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HomeMy WebLinkAbout03076 - Technical Information Report - Drainage V � � - ,.. ...,« _ m G ��1 G I �l E E B_S �1�_ - �_._._ _ . __. ._ '�' '� � DRAINAGE REPORT FOR FIRE STATION #12 CITY OF RENTON WASHINGTON Prepared For: City of Renton Fire Department And Rice Fergus Miller Architecture & Planning 0�C yr'��ErYi ,;, O�AF^f�C'rY,,r, ���� _. Prepared: May 8, 2002 '� 1� R���,�� �� 1�'0 � d � 720 South 348th S[reet Tet 12531 838 6113 Tacoma 12531 927 0619 Civ l Engineering Land Planning Federal Way. WA 98003 Fax 12531 838 7104 Seattle 1206) 623 5911 P-c�ect Management Public Works www.esmciviLcom Bremerton 1360)792 3375 Laed Surveying ' . . . _ .. . � � ��. / � DRAINAGE REPORT FOR ! FIRE STATION #12 CITY OF RENTON WASHINGTON _ Prepared For: City of Renton and Rice Fergus Miller Fire Department Architecture & Planning 1055 S. Grady Way 262 4th Street Renton, WA 98055 Bremerton, WA 98337 (425) 430-6400 (360) 377-8773 Prepared By: John S. Chadwell, P.E. ESM Consulting Engineers, L.L.C. 720 South 348th Street Federal Way, WA 98003 (253) 838-6113 ��oF wa���, o ��' � �C � 28792 � �G�,�FCISI'�RF�� �`�'� ♦ �'SS�ONAL��C} L May 8, 2002 S-�•o Exc�REs:s�2� r o�2, \esm-jobs19961011documentltir-May08.doc 720 South 348th Street Tel 12531 839 6113 Tacoma 12531 927 0619 � vi'. ��gineering Land Planning Federal Way. WA 98003 Fax (253)838 7104 Seattle 1206) 623 5911 Project Management Public Works www.esmciviLcom Bremerton 1360)792 3375 �3ad Surveying ' � � Drainage Report for Fire Station #12 May 8, 2002 � Page 2 TABLE OF CONTENTS I. TIR Worksheet II. Existing and Proposed Drainage Features and Construction III. Core and 5pecial Requirements IV. On-Site Detention Analysis V. Level 1 Off-site analysis Appendices • Figure 1 —Vicinity Map • Figure 2 — Soils Map & Description (2 Pages} • Figure 3 — Hydrologic Soils Group Table • Figure 4 — 2 Year King County Isopluvial Map • Figure 5 — 10 Year King County Isopluvial Map • Figure 6 — 100 Year King County Isopluvial Map • Figure 7 — SCS Curve Numbers Table • Figure 8 - Existing & Proposed Hydrology Basin StormShed Calculations • Figure 9 - Downstream Analysis Summary Map _...5 '+'%'.t� '�4 ' �.�sv.d.w`.�'�.`a_`'�� �.... Drainage Report for Fire Station #12 May 8, 2002 Page 3 SECTION I TIR WORKSHEET ������� � ' Paga 1 �9 2 ^ King County Building and Land Development Div(slon � TECHNICAL (NFORMATION REPORT (T1R) WORKSHEET - . � .� ��- i� - . , . � � ,��. � � �.. «-� . ProjectOwner C'fj' of �Qe��ah � ProjectName F'��L ffGf�On �' /z Address /OSS' S. (,�ady �wy — Location Phone �`1ZS) �/3b' Gy00 _ Township 23 tia�f'�, Praject Engineer Je tin -S• G hadwcll� P.�• R�9e S Ea,r,� ESM Co�,,J /�in n � zc• Sec;ion 'S� Company Project Size �2 AC Addrsss Phone 7ZOS.3y8' �!`�• F�d«�I W�y , ti/A� Upstream Drainage Basin Size � AC 2S3 g38-G�l3 • -��, �•I • �- • �-lii � Subcivisicn � DOF/G HPA i�1 Shoreline Mar.agement � � Short Suodivision Q COE 4C4 � Rodcery , � Grading � �OE Dam Safety � Structural Vaults � (i Commercial Cj FEMA Floodplain � Other Q Other � COE Wetlands � HPA , -� «. �� i � � �i� C� �i Communiry Drainage Basin � j EGrf' Ln�Cc WGd�in��0^ I ., - � .. G' River C Flocdplain � Stream � Wetlands 0 Critical Stream Reacn � SeepslSprings L_; DepressionsJSwales Cl High Groundwater Table � Laice Cj Groundwater Recharge � Staeo Slooes Q Other � � LakesidelErosion Hazard .�� Soil i y Slopes Erosio/n Potential Eresive Veloc;ties ° I��LrGTc 7�b .TL'V�YG /Qrtntd- f�) uWoO� 0 -/S �o ' �; AdditionaJ SheetsAttatched 1/'9a Page 2 af 2 King County Bufiding and Land Developmertt Divfslon -. TECHNICAL INFORMATION REPORT (TlR) WORKSHEET r�� � . • � � ;,�� �. ` - REFcRENCc L1MIT�TiONiSiTc L.ONS i r��N i � Ch.4-Oowns;ream Anafysis Nah� �0�'e� � � � Q � C Additional Sheats A�tatched � _.. � -i�,��� i MIi�VII1JIUl,!{E.71.+ REflUIREMcN�S MINI�IUM ESC r�cG'UIRE.41E�1TS DURfNG CONSTr�UCT(aN FOLLOWING CONSTAUCTION � Sedimentation Facilities � Stabilize Exposed Surface r f c�y, � Stabilizad Ccnstruction Entrance � Remove and Restore Tamporary ESC Facilities gf Perimeter Runo�f Control �.1 Clean and Remove All Silt and Debns � C(earing and Grading Restrictions Qr DateS Q Ensure Oparation of Permanent Facilities � Cover Practicas � F7ag Limits of NGPES � Constructian Sequence � Other 0 Other ' �, ' i « �- �,� ... I � Grass Lined Channel l� Tank � Infiltraron Method of Analysis � Pipe System Cj Vauit Q Depression S'�U h� �' Ooen Channel � Energy Dissapator I� Flow Cispersal Compensa6on�1vlitigation I � Dry Pond � Wedand Q Waiver o��i�i�minated Site Storage Q Wet Pond C1 Stream 0 RegionaJ Detention BnefDescriptionofSysiemOperation Co�/aef�on Gn� COnvG�Gn[G P�P� S'�J�er., �Onneetir.� ,--�---- I �'0 eX�.P��^4 .CyJ'�'en A��'e� JJkS,f�n4 t�tbV9� ��I �GJq�'cr .r�,oa��fer Facility Related Site Limitations C Additional St�eets Attatched Reterenca Facility Vmitation i- 7�� i� � .�� ,.; -.� �.i , .� �j Drainage Easament 0 Cast in Placs Vault C Other Q Access Easement C Retaining Wail � Native Growth Protection Easament 0 Rockery>4'High Q Tract I � Structural on Steep Slope I� Other - . ��-�. -�. 7 . � r. �7- II or a civil engineer under my supervision have visited the site. Actual � 9ite conditions a9 observed were incarporated into this waricsheet and the � � attatchments. To the best of my knowledge the informetion provided \I s-B�OZ J i here is accurate. � 59^'d0'�� � Drainage Report for Fire Station #12 May 8, 2002 Page 6 SECTION II EXISTING AND PROPOSED DRAINAGE FEATURES AND CONSTRUCTION ,�`��- �_ Drainage Report for Fire Station #12 May 8, 2002 � Page 7 SECTION II Existing and Proposed Drainage Features and Construction Existing Conditions The project site is located on NE 12th Street between Jefferson Ave NE and Kirkland Ave NE. The project site fronts onto all three streets. The project site was developed previously as a restaurant. The structure was recently removed, however the remainder of the site consists of a.c. pavement, curb, gutter, and sidewalks along with minimal areas of landscaping around the site perimeter. The site has an existing storm drain conveyance system consisting of six catch basins which drain into the existing storm drain system in NE 12th Street via two connections (10"0 and 6" f� pipes). The portions of the site fronting onto the three streets (curb, gutter and sidewalk) presently drain into the street and the storm water is picked up in one of three catch basins located along NE 12�' Street. For simplicity the project site drainage features were calculated from the curb face ' of the frontage roads in order to more fully describe the proposed projects impact, or in this situation, reduction of impact to drainage conditions. The existin site covera e is summarized below: Cover T e Acrea e Percenta e Buildin s 0.227 Ac. 16.6% Pavement 0.788 Ac. 57.4% Walks 0.088 Ac. 6.4% Landscapin 0.269 Ac. 19.6% Total 1.37 A. Soils The Soil Conservation Service (SCS) Maps indicate the presence of Alderwood Arents series soils throughout the project site (Fig. 2). These soils are hydrologic soils group "C" according to the King Count Surface Water Design Manual. Rainfall The design rainfall was obtained from the isopluvial maps in the 1990 King County Surface Water Design Manual. The 2-year 24-hour design rainfall is 2.0 inches, the 10-year 24-hour design rainfall is 2.9 inches and the 100-year 24-hour is 3.89 inches. The six-month design storm is calculated as 0.67 inches. ;� � -�' �� �� � x=��:�i:au� Drainage Report for Fire Station #12 May 8, 2002 Page 8 Proposed Conditions The proposed project site plan, developed by Rice Fergus Miller, includes the new fire station building along with parking areas, drive approaches, new curb, gutter and sidewalk afong the three road frontages, and landscaped area. This is a redevelopment project which proposes less than 5,000 s.f. of new impervious surface subject to vehicular use. In fact the project proposes less impervious surface than the previous use. For emphasis we note that the project proposes a site with 0.97 acres of impervious area, while the existing site has 1.10 acres of impervious area. The ro osed site covera e is summarized below: Cover T e Acrea e Percenta e Buildin s 0.281 Ac. 20.5% Pavement 0.471 Ac. 34.4% Walks 0.219 Ac. 16.0% Landsca in 0.400 Ac. 29.2% Total 1 .37 A. The proposed project will collect storm drainage from roof drains, yard drains (if needed) and catch basins, then conveyed into a water quality tank before being released to the existing storm drainage system located in NE 12�h Street. � �;T, �. , ;�.�-�_�.,�:; Drainage Report for Fire Station #12 May 8, 2002 � Page 9 I � SECTION III CORE AND SPECIAL REQUIREMENTS �- � , , ! , , � �� ,--. ', � � � i �� : � Drainage Report for Fire Station #12 May 8, 2002 Page 10 SECTION III CORE AND SPECIAL REQUIREMENTS This Section will describe how the project proposes to meet each of the applicable Core and Special Requirements. Core Requirement (1) — Discharge at a Natural Location The project site currently drains into an existing on-site storm drainage conveyance system which connects to the existing storm drain in NE 12th Street. The redevelopment of the site proposes to discharge at the same locations, utilizing existing storm drain laterals. ' Core Requirement (2) — Off-site Analysis Upstream - A small portion of ground to the north of the project site drains onto the site. The area is minimally landscaped and it is included in the existing and � proposed hydrologic calculations. '� Downstream — The hydrologic calculations for this proposal demonstrate that the site will not have any impact to downstream drainage systems, and proposes less than 5,000 s.f. of new impervious surface (defined as surfaces that increase the runoff curve number). As such a downstream analysis is not required. No impact to downstream drainage systems is demonstrated by the reduced peak flow rates shown in Section IV below. Core Requirement (3) — Runoff Control The project is exempt from On-site peak rate runoff control as the proposed project post-development peak rate runoff is less than the existing condition peak rate runoff for the 100 year 24 hour design storm. The project is also exempt from the bio-filtration requirement because the project does not propose 5,000 s.f. or more of new impervious surface subject to vehicular use. Core Requirement (4) — Conveyance System The conceptual level design performed to date assumes that 12-inch minimum storm drain lines will be used, with 6-inch or 8-inch lines connecting roof drains to the main storm drain system. The proposed drainage system sizing will be verified as meeting the requirements of this condition during the final design phase. Once the hydraulic grade line from the storm drain located in NE 12�h Street is determined, the on-site conveyance pipes will be sized such that 0.5 feet of freeboard will exist during a 25-year storm event and that storm structures do not overtop during the 100-year event. In keeping with the proposed plans to have no i Drainage Report for Fire Station #12 May 8, 2002 ', Page 11 ' drainage impacts to the existing storm drain conveyance lines in NE 12th Street, the existing 6-inch and 10-inch laterals will be used to connect the proposed on- site storm drainage collection system to the existing storm drain. Core Requirement (5) —Temporary Erosion and Sedimentation Control A Temporary Erosion and Sedimentation Control plan will be prepared with the final construction drawings. At this time it is assumed that a combination of the following Best Management Practices will be utilized: defined clearing limits, cover measures, perimeter protection by filter fabric fence, rock construction entrance, sediment traps and or rock check dams in interceptor ditches, storm drain inlet protection, and TESC measures maintenance. Special Requirement (1) — Critical Drainage Areas The project is located within Aquifer Protection Zone 2. Additional requirements include: • Biofiltration Swale — Not required as project does not propose 5,000 s.f. of new impervious surface subject to vehicular use or storage of , chemicals. • Lining of Drainage Ditches — Not applicable as project does not propose any surface drainage ditches or swales. • Wetpond — The project does not meet the threshold requirements for construction of a wetpond as the project will not construct rnore than one acre of new impervious surface and does not direct discharge to a receiving body of water or discharge to a type 1 or 3 stream or wetland. Special Requirement (2j — Compliance with Existing Master Drainage Plan Not applicable as project is not part of a Master Planned Development. Special Requirement (3) — Conditions Requiring a Master Drainage Plan Not applicable as the project does not meet the thresholds for requiring a Master Drainage Plan. Special Requirement (4) — Adopted Basin or Community Plans Not applicable as the project does not lie within an Adopted Basin or Community Plan. Special Requirement (5) — Special Water Quality Controls Not applicable as the project does not propose more than one acre of new impervious area subject to vehicular use or storage of chemicals. �s ' i.�.�.._�j ��:st='�"«,�'�� Drainage Report for Fire Station #12 May 8, 2002 Page 12 Special Requirement (6) — Coalescing Plate OiUWater Separators Not applicable as the project does not propose to construct more than 5 acres of impervious surface. Special Requirement (7) — Closed Depressions Not applicable as the project does not drain into a closed depression. Special Requirement (8) — Use of Lakes, Wetlands or Closed Depressions for Runoff Control Not applicable as the project does not drain into a lake, wetland, or closed depression for runoff control. Special Requirement (9) — Delineation of 100 Year Floodplain Not applicable as the project does not contain or abut a stream, lake, wetland or closed depression. Special Requirement (10) — Flood Protection Facilities for Type 1 and Type 2 Streams Not applicable as the project does not contain or abut a Class 1 or 2 stream. Special Requirement (11) — Geotechnical Analysis and Report Not applicable as the project does not propose to construct a pond or an infiltration system. Special Requirement (12) — Soil Analysis and Report Not applicable as the existing SCS soils maps are sufficient for determining the classification of the underlying soils. � � z3�.,-.,,. ��� Drainage Report for Fire Station #12 May 8, 2002 Page 13 SECTION IV ON-SITE DETENTION ANALYSIS �� ��, , ..�.:��<�.�-��. Drainage Report for Fire Station #12 May 8, 2002 Page 14 SECTION IV ON-SITE DETENTION ANALYSIS Existing & Developed Hydrology The existing hydrology for the project site was analyzed using the "Santa Barbara Urban Hydrograph" (SBUH) utilizing the StormShed software package (Engenious Systems). The project meets the exemption for based on 1.2.3-5 . . . The Arents-Alderwood series soils are hydrologic soil group "C". The detailed basin input and results summaries are included in the appendices. Due to the nature of the site being a redevelopment site, which proposes a reduced amount of impervious area, no on-site detention will be required. A summa of the eak flow rates is summarized below: Storm Event Existin Peak Flow Rate Pro osed Peak Flow Rate Chan e 2-Year 0.63 c.f.s. 0.61 c.f.s. -.02 � 10-Year 0.97 c.f.s. 0.94 c.f.s. -.03 ' 100-Year 1.34 c.f.s. 1.31 c.f.s. -.03 As noted previously for Core Requirement #3, the proposed project meets the criteria for exemption from On-Site Peak Rate Runoff Control. ��.y � ���.-�`�-� Drainage Report for Fire Station #12 May 8, 2002 � Page 15 SECTION V LEVEL 1 OFF-SITE ANALYSIS _��� Drainage Report for Fire Station #12 May 8, 2002 Page 16 SECTION V LEVEL 1 OFF-SITE ANALYSIS As noted previously under "Core Requirment #2" a detailed Level 1 Off-site analysis is not required. This is based on the "no-impact" nature of the proposal, which includes a reduction in total impervious surface, a reduction in impervious surface subject to vehicular use, a reduction in vehicle trips (vs. pre-existing restaurant), and a reduction in peak storm flow rates. Though a detailed Level 1 Off-site analysis is not required, the following description is provided as additional information. The existing on-site storm drain collection system connects to the existing storm drain in NE 12�' Street via a 10- inch and a 6-inch CMP lateral. For reasons of maintaining no impact to downstream storm drains, we are proposing to use the two existing laterals. The existing storm drain in NE 12th Street is a 36-inch CMP. The 36-inch storm drain line continues west in NE 12�h Street at slopes varying from 0.32% to 7.6%. Approximately 1,550 feet downstream of the site, at Edmonds Ave NE the storm flows proceed south in the storm drain system. A map of the downstream analysis area is in the appendices. �c�.� Drainage Report for Fire Station #12 May 8, 2002 Page 17 - APPENDICES � � ������ � �" +' r ���� ��� ■� , �C����i�t I� �� � ���� ��� � _ �� �� � � � � .N z ��f��� ��� �� � ,���' `��� � •.�. � , . � �I�kl�d ��� . 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E „ . _, '# ..!I`i ,�.t� � . . .�+... �rlrents Alderwood Material � Some areas are up to 30 percent inciuded soils ' that are similar to this soil material, but either � shallower or deeper over the compact substratum; rents, Alderwood material consists of Alderwood i and some areas are S to 10 percent very gravelly o s that have been so disturbed through urban- j Everett soils and sandy Indianola soils . z��ion that they no longer can be classified with � . Runoff is medium, and the erosion hazard is he Alderwood series. T'hese soils, however, have � moderate to severe. a similar features. The upper part of the soil, This soil is used for urban development. Ca- o depth of 20 to 40 inches, is brown to dark- pability unit IVe-2; woodland group 3d2. ruWn gravelly sandy loam. Below this is a grayish- rown, consolidated and impervious substratum. Arents, Everett material (An) .--'Ihis is a level 1 �s generally range from 0 to 15 percent. to gently sloping, dark-brown gravelly or very hese soils are used for urban development. gravelly sandy loam. It is very similar to Everett gravelly sandy loam (see Everett series) , but it has been disturbed and altered through urban de- ^ents, Alderwood material, 0 to 6 percent slopes velopment. Multicolored very gravelly coarse sand y ) .--In many areas this soil is level, as a is at a depth of 8 to 40 inches. Areas are common- , .��lt of shaping during construction for urban ly rectangular in shape, and range from 1 to 120 icilities. Areas are rectangular in shape and acres in size. u � from 5 acres to about 400 acres in size. Representative profile of Arents, Everett mate- :presentative profile of Arents, Alderwood rial, in a homesite, 440 feet west and 100 feet i�__:ial, 0 to 6 percent slopes, in an urban area, north of the center of sec. 11, T. 24 N., R. 6 E.: ,300 feet west and 350 feet south of the northeast �; �r of sec. 23, T. 25 N., R. 5 E. : 0 to 8 inches, dark-brown (7.5YR 3/4) gravelly sandy loam, brown (7.SYR 5/4) dry; massive; 1 26 inches, dark-brown (lOYR 4/3) gravelly soft, very friable, nonsticky, nonplastic; sandy loam, pale brown (lOYR 6/3) dry; few roots; 30 percent gravel content; massive; slightly hard, very friable, non- slightly acid; clear, smooth boundary. 8 to sticky, nonplastic; many roots; medium acid; 14 inches thick. abrupt, smooth boundary. 23 to 29 inches 8 to 60 inches, grayish-brown and light olive-brown thick. (2.5Y 5/2 and 5/4) very gravelly coarse � `- 60 inches, grayish-brown (2.5Y 5/2) weakly � sand, light gray and light yellowish brown consolidated to strongly consolidated glacial � (2.5Y 7/2 and 6/4) dry; single grain; loose, till, light brownish gray (2.5Y 6/2) dry; nonsticky, nonplastic; few roots; 55 percent common, medium, prominent mottles of yellowish gravel and 10 percent cobblestone content; brown (lOYR 5/6) moist; massive; no roots; medium acid. , medium acid. hlany feet thick. The upper part of the soil ranges from dark The upper, very friable part of the soil extends brown to olive brown and from gravelly sandy loam � ^ depth of 20 to 40 inches and ranges from dark to very gravelly loamy sand. The substratum ranges a sh brown to dark yellowish brown. from black to olive b mwn. ne areas are up to 30 percent included soils 'Ihis soil is somewhat excessively drained. The at are similar to this soil material, but either effective rooting depth is 60 inches or more. a"�wer or deeper over the compact substratum; Permeability is rapid, and available water capacity d �me areas are 5 to 10 percent very gravelly is low. Runoff is slow, and the erosion hazard e tt soils and sandy Indianola soils. is slight. This Arents, .4lderwood soil is moderately well This soil is used for urban development. Ca- a�nAd. Permeability in the upper, disturbed soil pability unit IVs-1; woodland group 3f3. t ial is moderately rapid to moderately slow, p� iing on its compaction during construction. Beausite Series e substratum is very slowly permeable. Roots nP*�ate to and tend to mat on the surface of the n; lidated substratum. Some roots enter the The Beausite series is made up of well-drained b� �atum through cracks. Water moves on top of soils that are underlain by sandstone at a depth e substratwn in winter. Available water capacity of 20 to 40 inches. These soils formed in glacial 7^��r. Runoff is slow, and the erosion hazard is deposits. They are rolling to very steep. Slopes i� „ are 6 to 75 percent. The vegetation is alder, fir, '1 s soil is used for urban development. Ca- cedar, and associated brush and shrubs. The annual �ility unit IVe-2; woodland group 3d2. precipitation is 40 to 60 inchos, and the mean annual temperature is about 50 F. The frost-free season ranges from 160 to 190 days. Elevation is F nts, Alderwood material, 6 to 15 percent � 600 to 2,000 feet. �F" (AmC) .--This soil has convex slopes. rlreas In a representative profile, the surface layer � rectangular in sliape and range from 10 acres to and the upper part of the subsoil are dark-brown �u 450 acres in size. KING COUNTY, WASHINGTOM, SURFACE WATER DESIGN MANUAL (2) CN values can be area weighted when they apply to pervious areas of simiiar CN's (within 20 �„ CN points). However, high CN areas shouid not be combined with low CN areas (unless the low CN areas are less than 1596 of the subbasinl. In this case, separate hydrographs should be � generated and summed to form one hydrograph. FIGURE 3.5?A HYDROLOGIC SOIL GROUP OF THE SOILS PY KING COUNTY HYDROLOGIC I-fYDF10LOG(C SOIL �ROUP GROUP' SOIL GROUP Gr�OUP' Alderwood C Orcas Peat D ' Arents, Ald2rw C Oridia D Arents, Everett Material B Ovall C Beausite C PlchucSc C i Belling�am D Puget D I Briscot D Ptryallup S 8uckley D Ragnar 8 Coastal Beaches Variable ftenton D j �arimQnt Silt �oam D Riverwash Varrab(e I Edgewick C Salal C �verett A/B �Sammamish D Indianola A Seattle D Kitsap C Shacar D Klaus C Si Sitt C i Mixed Allwial land Variable Snohomish 0 ! Neiiton A Sultan C Newoerg B Tukwila D Nooksack C Urban Variable � Normal Sandy Loam D Woodinville 0 I-EYOROLCG(C SOIL GROUP CL.�,SSIFICATIONS A. (Low runoif potential). Soils having high infiltration rates, even when thoroughly wetted, and consisting cniefly of deep, well-to�xcessivefy drained sands or gravels. These so�7s have a high rate of water transmission. B. (Moderately low runoff potential). Soils having moderate infiftration rates when thoroughly werted; and consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. C. (Moderately high runoff potentiai�. So�s having slow in�i tration rates when thoroughly wetted, and consisting chiefly of so�is with a layer that impedas downward movement of water, or sods with moderdtely "ne to fine textures. These so�is have a slow rate of water uansmission. D. (High runoff potential). Soils having very siow infdtration rates when tho�oughfy wetted and consisiing chiefly of ciay soils with a high swelling potential, so�is with a permanent high water table, sods with a hardpan or clay layer at or near the surface, and shatlow soils over nearly impervious material. These saas have a very slow rate of water transmission. ' From SCS, TR-55, Second Edition, June 1986, Exhibic A-1. Revisio�s made from SCS, Soi! Interpretation Record, Form �5, September t988. 1 . � 3.�.2-2 II/92 KING COUNTY, WASHINGTON, 5 URFACE WATER D ESIGN MAYUAL � FIGURE 3.5.1C 2-YEAR 24-HOUR ISOPLUVIALS '. 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' � _ � �� 0 1 2 3 4 S 6 7 8 Mlles � \ � �r�7 N ry�_� __ _�`- �,,,�1 i: sao.00a 3.5.1-8 `��� 1� KING COUNTY, WAS HINGTON, S URFACE WATER DESIGN MANUAL E FIGURE 3.S.IE 10-YEAR 24-HOUR IS�PLLJVIALS _ 2.y ----- - ,F,-�- �-.• -=�-- •--- •-- ---- --- ---•-•- 22 ,��, ' � '� '„ ' -- _ - � ' � �l � � � r � ;.� � �. 24 r 1 =o ��' 1 �;�r j� — . f — - < i � 4_;6-� , , - � 25 i � � T' 1 ��"� _ � ' _ O-� ,i''�'` � �; ,�_� ,— � V — ; a�. �. . `� / � � ? a � -8 t 2 i -�` � i I 1 ,"y a -- { •� _--� �� ` `�.� � �` � ; �� � " _� _ t � � 2`g ��. �� tr '''1'•�- r�.,�.,. � - _ �, t _ -�'. ' �-- - ; , � ,� I� i � ,� � � �� , •. �. �� { ; 1 , , _ \ �_ _` Yrr�i' 7 1 1 _ � � ..�.�i .I F, ,•' �r '-iLE + , v I� � ... ,� � 7 - ' / ,. __ � � -` 1 h _C.� I_'— ,G�' c ,, 3 y ,�, _ � '-'� .;i :::��.., ,: r: ,/��r ; �,� ` '� - j \ : ' '�1 � w�,�� ' �. ` � - � i� ,� .<,� �\ i "1 u�ar�.i ( 'a��� _ . .�� _��`. � I l. Y./ .� �'r i ri `� t � �1 u i � 32 � ,;, , r ;f.�� � I � __ . - — �: ��•' ) 1 • _ ' �.�. ' i � , �� —\ ° ��� � ' -_✓ ..- ``� �,,.: , ! 33 ;_ ' , �� � ' � `�' - iF �i " �� - ' `��fi� , �- ',' --�-=�- � - �� � ,,� � '�. � - � .•�;, � , � n: i = � . � � - � , i�� ' t � � 2.q�' � •� ' �� .4 r� ' , - _`_ �� �.-- /�� � - ' -_ ' _ � � ,. .� — -� - (� � i _ ` �� _\ I'1 +ie� � a.T _ .� \ I l ` � + l + -.•� � f v�'�— —� i� �j � ; �� I' 'A' � � `�: o , ' �i ' '` `�-" � � - � i � : ' ��� - I i� � �� '��( I � � �k ` � _ ,. .\'� � . � � ,' -� I 4 ` _ i' '� � C , , � I'J f! �';i 1 � C � �,L _ ' _ , � i j_I � � i : � � � -- _ G�' 1 i I � � M ' � � -�,�- � y � ) � �.\ \ � �� � !' �-� '= '� ; � ' � � _� � " I i ��� _ � 7 - ��� ` ' ,� _ -,=�, ,, ;� I� ��.. ,;F _ � _ , r. _ .ti' � - . �+r i � � — .' - � '�, d � �— ``' - �`, ` _ - � �- •'', p - \ i _ �- "s`—�--�-----�—�.,�y — ? i .' �� l• � �fI l i 4 , � � - -- � 10-YEAR 24—�-IOUR PREC�PITATION � ' i o� ' � -��.�4: � 3.4� ISOPLUVIALS OF 10-YEAR 24-#iOUR �' � _ TOTAL PREC1PfTATION IN INCHES r���,` ' � _ " ' � �. � _..�� � �. 0 1 2 3 4 S 6 J 8 Mlles - U � f� : � r in ���G, —� 4(1 KING CO UNTY, WASHINGTON, S URFaCE wATER DESIGN M ANUAL FIGURE 3.S.1H 100-YE�R 24-HOUR ISOPLUVIALS 3 p-----=,� - 1 _ , ,�. „��.. ._�__. . _.----- -� ------ � �� 3 r ` '. .� ' + ' -� _ . i _�c---------- �z �t - � � 3 � �, � .— � - � �, , ,•S 1 � � 34 , ' - � ' � , f —��•, _ -�-=� � ' � � .^... 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'� C�. � +"? \ � � ! � \ �\� � -'�=.� � �._. ` t �� � � �. .'. ' _� �'�' �� � � � ��• _� �' )0-YEAR 24-HOUR PRECIPITATION o - p�• + - . � ' ' , fi.0.� i 3.4��ISOPLUVIALS OF 100-YEAR 24HOUR p�� � — , 5.Jr � TOTAL PREClPITATION IN INCHES 0►• � � _ _ � , _ � �.. �..1 ` �J'��l 0 I 2 3 s S 6 7 8 Mlles � ��—�� 3.5.1-13 �`� �O ?�� ```�'• - .�,,. KING COUivTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TABLE 3.5'B SCS WESTERN WASHINGTON R[Ji�lOFF CURVE NUMBERS . �� SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982� Fiunoff curve numbers tor selected agricuitural, suburban and urban land usa for Type tA rainfail distribution, 24-hour storm duration. CIJRVE NUMBEAS BY HYDROLOGIC S GROUP LAND USE DESCAIPTION A 8 C 0 Cultivated land(1): winter condRion 86 91 94 95 Mountain open areas: low growinq orush and grasslands 7a 82 89 92 Meadow or pasture: I FS 78 85 89 Wood or `oresi lana: undisturbed or older second growth 42 64 16 81 Wood or `ores; land: young second gtowtn or brush �� 72 8� 86 Orchard: with cover crop 81 88 92 94 Open saaces, lawns, parks, golf courses, cemeceries. lands:,aping. good condRion: grass cover on 75% or more oi;he area 68 3C O 90 fair condrtion: grass cover on 50°,6 ro 75% of the area 77 85 � 92 Gravel raads and parking lots 76 85 89 91 � Dirt roads and parking lots ' 72 82 87 89 (r � t impervious surraces, r,avement, roofs, etc. 98 98 98 98 Cpen water bodies: lakes, wetlands, ponds, 2tc. I t 04 1 CO 0 t 0o � Sinqle Family Residentia! (Z) Dwelling Unit/Gross Ac;e � Impervious (3) 1.0 DU/GA 15 Separate curve numher t.5 OU/GA 20 shall be selected 2.0 DU/GA 25 for pervious and 2.5 DU/CA 30 impervious portian 3.o DU/GA 3a ot the site or basin 3.5 DU/GA �8 a.0 DU/GA a2 a.s au/�,� as s.o ou/�� � 5.5 DU/GA 50 . 6.0 DU/CaA 52 0.5 DU/GA �4 7.0 DU/Gr, 5& Planned unit developments. °6 impervious condominiums, apartments, must be camputed commercial business and industnal areas. � (1) For a more detailed descnption or agnculturat lana use curve numbers refer to National Engineenng Handbook, Section a, Hydrology, Chapter 9, August 1972. {2) Assumes roof and driveway runo'rf is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in qood condition for these curve numbers. r � ' � � 3.�.�-3 11/9_ Existing Condition Event Summary: BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event ------- (cfs) (hrs) (ac-ft) ac /Loss Existing Condition 0.63 7.83 0.1876 1.37 SBUH/SCS kc24hr 2 yr Existing Condition 0.97 7.83 0.2877 1.37 SBUH/SCS kc24hr 10 yr Existing Condition 1.34 7.83 0.3991 1.37 SBUH/SCS kc24hr 100 yr Drainage Area: Existing Condition Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs Intv: 10.00 min Area CN TC Pervious 0.2690 ac 90.00 0.08 hrs Impervious 1.1030 ac 98.00 0.08 hrs Total 1.3720 ac Supporting Data: Pervious CN Data: Landscaping 90.00 0.2690 ac Impervious CN Data: Buildings 98.00 0.2270 ac Pavment 98.00 0.7880 ac Walks 98.00 0.0880 ac Pervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Fixed Assumes 5 min. 0.00 ft 0.00% 5.0000 5.00 min Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Fixed Assumes 5 minutes 0.00 ft 0.00% 5.0000 5.00 min Redeveloped Condition Event Summary: BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event ------ (cfs) (hrs) (ac-ft) ac /Loss Redeveloped Cond 0.61 7.83 0.1800 1.37 SBUHlSCS kc24hr 2 yr Redeveloped Cond 0.94 7.83 0.2790 1.37 SBUH/SCS kc24hr 10 yr Redeveloped Cond 1.13 7.83 0.3369 1.37 SBUHlSCS kc24hr 25 yr Redeveloped Cond 1.31 7.83 0.3896 1.37 SBUH/SCS kc24hr 100 yr Redeveloped Cond 0.13 7.83 0.0427 1.37 SBUH/SCS kc24hr 6-month Drainage Area: Redeveloped Condition Hyd Method: SBUH Hyd Loss Method: SCS CN Number Peak Factor: 484.00 SCS Abs: 0.20 Storm Dur: 24.00 hrs Intv: 10.00 min Area CN TC Pervious 0.4000 ac 90.00 0.08 hrs Impervious 0.9710 ac 98.00 0.08 hrs Total 1.3710 ac Supporting Data: Pervious CN Data: Landscaping 90.00 0.4000 ac Impervious CN Data: Buildings 98.00 0.2810 ac Pavment 98.00 0.4710 ac Walks 98.00 0.2190 ac Pervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Fixed Assumes 5 min. 0.00 ft 0.00% 5.0000 5.00 min Impervious TC Data: Flow type: Description: Length: Slope: Coeff: Travel Time Fixed Assumes 5 minutes 0.00 ft 0.00% 5.0000 5.00 min I i , � � ; � � ' � i '�� � ��� ,� . 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