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Home My WebLink About02776 - Technical Information Report - Drainage City of Renton, Washington � � � �� Sto�m D�ainage Report Prepared by: Brett K. Pudists Reviewed by: Mark A. Reeves, P.E. — � — — �� TRIAD ASSOCIATES April 6 , 1998 Triad Job No . 97 - 006 2 7 7� City of Renton, Washington Storm D�ainage Repo�t Prepared by: ENGINEER'S STAMP NOT VALID � Brett K. PUC�1StS UNLESS SIGNED AND DATED A. RE �P��g W�S�y�� I `� �a Reviewed by: " �.� , � Mark A. Reeves, P.E. , �� o �� Zoao, o �`�,c�, �� sS ONA1.R��G\ EXPIRES: 4/26/ � � � � C� •� TRIAD ASSOCIATES April 6 , 1998 Triad Job No . 97 - 006 TABLE OF CONTENTS INTRODUCTION.................................................................................................................................. 1 VICINITYMAP.....................................................................................................................................2 DRAINAGECONCEPT........................................................................................................................3 DOWNSTREAMANALYSIS................................................................................................................4 DETEN'I'ION CALCULATIONS..........................................................................................................5 DE'TEN'TION VAULT........................................................................................................................6 Onsite Existing Condition Hydrographs.......................................................................................... 6 Onsite Flow Allowable Release Rates.............................................................................................. 7 Onsite Developed Condition Hydrographs...................................................................................... 7 OnsiteFlow Level Pool Routing...................................................................................................... 8 UpstreamArea Hydrographs.......................................................................................................... 8 Combined Flow Allowable Release Rates........................................................................................ 9 Combined Flow Level Pool Routing.............................................................................................. 10 Theoretical...............................................................................................................................................10 Actual.......................................................................................................................................................12 LiveStorage.................................................................................................................................. 13 WaterQuality............................................................................................................................... 13 OverflowRiser.............................................................................................................................. 14 � DETENTION PIPE..................................................................................................................... ...... Onsrte Existing Condrtion Hydrographs........................................................................................ 14 � Onsite Flow Allowable Release Rates............................................................................................ 1 S ' Onsite Developed Condition Hydrographs.................................................................................... 1 S OnsiteLevel Pool Routing......................�-�---............--�--.._..--•--..................................................... 16 Upstream Area Hydrographs........................................................................................................ 16 Combined Flow Allowable Release Rates...................................................................................... 17 Combined Flow Level Pool Routing.............................................................................................. 18 ' Theoretical...............................................................................................................................................18 Actual......................................................................................................................................................20 LiveStorage.................................................................................................................................. 21 WaterQuality............................................................................................................................... 21 OverflowRiser.............................................................................................................................. 22 CONVEYANCE CALCULATIONS...................................................................................................23 WESTCONVEYANCE SYSTEM.............................................................................................................. 24 EASTCONVEYANCE Sl STEM............................................................................................................... 24 ARCHC[JLVERT.................................................................................................................................. 25 REL.00ATED SWALE............................................................................................................................ 26 EROSION CONTROL CALCULATIONS......................................................................................... 27 SEDIMENTAT[ON VAULT..................................................................................................................... 27 SEDIMENT.4"CIOh PIPE ......................................................................................................................... 28 STOR1�1 DRAINAGE REPORT FOR TALBOT RIDGE-PAGE - i � h�: - . ; Y -:. - , - APPENDIX Soils Map TIR for Springbrook Downstream Exhibit Table 3.5.2B —W. Washington Runoff Curve Numbers 2, 10, & 100-Year Isopluvials Water Works Output Figure 4.4-7J—Riser Inflow Curves Table 4.3.3A—Runoff Coefficients HGL Calculations Upstream Area Exhibit Flow Estimate Arch Culvert Nomograph Arch Culvert Specifications Water Works Output— TESC In Pockets at End of Report Existing Conditions E�ibit Developed Conditions Exhibit Pipe Tributary Area E�ibit STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-ii INTRODUCTION The proposed project is to construct 18 single family dwelling units on approximately 4.55 acres located between Talbot Road and 102"d AVE SE in the City of Renton. Please refer to the vicinity map located on the following page. More generally, the site lies within Section 31, Township 23 North, Range 5 East W.M. In order to provide site access, 102'� AVE SE will be extended approximately 300 feet to the north. South 47�' Place will then be constructed to provide access from the site to 102nd Ave SE. The 4.55 acre site is covered predominantly with a combination of scattered trees and brush. The site slopes from east to west at approximately 5 to 40 percent. Runoff will be collected in a tightline conveyance system and routed to one of two underground detention facilities. According to the "Soil Survey for the King County Area", the site is under(ain with Alderwood type `C' soils (see Soil.s MaJ� in appendix). i STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 1 �� ia� ,ry � �. � o s •sn� � � sr � � q, �I� sis 4r � �PR�RfY ��[µ� . � �{ � . � � � � s �ee� sc �e�n�sT sT ; b g s �a�TM sr ,� � : � � < ' I � s ioon� sr sE roora st ' sc �9on+st s sstr sr 5 �a2Ho st ' se �an+o sr _ b� s i9�r.� � i� Ui ST p►Y�, g < a KfN� �TAY � �' �H�'� � < _ S 1961N ST � , , & SE 196TH ST S 19E111 ST � ll' � s q^r.f'�y y , � � S�S c f67 lge� < � P� ' � o N N N � � � � S t00M Si 8 g � $ � N y� y� se soon� si �i � � � 1 � 8 s 3 VICINI'TY MAP Not to Scale STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 2 DRAINAGE CONCEPT The storm drainage system for the proposed project was designed with reference to standards found within the 1990 King County Surface Water Design Manual (KCSWDM). The onsite drainage system will convey runoff, via a tighline conveyance system, from the developed site and a portion of the frontage improvements (S. 47�' Place) to an underground detention vault located near the west property line. The detention vault will provide both live storage for stream bank erosion control and dead storage for water quality enhancement. Detained storm water will ultimately discharge to an existing tightline conveyance system located in the Springbrook project just west of the site. ; Runofffrom the remainder of the frontage improvements (S. 47`h Place and 102"d Ave SE) will drain to the proposed detention pipe located on the north side of S. 47`�' Place. The detention pipe will provide both live storage for stream bank erosion control and dead storage for water quality enhancement. The detained storm water will then discharge to an e�sting swale which flows to the north of S. 47`� Place. ' Both detention facilities were designed to provide peak rate runoff control for the 2, 10, and 100-year, 24-hour storm events. The facilities were designed such that the post- developed peak runoff rates are attenuated to the pre-developed peak runoff rates for each of the 2, 10, and 100-year, 24-hour storm events. A 30-percent volume correction factor (factor of safety) was applied to the live storage volume for each facility. Water quality was provided through the use of dead storage in each of the detention facilities. The volume of water quality storage required is equal to the runoff generated by the 24-hour design stonn event using a rainfall precipitation equal to 33% of the 2-year, 24-hour design storrn precipitation. STORM DRAINAGE REPORT FOR TALBOT RIDGE- PAGE - 3 DOWNSTREAM ANALYSIS Runoff leaving the site will connect with the Springbrook project's conveyance system located west of the site. A downstream analysis for the Springbrook project was performed by Triad Associates. Please reference excerpts from the Springbrook Technical Information Report located in the appendix of this report. In general, the downstream conveyance system is considered in"good" condition and shows "no evidence of drainage related problems". Runoff leaving the detention pipe located in S. 47`� Place will discharge to an existing swale. The swale, labeled as tributary #0010 by The King County Basin Reconnaissance Program, flows into tributary #0060 approximately 0.4 miles downstream of the site. Please reference the Downstream Exhibit located in the appendix of this report. Ultimately both tributaries flow into the Black River stream bed and are conveyed to the Green River. STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-�l DETENTION CALCULATIONS Runoff from the site and approximately 0.47 acres of the frontage improvements will be conveyed to the proposed detention vault located near the west property line. A separate conveyance system will direct runoff from the remainder of the frontage improvements to a detention pipe located along S. 47`t' Place. Each of the facilities were designed in the same manner. The detention calculations were performed using Engenious Systems Inc.'s hydrology program Water Works. Hydrographs were developed using S.B.U.H. methodology with a King County Type I-A (User 1) 24-hour rainfall distribution. Separate S.C.S. curve numbers were used for the impervious and pervious portions of the site. Using the onsite existing condition hydrographs, the allowable release rates were determined for the site in accordance with City of Renton standards. Specifically, the facilities were designed such that the post-developed peak runoff rates are attenuated to the pre-developed peak runoff rates for each of the 2, 10, and 100-year, 24-hour storm events. The onsite developed condition hydrographs were then routed through a theoretical structure to determine the theoretical volume of live storage. The theoretical volume of live storage was then increased by a 30-percent volume correction factor (factor of safety) to determine the actual volume of live storage required. Runoff from upstream areas is tributary to each of the detention facilities (see Existirig Condition Exhibit in appendix). Once the required detention volume was determined based on onsite flows, the hydrographs for the upstream area were added to the hydrographs for the onsite area and routed through the detention structure. The allowable ' release rates for each of the facilities were then re-determined to take into account flows from upstream areas. The outflow control structures were re-designed to allow flows from the upstream area to pass through the facilities while detaining the required detention STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE -5 volume. Thus, each facility provides the required volume of live storage, as calculated ' based on detaining onsite flows, and has release rates based on the combined flows from upstream and onsite areas. �� Please refer to the Fxistirrg and Developed Coriditiorr exhibits as well as Table 3.�.2B — S.C.S. Western Washington Runoff Curve Numbers located in the appendix of this report. I Based on King County isopluvial maps (see appendix) the total precipitation for the 2, 10, ' and 100-year, 24-hour storm events are 2.00", 2.90", and 3.90" respectively. A summary of the detention calculations for each facility is provided below. DETENTION VAULT Onsite Existin� Condition Hvdrographs The e�sting condition area consists of approximately 0.47 acres associated with S. 47`� Place in addition to 2.90 acres associated with the project site. Total Area= 3.37 Ac Impervious Area = 0.00 Ac @ CN = 98 Pervious Area = 3.37 Ac @ CN= 76 (forest} Time of Concentration= 50.80 minutes Reach 1: 300 ft Sheet Flow @ 4.0%, `n'= 0.40 (woods/brush) Reach 2: 140 ft Shallow Concentrated Flow @ 14.4%,`ks'=5 (woods/brush) Existin Condition H dro ra h Summaries Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2-Year 2.00 0.096 5061 760 10-Year 2.90 0.305 11601 500 100-Year 3.90 0.660 203 3 5 490 STOR11'1 DR�►I'�ACE REPORT FOR TALBOT RIDGE- PACI�: - G Onsite Flow Allowable Release Rates Using the existing condition hydrographs, the allowable release rates for the detention vault were determined in accordance with City of Renton Standards. These release rates were then used to calculate the required detention volume. The allowable release rates are as follows: 2-Year Allowable Release Rate = 2-yr Pre-developed flow = 0.10 cfs 10-Year Allowable Release Rate = 10-yr Pre-developed flow = 0.31 cfs 100-Year Allowable Release Rate = 100-yr Pre-developed flow = 0.66 cfs Onsite Developed Condition Hvdrograqhs The developed condition area consists of the e�sting condition area plus appro�mately 0.3 5 acres associated with the proposed cul-de-sac located south of the project (refer to Developed Conditions e�ibit). The dwelling units per acre was calculated to be 6.2 D.U. /G.A. (18 D.U. /2.90 Ac) which corresponds to 53% impervious. Total Area= 3.72 Ac Impervious Area = 2.11 Ac @ CN = 98 (pavement, roofs) 0.19 Ac - paved portion of culdesac 0.38 Ac - paved portion of S. 47`'' Place (410' x 40') 1.54 Ac- onsite roofs and pavement—(6.2 DU/GA= 53% impervious) Pervious Area = 1.61 Ac @ CN= 86 (landscaping, lawns) Time of Concentration= 5.00 minutes (assumed) Develo ed Condition H dro ra h Summaries Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2-Year 2.00 1.383 18552 470 10-Year 2.90 2.249 29658 470 100-Year 3.90 3.244 42427 470 STORM DRAINAGE REPORT FOR TALBOT RIDGE- PAGE- 7 Onsite Flow Level Pool RoutinQ A theoretical detention vault was sized to determine the required depth and theoretical volume of live storage for the site. The following level pool table summary represents the results of routing the onsite developed area 2, 10, and 100-year hydrographs through a theoretical detention structure. Please note that in all cases the discharge rates are less than or equal to the onsite allowable release rates. Please refer to the Water Works output located in the appendix for actual program output. ONSITE FLOWS-LEVEL POOL TABLE SUMMARY Description Inflow Storage Dischrg P. Stage Volume Outflow P. Time CFS ID ID FT CF CFS Min 2 Year Release 1.38 TT�O 02 347.26 13008 0.095 1460 10 Year Release 2.25 TI-�EO 02 348.70 15211 0.306 900 100 Year Release 3.24 TI�O 02 349.54 *16488 0.660 660 * Theoreticai volume of li�•e storage= 16,488 cubic feet. Upstream Area Hvdro�raphs Total Area= 2.16 Ac Impervious Area = 0.00 Ac @ CN = 98 Pervious Area = 2.16 Ac @ CN= 76 (forest) Time of Concentration= 50.98 minutes Reach 1: 300 ft Sheet Flow @ 5.0%, `n'= 0.40 (woods/brush) Reach 2: 20 ft Shallow Concentrated Flow @ 10.0%, `ks'=5 (woods/brush) Reach 3: 440 ft Shallow Concentrated Flow @ 7.3%, `ks'=5 (woods/brush) U stream Area H dro ra h Summaries Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2-Year 2.00 0.062 3244 760 10-Year 2.90 0.195 7435 500 100-Year 3.90 0.422 13034 490 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-8 Combined Flow Allowable Release Rates The allowable release rates for the vault were re-determined by adding hydrographs for the existing onsite area to the hydrographs for the upstream area_ The combined allowable release rates are as foilows: 2-Year Combined Allowable Release Rate = 0.16 cfs = 2 Yr. Onsite Existing Condition Hydrograph + 2 Yr. Upstream Area Hydrograph 10-Year Combined Allowable Release Rate = 0.50 cfs • = 10 Yr. Onsite Existing Condition Hydrograph + 10 Yr. Upstream Area Hydrograph 100-Year Combined Allowable Retease Rate= 1.08 cfs = 100 Yr. Onsite Existing Condition Hydrograph + 100 Yr. Upstream Area Hydrograph COMBINED FLOWS-HYDROGRAPH SUMMARIES DESCRIPTION AYD PEAK TIlVIE VOLUME AREA NUM CFS Min CF Ac 2 YR EXISTING—ONSTI'E 1 0.096 760 5061 3.37 , 10 YR EXISTING—ONSITE 2 0.305 500 11601 3.37 I 100 YR EXISTING—ONSITE 3 0.660 490 20335 337 � 2 YR UPSTREAM 4 0.062 760 3244 2.16 � 10 YR UPSTREAM 5 0.195 500 7435 2.16 100 YR UPSTREAM 6 0.422 490 13034 2.16 2 YR COMBINED ALLOWABLE RELEASE (1+4) 7 0.158 760 8305 S.S3 I 10 YR COMBINED ALLOWABLE RELEASE(2+5) 8 0.500 500 19036 5.53 � 100 YR COMBINED ALLOWABLE RELEASE(3+6) 9 1.082 490 33369 5.53 2 YR DEVELOPED—ONSIT'E 10 1.383 470 18552 3.72 10 YR DEVELOPED—ONSITE 11 2.249 470 29658 3.72 100 YR DEVELOPED—ONSITE 12 3.244 470 42427 3.72 , 2 YR VAULT INFLOW (10+4) 13 1.400 470 21796 5.88 ; 10 YR VAiJLT INFLOW (11+5) 14 2.376 470 37093 5.88 100 YR VAITLT INFLOW(12+6) 15 3.551 �70 55461 5.88 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-9 Combined Flow Level Pool Routin� The following level pool table summary represents the results of routing the combined 2, 10, and 100-year hydrographs through the theoretical detention structure. The plan view dimensions of this theoretical detention vault were then increased by the required volume correction factor (factor of safety) to obtain the actual detention vault dimensions. Thus, the actual and theoretical structures provide the same depth however the actual structure's volume has been increased to account for the factor of safety. A summary of the detention calculations for each of the facilities is provided on the pages that follow. Theoretical The following level pool table summary represents the results of routing the developed area 2, 10, and 100-year hydrographs through a theoretical detention structure. Please note that in all cases the discharge rates are less than or equal to the combined flow allowable release rates. Please refer to the Water Works output located in the appendix for actual program output. COMBINED FLOWS—THEORETICAL LEVEL POOL TABLE SUMMARY Description Inflow Storage Dischrg P.Stage Volume Outflow P. Time I CFS ID ID FT CF CFS Min �, 2 Year Release 1.40 'THEO C 344.47 12347 0.159 1460 10 Year Release 2.38 T'HEO C 346.31 15166 0.452 890 , 100 Year Release 3.55 TI-�O C 3�37.20 16519 1.076 550 COMBINED FLOWS-OUTFLOW CONTROL STRUCTURE COMBINATION DISCHARGE ID No. C DescripUon: COMBINATION STRUCTURE ; Structure: O �� Structure: W MULTIPLE ORIFICE ID No. O ' Description: ORIFICE RELEASE-ONSIT'E F'LOWS Outlet Elev: 336.40 Elev: 334.40 ft Orifice Diameter: 1.4375 in. Elev: 344.80 ft Orifice 2 Diameter: 2.875 in. NOTCH WEIR ID No. W Description: WEIR Weir Length: 0.4375 ft. Weir height(p): 10.1300 ft. Elevation : 346.53 ft. Weir Increm: 0.10 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 10 COMBINED FLOWS-THEORETICAL STAGE/STORAGE/ DISCHARGE TABLE RECTANGULAR VAtJLT ID No.T'f-�O Description: Theoretical Vault Length: ]02.00 ft. Width: 15.00 ft. STAGE STORAGE STORAGE DISCHARGE FT CF Ac-FT CFS 336.40 0 0.0000 0.0000 336.50 153 0.0035 0.0177 337.00 918 0.0211 0.0434 337.50 1683 0.0386 0.0588 338.00 2448 O.OSb2 0.0709 338.50 3213 0.0738 0.0812 339.00 3978 0.0913 0.0904 339.50 4743 0.1089 0.0987 340.00 5508 0.1264 0.1063 340.50 6273 0.1440 0.1135 341.00 7038 0.1616 0.1202 341.50 7803 0.1791 0.1265 342.00 8568 0.1967 0.1326 342.50 9333 0.2143 0.1384 343.00 10098 0.2318 0.1440 , 343.50 10863 0.2494 0.1493 344.00 11628 0.2669 0.1545 344.50 12393 0.2845 0.1595 345.00 13158 0.3021 0.2646 345.50 13923 0.3196 0.3567 346.00 14688 0.3372 0.4193 346.50 15453 0.3548 0.4705 347.00 16218 0.3723 0.8786 i 347.20 16524 0.3793 1.079�1 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 11 r Actual The following level pool table summary represents the results of routing the developed area 2, 10, and 100-year hydrographs through the actual detention structure. For the actual detention structure the plan view dimensions of the theoretical vault were increased in order to accommodate extra volume associated with the 30% factor of safety. Please note that in all cases the discharge rates are less than or equal to the combined flow allowable release rates. COMBINED FLOWS-ACTUAL LEVEL POOL TABLE SUMMARY Description Inflow Storage Dischrg P. Stage Volume Outflow P. Time CFS ID ID FT CF CFS Min 2 Year Release 1.40 ACT C 342.96 13383 0.144 1460 10 Year Release 2.38 ACT C 345.67 18907 0.380 1020 100 Year Release 3.55 AC'T C 346.95 21519 0.825 680 COMBINED FLOWS-ACTUAL STAGE/STORAGE/DISCHARGE TABLE RECTANGULAR VAiJLT ID No. ACT Description: Actual Vault-(w/factor of safety) Length: 136.00 ft. Width: 15.00 ft. STAGE STORAGE STORAGE DISCHARGE FT CF Ac-FT CFS 336.40 0 0.0000 0.0000 336.50 204 0.0047 0.0177 337.00 1224 0.0281 0.0434 337.50 2244 0.0515 0.0588 � 338.00 3264 0.0749 0.0709 338.50 4284 0.0983 0.0812 339.00 5304 0.1218 0.0904 339.50 6324 0.1452 0.0987 I 340.00 7344 0.1686 0.1063 i 340.50 8364 0.1920 0.1135 �� 341.00 9384 0.2154 0.1202 341.50 10404 0.2388 0.1265 342.00 11424 0.2623 0.1326 342.50 12444 0.2857 0.1384 343.00 13464 0.3091 0.1440 343.50 14484 0.3325 0.1493 344.00 15504 0.3559 0.1545 344.50 16524 0.3793 0.1595 345.00 17544 0.4028 0.2646 345.50 18564 0.4262 0.3567 346.00 19584 0.4�196 0.4193 346.50 20604 0.4730 0.4705 347.00 21624 0.4964 0.8786 347.20 22032 0.5058 1.0794 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 12 Live Storage In accordance with King County standards, a 30% volume correction factor was applied to the theoretical live storage volume to determine the required live storage volume. The theoretical live storage volume for the detention vault is 16,488 cubic-feet. The actual detention volume required is therefore 21,435 cubic feet (1.30x 16,488). A construction factor of safety was also added to the live storage volume to account for inaccuracies which may occur during construction of the detention structure. As designed, the detention vault provides 21,930 cubic feet of live storag� Water Oualitv Water quality will be provided through the use of dead storage. According to King County standards, the required water quality volume is equal to the total runoff from the developed condition 24-hour design storm event using 33% of the 2-year, 24-hour precipitation. (0.33)(Pz�T)_ (0.33)(2.00 in) = 0.67 inches I, Water uali H dro ra h Summa I Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. Water ualit 0.67 0.284 3990 470 i I The required volume to be used for water quality storage is 3,990 cubic fee� As ' designed, the detention vault provides 4,104 cubic feet of water quality storag� � STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 13 Overtlow Riser The overflow riser was sized to convey the 100-year undetained combined flow of 3.55 cfs (see combined flow hydrograph summary). The riser was designed assuming one foot of available head. Please reference the calculation below as well as Figure 4.4.7-J located I� in.the appendix. Q«;t-�« = 3.782�D2)�)�r� 3.55 = 9.739(D)(1.0)'n D = 0.97 feet = 11.64 inches The overflow riser tivas chosen to be I2 inches in diafneter. DETENTION PIPE Onsite Ezisting Condition Hvdrographs Total Area = 0.60 Ac Impervious Area = 0.00 Ac @ CN = 98 Pervious Area = 0.60 Ac � CN= 76 (forest) Time of Concentration=27.84 minutes Reach 1: 200 ft Sheet Flow @ 0.5°/a, `n'= 0.011 (pavement) Reach 2: 100 ft Sheet Flow @ 3.3%, `n'=0.40 (woods/brush) Reach 2: 110 ft Shallow Concentrated Flow @ 14.5%,`ks'=5 (woods/brush) Egistin Condition H dro ra h Summaries Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2-Year 2.00 0.018 901 520 10-Year 2.90 0.072 2065 490 100-Year 3.90 0.155 3621 480 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 14 Onsite Flow Allowable Release Rates Using the existing condition hydrographs, the allowable release rates for the detention pipe were determined in accordance with City of Renton Standards. These release rates were then used to calculate the required detention volume. The allowable release rates are as follows: 2-Year Allowable Release Rate = 2-yr Pre-developed flow = 0.02 cfs 10-Year Allowable Release Rate = 10-yr Pre-developed flow = 0.07 cfs 100-Year Allowable Release Rate= 100-yr Pre-developed flow= 0.16 cfs Onsite Develoaed Condition Hvdrographs Total Area = 0.60 Ac Impervious Area = 0.47 Ac @ CN= 98 (pavement) Pervious Area = 0.13 Ac @ CN= 86 (landscaping) Time of Concentration = 5.00 minutes (assumed) Develo ed Condition H dro ra h Summaries Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2-Year 2.00 0.263 3428 470 10-Year 2.90 0.407 5297 470 100-Year 3.90 0.568 7412 470 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 15 'I Onsite Level Pool Routins A theoretical detention pipe was sized to determine the required depth and theoretical volume of live storage for the site. The following level pool table summary represents the results of routing the onsite developed area 2, 10, and 100-year hydrographs through a theoretical detention structure. Please note that in all cases the discharge rates are less than or equal to the onsite allowable release rates. Please refer to the Water Works output located in the appendix for actual program output. ONSITE FLOWS-LEVEL POOL TABLE SUMMARY Description Inflow Storage Dischrg P. Stage Volume Outflow P. Time CFS ID ID CF [CFS] (Min] 2 Yr. Release 0.26 TI�O O 384.60 2277 0.017 1460 10 Yr. Release 0.41 TI-IEO O 38521 2426 0.068 770 100 Yr. Release 0.57 TI�O O 385.83 *2660 0.149 540 *Theoretical live storage volume=2,660 cubic fee� Unstream Area Hvdrographs Total Area= 2.68 Ac Impervious Area = 0.05 Ac @ CN = 98 (existing house) Pervious Area = 2.63 Ac @ CN= 86 (short grass) Time of Concentration= 21.67 minutes Reach 1: 300 ft Sheet Flow @ 4.8%, `n'= 0.15 (short grass) Reach 2: 110 ft Shallow Concentrated Flow @ 6.7%, `ks'=11 (short grass} U stream Area H dro ra h Summaries Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2-Year 2.00 0.405 8427 480 10-Year 2.90 0.839 15541 480 100-Year 3.90 1.368 24112 480 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 16 ONSITE FLOWS-HYDROGRAPH SUMMARIES DESCRIPTTON HYD PEAK TIME VOLUME AREA NUM CFS Min CF Ac 2 YR EXISTING—ONSITE 1 0.018 520 901 0.60 10 YR EXISTING—ONSITE 2 0.072 490 2065 0.60 100 YR EXISTING—ONSIT'E 3 0.155 480 3621 0.60 2 YR DEVELOPED—ONSITE 4 0.263 470 3428 0.60 10 YR DEVELOPED—ONSITE 5 0.407 470 5297 0.60 100 YR DEVELOPED—ONSITE 6 0.568 470 7412 0.60 WAT'ER UALITY—ONSIT'E 7 0.063 470 *839 0.60 Combined Flow Allowable Release Rates The combined flow allowable release rates for the detention pipe were determined by adding hydrographs for the developed onsite area to the hydrographs for the upstream area. The combined allowable release rates are as follows: 2-Year Combined Allowable Release Rate= 0.42 cfs = 2 Yr. Onsite Existing Condition Hydrograph+ 2 Yr. Upstream Area Hydrograph 10-Year Combined Allowable Release Rate= 0.91 cfs = 10 Yr. Onsite E�cisting Condition Hydrograph + 10 Yr. Upstream Area Hydrograph 100-Year Combined Allowable Release Rate = 1.52 cfs = 100 Yr. Onsite Existing Condition Hydrograph + 100 Yr. Upstream Area Hydrograph COMBINED FLOWS-HYDROGRAPH SUMMARIES DESCRIPTION HYD PEAK TIME VOLUME AREA NUM CFS Min CF Ac 2 YR EXISTING—ONSI"TE 1 0.018 520 901 0.60 �I 10 YR EXISTING—ONSIT'E 2 0.072 490 2065 0.60 100 YR EXISTING—ONSITE 3 0.155 480 3621 0.60 2 YR DEVELOPED—ONSITE 4 0.263 470 3428 0.60 10 YR DEVELOPED—ONSITE 5 0.407 470 5297 0.60 100 YR DEVELOPED—ONSITE 6 0.568 470 7412 0.60 2 YR UPSTREAM 8 0.405 480 8427 2.68 10 YR UPSTREAM 9 0.839 480 15541 2.68 100 YR UPSTREAM 10 1.368 480 24112 2.68 2 YR COMBINED ALLOWABLE RELEASE(1+8) 11 0.420 480 9328 3.28 10 YR COMBINED ALLOWABLE RELEASE(2+9) 12 0.911 480 17606 3.28 100 YR COMBINED ALLOWABLE RELEASE(3+10 13 1.523 480 27732 3.28 2 YR PIPE INFLOW(4+8) 14 0.651 480 118�5 3.28 I 10 YR PIPE INFLOW(5+9) 15 1.217 480 20838 3.28 100 YR PIPE INFLOW(6+10) 16 1.R96 480 31524 3.28 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 17 Combined Flow Level Pool Routing ' The following level pool table summary represents the results of routing the combined 2, 10, and 100-year hydrographs through the theoretical detention structure. The length this theoretical detention pipe was then increased by the required 30°/a volume correction �'� factor (factor of safety) to obtain the actual detention pipe. Thus, the actual and '� theoretical structures provide the same depth however the actual structure's volume has been increased to account for the factor of safety. A summary of the detention calculations for each of the facilities is provided below. Theoretical The following level pool table summary represents the results of routing the developed area 2, 10, and 100-year hydrographs through a theoretical detention structure. Please note that in all cases the discharge rates are less than or equal to the combined flow allowable release rates. Please refer to the Water Works output located in the appendix for actual program output. COMBINED FLOWS—THEORETICAL LEVEL POOL TABLE SUMMARY Description Inflow• Storage Dischrg P. Stage Volume Outflow P. Time CFS ID ID FT CF CFS Min 2 Year Release 0.65 TI�O O 380.61 785 0.305 540 10 Year Release 122 Tf�O O 382.38 1751 0.698 520 100 Year Release 1.90 TI-IEO O 385.33 2818 1.300 510 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 18 TIiEORETICAL STAGE/STORAGE/DISCHARGE TABLE CUSTOM STORAGE ID No.TI�O Description: TI-IEORETICAL DETENTION STRUCTURE STAGE STORAGE STORAGE DISCHARGE FT CF Ac-FT CFS 379.37 0 0.0000 0.0000 379.10 0 0.0000 0.2231 379.50 207 0.0048 0.2475 380.00 467 0.0107 0.2751 380.50 726 0.0167 0.3001 381.00 1002 0.0230 0.3231 381.50 1277 0.0293 0.5143 382.00 1546 0.0355 0.6292 382.50 1814 0.0416 0.7172 383.00 2056 0.0472 0.8139 383.50 2297 0.0527 0.9697 384.00 2484 0.0570 1.0752 384.50 2671 0.0613 1.1662 385.00 2777 0.0638 1.2485 385.30 2793 0.0641 1.2947 385.40 2869 0.0659 1.3097 COMBINED FLOVVS-OUTFLOW CONTROL STRUCTURE MiJLTIPLE ORIFICE m No. O Description: Orifice Discharge Oudet Elev: 377.37 Elev: 375.37 ft Orifice I Diameter: 2.500 in. Elev: 381.15 ft Orifice 2 Diameter: 3.250 in. Elev: 382.98 ft Orifice 3 Diameter: 2.3750 in. i STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 19 Actual The following level pool table summary represents the results of routing the developed area 2, 10, and 100-year hydrographs through the actual detention structure. For the actual detention structure the length of the theoretical pipe were increased in order to accommodate extra volume associated with the factor of safety. Please note that in all cases the discharge rates are less than or equal to the combined flow allowable release rates. COMBINED FLOWS-ACTUAL LEVEL POOL TABLE SUMMARY Description Inflow Storage Dischrg P.Stage Volume Outflow P. Time CFS m ID FT CF CFS Min 2 Year Release 0.65 ACT O 380.31 833 0.291 540 10 Year Release 1.22 ACT O 381.99 2051 0.628 530 100 Year Release 1.90 ACT O 384.21 3407 1.114 520 ACTUAL STAGE/STORAGE/DISCHARGE TABLE CUSTOM STORAGE ID No. ACT Description: ACTUAL DET'ENTION PIPE STAGE STORAGE STORAGE DISCHARGE FT CF Ac-FT CFS 377.37 0 0.0000 0.0000 379.10 0 0.0000 0.2231 379.50 276 0.0063 0.2475 i 380.00 621 OA 143 0.2751 380.50 966 0.0222 0.3001 381.00 1333 0.0306 0.3231 381.50 1699 0.0390 0.5143 382.00 2056 0.0472 0.6292 382.50 2412 0.0554 0.7172 383.00 2734 0.0628 0.8139 383.50 3055 0.0701 0.9697 384.00 3304 0.0758 1.0752 384.50 3552 0.0815 1.1662 385.00 3694 0.0848 1.248� 385.30 3715 0.0853 1.2947 38>.40 3747 0.08fi0 1.3097 STORM DRAINAGE REPORT FOR TALBOT RIDGE- PAGE - 20 I i Live Storage In accordance with King County standards, a 30% volume correction factor was applied to the theoretical live storage volume to determine the reyuired live storage volume. The theoretical live storage volume for the detention pipe is 2,660 cubic-feet. The actual detention volume required is therefore 3,458 cubic feet (1.30 x 2,660). A construction factor of safety was also added to the live storage volume to account for inaccuracies which may occur during construction of the detention structure. As designed, the detentio►t pipe provides 3,717 cubic feet of live storag� Water Qualitv Water quality will be provided through the use of dead storage. According to King County standards, the required water quality volume is equal to the total runoff from the developed condition 24-hour design storm event using 33% of the 2-year, 24-hour precipitation. (0.33)(P2n)_ (0.33)(2.00 in) = 0.67 inches Water Quali H dro ra h Summa Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. Water ualit 0.67 0.063 839 470 The re uired volume to be used or water uali stora e is 839 cubic fee� As II 4 .f 4 h' g designed, the detention pipe provides 907 cubic feet of water quality storag� ', STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-21 Overflow Riser The overflow riser was sized to convey the 100-year undetained combined flow of 1.9 cfs (see combined flow hydrograph summary). The riser was designed assuming 0.5 feet of available head. Please reference the calculation below as well as Figure 4.4.7 J located in the appendix. Q��e = 3.782�2)�)in 1.90 = 9.739(D)(0.5)"� D = 0.84 feet = 10.1 inches The overflow riser was chosen to be 12 inches in diameter. �� STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-22 CONVEYANCE CALCULATIONS In accordance with the King County Surface Water Design Manual, the conveyance system is required to provide a minimum of six inches of freeboard within each catch basin for the 25-year, 24-hour design storm event. As designed, the tightline conveyance system provides a minimum of six inches of freeboard within each catch basin for the 100- year, 24-hour design storm event The hydraulic grade line calculations were performed using Eagle Point Software's computer program Storm Sewers. The program determines the flow rate in each pipe and then performs a standard step hydraulic analysis on the pipe network. The methodology used for non-uniform flow analysis is the standard step energy balance. This procedure is used to determine the hydraulic grade line throughout the pipe network and is identical to that used for any open channel water surface profile. The steady state energy equation (Bernoulli equation) is used between upstream and downstream sections of each pipe in the network. The friction slope is then calculated by applying Manning's equation at the upstream and downstream ends and averaging the slope between them. The program then performs three iterations to pinpoint the hydraulic grade line. Computations begin at the most downstream pipe and continue in an upward direction. The rational method of analysis, with an initial time of concentration equal to 6.3 minutes, was used to find the flow in each pipe based on the area tributary to each catch basin. Please reference the Pipe Tributary Area Map located in the appendix of this report. A weighted runoff coefficient, respective of the impervious (C=0.90) and pervious (C = 0.25) areas tributary to the conveyance system, was used in the Rational Method flow calculations. Dwelling Units/ Gross Acre = 18 DU/2.90 GA = 6.2 DU/GA STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-23 According to Table 4.3.3A - Kurroff Coefftcients for Ratiofial Method of Artalysis (see appendix) the Rational Method runoff coefficient is 0.61. Tables summarizing the amount of freeboard availabie in each structure are included below. Ptease reference the HGL Calculations exhibit, in the appendix of this report, for actual computer output (including flow estimates). WEST CONVEYANCE SYSTEM The west conveyance system directs flows to the proposed detention vault. 100 YEAR DESIGN Catch Basin Rim Elev. HGL Elev. Freeboard CB 2 350.41 349.63 0.78 CB 3 355.85 354.54 1.31 CB 4 363.84 362.06 1.77 CB 4A 365.59 362.51 3.07 CB 4B 369.16 365.78 3.38 CB 4C 369.16 365.97 3.18 CB 5 363.84 362.24 1.59 CB 6 367.63 365.60 2.03 CB 7 377.57 375.54 2.02 CB 8 377.57 375.55 2.01 CB 9 386.85 38�3.92 1.93 EAST CONVEYANCE SYSTEM The east conveyance system directs flows to the proposed detention pipe. 100 YEAR DESIGN Catch Basin Rim Elev. HGL Elev. Freeboard CB 12 387.00 385.34 1.66 END CAP 395.00 388.91 6.08 CB 13 391.34 388.76 2.57 CB 14 387.63 386.36 1.26 CB 15 387.63 386.36 1.27 CB 16 392.04 390.14 1.90 CB 17 393.37 391.55 1.81 CB 18 393.5� 391.55 2.00 STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE -2-1 ARCH CULVERT In the developed condition, S. 47�' Place will be placed in the path of an existing drainage course. An arch culvert was sized to convey flows associated with the swale underneath the proposed roadway. The culvert was sized to convey the peak rate of runoff from the 100-year, 24-hour design storm event. The flow was estimated using Engenious Systems Inc.'s hydrology program Water Works. Hydrographs were developed, based on S.B.U.H. methodology, using a King County Type I-A (User 1) 24-hour rainfall distribution. Separate S.C.S. curve numbers were used for impervious and pervious portions of the basin. Please refer to the Upstream Area Ezhibits located in the appendix of this report for basin delineation. A summary of the flow estimate and culvert sizing process is provided below. Area Tributary to Arch Culvert The upstream soils belong predominately to hydrologic group `C' therefore runoff curve numbers were chosen accordingly. The impervious area for the upstream area was conservatively estimated assuming it would be developed at the same density as the "Fredericks Place" project (see Upstream Area Ezhibit). The Fredericks Place project was developed at appro�cimately 4.6 DU/GA which conesponds to 47% impervious (see Table 3.S.2B in appendix). Refer to the Flow Estimate exhibit for actual computer output. Total Area = 38.90 Ac Impervious Area = 18.28 Ac @ CN - 98 (roofs, pavement) Pervious Area = 20.62 Ac @ CN - 86 (landscaping) Time of Concentration = 5.0 minutes (conservative) 100 Year Peak Flow =32.62 CFS STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE -25 Arch Culvert Sizin� Based on the nomograph for Corrugated Metal Pipe-Arch Culverts (see Nomograph exhibit and Arch Culvert exhibit in the appendix) a 50" x 31" arch culvert has a flow area of 8.7 square feet and can convey the 100 year peak flow of 33 cfs with a headwater depth of 3.33 feet [0.9 x (31" x 1'/12")]. Due to product availability, a culvert with a slightly larger flow area will be used. As designed, the arch culvert will be 49"x 33" with 8.9 square feet of flow area. RELOCATED SWALE The existing drainage course will be relocated just west of its existing course. The relocated swale was sized, using Manning's equation, to convey runoff from the 100-year, 24-hour design storm event (calculated above to be 33 cfs). Manning's Equation: 1.49 *A*R� *S� Q n Where: n = 0.030 (roughness coefficient -grass lined swale) s = 0.01 (minimum swale slope) A = 8.042 square feet Q�f,� = 33 cfs As designed, a grass lined swale having a three foot wide bottom, 3:1 side slopes, and a minimum botton: slope of 1.0% can convey the required flo3v of 33 cfs with a flow depth of approximately 1.2 feet(A=8.042 square feet). STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-26 EROSION CONTROL CALCULATIONS The temporary erosion and sedimentation control plan was designed to reduce the discharge of sediment laden runoff from the site. The plan is comprised of temporary measures (rock entrance, filter fence, etc.) as well as permanent measures (hydroseeding). In general, runoff will sheet flow across cleared areas into temporary interceptor swales and be conveyed to either the proposed detention vault or proposed detention pipe. The volume and surface area of the proposed detention facilities were calculated to determine if they met the required sedimentation pond criteria set forth by King County. Hydrographs were generated for the 2-year, 24-hour storm event assuming a tributary area equal to the area being cleared (see Water Works—TESC exhibit). The sedimentation facilities were designed to have a surface area large enough to settle out the design particle (medium silt) at a 2-year inflow rate. The permanent outflow control structure for each facility will be used as the temporary dewatering orifice. A summary of the surface area calculations for each of the facilities is provided below. SEDIMENTATION VAULT I' Cleared Conditions Total Area = 3.72 Acres - Impervious Area = 0.00 Ac @ CN = 98 • Pervious Area = 3.72 Ac @ CN= 87 (bare dirt) Time of Concentration= 5.00 minutes Sediment Vault - H dro ra h Summa Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2 Year Cleared 2.00 0.809 12229 3.72 Required Surface Area= 2(Q2,�.)/0.00096 Required Surface Area= 2 (0.81)/0.00096 Required Surface Area= 1,688 square feet As designed, the Sediment i�ault provides approximately 2,040 square feet of surface area. STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE-27 SEDIMENTATION PIPE Cleared Conditions Total Area= 0.60 Acres Impervious Area = 0.00 Ac @ CN= 98 Pervious Area = 0.60 Ac @ CN= 87 {bare dirt) Time of Concentration = 5.00 minutes Sediment Vault - H dro ra h Summa Storm Precip. Peak Flow Volume Time of Peak Event in cfs ft3 min. 2 Year Cleared 2.00 0.130 1 972 0.60 Required Surface Area=2(Q2�.)/0.00096 Required Surface Area= 2 (0.13)/0.00096 Required Surface Area = 271 square feet As designed, the Sediment Pipe provides approximately 736 square feet of surface area at a depth of four fee� i � STORM DRAINAGE REPORT FOR TALBOT RIDGE-PAGE- 28 � � A � W a � � � � • • ec n lca n o��atlon �� e o�� SP GBROOK CITY OF RENTON, WASHINGTON TRIAD ASSOCIATES 11814 - 115th Avenue N.E. Kirkland, WA 98034 Phone: (206} 821-8448 Prepared by: Shawn G. Moore, E.I.T. Reviewed by: , Roy E. Lewis, Jr., P.E. ', .......�� Oy �, IEW�'•.� " �� •• , �,dF'K"sy,,� � r � � � ��A �`4�'�' � = «"'"'��,��'.: �� -""t� �� - ,��ti�� TRIAD ASSOCtATES `� I�� APRIL 24 1996 TRIAD JOB # 95 - 202 Section III: OFF-SITE ANALYSIS A downstream drainage analysis was performed on December 7, 1995, a cloudy and cold day. Please refer to the Downstream Drainage Map, located in the Appendix, along with the following description of the downstream system. There was a small quantity of runoff �, being conveyed within the existing drainage ditches and tightline storm drainage systems. ' Runoff from the site currently sheet flows in a westerly direction and is collected within ' the existing drainage ditch located on the east side of Talbot Road South. The drainage ditch is appro�cimately two to three feet deep and has side slopes of 2:1, with a one foot base width. The ditch runs northerly along Talbot Road South, at a slope of approximately one-half to one percent, while conveying flows through a series of(3) 12- inch diameter culverts. Immediately north of the subject property, flows are conveyed beneath an existing driveway via a 12-inch diameter HDPE culvert. Runoff then continues northerly within the ditch for appro�umately 200 feet. Then, runoff is collected within a City of Renton storm drainage system via a 12-inch diameter CMP culvert (located across from South 45th Place). Runoff is conveyed within this tightlined conveyance system to a point beyond one quarter-mile downstream. The downstream conveyance system was in good shape and showed no evidence of drainage related problems (flooding, erosion, etc.). The system appears to have more than adequate capacity to handle the e�cisting flows. The King County Sensitive Areas Folio was researched and the site was not found, nor was it tributary to (within at least a quarter mile), any sensitive areas (wetlands, erosion hazard areas, etc). As such, it is our opinion that a detention standard more restrictive than matching the pre-e�sting flows for the 2, 10, and 100-year, 24-hour storm events is not warranted. ' TECHNICAL INFOR117ATION REPORT- Pagc III-1 � � '`•r � i'� q I��• - �*�a,.�. 1 h�� 1�: �r u,:M,'U � ��: 4� . � • . 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I�� l � -.c. � � .. . � . �— � ... k:0.. � . r:� '�X. � h's'r�". . .,..,�� ., y . � i � + ` z � , �(�__._, _ � � O i� * �� i. � '�`: .�, pkp� ,Q l,r,� � � � N �� yv ._`- � �-�' '�'�U�: '`.' � - �Kr` � . ��+T'+ � •R d ,,�'#�F< .�Yi;. � � � � � . .. � Z "�' i. �b� . �'' � � ,'� �i =. � ..i•it � � �` r '� + z P ,_ � �; 3 ri , � i ;r.. y«, r�� ..y 7 � � � m I �y �,r� , r,,+' 'i, a � • 3 � cV I " � � c ,[:. .. . �..,.�R --- '" �,�!�' �X . �o r . �.•r � , � �A�fiF' �:� �`^w ' �. ,.:.�'J"�jl'J,Y�, t�r �,� •`,' • b1: � �w. � � OOtYJIH� ��, - � 3ava �,"t-'- --� �';� pV IY21 ,� �,... � ----, � ,e�u Q' .i_ W,: ~ � '' •� �� -��'� �� I .' � '' �� ji 1 �\ . ' ' �4 " "y, ..,`, .y . . . p , � '•- .., � � . � � , K • � 2.�. ' � .� .� �� ! � 1;�".'3 �?�,- `�w� n .y w m _ 'ity.�O �?a. � a Y I-. )� _ � ~� ,y __.. � _ �. _ ��--� Y� .. �' ` . r � r v — � . �r 7� . (�_ . ` .. SOIL LEGEND The fus�caD��al letter is the initiol one oF the soil�ome. A second copitol ktler, A, B,C,D, E,or F, indico�es�he closs of zlope. $Ymbols wilhoul a slope letter ore�hose of�early level soils. SYMBOL NAME Ag8 Aldervvood grovelly sandy loam,0 ro 6 percenr slopes AgC Alderwood ravell sondy loom,6 to 15 percenr slopes AgD Alderwood g�ave ly sandy loom, 15 to 30 percent slopes AkF Alderwood and Kitsap soils,very steep AmB Arents,Alderwood material,0 ro 6 percenr slopes• AmC Arents,Alderwood material,6 to 15 percenr slopes• An AreMs,Everett moterial• . BeC � Bea�site gravally sandy loam,6 to 15 percent slopes BeD Bea�site gravelly sandy loam, 15 to 30 percenr slopes BeF Bwusi�e gravelly sOr�dy.{oom;40�0�5 perccnt�!opco - - - Bh Bellirghom silf loom Br .Briscot silt�oom Bu Buckley silt loam Cb Coostal Bexhes Ea Earlmont silf loom Ed Edgewick fi�e sordy loam Ev8 Everett grovelly sandy loam,0 to 5 percent slopes EvC Everctt gravelly sardy loom,5 to 15 percent slopes � EvD Everett pravelly sandy loam, 15 to 30 percenr slopes EwC Everett-Alderwood gravelly sandy loams,6 to 15 pe�cent slopes InA Indianola laamy fine sond,0 to 4 percene slopes InC Indianola loamy fine sand,4 to 15 percent slopes � InD Indianola loomy Fine sa�d, 15 to 30 percent slopes Kp8 Kitsap silt loam,2 to 8 percent slopes KpC Kitscp silf loam�8 to 15 percent slopes Kp0 Kitsap zilt loam, 15 to 30 percenr slopes KsC Kla�s gravelly loomy sand,6 to 15 percent slopes Mo Mixed alluvial land NeC Nei�fon very gravelly loamy sa�d, 2 ro 15 percenr slopes Ng Newberg silt loam . Nk Nooksack silt loam � No Nwma sandy loam O� Orcas peot Os Qridia silt loom O+C Ovoll grovelly loam, 0 ro 15 percent slopes Ov0 Ovall grovelly loom, 15 io 25 percent zlopes OvF Ovall gravelly loam,40 to 75 percenr slopes Pc Pilchuck loamy fine sand Pk pilchuck fine sandy loam � P� Puget silty clay loam Py Pvyallvp fine sandy loam RaC Ragnar fine sandy loam,6 to 15 percent slopes RaD Rogr+ar fine wndy loom, I$to 25 percent siopes RdG Ragnar-Indianola assxiation,sloping• � 12dE Roqnar-Indianola association,moderately steep• Re Renton silt loam Rh Riverwosh Sa $alal silt loam $h $ommnmish silr loam Sk $eottle m�ck $m $Fqlcar m�ck Sn Si si�t loom . So $nohomish silf loom Sr Snohomish silf loom,thick surface variant Su $�Itan silt loam Tu T�kwila muck lk Urban land Wo Woodinville siit loom • The compositlon of these units Is more voriable rhan that of 1he orhers in�he orea,b�r It has been controlled well en«gh to interpret for the � expected vse of the soils. . � h I N (; (' O U N "1' 1", �1' �� S f 1 I h G l� O N, S 11 R F A C L-: W A 'I' E R [� E S I G N i�1 A N U A L (2) CN values can be area weighted when they apply to pervious areas of similar CN's (within 20 CN points). However, high CN areas should not be combined with low CN areas (unless the low CN areas are less than 15% of the subbasinl. In this case, separate hydrographs should be generated and summed to form one hydrograph. FICURE 3.5.2A HYDROLOGIC SOIL GROUP OF THE SOILS IN �:ING COUNTY HYDROLOGIC HYDROLOGIC SOIL GROUP GROUP• SOIL GROUP GROUP* Alderwood � Orcas Peat D Arents, Aldenvood Material Oridia D Arents, Everett Material B Ovall C Beausite C Pilchuck C_ Bellingham D Puget D Briscot D Puyallup B" Buckley D Ragnar B Coastal Beaches Variable Renton D Ea�tmont Silt Loam D Riverwash Variable Edgewick C Salal C Everett A/B 'Sammamish D Indianola A Seattle D Kitsap C Shacar D Klaus C Si Silt C Mixed Alluvial land Variable Snohomish D Neilton A Sultan C Newberg B Tukwifa D Nooksack C Urban Variable Normal Sandy Loam D Woodinville D ' HYDROLOGIC SOIL GROUP CLASSlFICA710NS A. (Low runoff potential). Soils having high infiltration rates, even v;hen thoroughly wetted, and consisting chiefly of deep, well-to-excessively drained sands or gravels. These soils have a high �ate of water transmission. B. (Moderately low runoff potential). Soils having moderate infiltration rates when thoroughly wetted, and consisting chieffy of moderately fine to moderately coarse texiures. These soils have a moderate rate of water transmission. CO. (Moderately high runoff potentiai). Soils having slow infiltration raies when thoroughly wetted, and consisting chiefiy of soils with a layer that impedes downward movement of water, or soils with moderately fine to fine textures. These soils have a slow rate of water transmission. ID. (High runoff potential). Soils having very slow infiltration rates when thoroughly wetted and consisting i chie(ly of clay soils with a high swelling potential, soils with a permanent high water table, soils wtth a ; hardpan or clay layer at or near the surface, and shallow soils over nea�ly impervious mater'�al. These soils have a very slow rate of water transmission. ` From SCS, TR-55, Second Edition, June 1986, Exhibit A-t. Revisions made from SCS, Soil Interpretation Record, Form �5, September 1988. 3.5.�_� 11/9� `` , � ".i. (%�-1_��, `�_ , , - -._._ I BLACK RIVER BASIN y_� - � �____ Renro� , : , ' ' � . J. l I ', � \. �� , �_�- �� Basin Boundary � • \, ---- . , Subcatchment Boundary '� �_\�� .—', ; ,1 - _ . _ - 0 3 '� ° � 9 Collection Point !,�, �i' °o � � o ��, -� �, o I �� Stream ','�, : i" 4 �-_.. ` � .,.-.J'' ��'� 000s Tributary Number _..., �' `�r�Kw�i� 1''� f �-- — —,} , ,� �0301 Proposed Project � �J `�� ! �i � ��. �.� -' � � �- I ,. ,�; ' - 0006� •. ,` r � E. , i �' ' I, ., i'� � � 7 � � ��'==� -. ; p 06A `, N i • ' � e. I � �I b G': �`- ,. �I � ' 3 � �; O��' I I _,o ____1�. � � � ; _ i �._ _ -_ I - . , ' j , l o � -�Z'��nn P i ,, ��.a� 1 .-,. .; � � ' z.,. o � t � 2 � SITE 1M 11. < . . . -'/.- Q d � : X�O� ,I �. -l- � JulY.1987 ;i/ -- � O i �I_ _ ' . �J -� I _ = s� .�hi F h � ` _ - �Y .. � _ __ -- ',-__ � � �I � � J � ..� . � �-- O . ... O., �� ' i ` -�_ � ;, t � 30 0301 i . � ,_ .. ,. I , � � 14 -}'. _ _ .___ � --�--- ,.�/ ' O . ; �. , _, -- 03 . � (': , � _- = _—i , i _ 14 � o �o2s� - -- -- �� ;1 � ; i ;, � ; - — -o � _ , ; - - - - �,� -- _ _ ; �; ! � 00�2 ,._ _�-=, ----- --- - --� - % - - - -030 , , �� - i {i� 16 1 � �, - - - -� � � 0 0 � � Des Mo;ne� ' , ;i ; -- , O �; ` �i ; � �+ -�� j 5 j � � . , �,, �.� � - • ��( �', / 1 �p? �� =� li' Kent i _ 0 5 ' �' / �`� '�/ i �. � \� '/,i ' - . i � ..� � . Y: , � � . i _ . � - . �n., : :�, . . _,,.ne �- �.. .�,�i.,.�,� . \ � �_. •� ;� � � ---O�p - - � --- -� - --- � _ .�.,.�.:�� .. .. f. I ;:.. � . .. � ,� {;— ---- t`' 1� jl I: . ; r c;-�. -- - - $ ... � , \ , - r �' � `� E:; � ` J' i : . ' __ — � , - - 0 6 0 , . �` ,'.• � - --- , �p�y o 00 � o ; � 1 _. ; oo •��.� op - %� 1�_` �-=� j os ; , , j - ` - � % � � � '_ � , - , � , � 9 0 7 , ., . :i ! ', , i �� . , �� i � ;. � , - I }� ; �-, � � ; -- � - � ;i °o�, G ' � ��I � —�� -- �- '!� —_ _._ � � ;' �; � ... ..... , ' ' � � _ � . _ 1�\`� I i i . � , ' I jl ! �� DOWNSTREAM EXHIBIT "1'rih. �C Colicct. Eristing Anticipatcd Itcm Rivei• Milc I'oint Cate�oi�v I'rop. I'roj. ConJitions and Prohlems Conditions and Problems Recommendations 12 OOOG 4, 10 Gcolo�y Channel downcuttin� at Problem will get much worse - Provide additional R/D facilities RM 1.40- upper end; bank erosion and as development proceeds in upper basin. 2.G0 ma�.s-wasting. Deposition along the r�vine and in the - Restrict development along ravine ahove 140th and at wet- upper basin. Ravine is edges. land below 'I'albot Rd. se;nsitive to hich flows in - Route n�noff around ravine or channel, and slopes are tightline it to bottom in a safe, susceptiblc to gullying. nonerosive manner (e Ily at Scdimcnt is filling a major RM 2.50). wetland. l:� OOOh 7 IIabitat Alluvial fan from upstream Killing of trces from sedi- Provide a sediment pond and increascd ItM 1.50 erosion; landslides filling ment inundation. Little or maintenance or reduce flows upstrcam wetland and blockinc no fish pas.s��ge. to nonerosive levels. stream for fish use. 1-� 0006 R Ilabitat 3' drop out of culvcrt Condition will remain. Improve system only if a fisheries IZM 1.70 under Talbot Rd with biologist deems thc Panther Creck no pool. Potential fish system viable for fish. barriers. IS OOOG 8 Ilahitat Two debris jams pose Condition will remain. Remove debris or improve passage IZM 1.75 potential fish barriers. through the debris jams. I�� 000�i lO [iahitat Extensive bank erosion, Worsening o[ current condi- Same as Trib. 0006, RM 2.55-3.00. RM 1.�0- channel downcuttina and tions. (See Item 19 below.) �.SS sedimentation has elimi- nated most pools, fish, and Uenthic org�nisms. I3oth largc organic dchris and bedlo�d material are active. 17 000�, � Ilabitat 12' waterfall and concrete No futurc fish access to If the upstream habitat justifies RM 1.95 channel creatinc fish upstrcam areas. improvement, then a fish ladder should barrier. be constructed over the falls. P:I3R.APC/mlm C-4 Trib. & Collcct. Cxisting Antic:ipated Item River Milc Point Cate�orv Prop. Proj. Conditions and Prol�lems Conditions and Problems Rccommendations l� 0006 ,4 Geology I.,��rge landslide (transla- Slide will continue to Direct surface n�noff away from RM 2.15 tional and rotational contribute to sedimentation top of slope to gravel pit f�ilure), with raw slope downstream. (to west). , remaining; ��Ilying of slope. Apparently c�u.sed I� hv combination of under- cutting by stream �nd routing of road drainage over slopc from abovc. 19 OOOC, 10 IIabitat Stream in good condition. Possible erosion and loss of - Maintain stream flows at non- RM 2.$5_ Setbacks and protective habitat if future develop- erosive levels 3.00 vegetation needed at points ment increases volume and - Maintain a natural stream corri- along the stream. Some rate of flow. dor from Panther I.ake down into cood pools and spawning and along Panther Creek. gravel in a few places. 20 0006 10 IIydrology 0301 Panther Iake is a #1-C Fut►�re development in this The sensitive nature of the I2M 3.40 wetland that provides a area will triple the amount wetland would require precise large amount of natural of impervious are�. The bound�ry surveys and control over storage; the downstream available area for regional the amount of water artificially system is in fair R/D facilities may soon be retained by the proposed control. condition with some exausted and the system Use Panther Lake as an R/D facili- eros�on. "The contributing will continue unchecked ty by constructing earthen berms drainage arca is not downstrcam. Erosive on the north and west sides of the currently densely devel- soils throughout the area wetllnd area; construct a control opcd. are further threatened outlet, enhance and increase the as higher �mounts of runoff capacity of the downstream channel will increase the rate at (stabilize with vegetation), and which the existing stream obtain easements. erocics. I i P:BR.APC/mlm GS �I K I N G C U U N '1� 1 , �'V ;� S I I I N G "I� O N, S U R F A C E W A "[' l: R D E S I G N M A N U q L TAI3LF;3.5.28 SCS 1i'I:STEI2N WASHING"fON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in igg2) Runoff curve numbers for selected agricultural, suburban and urban land use for Type tA rainfall distribution, 24-hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP LAND USE DESCRIPTION A B C D Cultivated land(t): winter cond'Rion 86 91 94 95 Mountain open areas: low growing brush and grasslands 74 82 89 92 Meadow or pasture: 65 78 85 89 Wood or forest land: undisturbed or older second growth 42 64 �6 8� Wood or forest land: young second growth or brush 55 �2 86 Orchard: with cover crop 81 88 92 94 Open spaces, lawns, parks, golf courses, cemeteries, i landscaping. good condition: grass cover on 7596 or more of the area 68 80 O 90 fair condition: grass cover on 50°,G I to 75°� of the area 77 85 90 92 , Gravel roads and parking lots 76 85 89 91 Dirt roads and parking lots 72 82 87 89 � Impervious surfaces, pavement, roofs, etc. 98 98 98 98 Open water bodies: lakes, wetlands, ponds, etc. 100 100 t00 Single Family Residential (2) Dwelling Unit/Gross Acre °,6 Impervious (3} 1.0 DU/GA t5 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.Q DU/GA 34 of the site or basin 3.5 DU/GA 38 4.0 DU/GA 42 y b 4.5 DU/GA 46 y� 5.5 DU/GA SO �.L 6.0 DU/GA 52 5� ' 6.5 DU/ A 54 7.0 DU/GA 56 Planned unit developments, �� impervious condominiums, apartments, must be computed commercial business and industrial areas. (i) For a more detailed description of agricultural land use curve numbers refer to National Engineering Handbook, Section 4, Hydrology, Chapter 9, August t972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are co�sidered to be in good condition for these curve numbers. - I1/9'_ 3.�.?-3 N. � � e So � �� p � 7 � �;7 =_____ __=___ --, -- -- � -- � I • ,� :' '` .� �; - �u;A; Wo ".^.T , -- .. � f; i �1 .- i W� � � . ., �M�94� !�, i i t , /•�7{�' � �� '�' i � i �� •z ,�`� � iyi4,�y � �� ' � �/�m• • } �j'f i�` .., � . J . .. , �. _` � c� t, ��. t ��, l�ti• � •• I�� 4 •; "~ Uf I � 4 � C15� �� • +�� J��. •,�•' ,'� •!�� •�� I _ :�. .��. , 11 �� _ . 1 '.� � � *� ' '='�' .py � � ,, •:� , �. .� � t ��,s Y ., ,r�:�' Ng i � �,,, �,�-. ' •� ; , . �a �; . � o� t {fi `. f C�� .� ' M:. � . �. �,. 3 . � - , . � � '� "'� � � `�� "�,. � �, ��, ,,. SITE ' �. ..� . ., �'r.:. � : . � .r,�r',��. 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' • �I�� .. � . - . � . . - • . � � �'��/�� . , � /�►l�i i�� . � • • • �� • . �.��'�,� - • • ' ��1 � , ��"': � . �-, -------- � ` ,..��, .. ... .� BASIN SUIvIlviARY BASIN ID: A1 NAME: 2 YEAR EXISTING-ONSIT'E SBUH METHODOLOGY TOTAL AREA..: 3.37 Acres BASEFI,OWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 2.00 inches AREA..: 3.37 Acres TIIvIE INTERVAL..: 10.00 min CN..: 76.00 TIl�1E OF CONC..: 50.80 min IIvIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 TcReach-Sheet L: 300.00 ns:0.4000 p2yr:2.00 s:0.0400 TcReach- Shallow L: 140.00 ks:5.00 s:0.1440 PEAK RATE: 0.10 cfs VOL: 0.12 Ac-ft TIME: 760 min BASIN ID: A2 NAME: 10 YEAR EXISTTNG-ONSITE SBUH METHODOLOGY RAINFALL TYPE..: USERl PERVIOUS AREA PRECIPITATION..: 2.90 inches AREA..: 3.37 Acres TIIvIE INTERVAL..: 10.00 min CN..: 76.00 TIME OF CONC..: 50.80 min IIviPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 TcReacli -Sheet L: 300.00 ns:0.4000 p2yr: 2.00 s:0.0400 TcReach -Shallo��L: 140.00 ks:5.00 s:0.1440 PEAK RATE: 0.30 cfs VOL: 0.27 Ac-ft TIME: 500 min il BASIN ID: A3 NAME: 100 YEAR EXISTING-ONSITE SBUH METHODOLOGY TOTAL AREA..: 3.37 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USERI PERVIOUS AREA PRECIPITATION..: 3.90 inches AREA..: 3.37 Acres I TIlvIE INTERVAL..: 10.00 min CN..: 76.00 TIIvIE OF CONC..: 50.80 min IMPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres I CN..: 98.00 I TcReach -Sheet L: 300.00 ns:0.4000 p2yr: 2.00 s:0.0400 I�I TcReach -Shallo�i�L: 140.00 ks:5.00 s:0.1440 PEAK RATE: 0.66 cfs VOL: 0.47 Ac-ft TIME: 490 min ' �' File: 9700fivault Detention Vault �Vater 1�1 orks Output BASIN SUMMARY BASIN ID: B1 NAME: 2 YEAR DEVELOPED-ONSITE SBUH METHODOLOGY TOTAL AREA..: 3.72 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USERl PERVIOUS AREA PRECIPITATION..: 2.00 inches AREA..: 1.61 Acres TIME INTERVAL..: 10.00 min CN..: 86.00 TIIv1E OF CONC..: 5.00 min IlvIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 2.11 Acres CN..: 98.00 PEAK RATE: 1.38 cfs VOL: 0.43 Ac-ft TIME: 470 min BASIN ID: B2 NAME: 10 YEAR DEVELOPED-ONSITE SBUH METHODOLOGY TOTAL AREA..: 3.72 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USERI PERVIOUS AREA PRECIPITATION..: 2.90 inches AREA..: 1.61 Acres TIME INTERVAL..: 10.00 min CN..: 86.00 TIME OF CONC..: 5.00 min IIVIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 2.11 Acres CN..: 98.00 PEAK RATE: 2.25 cfs VOL: 0.68 Ac-ft TIME: �370 min BASIN ID: B3 NAME: 100 YEAR DEVELOPED -ONSIT'E SBUH METHODOLOGY TOTAL AREA..: 3.72 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USERI PERVIOUS AREA PRECIPITATION..: 3.90 inches AREA..: 1.61 Acres TIIvIE INTERVAL..: 10.00 min CN..: 86.00 TIME OF CONC..: 5.00 min IMPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 2.11 Acres CN..: 98.00 PEAK RATE: 3.24 cfs VOL: 0.97 Ac-ft TIME: 470 min File: 97006vault Detention Vault Water Works Output BASIN SUMMARY BASIN ID: C 1 NAME: 2 YEAR EXISTING-UPSTREAM SBUH METHODOLOGY TOTAL AREA..: 2.16 Acres BASEFI,OWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PREC�ITATION..: 2.00 inches AREA..: 2.16 Acres TIIvIE INTERVAL..: 10.00 min CN..: 76.00 TIIvIE OF CONC..: 50.98 min IMPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 TcReach-Sheet L: 300.00 ns:0.4000 p2}7: 2.00 s:0.0500 TcReach-Shallow L: 20.00 ks:5.00 s:0.1000 TcReach-Shallow L: 440.00 ks:5.00 s:0.0730 PEAK RATE: 0.06 cfs VOL: 0.07 Ac-ft TIME: 760 min BASIN ID: C2 NAIviE: 10 YEAR EXISTING-UPSTREAM SBUH METHODOLOGY TOTAL AREA..: 2.16 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 2.90 inches AREA..: 2.16 Acres TIIviE INTERVAL..: 10.00 min CN..: 76.00 TIIvIE OF CONC..: 50.98 min IIvIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 PEAK RATE: 0.20 cfs VOL: 0.17 Ac-ft TIME: 500 min BASIN ID: C3 NAME: 100 YEAR EXISTING-UPSTREAM SBUH METHODOLOGY TOTAL AREA..: 2.16 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA � PRECIPITATION..: 3.90 inches AREA..: 2.16 Acres TIIvIE INTERVAL..: 10.00 min CN..: 76.00 �, TIIvIE OF CONC..: 50.98 min IMPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 � PEAK RATE: 0.42 cfs VOL: 0.30 Ac-ft TIME: 490 min File: 97006vault Detention Vault Water Works Output BASIN SUNIMARY BASIN ID: WQ NAME: WATER QUALITY-ONSITE SBUH METHODOLOGY TOTAL AREA..: 3.72 Acres BASEFI.OWS : 0.00 cfs RAINFALL T'YPE..: USER1 PERVIOUS AREA PRECIPITATION..: 0.67 inches AREA..: 1.61 Acres TIME INTERVAL..: 10.00 min CN..: 86.00 TIIvIE OF CONC..: 5.00 min IIvIPERVIOUS AREA ABSTRACT'ION COEFF : 0.20 AREA..: 2.11 Acres CN..: 98.00 PEAK RATE: 0.28 cfs VOL: 0.09 Ac-ft TIME: 470 min i ' i File: 97006vault Detention Vault Water Works Output Using the onsite existing condition hydrographs, the allowable release rates were determined for the site in accordance with City of Renton standards. These release rates were then used to calculate the required detention volume. The onsite developed condition hydrographs were then routed through a theoretical structure to determine the required depth of live storage. Once the required detention volume and depth were determined, the combined flows from the upstream and onsite areas were routed through the detention structure. The allowable release rates from the vault were then re-determined to take into account flows from upstream areas. The Outflow Control Structure was redesigned to allow flows from the upstream area to pass through the vault. Thus, the vault provides the required volume of live storage, as calculated based on detaining onsite flows, and has release rates based on the combined flows from upstream and onsite areas. Refer to the Onsite Flow and Combined Flow data on the pages that follow. ONSITE FLOWS-HYDROGRAPH SUMMARIES DESCRIPTION HYD PEAK TIME VOLUME AREA NUM CFS] Min] [CF] Ac] 2 YR EXISTING—ONSITE 1 0.096 760 5061 3.37 10 YR EXISTING—ONSITE 2 0.305 500 11601 3.37 100 YR EXISTING—ONSITE 3 0.660 490 20335 3.37 WATER UALITY 20 0.284 470 *3990 3.72 2 YR DEVELOPED—ONSITE 4 1.383 470 18552 3.72 10 YR DEVELOPED—ONSITE 5 2.249 470 29658 3.72 100 YR DEVELOPED—ONSIT'E 6 3.244 470 42427 3.72 *Required water quality volume Allowable release rates based on detaining onsite flows only: 2 Year =2 Year Existing = 0.10 cfs 10 Year = 10 Year Existing = 0.31 cfs 100 Year = 100 Year Existing = 0.66 cfs ONSITE FLOWS-LEVEL POOL TABLE SUMMARY Description Inflaw Storage Dischrg P. Stage Volume Outflo«� P. Time �, CFS ID ID FT CF CFS Min I 2 Year Release 1.38 TI�O 02 347.26 13008 0.095 1460 10 Year Release 225 TI�O 02 348.70 15211 0.306 900 100YearRelease 324 THEO 02 349.54 *16488 0.660 660 * Theoretical volume of live storage= 16,488 cubic feet. Filc: 97006��ault Detention Vault Water Works Output COMBINED FLOWS-EXISTING CONDITION HYDROGRAPH SUMMARIES DESCRIPTION HYD PEAK TIME VOLUME AREA NUM CFS Min CF Ac 2 YR EXISTING—ONSITE 1 0.096 760 5061 3.37 10 YR EXISTING—ONSITE 2 0.305 500 11601 3.37 100 YR EXISTING—ONSITE 3 0.660 490 20335 3.37 2 YR UPSTREAM 4 0.062 760 3244 2.16 10 YR UPSTREAM 5 0.195 500 7435 2.16 100 YR UPSTREAM 6 0.422 490 13034 2.16 2 YR COMBINED ALLOWABLE RELEASE 7 0.158 760 8305 5.53 HYD. 1 +HYD. 4 10 YR COMBINED ALLOWABLE RELEASE 8 0.500 500 19036 5.53 HYD. 2+HYD. 5 100 YR COMBINED ALLOWABLE RELEASE 9 1.082 490 33369 5.53 HYD. 3 +HYD. 6 Allowable release rates based on combined flows 2 Year =2 Yr Existing onsite+2 Yr Existing Upsveam =0.16 cfs 10 Year = 10 Yr E�sting onsite+ 10 Yr Existing Upstream =0.50 cfs 100 Year = 100 Yr Existing onsite+ 100Yr Existing Upstream = 1.08 cfs COMBINED FLOWS—DEVELOPED HYDROGRAPH SUMMARIES DESCRIPTION HYD PEAK TIME VOLUME AREA NUM [CFS] Min] [CF) Ac] WATER QUALITY 20 0.284 470 3990 3.72 2 YR DEVELOPED—ONSITE 1 1.383 470 18552 3.72 10 YR DEVELOPED—ONSITE 2 2.249 470 29658 3.72 100 YR DEVELOPED—ONSITE 3 3.244 470 42427 3.72 2 YR EXISTING—UPSTREAM 4 0.062 760 3244 2.16 10 YR EXISTING—UPSTREAM 5 0.201 490 7435 2.16 100 YR EXISTING—UPSTREAM 6 0.435 490 13034 2.16 2 YR VAULT INFLOW=HYD. 1 +HYD. 4 14 1.400 470 21796 5.88 10 YR VAiJLT INFLOW=HYD. 2+HyD, 5 15 2.376 470 37093 5.88 100 YR VALTLT INFLOW=HYD. 3+HYD. 6 16 3.551 470 55461 5.88 2 YR TI�ORETICAL RELEASE 18 0.159 1460 19726 5.88 10 YR TI�ORETICAL RELEASE 19 0.452 890 34557 5.88 100 YR TI-�EORETICAL RELEASE 20 1.076 550 52621 5.88 2 YR ACTUALRELEASE 21 0.144 1460 18323 5.88 10 YR ACTUALRELEASE 22 0.380 1020 31171 5.88 100 YR ACTUALRELEASE 23 0.825 680 48996 5.88 *Required water quality volume. File: 97006vault Detention Vault Water Works Output COMBINED FLOWS-OUTFLOW CONTROL STRUCTURE COMBINATION DISCHARGE m No. C Description: COMBINATION STRUCT'URE Structure: O Structure: W MULTIPLE ORIFICE ID No. O Description: ORIFICE RELEASE-ONSITE F'LOWS Oudet Elev: 336.40 Elev: 334.40 ft Orifice Diameter: 1.4375 in. Elev: 344.80 ft Orifice 2 Diameter: 2.875 in. NOTCH WEIR ID No. W Description: WEIIt Weir Length:0.4375 f[. Weir height(p): 10.1300 ft. Elevation : 346.53 ft. Weir Increm: 0.10 COMBINED FLOWS-THEORETICAL STAGE/STORAGE/DISCHARGE TABLE RECTANGLJLAR VAULT ID No.TI�O Description:Theoretical Vault Length: 102.00 ft. Width: 15.00 ft. STAGE STORAGE STORAGE DISCHARGE FT CF Ac-FT CFS 336.40 0 0.0000 0.0000 336.50 153 0.0035 0.0177 337.00 918 0.0211 0.0434 337.50 1683 0.0386 0.0588 338.00 2448 0.0562 0.0709 338.50 3213 0.0738 0.0812 339.00 3978 0.0913 0.0904 339.50 4743 0.1089 0.0987 340.00 5508 0.1264 0.1063 340.50 6273 0.1440 0.1135 341.00 7038 0.1616 0.1202 341.50 7803 0.1791 0.1265 342.00 8568 0.1967 0.1326 342.50 9333 0.2143 0.1384 343.00 10098 0.2318 0.1440 343.50 10863 0.2494 0.1493 344.00 11628 0.2669 0.1545 I 344.50 12393 0.2845 0.1595 345.00 13158 0.3021 0.2646 345.50 13923 0.3196 0.3567 346.00 14688 0.3372 0.4193 346.50 15453 0.3548 0.4705 347.00 16218 0.3723 0.8786 347.20 16�24 0.3793 1.0794 File: 97006vau1t Detention Vault Water Works Output COMBINED FLOWS-THEORETICAL LEVEL POOL TABLE SUMMARY Description Inflow Storage Dischrg P. Stage Volume Outflow P. Time CFS ID ID FT CF CFS Min 2 Year Release 1.40 TF�O C 344.47 12347 0.159 1460 10 Yeaz Release 2.38 TI-IEO C 346.31 15166 0.452 890 100 Year Release 3.55 THEO C 347.20 16519 1.076 550 COMBINED FLOWS-ACTUAL STAGE/STORAGE/DISCHARGE TABLE RECTANGiJLAR VAULT ID No. ACT Description: Actual Vault-(H�/factor of safety) Length: 136.00 ft. Width: 15.00 ft. STAGE STORAGE STORAGE DISCHARGE FT CF Ac-FT CFS] 336.40 0 0.0000 0.0000 336.50 204 0.0047 0.0177 337.00 1224 0.0281 0.0434 337.50 2244 0.0515 0.0588 338.00 3264 0.0749 0.0709 338.50 4284 0.0983 0.0812 339.00 5304 0.1218 0.0904 339.50 6324 0.1452 0.0987 340.00 7344 0.1686 0.1063 340.50 8364 0.1920 0.1135 341.00 9384 0.2154 0.1202 ' 341.50 10404 0.2388 0.1265 � 342.00 11424 0.2623 0.1326 II 342.50 12444 0.2857 0.1384 343.00 13464 0.3091 0.1440 343.50 14484 0.3325 0.1493 344.00 15504 0.3559 0.1545 344.50 16524 0.3793 0.1595 345.00 17544 0.4028 0.2646 345.50 18564 0.4262 0.3567 346.00 19584 0.4496 0.4193 346.50 20604 0.4730 0.4705 347.00 21624 0.4964 0.8786 347.20 22032 0.5058 1.0794 COMBINED FLOWS-ACTUAL LEVEL POOL TABLE SUA'IMARY Description Inflow Storage Dischrg P. Stage Volume Outflow P. Time CFS] ID ID FT [CF CFS Min] 2 Year Release 1.40 ACT C 342.96 13383 0.144 1460 10 Year Release 2.38 ACT C 345.67 18907 0.380 1020 100 Year Release 3.55 ACT C 346.95 21519 0.82� 680 File: 970(K�vault Detention Vault Water Works Output BAS1N SUMMARY BASIN m: B1 NAME: ROAD 2 YEAR DEVELOPED-ONSITE SBUH METHODOLOGY TOTAL AREA..: 0.60 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 2.00 inches AREA..: 0.13 Acres TIIv1E INTERVAL..: 10.00 min CN..: 86.00 TIIvIE OF CONC..: 5.00 min IlVIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: � 0.47 Acres CN..: 98.00 PEAK RATE: 0.26 cfs VOL: 0.08 Ac-ft TIME: 470 min BASIN ID: B2 NAME: 10 YEAR DEVELOPED-ONS1T'E SBUH METHODOLOGY TOTAL AREA..: 0.60 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USERl PERVIOUS AREA PRECIPTTATION..: 2.90 inches AREA..: 0.13 Acres TIlV1E INTERVAL..: 10.00 min CN..: 86.00 TIlViE OF CONC..: 5.00 min IlvIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.47 Acres CN..: 98.00 PEAK RATE: 0.41 cfs VOL: 0.12 Ac-ft TIME: 470 min ' BASIN ID: B3 NAME: 100 YEAR DEVELOPED-ONSITE ' SBUH METHODOLOGY , TOTAL AREA..: 0.60 Acres BASEFLOWS : 0.00 cfs ' RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 3.90 inches AREA..: 0.13 Acres TIME INTERVAL..: 10.00 min CN..: 86.00 TIIvIE OF CONC..: 5.00 min IMPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.47 Acres CN..: 98.00 PEAK RATE: 0.57 cfs VOL: 0.17 Ac-ft TIN1E: -170 min � BASIN SUMMARY BASIN ID: C1 NAME: 2 YEAR UPSTREAM AREA SBUH METHODOLOGY TOTAL AREA..: 2.68 Acres BASEFLOWS : 0.00 cfs RAINFALL T'YPE..: USER1 PERVIOUS AREA PRECIPITATION..: 2.00 inches AREA..: 2.63 Acres TIIvIE INTERVAL..: 10.00 min CN..: 86.00 TIIVfE OF CONC..: 21.67 min IlvIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.05 Acres CN..: 98.00 TcReach-Sheet L: 300.00 ns:0.1500 p2yr:2.00 s:0.0480 TcReach-Shallow L: 110.00 ks:11.00 s:0.0670 PEAK RATE: 0.41 cfs VOL: 0.19 Ac-ft TIME: 480 min BASIN ID: C2 NAME: 10 YEAR UPSTREAM AREA SBUH METHODOLOGY TOTAL AREA..: 2.68 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USERI PERVIOUS AREA PRECIPITATION..: 2.90 inches AREA..: 2.63 Acres TIlvIE INTERVAL..: 10.00 min CN..: 86.00 TIIVIE OF CONC..: 21.67 min IIv1PERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.05 Acres CN..: 98.00 TcReach-Sheet L: 300.00 ns:0.1500 p2yr:2.00 s:0.0480 TcReach-Shallow L: 110.00 ks:11.00 s:0.0670 PEAK RATE: 0.84 cfs VOL: 0.36 Ac-ft TIME: 480 min I BASIN ID: C3 NAME: 100 YEAR UPSTREAM AREA SBUH METHODOLOGY TOTAL AREA..: 2.68 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 3.90 inches AREA..: 2.63 Acres TIlvIE INTERVAL..: 10.00 min CN..: 86.00 TIME OF CONC..: 21.67 min IMPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.05 Acres CN..: 98.00 TcReach-Sheet L: 300.00 ns:0.1500 p2yr: 2.00 s:0.0480 TcReach-Shallow L: 110.00 ks:11.00 s:0.0670 PEAK RATE: 1.37 cfs VOL: 0.55 Ac-ft TIME: 480 min FILE: 97006PIPE DETENTION PIPE WATER WORKS OUTPUT BASIN SUNIlvIARY BASIN ID: WQ NAME: WATER QUALITY SBUH METHODOLOGY TOTAL AREA..: 0.60 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 0.67 inches AREA..: 0.13 Acres TIl��1E INTERVAL..: 10.00 min CN..: 86.00 TIME OF CONC..: 5.00 min IMPERVIOUS AREA ABSTRACTION COEFF : 020 AREA..: 0.47 Acres CN..: 98.00 PEAK RATE: 0.06 cfs VOL: 0.02 Ac-ft TIME: 470 min FILE: 9700fiPIPE DETEVTION PIPE 1'�'ATER 1�'ORKS 011TPUT Using the onsite existing condition hydrographs, the allowable release rates were determined for the site in accordance with City of Renton standards. These release rates were then used to calculate the required detention volume. The onsite developed condition hydrographs were then routed through a theoretical structure to determine the required depth and volume of live storage. Once the required detention volume and depth were determined, the combined flows from the upstream and onsite areas were routed through the detention structure. The allowable release rates from the detention pipe were then re-determined to take into account flows from the upstream area. The Outflow Control Structure was redesigned to allow flows from the upstream area to pass through the detention pipe. Thus, the detention pipe provides the required volume of live storage, as calculated based on detaining onsite flows, and has release rates based on the combined flows from upstream and onsite areas. Refer to the Onsite Flow and Combined Flow data on the pages that follow. ONSITE FLOWS-HYDROGRAPH SUMMARIES DESCRIPTION HYD PEAK TIME VOLUME AREA NUM CFS Min CF Ac 2 YR EXISTING—ONSITE 1 0.018 520 901 0.60 10 YR EXISTING—ONSITE 2 0.072 490 2065 0.60 100 YR EXISTING—ONSITE 3 0.155 480 3621 0.60 2 YR DEVELOPED—ONSITE 4 0263 470 3428 0.60 10 YR DEVELOPED—ONSIT'E 5 0.407 470 5297 0.60 100 YR DEVELOPED—ONSIT'E 6 0.568 470 7412 0.60 WATER UALITY—ONSITE 7 0.063 470 *839 0.60 *Required«�ater quality volume Allowable release rates based on detaining onsite flows onl��: 2 Year =2 Year Existing = 0.02 cfs 10 Year = 10 Year Existing = 0.07 cfs 100 Year = 100 Year E�sting = 0.16 cfs ONSITE FLOWS-LEVEL POOL TABLE SUA'IMARY Description Inflow Storage Dischrg P. Stage Volume Outflo�v P. Time [CFS] ID ID [FT] [CF] [CFS] [Min] 2 Yr. Release 0.26 TF�O O 384.60 2277 0.017 1460 10 Yr. Release 0.41 TI-�O O 38521 2426 0.068 770 100 Yr. Release 0.57 THEO O 385.83 *2fG0 0.149 540 *Theoretical li��e storage volume FILE: 97006PIPE DETENTION PIPE WATER WORKS OUTPUT COMBINED FLOWS-HYDROGRAPH SUMMARIES DESCRIPTION HYD PEAK TIME VOLUME AREA NUM CFS Min CF Ac 2 YR EXISTING—ONSITE 1 0.018 520 901 0.60 10 YR EXISTING—ONSITE 2 0.072 490 2065 0.60 100 YR EXISTING—ONSITE 3 0.155 480 3621 0.60 2 YR DEVELOPED—ONSITE 4 0.263 470 3428 0.60 10 YR DEVELOPED—ONSITE 5 0.407 470 5297 0.60 100 YR DEVELOPED—ONSITE 6 0.568 470 7412 0.60 2 YR UPSTREAM 8 0.405 480 8427 2.68 10 YR UPSTREAM 9 0.839 480 15541 2.68 100 YR UPSTREAM 10 1.368 480 24112 2.68 2 YR COMBINED ALLOWABLE RELEASE 21 0.420 480 9328 3.28 (HYD. 1 +HYD 8) 10 YR COMBINED ALLOWABLE RELEASE 22 0.911 480 17606 3.28 (HI'D. 2+HYD 9) 100 YR COMBINED ALLOWABLE RELEASE 23 1.523 480 27732 3.28 (HYD. 3 +HYD 10) 2 YR INFLOW=HYD. 4+HYD. 8 11 0.651 480 11855 3.28 10 YR INFLOW=HYD. 5+HYD. 9 12 1.217 480 20838 3.28 100 YR INFLOW=HYD.6+HYD. 10 13 1.896 480 31524 3.28 2 YR TI�ORETICAL RELEASE 15 0.305 540 11854 3.28 10 YR T�-IEORETICAL RELEASE 16 0.698 520 20838 3.28 100 YR T'HEORETICAL RELEASE 17 1.300 510 31558 3.28 2 YR ACTUAL RELEASE 18 0291 540 11855 3.28 10 YR ACTUAL RELEASE 19 0.628 530 20838 3.28 100 YR ACTLJAL RELEASE 20 1.114 520 31539 3.28 Allowable release rates based on combined flo�vs: 2 Year =2 Yr Existing onsite+2 Yr Existing Upstream =0.42 cfs 10 Year = 10 Yr Existing onsite+ 10 Yr Existing Upstream =0.91 cfs 100 Year = 100 Yr Existing onsite+ 100Yr Existing Upstream = 1.52 cfs COMBINED FLOWS—OUTFLOW CONTROL STRUCTURE MLJLTIPLE ORIFICE ID No. O Description: Orifice Discharge Outlet Elev: 377.37 Elev: 375.37 ft Orifice 1 Diameter: 2.500 i►t. Elev: 381.1�ft Orifice 2 Diameter: 3.2�0 in. Elc�� 2.98 ft Orifice � Diameter: ?_�,�i� i�l. THEORETICAL STAGE/STORAGE/DISCHARGE TABLE CUSTOM STORAGE ID No.TI�O Description:TI�ORETICAL DETENTION STRUCTURE STAGE STORAGE STORAGE DISCHARGE FT CF Ac-FT [CFS 379.37 0 0.0000 0.0000 379.10 0 0.0000 0.2231 379.50 207 0.0048 02475 380.00 467 0.0107 02751 380.50 726 0.0167 0.3001 381.00 1002 0.0230 0.3231 381.50 1277 0.0293 0.5143 382.00 1546 0.0355 0.6292 382.50 1814 0.0416 0.7172 383.00 2056 0.0472 0.8139 383.50 2297 0.0527 0.9697 384.Oa 2484 0.0570 1.0752 384.50 2671 0.0613 1.1662 385.00 2777 0.0638 1.2485 385.30 2793 0.0641 1.2947 385.40 2869 0.0659 1.3097 COMBINED FLOWS-THEORETICAL LEVEL POOL TABLE SUMMARY Description Inflow� Storage Dischrg P. Stage Volume Outflow P. Time CFS ID ID FT CF CFS Min 2 Year Release 0.65 TI-IEO O 380.61 785 0.305 540 10 Year Release 122 THEO O 382.38 1751 0.698 520 100 Year Release 1.90 THEO O 385.33 2818 1.300 510 FILE: 97006PIPE DETENTION PIPE WAT'ER WORKS OUTPUT ACTUAL STAGE/STORAGE/DISCHARGE TABLE CUSTOM STORAGE ID No. ACT Description: ACTUAL DETENTION PIPE STAGE STORAGE STORAGE DLSCAARGE FT CF Ac-FT CFS 377.37 0 0.0000 0.0000 379.10 0 0.0000 0.2231 379.50 276 0.0063 0.2475 380.00 621 0.0143 0.2751 380.50 966 0.0222 0.3001 381.00 1333 0.0306 0.3231 381.50 1699 0.0390 0.5143 382.00 2056 0.0472 0.6292 382.50 2412 0.0554 0.7172 383.00 2734 0.0628 0.8139 383.50 3055 0.0701 0.9697 ' 384.00 3304 0.0758 1.0752 384.50 3552 0.0815 1.1662 385.00 3694 0.0848 1.2485 385.30 3715 0.0853 12947 385.40 3747 0.0860 1.3097 COMBINED FLOWS-ACTUAL LEVEL POOL TABLE SUMMARY Description Inflow• Storage Dischrg P. Stage Volume Outflow P. Time CFS ID ID FT CF CFS Min 2 Year Release 0.65 ACT O 380.31 833 0.291 540 10 Year Release 1.22 ACT O 381.99 2051 0.628 530 100 Year Release 1.90 ACT O 384.21 3407 1.114 520 FILE: 97006PIPE DETENTION PIPE WATER WORKS OUTPUT STAGE STORAGE TABLE LJNDERGROUND PIPE ID No. P Description: DETENTION PIPE Diameter: 8.00 ft. Length: 92.00 ft. Slope...: 0.0050 ft/ft STAGE STORAGE STORAGE FT CF Ac-FT 376.87 0 0.0000 376.90 0.058 0.0000 377.00 2.286 0.0001 377.10 9.484 0.0002 377.20 23.298 0.0005 377.30 44.981 0.0010 377.40 68.794 0.0016 377.50 96.750 0.0022 377.60 129.28 0.0030 377.70 165.51 0.0038 377.80 204.94 0.0047 377.90 247.21 0.0057 378.00 292.03 0.0067 378.10 339.18 0.0078 378.20 388.48 0.0089 378.30 439.76 OA101 378.40 492.88 0.0113 378.50 547.72 0.0126 378.60 604.15 0.0139 378.70 662.08 0.0152 , 378.80 721.40 0.0166 378.90 782.04 0.0180 379.00 843.89 0.0194 � � 379.10 906.90 0.0208 I 379.20 970.97 0.0223 ' 379.30 1036 0.0238 379.40 1102 0.0253 ; 379.50 1169 0.0268 ' 379.60 1237 0.0284 379.70 1305 0.0300 I 379.80 1374 0.0315 379.90 1444 0.0331 i 380.00 1514 0.0348 380.10 1585 0.0364 38020 1657 0.0380 I 380.30 1728 0.0397 380.40 1801 0.0413 I 380.50 1873 0.0430 I 380.60 1946 0.0447 380.70 2019 0.0463 380.80 2092 0.0480 ' 380.90 2165 0.0497 381.00 2239 0.0�1�1 DETENTION PIPE EXHIBIT ' i� 381.10 2312 0.0531 381.20 2386 0.0548 381.30 2459 0.0565 381.40 2532 0.0581 381.50 2606 0.0598 381.60 2679 0.0615 381.70 2751 0.0632 381.80 2824 0.0648 381.90 2896 0.0665 382.00 2968 0.0681 382.10 3039 0.0698 382.20 3110 0.0714 382.30 3180 0.0'730 382.40 3250 0.0746 382.50 3319 0.0762 382.60 3388 0.0778 382.70 3455 0.0793 382.80 3522 0.0809 382.90 3588 0.0824 383.00 3653 0.0839 383.10 3718 0.0853 383.20 3781 0.0868 383.30 3842 0.0882 383.40 3903 0.0896 383.50 3962 0.0910 383.60 4020 0.0923 383.70 4077 0.0936 383.80 4132 0.0948 383.90 4185 0.0961 384.00 4236 0.0972 384.10 4285 0.0984 384.20 4332 0.0995 , 384.30 4377 0.1005 384.40 4419 0.1015 384.50 4459 0.1024 I 384.60 4495 0.1032 � 384.70 4528 0.1039 384.80 4556 0.1046 384.90 4580 0.1051 385.00 4601 01056 � 385.10 4615 0.1059 ' 385.20 4622 0.1061 , 385.30 4624 0.1062 385.33 4624 0.1062 � Dead/Live interface at elevation 379.10 DET'ENTION PIPE EXHIBIT K I N (� CO l) N l' 1', �1' �� S I I I N (; �[� O N, ti l� IZ I� �1 C' E W A T G I2 [� E ti I (� N �t ,\ N U �� L FIGURE 4.4.7J RISER INrLOW CURVFS — Weir Flow Orifice Flow ----- �_ -- _- - - -- ' 36 100 '' • �. ' — - 33 — �� 30 . � 27 c � ° — 24 t U a� U � � 21 � d � a � .. a� �' - 18 E U — � 7 � � 15 �, d � � . 12 10 � • 10 . � ---� ' _a - -- -- - � 3. 5 5 — -. �- - - . _— - - - �-- -.-� 1.9 O _._— - - _1 — - - T — — -- -- - � � - — 0.t o.s 1.0 10.0 HEAD IN FEET (measured from crest of riser) SOURCE: USDA-SCS QwiEq = 9.739 DH� QoaiFicE = 3•782 DzH1z Q in cfs, D and H in feet a.4.7-tO t/`x� I. I \ (� ( (1 l � N I 1 . \1 :\ S II I \ ( � IO \. ti � ' I: I :\ l I \1 \ I I I: I� I. 1 I ( � � \1 \ '� �I ,� � "C" Values The allowable runoff coefficients to be used in this method are shown in Table 4.3.3A by type of land cover. These values were selected following a review of the values previously acceptable for use in the Rational Method in King County and as described in several engineering handbooks. The values for single family residential areas were computed as composite values (as illustrated below) based on the estimated percentage of coverage by roads, roofs, yards and unimproved areas for each density. For drainage t�asins containin��Ye�'al_lanc�Gpyer types, the following formula may be used to compute a composite runoff coefficient "C�". C� _ ((C, x A,) + (Czw42)+... + (C„xA„))/A, where: A, = total area (acres) A,2� = areas of land cover types (acres) C,�,� = runoff coefficients for each area land cover type � TABLE 4.3.3A RUNOFF COEFFICIENTS - "C" VALUES FOR THE RATIONAL METHOD� _ _ T_ _ GENERAL LAND COVERS II IAND COVER � C � LAND COVER C II � Dense forest ! 0.10 Playgrounds 0.30 Light forest � 0.15 Gravel areas Pasture � Pavement and roofs 0:90 Lawns � 0.2 ! Open water (pond, lakes, wetlands) --------- -----1------- SINGLE FAMILY RESIDENTIAL AREAS I (Density is in dwelling units per gross acreage (DU/GA)) � ----- ---- - --- ------- -_ _ .__.. . ------ - - -- -- -----------� l LAND COVER � T LAND COVER ; � DENSITY � C � DENSITY � C j ; ' I I i � 0.20 DU/GA (1 unit per 5 ac.) 0.17 •• 3.00 DU/GA , 0.42 � � 0.40 DU/GA (1 unit per 2.5 ac.) � 0.20 � 3.50 DU/GA i 0.45 � � 0.80 DU/GA (1 unit per 125 ac.) � 0.27 I 4.00 DU/GA � 0.48 ; � 1.00 DU/GA � 0.30 : 4.50 DU/GA � 0.51 ; 1.50 OU/GA ; 0.33 � 5.00 DU/GA � 0.54 ; 2.00 DU/GA � 0.36 I 5.50 DU/GA 0.57 � 2.50 DU/GA 0.39 ' 6.00 DU/GA 0.60 ---- --- - --__l �-- For land covers not listed above, an area-weighted "C x At" sum should be computed based on the following equation: C x A, _ (C,xA,). + (CZxA2) � ...+(C„xA„). where A, _ (A, + AZ + ...+A„), the total drainage basin area. � (For use only in determining peak ciesign flow for analyzing and sizing pipes, culverts or channels) :� � Z-� 1 'n0 04/02/98 STORM SEWER SUhA'f11RY REPORT 100 YEAR DESIGN FILE: 97006.STM RAINFALL FILE: RENTON98.RND 100 YEAR DESlGN STORM I = 10.180/ ( Tc + 0.000) " 0.630 LINEAI DESCRIPTION IINC ARIRUNOFFCIINLTIMEIINLT IIINC CIAI INPUTQ IUNIFORMISIZE/IINVERT IPIPE I NVAL IHGLSLOPEIHYD GRD � VEL I DOWNLINEt ITOT ARIWEIGHTDI Tc ITOTL IITOT CIA1 TOTALQ IFLOWCAPITYPE IUP/DOWN ILEN IINVSLOPI JLC IUP/DOWN IUP/DOWN I I (ac) I C I (min) I(in/h) I (cfs) I (cfs) I (cfs) I(in) I (ft} I(ft) I(ft/ft) I (ft/ft) I (ft� � (ft/s) I I I I I I I I I I I I I I I 1 I CB 2 I 0.61 0.601 6.301 3.191 1.191 0.001 I 12D1 397.011 81 0.0121 0.0221 396.091 9.96 I DNLN = 0 1 4.91 0.621 8.881 2.571 7.821 �.821 3.91 12D1 346.931 I 0.0101 1.00 I 397.921 9.99 I I I I I I I I I I I I i I I 2 I CB 3 I 0.11 0.601 6.301 3.191 0.271 0.001 I 12D1 352.351 971 0.0121 0.0791 353.331 8.85 I DNLN = 1 I 4.3� 0.621 8.791 2.591 6.911 6.911 13.01 12D1 347.011 I 0.1191 1.00 I 399.631 8.80 I I 1 I I I I I I I I I I I I 3 I C8 9 1 0.11 0.601 6.301 3.191 0.231 0.001 I 12D1 359.901 1291 0.0121 0.0491 360.881 6.79 I DNLN = 2 I 9.11 0.621 8.591 2.641 6.621 6.B21 9.31 12D1 352.351 I 0.0591 1.00 I 354.541 B.6B I I I I I I I I I I I I I I I 9 I CB 5 I 1.21 0.601 6.301 3.191 2.221 0.001 I 12D1 360.341 311 0.0121 0.0061 362.291 2•83 I DNLN = 3 I 1.21 0.601 6.301 3.191 2•2z1 2•221 4.61 12D1 359.901 I 0.0191 1.00 I 362.061 2•83 I I I I I I I I I I I I I I I 5 I CB 6 � D.11 0.601 6.30� 3.191 0.111 • 0.001 I 12D1 364.13� 113� 0.0121 0.0261 365.021 6.07 I DNLN = 3 � 2.51 0.691 7.BB1 2-771 4.991 9•991 7.51 12D1 359.901 I 0.0371 1.00 I 362.061 5.72 I I I I I I 1 I I I I I 6 I I 6 I CB 7 I 0.11 0.901 6.301 3.191 0.321 0.001 I 12D1 374.071 1201 0.0121 0.0781 374.961 6.10 I DNLN = 5 I 2.51 0.691 7.541 2.B51 4.521 4.521 11.11 12D1 364.131 I 0.0831 1.00 I 365.601 5.75 I I I I I I I I I I I I 1 I I 7 I CB 8 I 0.11 0.901 6.301 3.191 0.321 0.00� I 12D1 374.571 301 0.0121 0.0001 375.551 0.41 I DNLN = 6 I 0.11 0.901 6.301 3.191 0.321 0.321 5.01 12D1 379.071 I 0.0171 1.00 I 375.541 0.90 I I I I I I I I 1 I I I I I I B I CB 9 I 0.11 0.901 6.301 3.191 0.341 0.001 I 12D1 383.351 2001 0.0121 0.043� 384.241 5.96 I DNLN = 6 I 2.21 0.621 6.901 3.161 9.38� 9.381 8.31 12D1 379.071 I 0.0461 1.25 I 375.541 5.58 I I I I I I i I I I I I I I I 9 I CB 10 I 2.11 0.601 6.301 3.191 9.081 0.001 I 12D1 383.851 301 0.0121 0.0201 385.511 5.20 I DNLN = 8 I 2.11 0.601 6.30� 3.191 4.081 9.081 5.01 12D1 363.351 I 0.0171 1.00 I 389.921 5.20 I I I I I I I I I I I I I I I 10 I CB 9A I 0.11 0.601 6.301 3.191 0.111 0.001 I 12D1 362.091 911 0.0121 0.0041 362.411 2.62 I DNLN = 3 I 0.31 0.601 7.631 2.831 0.561 0.561 6.01 12D1 359.901 I 0.0241 1.00 I 362.061 0.71 I I I I I I I I I I I I I I I 11 I CB 48 I 0.11 0.601 6.301 3.191 0.211 0.001 I 12D1 365.361 125I 0.0121 0.0251 365.661 2.53 I DNLN = 10 I 0.31 0.601 6.621 3.101 0.501 0.501 6.21 12D1 362.091 I 0.0261 1.25 I 362.511 1.58 I I I I I I I I I I I t I I I 12 I CB 9C I a•21 0.601 6.301 3.191 0.311 0.001 I 12D1 365.661 301 0.0121 0.0061 365.971 2.18 I DNLN = 11 I 0.21 0.601 6.301 3.191 0.311 0.31I 3.91 12D1 365.361 I 0.0101 1.00 I 365.781 0.97 STORM SEWER CUSTOM REPORT ' 100 YEAR DESIGN Catch Basin Rim Elev. HGL Elev. Freeboard CB 2 350.41 349.63 0.78 CB 3 355.85 354.54 1.31 CB 4 363.84 362.06 1.77 CB 4A 365.59 362.51 3.07 CB 4B 369.16 365.78 3.38 CB 4C 369.16 365.97 3.18 CB 5 363.84 362.24 1.59 CB 6 367.63 365.60 2.03 CB 7 377.57 375.54 2.02 CB 8 377.57 375.55 2.01 CB 9 386.85 384.92 1.93 FILE: 97006VAULT WEST CONVEYANCE SYSTEM HGL CALCULATIONS 04/02/98 STORM SEWER SUh4MRY REPORT 100 7EAR DESIGN FILE: 97006E.S1'M RAINFALL PILE: RENTON98.RND 100 YEAR DESIGN STORM I = 10.180/ ( Tc + 0.000) ^ O.c_� LINE#I DESCRIPTION IINC ARIRUNOFFCIINLTIMEIINLT IIINC CIAI INPUTQ IUNIFORMISIZE/IINVERT IPIPE I NVAL IHGLSLOPEIHYD GRD I VEL I DONNLINE/ ITOT ARIWEIGHTDI Tc ITOTL IITOT CIAI TOTALQ IFLOWCAPITYPE IUP/DOWN ILEN ISNVSLOPI JLC IUP/DOWN IUP/DGw1 I I (ac) I C I (min) I {in/h) I (cfs) I (cfs} I (cfs) I(in) I (ft) I(ft) I(ft/ft) I (ft/ft) I (ft) I (ft/s; I I I I I I I I I I I I I I I 1 I CB 12 I 0.11 0.901 6.301 3.191 0.901 0.001 I 36D1 380.091 21 0.0121 0.0001 385.331 0.7- I DNLN = 0 I 3.4� 0.651 9.511 2.961 5.971 5.471 51.11 36D1 380.031 I 0.0051 1.00 I 385.331 0.'- I I I i I I I I I I I I I I I 2 I END CAP I 0.01 0.901 6.301 3.191 0.031 0.001 I 12D1 388.821 511 0.0121 0.0701 388.911 1.1? I DNLN � 1 I 0.01 0.901 6.301 3.191 0.031 0.031 12.21 12D1 383.751 I 0.0991 1.00 I 385.341 0.0; I I I I I I I I I I I I I I I 3 I CB 13 I 0.11 0.901 6.301 3.191 0.231 0.001 1 12D1 383.931 351 0.0121 0.0091 385.651 6.55 I DNLN = 1 I 3.21 0.641 9.431 2.481 5.171 5.171 2.81 12D� 383.751 I 0.0051 1.00 I 385.341 6.55 I I I I I I I I I I I I I I I 4 I CB 14 I 0.11 0.901 6.301 3.191 0.341 0.00� I 12D1 384.481 1101 0.0121 0.0001 386.391 0.8' I DNLN = 3 I 0.31 0.901 7.311 2.911 0.681 0.661 Z•71 12D1 383.931 I 0.0051 1.25 I 366.331 0.87 I I I I I I 1 I I I I I I I I 5 I CB 15 I 0.11 0.901 6.301 3.191 0.401 0.001 I 12D1 384.631 311 0.0121 0.0001 366.361 0.5: � DNLN = 4 I 0.11 0.901 6.301 3.191 0.401 0.401 2.71 12D1 389.481 I 0.0051 1.00 I 366.361 0.5: I I I I I I I I 1 I I I I I I 6 I CB 16 I O.OI 0.901 6.301 3.191 0.091 0.001 I 12D1 388.591 501 0.0121 0.0141 389.461 6.59 I DNLN - 3 � 2.91 0.611 7.761 2-801 4.991 4.991 4.61 12D1 367.891 I 0.0191 1.00 I 388.761 6.59 I I I I I I I I I I I I I I I 7 I CB 17 I 2.81 0.601 6.301 3.191 5.391 0.001 I 12D1 389.791 571 0.0121 0.0101 390.711 6.57 � DNLN = 6 I 2.91 0.611 7.621 2.831 4.971 4.971 5.71 12D1 386.591 I 0.0221 1.25 I 390.141 6.33 I I I I I I I I I I I I I I I 8 1 CB 18 I 0.11 0.901 6.301 3.191 0.261 0.001 I 12D1 390.051 261 0.012� 0.0001 391.551 0.33 I DNLN - 7 I 0.11 0.901 6.301 3.191 0.261 0.261 3.91 12D1 389.791 I 0.0101 1.00 I 391.551 0.33 STORM SEWER CUSTOM REPORT , 100 YEAR DESIGN '�, Catch Basin Rim Elev. HGL Ele�. � [�ree�u:irei CB 12 387.00 385.34 1.66 END CAP 395.00 388.91 6.08 CB 13 391.34 388.76 2.57 CB 14 387.63 386.36 1.26 CB 15 387.63 386.36 1.27 CB 16 392.04 390.14 1.90 CB 17 393.37 391.55 1.81 CB 18 393.55 391.55 2.00 FILE: 970(KiPIPE EAST CONVEYANCE SYSTEM HGL CALCULATIONS � '��'"�- V• . AREA TRIBUTARY TO CULVERT = 38.90 Ac � AREA TRIB. TO DETENTION PIPE = 2.68 Ac . � .. ICULVERT .� I 47T" PL �; 6i1.07 40 �• �' �r • _ :. � + � 1.9 �- Time o f � � _;.._ . Conc. �a I k ' �3 i2 ii �� , I 4 _ � SCALE: 1" = ZUU' , „ �s „ � ' � � `�� o; 19 �1$ 17 16 u �� "st.i.7 , - -�16 \`` N m � o � ( IV_ .� l5 , ,�,6 �� ei 4 �z74r�� ` ` `- � � � . �,�e x� 399 A. ir�e.z� ,� �. ny � �� e, co . � ,a ,s � ip 3; " . i Ac, • � � s S.E. I 8 5TH. '�f� � _. .;�___C la re C. Bou�geo�s �,,3�` �e ai m �. a� � �— 1.69Ac. � � � 6 �7�� r a4 IS6 67Y! 6Q09 E012 6Q15 fA.1E 52.55 5� \ -v R4, r 4� 9 1 . I At. iB4�/ =' � � I R p F3 ( �G �H 6� �57 • 8'� - � ,isos 13 �-e,� Q !7 l76 m f � �.9i 60 b RST�� - IZ � � �i r� s: ao n t�.� �o r�: oi s �" .� E .41AC. ,��,�� z'a I 2 ;�•�3 4 5 � 6 7 , 8 y.;�r �� .� �% �4 - �, ,� • �BTr-+ � � � $ �I� � � a lo pJ � 137.4 27 D - �� I � . 62 �� .� � e,`, �.' � ra aP !„� .\ �30 ,_ � 37 60 - 60 39 � SS � Q � I$ .•�._� � ---------�'�+ '•9 �'S.G. 186TH c+ �l6� � 9 ' b` (O�N $ y,ty ,j21 �35k N7F ..a6\` , � �b� u . zae � so.si J� � '�`�\��?�� µ�'�� 4� 16 . �Q v � i o 'I; � • � � � h �r °� — o TR. C 8± �S �ab� q^ ,� r,r ►:1� i I I �� Y �s�': �ro� T$63 r• 6P , � cJ� 18toe,, � iseil I � o. ;- TR. 8 9 -^6463 S 61 �,�9 19 �pot 4, � i8 �l �,___: �. t_ -.—.�'07 �3574 � i �s� � r ,o �21 '�s ` � S"TRAC7 i.i� E,=, S5 '�� 46�` 47 sf � 20 � � 22 9g p5 a 0. ^�s o� � : �;, 45 s =' , 48�ft,�r. 59 � "' ,��'9 ,y�, -,s � Ve6Y r o �I4 L.J :- � � a3� r�s •� �� ,rJ 5 8 g'St SE. �0� 2 3 i R A C T E .+. ' '` 49 �Cj �s u , '�I��S i,�---- rjg�5�6 !3,r� ioo .h 5 R6.63 �ia �'.r l8?t tls� '� - I I o 0. 4 A c �B5 � �l _ n y�,Jrs�, ,� r � '.. u�' S� y X,y, 3tM ti`��5� r �e�. � � �- _ t3ao7 � a ,9� �5 SO N � v �, 24 � i2o i.IS 200. 42., 6,� y+�44 4B o rjJ.P$ �� A � � ��6 SC�32f q� ,� 105. 5 6 qa 1. 5 6 � 7S.P. 8.��4 " �10�,'� 138.9 g1731 6735 ; �6 65 � 29 (2) __,, l '�`°y'� q3 � � 52 �53 54 55 �' � 27 28 °' a` s _ /6 3 �`� '," �'" u9S a.� F' � � - ,,��t .tp �; ��J`� I � � �237 � i3637 .�. d3 35 65 6 �3 �bq �s M `e ,s ,j� 1250.5 �w �O` e �, ,,e m 42 ti,�, ,� S.E. � 187TH gPL'� g 556 eoo� S.P.683076 « �;�� tiy �J �'' .�s �9c `°9 �� '9a� r, �it a 6j ae .r � �c�3 �2� Sf �J ;i � � 6�. j� . m i� ` �l� Q� '�� m ao � �n �68 j�S ��. �o� � � �37 g 36 v '�° � _ rs ue $, a0 '' 39 -38� 3 ^ 35- 34 g 33 '� 32 1 � a�� 50�.�. ��/ �¢ 66� b 61.67 i4�J2 "' 13 0 1&�J.4T-- �So � 62585 74Aa `�9 7t N T 10 II ZSz.sO 124.55 90 6i �� .r � 9 0 4 4J ,;� (: � -w�.t N .� ios.z��l f , �'� < Tn'n : O 7 � � Y � ,� '� � !8 Z e. � S T.1'°' 60 � � no 50 'p,b �t-1''- j 5o ao (3) _ _. ,R F - ... � , i3 �Q9 S � e� ` 6 � � 8�tis � - 12 � . 'a �� '°- __��_ (2) `�r, .� � ,�� . ze13� i g ---= N o9 e� ' ♦ 5 ^�S.E.��,^ �,r . Cartw�;g t � Q �� "__. .. � ` UPSTREAM AREA g �� S.P 383067 �" � - - — 3098 I574_ _ � - '�°� ' � EXHIBIT - �»z �sc � i�, �P t,�. � � � F ,, � -'�� r (2)� � � (3) �� `v ' � '�_ �,� � ,-.�� 2 A �� m � l3) T,L "�� a ' ,rFyy�ls s9� �. _ \ \ , ��n � � � , • �� ,� A � r-� ' , ,.-� - , ♦ - � �:� c .• ,� � ; _.,� � �''/ . - � ��w - -'r ► � /� ' r'�" , ,, � � , , ,�" �' ' • . � � � � • � .+�► : = � �� • - . � � � . , � . , ; ' : ' � .,,� , � ' ■ ��/V- •� � . ' � � �-� ' , �L��il'iiT:Z�./�..�.�� /' 1 � � � ' � � � � � � � , � � � . . � �► �-�r ■ i � � � �i � � . � ■ � � �'�='� � _ , . . , � . � � : . , ■ � � . � . .- � ., � � , � ; , � , , -_ •rr . , -- . . - � - __ �- _ - � � � - �-.., � : � r , � � � � . i. =� ► �� y � � • : � -- ' � ■ ; C� l�J � � ► � ► / � i � 11`"'�" . , • ► � � � � ' � � � � � � � ► , BASIN SUNIIvIARY BASIN ID: D1 NAIvIE: 100 YR-AREA TRIB TO CULVERT SBUH METHODOLOGY TOTAL AREA..: 38.90 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 3.90 inches AREA..: 20.62 Acres TIME INTERVAL..: 10.00 min CN..: 86.00 TIME OF CONC..: 5.00 min IIvIPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 18.28 Acres CN..: 98.00 PEAK RATE: 32.G2 cfs VOL: 9.80 Ac-ft TIlVIE: 470 min FILE: 97006PIPE CULVERT FLOW ESTIMAT'E � e CHART a-6 5,000 �� s�-�•x �o�-i• a,000 a �2�N ' � �0 15'-4'x 9'-3' 3,000 EXAMPLE — ` W, 0 3) �� Siz�: 36'R Y2' � 4 � �: 2 000 0• POef• �- 12�-IO�x 8�-4' • � ;� 3 n� Hw* Nw W J D (f��t) 3 .' � o^ j =N II'-5'x 7'-3' I 000 ��) �.�0 2.0 d � (2) I.IS 2.1 2 _< :y 800 (3) 1.22 2.2 `' 9'-6' x 6'-5' 2 � �� 600 *p fn t��t Y . � ".= 500 : " I.'S = 8'-2' z 5'-9' 400 I300 I.� 1.5 7'-0' z S'-I' 200 -L- v 6'-I' x 4'-T' - --� ---i oC � Q � � ,, 0 1.0 1.0 � �- a 72' x 44' v 8O� /� = I.0 ` Z �,E./ •9 .9 � 65' z 40' � 60 �,�'j� N IN . . W 50 �=33 c FS/� � e .e .� D— ^ o' y� � 58 x 36 � 40 —� p x Q .8 Z V 30 �/ � Ia x 31' N / W .T � N � 20 F' i w HW SCALE ENTRANCE ? •7 I I ^_� 43'z 2T' /� 0 TYPE _ N / (I) H�adwoll W .6 .6 � 10 � � (2) Mit�r�d fo eo�lo�w � ,6 ' / 8 to slop• � C) �36'x 22' �3� Proj•ctiea a c 5 Q a � a W 'S .s .5 � To us• seolt (21 or (3) Dre�ttt = 29' z 18� 3 hori:onlally to •eala (I), th�e us• �troipht lnclin�d ifn• Mrouah 0 und C teol�t, or r�r�rs• ot 25' x 16' 2 i�lustror•e. .4 4 .4 2 2' x 13' ��—8 � I.0 I ` I .8 � .6 .35 '3� 18' x l l' .5 .35 HEADWATER DEPTH FOR C. M. PIPE-ARCH CULVERTS BUREAUOFpUBLICROAOSJAN.1963 WITH INLET CONTROL ARCH CULVERT NOMOGRAPH FULL , 90 �� Wetted Perimeler ' I � 80 I Aree � 70 � �I � P� N d I � .� � BO . Q,° 90 0 I m r 50 I ° Discharge � ,�� I Span '� Q I Fig. 1. Nomenclature of corrugared pipe-a�ch. 30 ' 20 � Hydraulic Redius � o• <�s A.a e��a ➢�" +, q��'`� 4,�,x'�'� v, a�� 0 �� r�',��r,at,�.s��,ca�,� �a-r�r��: � 'f' �, +� y �,��,;�� t �.>;� � x� � f.:.:*� s`.E�. '„�Y�H{�c��s,�`��,,�k ►�3��t�.'�'��r,� ?� � ^ 0.1 0�2 P oporUonal Valuea Ba ed n Full Condll ons, , � 2 � � :J,i�� I I,ntioul llimrn_v"n. xEqual Waferway , Penphery, S{xin, Nise, Area. B R�� Ri R�� ^ Inchea lnches` /nchea' SqF't Inchta (nches Inchea lnches F�9Uf6 3.51 Hydraullc elemenls 0� CI(Ct118f COffu9218d SIBB� and SIfUG1Uf81 � l 1 � 1 , 1 pipe-arches. � 15 18 11 1.1 4/Z 3/Z 10;,; 19/e 18 22 13 1.6 4 3/4 4 117/� 37-� �"r 21 25 16 2.2 5�/4 4 12�/4 33�/Z C 24 29 18 2.8 51/z 41/x 143/4 55 I.�y 30 36 22 4.4 6�/4 5 181/4 731/� � 36 43 27 . 7 5�/Z 21,",; 91-,p,; 42 50 31 8.7 8 6 25�/8 971/a � 58 36 . 9�/4 7 29�/e 1151� 54 65 40 14.3 0�/2 8 323/4 129t',, Table 3.15 Full-Flow Dala lor Corrugated Sleel Pipe Arches � 60 72 44 17.6 13/� 9 36;',: 142;� Corrupalions 2� x �h In. Corrugations 3 x 1in.and 5 x tln. � 66 79 49 21.3 13 y� 10 393/4 1451/2 - 72 85 54 25.3 41/Z 11 425/8 1541/2 Pipe• P�Pe � p�� Hydraulic Arch Hydr� � Equiv. Walarway fladius, Equiv. Watenvay RadF � piameler, Size, Area. A/nD Oiameler, Size. Ares, A/R � in. In. tt� It in. In. 11° h � 15 17 x 13 1.1 0.280 54 60 x 46 15.6 1.1( /1 1A 21 x 15 1.6 0.340 60 66 x 51 19.3 1.2< l 1 21 24 x 18 2.2 0.400 66 �3 x 55 23.2 1.3� � 24 28 x 20 2.9 0.462 72 B1 x 59 27A 1.�: � 30 35 x 24 4.5 0.5�3 78 87 x 63 32. � � 36 42 x 29 � 0.690 84 95 x 67 37.0 1_6( O q2 49 x 33 8.9 0.810 90 103 x 71 42.� 1.8( 4B 57 x 38 1 0.924 96 112 x 75 �8.0 1.8' Z 54 64 x 43 14.7 1.040 102 117 x)9 54.2 2.0: � 60 �1 x47 18.1 1.153 tOB 128xB3 60.5 2.1� 66 77 x 52 21.9 t 26B 114 137 x 87 67.� 2.2: 72_ _�x�L 2s.o � eo _120 4�x� ; BASIN SUNIIv1ARY BASIN ID: A1 NAME: SEDIMENT VAULT-2 YR CLEARED SBUH METHODOLOGY TOTAL AREA..: 3.72 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 2.00 inches AREA..: 3.72 Acres TIME INTERVAL..: 10.00 min CN..: 87.00 TIME OF CONC..: 5.00 min IIvfPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 PEAK RATE: 0.81 cfs VOL: 0.28 Ac-ft TIME: 480 min BASIN ID: B 1 NAME: SEDIMENT PIPE-2 YEAR CLEARED SBUH METHODOLOGY TOTAL AREA..: 0.60 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USERI PERVIOUS AREA PRECIPITATION..: 2.00 inches AREA..: 0.60 Acres TIIvIE INTERVAL..: 10.00 min CN..: 87.00 TIIvIE OF CONC..: 5.00 min IIvfPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 PEAK RATE: 0.13 cfs VOL: 0.05 Ac-ft TIME: 480 min BASIN ID: B2 NAME: SEDIMENT PIPE-2 YEAR CLEARED SBUH METHODOLOGY TOTAL AREA..: 0.60 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE..: USER1 PERVIOUS AREA PRECIPITATION..: 2.00 inches AREA..: 0.60 Acres TIIvIE INTERVAL..: 10.00 min CN..: 87.00 TIIvIE OF CONC..: 5.00 min IMPERVIOUS AREA ABSTRACTION COEFF : 0.20 AREA..: 0.00 Acres CN..: 98.00 PEAK RATE: 0.13 cfs VOL: 0.05 Ac-ft TIME: 480 min I HYDROGRAPH SUMMARY DESCRIPTION HYD PEAK TIME VOLUME AREA NUM CFS Min [CF [Ac] 2 YR CLEARED-VAULT 1 0.809 480 12229 3.72 2 YR CLEARED -PIPE 2 0.130 480 1972 0.60 FILE: 97006TESC TALBOT RIDGE WATER WORKS -TESC