' 1 y � ' ' :.,' �' ��"� �, � "'� � iN��1:• �;�,�� ►� � � ��d'AI. �� "��; � -- .��E �,. � T�;k ,�� - �� '''�'. � i� •��i��r� �� , ., !�� , �� ' �� ' � 1 �� ,��j�� ,� , . � � �� "� �,r�l, - �. . �� , , _� , � �� e �► ,`�,-� � �� i�. � �r�i� � � = �, �� C' ,!�� ,�■,�� *r " �_ . �� ; � .!��; s . , ��u�� s� � �� ' ��A� � � �� ..� � �I�w�� '�� .,:1�� _ — ` L — 'T� r� � - ` �� - ,�y�,1, ��1 � ,, � • „(�? � - j�� , �� , ,r _, �� r ;r�!i�,�'�- �!S �r � �, �� '� � �� 1 � � l�j . . '� " �, .� � . �l. � - s��:��,�i��i 1 . • . � • . . . � �I��!�I I�. �. • ` A��►�%:� . • • . � . ��i��''�� - - � • � � � �r �� . �� -------- � , ��,, .. .., � .� ! � • � . � � . . , � . � . �' .�+� : � •� - �,, �i� ��+�i'�' f � � l��„r d��l{{, ►�� r� ,'- ,��C � `,� � ,� i� ��-�,;`■ I�� / .� ! '� ��•� �� 7 � �, • �i�,�� ,�...� �' � ��- = - � _ � _•�� . �� . ,��„� "!'� �� ► ;� 1 e � e�.,.,.. ` • '�s�V�.,�� ;�. �_- �� ' � ��i� ��k•�a�►y �1�r.��, �� "" � . --�� ,, .,..�- �� .�. .�. �=. .— .� . � . � � ,! �w�� ,,,..�►_...�o�� ,.. _ �,��- _,�.�- .�N, �., � , ��•—��_�, - _ "0 !�� ,, a� � � ♦ � ��a Qr.lr/�� '6/��y �" �i� � �� • �' � • �� r�� ` �w`� � � /�IG� � �� \ �r � � ` � -L ��'��ri _ �� l` �• , f��.��!�'��-ar _ �.—:.. � � �� _ � � � � • � i _ 4�� "��: �� .� � , - � �. � � � � ��. ,A�,�,_ � � �. . � ,:*d,��F �. � �,,+1 �\ ��` � � ��! � • I��i� � \��1�.= � y . � ` _ ;�'.�� . , �� M� ��._,� ""► �� -;,..� � -- _. c ,I��,:°��, :�,'�►�� ' �, .. � , * . �t� , ,E a�� . _,:. � . _ a �i��1, �r�i - �'�, ��►,� ' � � •'-#t ;��g��d��1�,�~i ,^�--�*,� � .:`� ��" �a, �: �' � �� .� �� H �',` ,, ��,1�� ', �� - �1 1�� . � �~r ` �1 i' ��✓ �_ ��1.�1 � ;� • �,� - � � �i � �,�,�.�� _ : � �� ' � ��` � � � , � �� , '�� :`- �. �� ' � ��r�� _��._ � ; ��.�� 1��i ��, �?�� , �� ' . � I _. , � � , � . �'' � L� .� ��wlv . � ! .� / �a�r,w�i� �— �,� = - - � . � !� - �, ) , � ��..'� • a ,� �Q %'�1I'y��- l _ � . � ,' �� , ��' � �. �' s � , / �1 �- � " �1.. �� '�li� '��'�" �I +��^ � �� ' �� , • : �� r . � � ,� • ��r � ' • ��:�� . - , . . . . . . . �"��/� �� • � ' �� `��:� . � . • . �r . ' �� - � � ' � � . :�, . ' ------- � ` ��_-'. .. ... � .� � �� ' :� , �-. , � � ;t , � � ;�:d'��;> ,\•, � - , r� - i_ ,11,�,.,�, ��l , __`' 4.� . �'\., �C.J_�� I �,I��-1; `� L�� . I ' � . � BLACK RIVER BASIN ia�� _ '� .J� � tr� �+� � i �,� ; J � � =i .s ,';^ , �� .�," ��, �' e �/ i _ � \ ` � �� A � � �' . � -1 r"' � � --'� � �'::��' •'�'•r L �s �� ics - . . � �� Basin Boundary S -� `�, �``�� 1,,`�Y� � z:-� . . _ . • „ �,.. t. , /,.. •- - :,, --_ ,��. „ , _ Subcatchment Boundary �� + ' � - ��- ' 3 0 � `� �� i _ -� � Yr,. i \ �, ; O , .. . �: ,,, ` � i J '�`' _. � 9 Collection Point ' — ��ti . '` .<• , °o� o _� � ...,, i,�, x��. , -�.:, . � _ , ,, 4 :: �1� Stream ' ' � ' � � � � ^`� ... .._ , . 000s Tributary Number "'_�T„k,�,ia � i�� o � .��' ' . _ , �. �0301 Proposed Pro�ect \ ' ;� ` � _ � \ j \ � 1 ' � �a0� ,`� •.` _ _.. � _'11 1 � .�i7�`C S � (� E .. __ 1 i �`�� S i1 ' � � ��06. � c, . _ -}: 1 lJ I "'1' ` 1 9 � ' '4 � � � !..` S '- I � ;� �'}. �� - '- � � r-`� -� � � '�• , � I o0�06%� � t i �, x ��; � � f� 1/ I�)__ � i° . . : -� .� ",_ _i i. . � . , , i � � - , . , � ., � - - � _ -� - � -- ' oc, _ _ _ �� '' - .i, � � __ 1 ; , o 'x = - ,� - '° i - - -� _ �. , a! S�' �` � i ,: - -- 0 ; ; i - � _�i , , o ,�,� � �. �; �; � 2,� , , �, ( -- : 1 � �' o� . --- -!�:- " - - ' 1 / o - : � ' o . . Ju �� : . IY 1987 . - . t . . - �� - •I ;_ . ! : �� '�� ' - 1+_` _ ,, , r,, �, � : ' -- - � ,�. .� ;: - ;i f -! : ,.; F .1 N _ � - ---- -=.�-�--- . _`�T - �� ° _ _- . _ - �v , � . �,� _ , ;_ " _ ..:.1 . ..s . , '1 .�. .... ,.. r :. �- - - o °o - 0301. . - � ,o,: .�- -, � �� . - - , 030 - _ , �� _ �� , , j . , , � _ . ,�, ,: , . , .;;., I,;, . �:• :�„ • . ' -� ' _ _ , � , - .. . - � .. �.. , , • % �i � ; ` _. � _ ,r�`._ .. ._ - _!' c. i, _, 1 ; ..,, __ . _ _ _ --. ��,zy,. . . a �.7 I '. tst "� � '��'..!: _ �"� . .�� .: __ �i � .� / ��14 ,, / �_.,: ., 1_ : �� , . , � , ; o � ;030 -_ ( � � .. - :- _ r � I _ , �� :. fy 1 �. : 5i .._s - � ��V --(�� { . _: / � , .. . -i� � '.. �`s� �, .� ,, . ..�.1. ...+ - � � �� ; . f� .�.t �...� � '..:. � i � �� • `.'i .- ' "� . _ � ..L 1 . �.• ..i � �_ __ _:....i n..� - ''i- 4V. .. � ��2 I I � (; `5; �� - . fl30 i , _., � ;; — ` � .; � - ,- _. , , ,.�� , : Ii . •. - � � � _. . - r ..... - ... � � w ,i � r 1 ' ' . ., , � �, r . � I 'I � 'J c'c� - ! . r- . _ . � � b ` i„ I ' `� : I p�s�i�n1e� ,; � �.. ., �� _ _ _ � O? :, - ' . ., �. R - - , , ; ` .. . � � , : , ,� ,-. �ti, ;-., �' :..:� � 1 � �. ,� .-, ; � � �. � ,, � --- �--- ,,, _ fi °�� i �` .,�, �� ,� � . � 0 5 _ �' -_ - - `. L „�_-.,y -, : - 1 T I . ,. . � � } ' � II 1 .. �� ( .��\ I �"�" � `� :� �/` ' �. i ^i , ,. I ' , � � ` _ �' � ��' � ' � � ' I p - - ,• f �, ��L�f � � r �; r o � � oc Mw,es d : �.�, . s , I --. . _ �� . ; ? - ; ..�,��:i r. ��s�• y � I � _ . ,.1 ; - , i I I` ' _1 J J,.. �'� I ' � ,� �� 1 '�I i � ' � , . - r:k� ,� � ! .I I , . . �� L\' ' � � . '- � y� , ' M1-n�.L�. <" t ' � - f � 'l i I+ �: �I - . __� � .-` i` �} �k \ . �� ___ � "� _ � F 1 f � ` ' + �' •' 1 _. , : . ." � f , ' '. .. . � �.. �` � ir..-- . +;, /-` ' 3 , - � ; �, _ �s � _ ;: j r - 26 � oo. .,� "� , - "�� ;� i ��.y ,.0� j o o _ '. � � �' u� O %�—� ;� �6 �—,— l, � . ��; �.� ,� { ap I' I �. ,, i�,'. a � �� `cS` i ' ` � ' � C - � �� - ,'« ,� ; � " �� _ __ � �` / i� �� : _ `�� ` � 1; �" ;..�. 7� ,� i u tl'�.�uh�r i�� '.[ . "�/ .I i _ � �� 1 �i .,.Jf � . ' � . I ! ��( ' � I � �, ��. � ,- ;---t'-, —�-��` � -- h �; --�-a : �' �;G 1 �� ''s„�: �`r I� . . ,,, . , '� � �� , . . I i � ,. . . � - _ '!� � � � �.i , , y, �,� _ ;�--.- -- , I - r ; � �i• r' � - �r:,�,,., , _ 1 ;i �,J.. ' - � - ` ` • . ��I r - 1 ,.� /� � .� .. � . � ' . ;(- � . �__. � �' �. I • I S .� . � . ��: . . �I ..��, f11I I.. i � � � IJ . � _ 0 f 7 : ` � ,: ' . .. . ' i � "- � '� �.� �. I . � . 1 j i ��.� I ' ,��`.i .. . i ;� �I` I- ; �—_ — _. . � j' � ' �,� � . I. � . � , . � .. , �! - � . I I RECONNAISSANCE REPORT NO. 14 � BLACK RIVER BASIN I JUNE 1987 Natural Resources and Parks Division and Surface Water Manaoement Division Kinb County. Washington P:BR.TOC/mlm l - . I . , xing co�nty Executive Tim Hill f King County Council Audrey Gru�er, District 1 Cynthia Sullivan, Distric[ 2 Bill Reams, District 3 Lois North, District 4 Ron Sims. District 5 Bruce Lainb, District 6 Paul Barden. District 7 Bob Grieve, District 8 Gary Grant, District 9 � Departmeat of PubGc Works Parks, Planaing and Resources Don LaBelle, Director Joe Nagel, Director SurCace Water Management Division Natural Resources and Parks Division Joseph J. Simmler, Division Manager Russ Cahill, Division Manacer Jim Kramer, Assistant Division Manaber Bill Jolly, Actinb Division Manaber � Dave Clark, Manaoer, River �� Water Derek Poon, Chief, Resources Planninb Section Resource Section Bill Eckel; Manaber, Basin Plannin� Procram L..arry Gibbons, Manaoer, Pro,jecr Manabement and Desi�n Section Contributing Sta[f Contributing Staff � Dou� Chin, Sr. Enbineer Ray Heller, Project Manaaer & Team Leader Randall Parsons, Sr. En�ineer Matthew Clark, Project Manaber Andy Levesyue, Sr. En�ineer Robert R. Fuerstenberb, Bioloaist �� Team Leader Bruce Barker, Encineer Matthew J. Bn,enbo, Geolobist Arny Stonkus, Engineer Lee Benda, Geologist Ray Steiber; Enoineer Derek Booth, Geolobist Pete Rinoen, Enbineer Dyanne Sheldon, Wetlands Biolo�ist Cindy Baker, Earth Scientist Di Johnson, P[anninc Support Technician Robert Radek, Plannin� Support Technician Randal Bays, Planninb Support Technician Fred Bentler, Planninc Support Technician Consalting Staff Mark Hudson, Planninb Support Technician Sharon Clausen, Plannin� Support Technician Don Spencer, Associate 'Geolo�ist, Earth David Truaa, Planninb Support Technician Consultants, Inc. Brian Vanderbui•r, Plannin� Support Technician John IIethel, Soil Scientist, Earth Carolyn M. Byerly, Technica] Writer Const�ltants, Inc. Susanna Hornib, Technical Writer Virginia Newman, Graphic Artist Marcia McNulty, Typesetter Mildred Miller, Typesetter Jaki Reed, Typesetter Lela Lira. Office Technician Martv Co�. Office Technician � - � � C" P:CR ' r TABLE OF COrITENT'S I. SUMMARY 1 II. INTRODUCTION 1 III. FINDINGS IN BLACK RIVER BASIN 2 A. Overview 2 B. Effects of Urbanization 4 C. Specific Problems 5 IV. RECOMMENDATIONS 7 A. Expand existinb and/or construct additional R/D facilities 7 B. Preserve wetlands on plateau to provide natural storage 7 C. Protect steep valley walls from erosion and landslides - D. Reduce sedimentation in streams along valley floor E. Enforce prohibitions a;ainst dumping domestic trash �, F. Increase the overall effectiveness of swrface water manabement 5 V. MAP 9 APPENDICES APPENDIX A: . Estimated Costs A-1 APPENDIX B: Capital Improvement Projects Rating List B-1 APPENDIX C: Detailed Findinb and Recommendations C-1 P:BR.TOC/mlm � I. SUMMARY , Black River Basin, ]ocated in south King County, is named for a river that ceased to exist in 1917. after major alterations to river systems were made to build the Lake Washington ship canal. The reconnaissance was conducted along the streams and tributaries still remaining in this basin. Development in the basin in and around the cities of Kent, Renton, and Tukwila has produced eatensive areas of impervious surface, which are ea-pected to double by the time the basin reaches its development capacity. Storm runoff from impervious surfaces is drained throubh pipes and discharges in some cases directly into the stream system. Field investi�ation of problems in the Black River Basin revealed that volumes and rates of stormwater flows have mntnbuted to serious aoceleration of erosion of streambanks and lower slopes and have pnodueed downcutting and landslides in some places. Sedimentation resultinb from these processes has, in turn, clogged e�asting coaveyance systems, renderinb n�any of them ineffective, and destroyed E�sh habitat for spawning, rearing, and migrating. In addition, the general inefficienry of the basin drainage system has increased the potential for floodiag. Another problem cited was vis��bly poor water quality resulting from larbe amounts of domestic trash placed in streambeds and from commercial/industrial runoff, particularly near the L.onbacres Racetrack in Renton. Recon�mendations for action in the Black River Basin include: 1) expanding R/D facilities and preserving wetlands to assure adequate stormwater storage, 2) taking measures to protect steep vallcy walls from erosion and landslides, 3) reducing sedimentation on the valley floor with sediment traps, 4) increasing enforcement of regulatioas against the dumping of tra.sh into streams, and 5) increasing the overall effectiveaess of surface water management in the basin throu�li doinb more maintenance of facilities, continuing inte oovernmental abreements, lowering volumes and rates of release for stormwater, and other measures. II. INTRODUCTION: History and Goals of the Pingram In 1985 the Kina County Counci( approved funding for the Plannino Division (now called th� Natural Resources and Parks Division), in coordination with the Surface Water Manacemen� Division, to conduct a reconnaissance of 29 major drainage basins located in King Count�. The effort beban with an initial investigation of three basins -- Evans, Soos, and Hylebos Creeks -- in order to determine existina and potential surface water problems and to rc;com- n�end action to mitigate and prevent these problems. These initial investioations used available data anci new field observations to examine aeology, hydrolow and habitat conditions in each basin. Findin�s from these three basins led the Kino County Council to adopt Resolution 6013 in April 1986, calling for reconnaissance to be completed on the remainino ?6 basins. The Ba�sin Reconnaissance Probram; which was subsequently established, is now an important ele- ment of surface water manabement. The goals of the program are to provide useful data with repard to 1) critical problems needino immediate solutions, ?) basin characteristics for use in the preparation of detailed basin manabement plans, and 3) capital costs associated with the early resolution of draina�e problems. The reconnaissance reports are intended to provide an evaluation of present drainage con- ditions in the Couniy in order to transmit information to policymakers to aid them in deve- lopinb more detailed re�ulatory measures and specific capital improvement plans. They are not intended to ascribe in any conclusive manner the causes of drainape or erosion problems; instead, they are to be used as initial surveys from which choices for subsequent detailed enoineerin� and other professional environmental analyses may be made. Due to the limited amount of time available for the field w�ork in each basin, the reports must be viewed as P:BR/jr 1 • Black River Basin � (continued) I 4 descriptive environmental narratives rather than as final engineerinp conc(usions. Recommendations contained in each report provide a description of potential mitirative measures for each particular basin; these measures might provide maximum environmental protection through capital project construction or development approval conditions. The appropriate extent of such measures will be decided on a case-by-case basis by County offi- cials responsible for reviewing applications for permit approvals and for choosinb amono com- petina projects for public construction. Nothing in the reports is intended to substitute for a more thorough environmental and en�neerinb analysis possible on a site-specific basis for any proposal. III. FINDINGS IN BLACK RIVER BASIN The field reconnaissance in Black River Basin was conducted in February 1937 by Ray Heller; resource planner; Ray Steiger and Doub Chin, en�ineers; and Matthew J. Brunenbo, geolocist. Their findincs and recommendations are presented here. A. Overview of Black River Basin Geographic and land use features. Black River Basin is generally bounded on the north by the cities of Renton and Tukwila and on the south by the city of Kent. The western and eastern boundaries are formed by the Green River and 116th Avenue SE, respectively, in this southern King County basin. The Black River, which oives its name to this basin, actuaily ceased to eaist in 1917, when the Lake Washinbton ship canal was �� built and the level of Lake Washinbton was lowered, cutting off flow to the Bfack River. The 23-square-mile basin investibated by this field team includes what remains of the network of tributaries that fornierly connected with the Black River. The Black River Basin is split nearly equally into an eastern upland plateau and a western floodplain in the Low•er Green River Valley along State Road (SR) 167. The floodplain is almost wholly contained within the cities of Tukwila, Renton, and Kent, where eatensive development in the last two decades has chan�ed the landscape from a rural farminb area to a commercial and industrial one. While open space and farming still exist here, the area will be infilled, primarily by a comUination of commercial, industrial, and some multi-family compleaes, by the year 2000. The Kinp County Comprehensive Plan shows that the upland area will be developed at urban densities. This transition is already in progress, with commercial developments emer�in� alon� the Kent-Kaneley Hibhw�ay (SR 516), the Benson Hi�hway (SR 515), and the Carr Road-176th Street SE-Petrovitsky Road corridor. Multi-familv land use occurs in the uplands also and surrounds commercial developments. New single-family units are beinb built throuchout most of the eastern upland portion of the basin. The amount of impervious surface is e�pected to nearly double between 1935 and the time the basin is fully developed. This will rec�uire strict controls on surface water discharce to assure prevention of furtl�er de�radation of the stream system, which has alreadv be�un to exhibit adverse environmental impacts resultinp from urbanization. Other factors of concern in this basin are those sensitive areas occupied by wetlands, streams. floodplains, coa(-mine zones, and landslide zones. Mostly located in the eastern � portion of the basin, these areas have already Ueen damaced by the effects of de��elop- � P:BR!jr 2 • � Black River Basin (continued) ment. Details of the damage, along with su�estions for mitigation, are contained in later section of this report. Dominant geologic and geomorphic features. Black River Basin consists of the part of the Duwamish Valley east of the Green River and the western edge of the Covinbton drift plain, a plateau underlain by glacial deposits. Small creeks, which flow across its rollinc surface, have eroded deep, nanow ravines up to 1.5 miles into the plateau. Downcutting is miorating headw•ard in the upper reaches, and erosion of banks and lower slopes causes ]andsliding in the canyon walls, most of which are naturally unstable. Both of these processes are accelerated by increased flows attributable ro urbanization. '� Sediment is deposited where the streams flow onto the valley floor. i The surface of the Covinoton drift plain is dominantly basal till; mantled in places with �I recessional outwash or deposits of post-glacial lakes. Near the edge of the plateau are �, several lenses of sediment deposited adjacent to a glacier lobe in the Duwamish Vailey. i Older sediments are exposed in the ravines and bluffs. In the north, unconsolidated � sediments lap up onro the southern limb of the Newcastle anticline; sedimentary and � volcanic: rocks crop out in the bluffs north of Panther Creek and form the Renton, ii Talbot. and Earlinbton Hills in the northern end of the valley toward Tukwila. Coal � w�as mined from this area from 135; until the 1940s. j The Duwamish Valley is part of a trough carved into the drift plain during the last blaciation; it later became an arm of Puget Sound. A catastrophic mudflow oriainatinb on Mount Rainier approximately 5700 years a�o dumped massive amounts of debris into the troubh. This and other events, plus the deposition of alluvial sediment, expelled the salt water. Throu�h the nineteenth century, the combined White and Green Rivers meandered throubh the valley. Near Renton, the Cedar River flow�ed into the Black w�hich drained Lake Washinb on and flow•ed into the Duwamish. Bebinnino in 1906 a series of chanbes was made to these river systems. The Cedar River was diverted into I��ke Washin�ton, and the White River w•as diverted south to the Puyallup. The Black River itself ceased to exist. Geomorphic processes in the Black River Basin are most active on the western edDe of the plateau. Lakes and wetlands formed here in the poorly drained s�•ales. Where conditions of drainaoe and pemolation are appropriate, small streams flow between the drumlins, erodino deep ravines into the unconsolidated sediments in the process. Over time, the ravines have been widened by mass-wasting of their walls (a process aided by �roundw�ater) and erosion by trihutary creeks; their upper ends have mio ated their upstream into the plateau. Sediment carried by these streams w�as deposited in the Duwamish trouph; after the trouoh became an al[uvial valley, small fans formed on its ed�e. Hydrologic and hydraulic features. There are three distinct georraphic features asso- ciated w�ith the hydraulics of Black River Basin: the plateau east of the L.ower Green River Valley, the steep (5-35°) erosive hillsides, and the flat floodplain of the valley floor. Mill, Ciarrison, Sprinbbrook, and Panther Creeks, as well as three small, unnamed tri- butaries (0023, 0006B, and 0006C), all oribinate from locations on top of the plateau. Panther Creek orib nates from Panther Lake and tt�e surroundina wetlands. The P:BR/jr 3 __ _ I ' I Black River Basin � (continued) � ' �I remaining tributaries originate primarily from surface water stored in natural depressions I', and wetland areas alono the top of the hill. The surface water is collected and routed general(y north and west via natural swales, open roadside ditches; culverts, and pipelines within street rights-of-way and, finally, down the steep hillsides to the valley floor. Mill Creek, located at the southernmost end o�' the Black River Basin, flows north , between the Green River and SR 167 and then.crosses under the highway at various , locations. Mill, Springbrook, and Garrison Creeks mntinue north alono the west side of � SR 167 and eventually combine as Springbrook Creek before being pumped into the Green River through Kino County's Black River pump station. Tributaries 0006B and ' 0006C flow north independently down the hillside adjacent to Interstate 405 and into ' Renton, where they enter the city's storm drain system. , Habitat characteristics. The use of natural streams for urban stormwater conduits has had a detrimental effect on most stream systems in the Black River Basin. Increased ', stormwater release rates that are higher than streams can convey without problems have resulted in extensive erosion, sedimentation, and landslides. Water quality problems ; caused by domestic barbaae placed in streams and point discharces of pollutants are i additional factors. � What is strikino about this basin is that these habitat problems exist everywhere. While some problems are worse than others, their impact on the fish habitat of each stream examined was profound. No fish were observed in any streams durinb the investi�ation. For this reason it is surprisino that the fish counter at the Black River pump plant 5 located on Monster Road (throuoh which all water in the basin is discharbed into the Green River recorded 34 fish enterinp the stream system in 1936. While this fib re is hi�l�er than that for fish counts in the previous five years, it is si�nificantly lower than historical levels or the potential levels that miaht be achieved if streams were in better condition for spawninp. The current habitat conditions offer little hope for the future of these salmon runs. To reach spawning areas fish must first pass throu�h an open flood-control drainace ditch for a minimum of five miles. This ditch has no vegetation or pool protection for fish to take refuge against predators or water-temperature increases. In addition, water quality is visiE�ly poor. The eob of fish that do reach spawnino territory are likely to be smotltered with sediment or washed out durina heaw rainstorms: If these problems associated with development worsen, stream systems will probably be left biologically sterite. Reversing this pattern of debradation is dependent on revisinb the policies and priorities in the planning and zoninr activities; the develop- ment review processes on the Surface Water Management probrams of Kina County, Renton, Tukwila, and Kent. B. Effccts of Urbanization in the Basin The existin; upper reaches of the Black River Basin were once heavily vegetated, and natural depressions retained much of the surface water. Water was released slowly then, and the stream systems could convey flows easily. Development has broubllt about the removal of this vebetative cover and fillinp of the natural depressions. Many streams are now Ueing piped. Impervious surfaces are increasin� and w•ill eventually account for 50 percent of the basin's surface area. In general, surface water is enterin� natural systems at a faster and hi�her rate than before development accelerated tw�o decades ��O. P:BR!jr �3 � Black River Basin (continued) Earlier discussions pointed out the serious effects this is producing in the form of ero- sion and sediment transport to lower stream reaches. Additionally, sedimentation decreases the efficiency of the entire basin drainage system by filling culverts and chan- nels. This in turn increases the potential for flooding. The city of Kent removes an estimated 1,100 cubic yards of sediment annually from its sediment facility at Mill Creek Park. The Washington State Department of Transportation also employs a reb lar cleaning schedule to remove gravel and sediment from its culvert under South 212th Street on Tributary 0023. Sediment from Sprin�brook Creek has been transported downstream from the erosive hillside to a pri- vate trout farm west of Talbot Road and rendered it inoperative. Similar eaamples occur throubhout the basin alona the bottom of the steep hillsid� and east of State Road 167. . Erosion is further accelerated by drainage outlets from developments and public areas. Discharbe from a pipe into Garrison Creek adjacent to Benson Road freefalls for approaimately 10 feet before scourina the ravine it enters. Similar erosion occurs on Tributary 0006B where water is discharged fron� the Fred Nelson Junior Hibh School across Benson Road to the top of a severely eroded ravine. An onsite detention farility downstream at the Victoria Hills housing development accumulates la pe amounts of sediment. Its capacity is decreasina, and the function of the facility is threatened. The development trends in this basin mean that land for reoional R/D facilities will become more difEicult to obtain at the same time that erosion and potential for floodin� are increasinp. Additional problems may arise if existing onsite R/D systems malfunction from improper design or construction or from lack of maintenance. An onsite facility for a privately developed trailer park, located west of the Benson Road I adjacent to Garrison Creek, e�emplifies the potential hazard. Unstable fill was placed on the steep ravine and an R/D pond built on its edbe. The fill becomes saturated w•hen the pond is in use, and tension cracks in the fill alon� the slope indicate potential failure. Such an event would add larbe amounts of sediment to the drainabe system. Development may create similar problems elsewhere if the proper desib, construction, inspection, and maintenance of R/D facilities is neblected. C. Specific Problems Identi6ed Black River Basin exhibits serious problems throubhout its system, with exceptions only in the south fork of Sprinpbrook Creek and on Panther Creek in subcatchment 10. The most si�nificant problems noted by the field team during its investioation are listed below. 1. Stream channel erosion aooelerated by the routing of runoff fmm deveIoped areas into streams. Major problems eaist in the ravines, where streams are cuttinp into till at the upper ends of canyons and associated landslidina and surface erosion occur (see section 3 below). Although these processes have been taking place naturallv for a lonr time, increased runoff from developin� areas on the plateau is causinb acceleration of the erosion. a. The worst cases of erosion observed include those on Mill Creek (0005), P:BR/jr 5 . ,� Black River Basin . (continued) . � Garrison Creek (002?) and its tributaries (0023, 0024, and 0025), the north fork of Springbrook Creek (0021), and Panther Creek (0006). b. Prominent examples of gullyin; at drainage-structure outfaqs are in Mill Creek (0005), Sprinbbrook Creek (0021), Panther Creek (0006), and below Benson Road on both Garrison Creek (0022) and Talbot Creek (0006B). c. Examples of accelerated downcutting resulting from increased runoff from developing areas are located in Talbot Creek and two small streams (0064A and 0006C) in Renton. 2_ Landsliding assoc,iated with stz+eam einsion in ravines, as a result of steep slopes and saturated soils. Instability oenerally takes the forni of rotational failures or debris slides triggered by stream undercutting. In many cases, natural instability is eaaeerhated by fillinb and/or by construction on canyon wails; for example, a new fill above Garrison Creek at Benson Road is failin�, and old .fiils are bein� under- rut. All of the ravines should be considered landslicie-hazard areas. The same is true of the Uluffs at the western edbe of the plateau, even thou�h there have not been many problems yet. These are moderate to steep, landslide-susceptible slo- pes, especially in the northern (Renton) and southern (Kent) ends of the basin -- the area under the most deveiopment pressure. 3. Damage to (or destruction ot) habitat due to: a. High flaws and high velocities, which remove macrophytes and benthic orba- ' nisms, plants; insects, and possibly fish. Visible evidence of hiph velocities was noted on all the streams in this basin except the south fork of Sprinbbrook Creek. , b. Sedimentatioa from ezcessive erosioq which is filling pools, chokina spawning �ravels, and in some cases fillino stream beds ro the point of makinp channels , impassible to fish. All of the four bio stream systems in Black River Basin exhibit this problem. The Kent parks department annually removes 1,100 cubic yards of material from Mill Creek. A larbe sediment flow has filled the , Sprincbrook Creek stream channel to a depth of approximately 5 feet, and Panther Creek just north of Valley General Hospita! has a large alluvial fan. c. Visibly poor water quality: I 1) Laroe amounts of domestic trash have been deposited in these stream 'I canyons. Mill Creek has become a dump for appliances at river mile I 9.60, and Garrison Creek appears to be more of a landfill than a creek at 1.30. Such practices have a detrimental effect on w�ater qualitY as well as the visual quality of the environment. , 2) Commercial and industrial enterprises are producing runoff that causes m<1ny streams to be oily, ttirbid, and sudsy. Sprin�brook Creek (Trib. 0005 at RM 1.30). flowin� under the bridbe of Southw�est 16th Street just east of Loncacres in Renron, is one of the worst examples noted. The �- Western Processinb facility just upstream has been identified as a source of to�ic wastes enterin� both surface and groundw�ater systems. ' � P:BR/jr 6 I Black River Basin (continued) IV. RGCOr�IIviENDATIONS FOR ACTION Habitat, erosion, landslidinb, and flooding problems in the Black River Basin can be addressed hy the measures identified befow. Most of the solutions listed here will mitigate specific problems observed during field investigation or will prevent similar problems in the ft�ture. However, additional recommendations have been included to suboest administrative or re�latory measures that would increase the overall effectiveness of surface water manabement in this basin. � Ezpand e�asting aridlor coostrud additioaal ie�onal R/D faciliries on the plateau in order to contro! storm flows that oribinate there. Site facilities upstream of the four larae creek ravines that are experiencino the worst dama�e. Facilities should .be regional in scope and should follow the general specifi- cations outlined in Appendix A of this report. These will impede the direct conveyance of runoff into the steep; naturally erosive ravines, thereby reducin� erosion rates that result in sediment transport and slope instability and that damaoe habitat. B. Preserve wetlands on the plateau to pmvide natuial storage. In addition, reconsider Panther I.ake for use as a rebional R/D site. Althoubh the lake has been classified as a #1-C wetland, the amount of storage it offers is substantial with a moderate addi- tional (.25-to .50-foot} fluctuation in depth. - C. Protect steep valley walls from erosion and landsiides caused from direct discharges of storn�water: 1. Tightline discharges or provide other appropriate nonetnsive mnveyance wer steep hillsides; provide enerby dissipation at the outfalls. This has already been done a: several points on Miil Creek (Tributary 0005) with good results. 2. Consider rerouting f(aw in cases where tig�tlining or other methods are not 'i feasible. For example, runoff from the area southeast of Sprinrbrook Creek micht ' be piped dow�n Southeast 200th Street rather than routed into the nortll fork (0021) as it is now. 3. L.owcr the potential for landslides by restricting developmcnt in and along the tops of ravines. In particular, stron�ly discourabe filling alonb the edbes; the fill ', at Benson Road above Garrison Creek (00?2) will probably have to be removed. ' D. Reduce sedimeotatioa in streams along the valley floor in cases w�here sedimentation is I not adequately prevented by R/D and other upstream measures. In extreme cases (prob�ibly includina Panther Creek [0006]), construct sediment traps (with convenient access for removal of accumulated material) at points where streams flow onto the 'I vall�v ffoor. C. Increa.se enforcement of regulations against the dumping of domestic trash into ravines and stream channels. The Seattle-King County Health Department and the Kin� County office of Building and Land Development should be asked to investiaate tl�is on�oin� problem and to take appropriate action when violators are identified. P:BR/jr 7 Btack River Basin (continued) l F. Increa.se the oveiall effectiveness of surface water management in the Black River Basin: 1. Continue cooperative intergovernmental arrangements between the cities of Tukwila, Kent, and Renton; the Washinb on State Department of Transportation; and the King County Surface Water Management Division to identify and propose solutions to habitat and hydraulic problems in the basin. These efforts should include de- veloping cost-sharina agreements where capital improvements are required. 2. Evaluate and reduce, if appropriate, the volumes and rates of release for stormwater orib nating from developments. Present release rates and volumes are causina erosion, sedimentation and habitat problems. 3. Increa.se the maintenanee and inspection of existing King County and city drainage systems to ensure that they are functioninb properly. 4. Enmurage pubGc participation in maintaining water quaGty and ia stormwater management in the basin, including citizen action projects to clean trash from streams and education about citizens role in maintainino clean water and stream systems. 5. Perform more detailed and mmprehen.sive hydrologic/hydraulic analysis of all drainage systems within the basin to determine how the existing facilities will ' function under existing and future flows. � �. 6. Prepare a mmprehensive basin plan with participation by all a�encies concerned with surface water manacement in the basin. The plan should assess the econo- mic, hydroioo c, and habitat impact oE individual projects on a basin-wide scale. � P:BR/jr `� i � � � L i��l�l�JI� � � �I �� 4FF-SITE BACKWATER ANALYSI� � . i - ------------------ Beginning Calculation Cycle ------------------- � Discharge: 0 . 32 cfs at node DET-1 , � Discharge: 0 . 32 cfs at node J-1 " Discharge: 0 .32 cfs at node Outlet-1 Beginning iteration 1 Discharge: 0 .32 cfs at node DET-1 Discharge: 0.32 cfs at node J-1 Discharge: 0.32 cfs at node Outlet-1 Discharge Convergence Achieved in 1 iterations: relative error: 0 . 0 ** Warning: Design constraints not met. ** Problem: Flooding in system Information: Outlet-1 Known flow propogated from upstream junctions. Violation: P-2 does not meet minim�m velocity constraint. ' Information: J-1 Known flow propogated from upstream junctions. Violation: P-Z does not meet minimum cover constraint at upstream end. Information: DET-1 Flooding condition. --------------------- Calculations Complete ---------------------- ** Analysis Options *} Friction method: Manning's For: : :_ HGL Convergence Test: 0. 00100` Maximum Network Traversals : 5 Number of Pipe Profile Steps: , Discharge Convergence Test: 0 . ��_�� ' ' Maximum Design Passes: 3 ----------------- Network Quick View ------------------------ I Hydraulic Grade I Label � Length I Size � Discharge � Upstream � Downstream I P-1 40. 00 12 inch 0.32 14 .53 11. 63 P-2 78 . 00 24 inch 0.32 11. 63 11. 63 I ----------- Elevations ---------------- I Label I Discharge � Ground � Upstream HGL � Downstream HGL � DET-1 0.32 14 .30 14.30 14.30 J-1 0 .32 16. 90 11. 63 11. 63 Outlet-1 0 .32 16. 94 11. 63 11 . E3 �lapsed: G minute �sj 3 secer.d (sj Project Title: Unifirst Commercial Laundry Facility Project Engineer:Harold Peterson d:ldatalprojecls�trec0004�unifirst.stm StormCAD vt.0 10101/J7 04:39:49 PM Haestad Methods, Inc. 37 Brookside Road Waterbury,CT 06708 (2o3)756-1666 Page 1 of 1 i -. � � Dutlet- 1 ��,, ; �, � . � � � ! P -2 � � � ; � � , � J - 1 �, � ; � � . � ; � � � � �� P - 1 I � I � I � DET- 1 , � � � Project Title:Unifirst Comme►cial Laundry Facility Project Engineer:Harold Peterson d:ldatalprojeUsltrec00041unifirst.stm StortnCAO �1 A 10/D'1/97 07:48:07 AM Haestad Methods,Inc. 37 Brookside Road Waterbury,CT 06708 (203)75�1666 Page 1 of 1 ^ Combined Pipe/Node Report '•� pipe Upstream Downstream Length Inlet Iniet Inlet Total In{et Section Capacity Average Upstream Downstream Constructed Node Node (ft) Area C CA CA Discharge Size (cfs) VelocRy Invert Invert Slope (acres) (acres) (acres) (cfs) (ft/s) Elevation Elevation (ftlft) (ft) (ft) P-1 DET-1 J-1 40.00 0.78 0.00 0.00 0.00 0.00 12 inch 11.27 1.35 14.30 10.30 0.100000 P-2 J-1 Outiet-1 78.00 N/A N/A N/A O.OQ N/A 24 inch 16.00 0.13 10.30 9.91 0.00`�N il Project Title:Unifirst Commercial Laundry Facility Project Engineer: Harold Peterson III d:ldatalprojectsltrec00044inifirst.stm StortnCAD v1.0 10V02197 07:4724 AM Haestad Methods,Inc. 37 Brookside Road Waterbury,CT 06708 (2Q3}75Er1666 Page a of 7 j � , � 1 � Outlet � � I I I i p_7 i ; J-4 ' P-5 � J-3 �-- P-4 J-2 ,�� \ �, �� ., \�'� P-3 '� \ � \� \—DET-2 �i Project Titie:Unifirst Project E�gineer.Harold Peterson d:lhaestad\stmc�uni.stm StormCAD v1.0 10/0'1197 07:46:05 AM Haestad Methods,Inc. 37 Brookside Road Waterbury,CT 06708 (2Q3)75Fr1666 Page 1 of 1 � ------------------ Beginning Calcula�i�n Cyc�e ------------------- •` Discharge: 0. 89 cfs at node DET-2 , � Discharge: 0. 89 cfs at node J-2 Discharge: 0. 89 cfs at node J-3 Discharge: 0. 89 cfs at node J-4 Discharge: 0. 89 cfs at node Outlet Beginning iteration 1 Discharge: 0. 89 cfs at node DET-2 Discharge: d. 89 cfs at node J-2 Discharge: 0. 89 cfs at node J-3 Discharge: 0. 89 cfs at node J-4 Discharge: 0. 89 cfs at node Outlet Discharge Convergence Achieved in 1 iterations: relative error: 0. 0 ** Warning: Design constraints not met. ** Problem: Flooding in system Warning: No Duration data exists in IDF Table Information: Outlet Known flow propogated from upstream junctions . Information: P-7 Surcharged condition Violation: P-7 does not meet minimum velocity constraint. Information: J-4 Known flow propogated from upstream junctions. Information: P-5 Surcharged condition Violation: P-5 does not meet minimum velocity constraint. Information: J-3 Known flow propogated from upstream junctions. Violation: P-4 does not meet minimum cover constraint at upstream end. Information: J-2 Known flow propogated from upstream junctions. Violation: P-3 does not meet minimum cover constraint at downstream end. Information: DET-2 Flooding condition. --------------------- Calculations Complete ---------------------- ** Analysis Options ** Friction method: Manning's Formula HGL Convergence Test: 0.001000 I Maximum Network Traversals: 5 Number of Pipe Profile Steps: 5 Discharge Convergence Test: 0. 001000 Maximum Design Passes : 3 ----------------- Network Quick View ------------------------ � Hydraulic Grade � Label � Length � Size � Discharge � Upstream � Downstream I P-3 155.00 12 inch 0.89 15 .40 12.48 P-4 100.00 12 inch 0.89 12.48 11.54 P-5 18.00 12 inch 0.89 11.54 11.53 P-7 60.00 15 inch 0. 89 11.53 11.52 I ----------- Elevations ---------------- I Label I Discharge � Ground � Upstream HGZ I Downstream HGL I DET-2 0.89 15.00 15. 00 15.00 J-2 0. 89 16.50 12.48 12.48 J-3 0.89 16.10 11.54 11.54 Outlet 0.89 16.94 11:52 11.52 J-4 0.89 16.14 11.53 11.53 Elapsed: 0 minute (s) 4 second(s) Project Title:Unifirst P�oject Engineer:Harold Peterson d:lhaestad\stmc4ini.stm StormCAD v1.0 10I01197 06:11:09 PM Haestad Methods,Inc. 37 Brookside Road Waterbury,CT 06708 (203)75�16'66 Page 1 of 1 ' Combined Pipe/Node Report ' : � pipe Upstream Downstream Length Inlet Inlet Inlet Total Inlet Section Capacity Averege Upstream Downstream Constructed Node Node (ft) Area C CA CA Discharge Size (cfs) Velocity Invert Invert Slope (acres) (acres) (acres) (cfs) (fUs) Elevation Elevation (R/(t) (ft) (ft) P-3 DET-2 J-2 155.00 0.00 0.00 0.00 0.00 0.00 12 inch 4.89 3.08 15.00 12.08 0.018839 P-4 J-2 J-3 100.00 N/A N/A N/A 0.00 N/A 12 inch 4.90 2.11 12.08 10.19 0.018,900 P-5 J-3 J-4 18.00 N/A N!A N/A 0.00 N/A 12inch 2.52 1.13 10.19 10.10 0.005000 P-7 J-4 Outlet 60.00 N/A N!A N1A 0.00 N!A 15 inch 4.57 0.73 10.10 9.80 0.005000 Project Title:Unifirst Project Engineer:Harold Peterson d:\haestadlstmc�uni.stm StortnCAD v1.0 10/02/97 07:44:47 AM Haestad Methods, Inc. 37 Brookside Road Waterbury,CT 06708 (203)7r.�rt 666 Page 1 of 7