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Home My WebLink AboutMISCNantucket Avenue Plat 2820 Park Avenue North Renton, Washington 98056 LUA14-001272 DRAINAGE REPORT October 14, 2014 Revised January 30, 2015 Prepared for: Nantucket Avenue, LLC Attn: Kathleen Nash 2812 257th Place SE Sammamish, Washington 98075 (206) 909-7308 Prepared by: Offe Engineers, PLLC Darrell Offe, P.E. 13932 SE 159t4 Place Renton, Washington 98058-7832 (425) 260-3412 office C" OF RENTON (425) 227-9460 fax RECENED darrell.offe@comcast.net JAN 3 4 BUILDING DIVISION (�Y Table of Contents • Technical information Worksheet • Section 1: Project Overview • Section 2: Conditions and Requirements Summary • Section 3: Offsite Analysis • Section 4: Flow Control and Water Quality Facility Analysis and Design • Section 5: Conveyance System Analysis and Design • Section 6: Special Reports and Studies • Section 7: Other Permits • Section S: CSWPPP Analysis and Design • Section 9: Bond Quantities, Facility Summaries, and Declaration of Covenant • Section 10: Operations and Maintenance Manual City of Renton TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner: Nantucket Avenue, LLC Address: 2812 257'' Place SE Sammamish, WA 98075 Phone: (425) 432-5932 Project Engineer: Darrell Offe, P.E. Company: Offe Engineers, PLLC Address/Phone: 13932 SE 159th Place Renton, WA 98058 --.(425) 260-3412 Part 3 TYPE OF PERMIT APPLICATION Subdivision Short Subdivision ❑ Grading ❑ Commercial ❑ Other Part 2 PROJECT LOCATION AND DESCRIPTION Project Name: Nantucket Avenue Plat Location Township: 24 North Range: 5 East Section: 32 Part 4 OTHER REVIEWS AND PERMITS ❑ DFW HPA ❑ COE 404 ❑ DOE Dam Safety ❑ FEMA Floodplain Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community Upper Kennydale Area, City of Renton Drainage Basin Lake Washington Part 6 SITE CHARACTERISTICS ❑ River ❑ Stream ❑ Critical Stream Reach ❑ DepressionslSwales ❑ Lake ❑ Steep Slopes ❑ Shoreline Management Rockery Structural Vaults Other NPDES ❑ Floodplain ❑ SeepsJSprings ❑ High Groundwater Table ❑ Groundwater Recharge ❑ Other Part 7 SOILS Soil Type Slopes Erosion Potential Erosive Velocities Qva 10-25% minor ❑ Additional Sheets Attached Part 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT (❑ Ch. 4 — Downstream Analysis ❑ ❑ Additional Sheets Attached Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION ❑ Sedimentation Facilities ❑ Stabilize Exposed Surface ❑ Stabilized Construction Entrance ❑ Remove and Restore Temporary ESC Facilities ❑ Perimeter Runoff Control ❑ Clean and Remove All Silt and Debris ❑ Clearing and Grading Restrictions ❑ Ensure Operation of Permanent Facilities ❑ Cover Practices ❑ Flag Limits of SAO and open space ❑ Construction Sequence preservation areas Other L❑ Other Part 10 SURFACE WATER SYSTEM ❑ Grass Lined Dispersion Infiltration Method of Analysis ❑ Energy Dissipater ❑ Flow Dispersal 2009 City of Renton Pipe System ❑ Drainage Manual ❑ Open Channel Ll Wetland Waiver CompensationlMitigati ❑ Dry Pond 11 Stream Regional Detention on of Eliminated Site Storage Brief Description of System Operation: Catch basins within private access road and along the frontage will convey stormwater runoff into a new stormwater vault located in the SW corner of the property. Vault will discharge into an existing stormwater pipe in Park Avenue North. Facility Related Site Limitations Reference Facility Limitation Part 11 STRUCTURAL ANALYSIS Cast in Place Vaul ❑ Retaining Wall Rockery > 4' Nigh L Structural on Steep Slope u Other Part 12 EASEMENTS/TRACTS Drainage Easement ❑ Access Easement Tract Other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. . x'76./�./QW- Section 1: Project Overview The proposal is to create eight (8) individual single family lots and one (1) stormwater tract from this 62,520 square foot parcel located in the City of Renton, Washington. The proposal is two existing tax parcels: 2820 Park Avenue North - King County Tax parcel #334210-3281 and 2802 Park Avenue North — King County Tax parcel #334210-3282. The existing residences, impervious areas, and out buildings on the properties will be removed to create these nine new lots, The property slopes from the east towards Park Avenue North on the west. The property is located within the "Peak Rate Flow Control Standard (Existing Site Conditions) "a rea of the drainage basin map. There are no sensitive areas on the project site. The property has a gentle slope of approximately 15% towards the southwest corner of the property. The soils on the site have been identified by a Geotechnical Engineers as "recessional deposits — sands and gravels" (Qvr). These soils are exceptionally well drained and will provide for suitable Full Infiltration of stormwater runoff. The soil logs indicate dry sands and gravels to depths below 8 feet on the property. The drainage calculations within this report will show that the developed runoff from this project match the existing condition runoff. A stormwater (water quality) vault has been sized to provide for water quality treatment only. The developed flows using full infiltration of impervious surfaces from the individual lots will generate less downstream runoff than the existing site conditions. Section 2: Conditions and Requirements Summary Preliminary Conditions of Plat Aooroval — forth comino An overview of the Core Requirements is outlined below, further discussion of these requirements can be found within the remainder of this report. Core Requirement No. I — Discharge at Natural Locadon The current property sheet flows towards the southwest corner to the intersection of Park Avenue North and North 28th Street. The developed condition will be to discharge to stormwater facility into the existing catch basin at the southwest corner of the property. The project will connect to the existing natural discharge location. Core Requirement No. 2 — 00site Analysis The downstream system was walked (where possible) below the project in September 2014. The site drainage currently sheet flows across the property to the southwest corner. The flow is collected into a catch basin located within the northeast portion of the intersection of Park Avenue North and North 281h Street. The catch basin collects runoff from a portion of the existing streets together with the runoff from the project area. The catch basin flows within a 6" concrete pipe (at slope = 8.82%) across the intersection towards the southwest. The pipe discharges into a large wooded and heavily vegetated area. The end of the 6" pipe is exposed in the under story. The 6" pipe end has minor debris at the outlet. The stormwater flow from the end of the 6" pipe to the bottom of the ravine was not exposed due to the heavy overgrowth of vegetation. The ravine flows towards the west and can be observed at two downstream road crossings; North 27th Place (bridge) and Lake Washington (culvert). The channel flow daylights into Lake Washington along the boardwalk within Gene Coulan Park. At the three downstream observation points, the channel had minor water within it. The channel, at the two crossings, showed no signs of scouring or heavy erosion. The bottom of the channel is difficult to observe due to the over growth. The 6" concrete pipe and the drainage channel downstream of the project have adequate capacity to convey the peak existing condition runoff. Core Requirement No, 3 — Flow Control The property is located within the City of Renton, Flow Control Duration Standard, Existing Conditions. The proposal is to mitigate on all the lots using full infiltration of developed impervious surfaces by using dry wells or infiltration trenches. This will reduce the developed runoff of the overall project. A storm water wet vault will be installed at the corner of North 28th and Park Avenue (Tract A) to provide water quality treatment of the developed impervious surface runoff. A preliminary stormwater vault has been sized using the "Peak Flow Control Existing Conditions" runoff of the existing site area modeled with a proposed developed condition runoff. The preliminary stormwater vault would be 23'x 48' long x 6' deep. The stormwater vault sizing calculations are attached to this section. Core Requirement No. 4 — Conveyance System The proposed on-site conveyance improvements will include curb, catch basins and a pipe network for collection of surface runoff from landscape, driveways, roadways, and sidewalks. The review and analysis of this proposed conveyance system includes calculations that are provided as part of this report. The proposed runoff is controlled by a stormwater vault located on the project. The vault will control the outlet flows up to a 100 year storm event; per KCRTS modeling and the City of Renton Drainage Manual standards, Head Water elevation within the connecting catch basin will be 0.25 feet above the outlet elevation of the 6" concrete pipe. The analysis indicates that at no point does the Head Water rise above (or leaves) the top of the connection catch basin. The backwater analysis shows the existing 6" concrete pipe at the existing slope of 8.47% is adequate convey the "peak flow rate" discharging for the stormwater vault. A second analysis was evaluated on the existing 6" concrete pipe. A Nomograph (Figure 4.2.1.F, page 4-22) was used to calculate the "flowing full" capacity of the pipe. The 6" concrete pipe at 8.47% slope, flowing full, will convey 1.75 cubic feet per second (cfs). The developed "peak flow rate" from the stormwater vault is 0.43 cfs during a 100 year storm event. Core Requirement No. 5 — Erosion and Sediment Contra/ A Temporary Erosion and Sediment Control Plan implementing the Best Management Practices will be included within the civil plans. The project exceeds the State requirements of clearing over 1 acre in size. Therefore the developer/contractor will need to obtain the necessary State permits. A temporary pond facility will be sized using the 2 year — 15 minute interval storm event. The calculations for the temp. pond will be included within a final report. Cone Requirement No. S — Maintenancze and Operations The Maintenance and Operations for the Nantucket Plat will include both a public and private system. Within the final report will be the maintenance requirements for the facilities being installed as part of the plat and the facilities to be installed as part of the residential building permits. Cone Requirement No. 7 — Financial Guarantees and Liability The Financial Guarantees and Liabilities will be required prior to the project being finalized by the City of Renton. Bond Quantity worksheets will be provided within the final report. Core Requirement No, 8 — Water Qualify The project is required to provide water quality (WQ) treatment. The WQ has been provided within the stormwater treatment facility. Sizing for this portion of the facility is included within section 4. Section 3: Of -site Analysis The downstream system was walked (where possible) below the project in September 2014. The site drainage currently sheet flows across the property to the southwest corner. The flow is collected into a catch basin located within the northeast portion of the intersection of Park Avenue North and North 28d' Street. The catch basin collects runoff from a portion of the existing streets together with the runoff from the project area. The catch basin flows within a 6" concrete pipe (at slope = 8.47%) across the intersection towards the southwest. The pipe discharges into a large wooded and heavily vegetated area. The end of the 6" pipe is exposed in the under story. The 6" pipe end has minor debris at the outlet. The stormwater flow from the end of the 6" pipe to the bottom of the ravine was not exposed due to the heavy overgrowth of vegetation. The ravine flows towards the west and can be observed at two downstream road crossings; North 27" Place (bridge) and Lake Washington (culvert). The channel flow daylights into Lake Washington along the boardwalk within Gene Coulan Park. At the three downstream observation points, the channel had minor water within it. The channel, at the two crossings, showed no signs of scouring or heavy erosion. The bottom of the channel is difficult to observe due to the over growth. The 6" concrete pipe and the drainage channel downstream of the project have adequate capacity to convey the peak existing condition runoff. 3.2 C7 C N 7 n � = b � s 's m o% < d' C m U a y Y 3 C � � 00®q eel @I('is101 � w , m s � D 0 36 5 Z 7 e w o.1 d 3 a a w � N C/) CD 0 0 z C) CD CD 71 44b (J"I -4- ITS C) CD Cf) CJS W CD •-4 OMSC) C. 1C) o ARIk AM d0k. AM dW W% ML .p. z m O CFI -^! N w Z x O Ch m Z m .�A T uV 1 40i'd r%.U,)L. ivy 11-t a M, WIN ,1 & 7T I - i z _Meadow Ave N A LIJ E.1 L I- -i 7.11 40 1-405. FVVY,� 1-405. FWY-. e -i A NI 21 i7 ji to 43L: :j� Lg%ui u.yl,hyIm Lail yo Z; 0 to 7i A.Ave- (jptaku i - - . C C:) LE 9L 'Bd SIE 3N 390M Nrzi go 13MIG LL71 7A cn J-2 z Park Ave N CD Ln m cr) _0 z _Meadow Ave N A LIJ E.1 L I- -i 7.11 40 1-405. FVVY,� 1-405. FWY-. e -i A NI 21 i7 ji to 43L: :j� Lg%ui u.yl,hyIm Lail yo Z; 0 to 7i A.Ave- (jptaku i - - . C C:) LE 9L 'Bd SIE 3N 390M Nrzi go 13MIG Section 4: Flow Control and Water Quality Facility Analysis and Design FLOW CONTROL REVIEW Based upon the City Drainage Manual, the following steps are required to determine the mitigation of storm water runoff of the developed project: Full Dispersion — NJG (no good) — the property does not have 100 feet of flow path available on each new lot; Full Infiltration — Acceptable — the underlying sands and gravels provide excellent opportunity for full infiltration of individual lots — this will be accomplished using either dry wells or infiltration trenches per the 2009 City of Renton Drainage Manual. The proposal is to mitigate on all the lots using "Fulllnfiltratiolf of developed impervious surfaces. Based upon the KCRTS modeling (see detention calculations within this Section), the difference between the 100 -year developed runoff and the existing condition runoff is (0.469 — 0.453) 0.016 or 0.02 cfs (cubic feet per second). The difference is less than 0.10 cfs; therefore stormwater detention is NOT required per the Drainage Manual. WATER QUALITY REVIEW The 2009 City of Renton Drainage Manual requires water quality treatment for projects that add 5,000 square feet or more of "new" pollution generating imperious surfaces (PGIS). The proposed developed (PCIS) exceed this requirement and therefore water quality (WQ) treatment has been sized within a wet vault. The WQ portion of the vault will be sized to provide the required volume of 3,519 cubic feet (see Water Quality calculations within this Section). A "wet vault" has been sized to 23'x 48` 6` deep to be placed within Tract A. This facility and Tract will be owned and maintained by the City of Renton. CALCULATIONS DETENTION CALCULATIONS NANTUCKET — EXISTING CONDITIONS Area t Till Forest 0.00 acres Till Pasture 0.00 acres Till Grass 1.43 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 0.32 acres Total - 1.75 acres Scale Factor: 1.00 Hourly Reduced Time Series: iNantucket Exisitng Condit"son » Compute Time Series Modify User Input File for computed Time Series [.TSF] Ficav Frequencv �ria1yS1 --------------------------------------------------------- Time Series File nantucket ex1_itng cc-n-jition - t.uf 2Tc.-ecr 7 Tyar,on- Sea -Tac ----;annual Peak Flow Rates--- _-_F1r3L! Frequenc'7 Ffia,l}rvl - _, _-__ Flow Rat: Rank Time of Fe,sk. - Peaks - - Ronk Return Frrb i C FS i CFS j Period U 200 4 2%09 `01 2 00 �j 45 1 10 C1 CIO U 9 0 CI 1a4 1�0q/021 16 CIO FI 2?S4 2 L5 liT) 0 960 0 2S,4 _ %7,7 7 00 i_I 214 _ 10 00 C1 9CIO G ICI % ? 26: 04 2 00 0 205 4 S. 0 C 1D :;00 0 13.7 I0 '20x'04 IE. 013 0 19? S 00 0 0 214 3 I/I$''06 16, CI C1 0 137 s _'.00 13 413Cj CI la? r lI%24,,[16 - 00 0 134 7 1 31 CI 0 ?''1 0 4S:� 1 I `09,-0s 6 00 CI 107 .; 1 10 0 091 COMPuted Peak,S fl 3$: so . 00 0 U$CI NANTUCKET — DEVELOPED CONDITION Area ?� Till Forest 4.00 acres Till Pasture 0.00 acres. Till Grass 1.37 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.40 acres Impervious 0.34 acres Total 1.75 acres Scale Factor: 1.00 Hourly Reduced rime Series: iNantucket Developed Condition ?7 Compute Time Series Modify User Input Fife for computed Time Series [.TSF] Flow Fregizen j' An.rylVaiS ----------------------------------------------------------- Time Series F11e nantucket developed conditl(7,ri rsf Frolect Locarloft Sea -Tac ---Annual Peak. Flow Fates----- ----------Flou Fregizency Analysis ------- Flow Rate Rank TIME- of Peak - - Peak-- - - Rank Return Prot. (CFS) +(-FS) Per Iod 0 214 4 2,109; 01 2 00 0 _ 469 1 1013 ran 4'40 11 1.44 1/OS%02 lE 00 0 265 2 25 00 0 9F,i1 0 255 27iC1 00 ft 224 3 10 00 U 5130 C. 7?i3 6,'04 = 00 0 214 4 5.1J0 'i 000 0 15.. 6 10!20'04 1 00 0 -'07 S 3. a0 sj b67 0 224 1,15:105 16 nn 0 153 h 2 00 0 100 0 207 S 11,'24;'05 = 03l A 144 1. 0 j 231 0 469 1 1/09,-088 6 130 0 12fi Y 1 10 0 0 1 rop,puted Peak= 0 401 SO 00 0 980 41 1 lJ z 4 � 4 N 4 � � Ln ti Ln a M a z 4 � 4 y Q y � ti ti 4.4 a III 4 � 0 N y Q y � ti 4.4 a C 3 v 0 c$ o z 0 4 III v 2 lu q) ro 0 O 00 M y ti Ci v 2 lu q) ro 0 O 00 M t- 4 MLri ,Qy N c�i t� OD a V '� h M q l N IT d 00 Ln Ln C) 00 ip N k.0N LL m M —1 m 1.0OD r. Ln to (IJ _0 (1) b ru (O q N fo ++ N % O y n cu CD W � y C 00 w tin qz Ln +t ri Cn N 4 —jv 0 W % *40, 000,00 . _ _ t� ,� ALI-- IL` k�m 0 116th Reference 11-A Flow Control Standards Pack Rate Flow Control Standard (Exisling Site Conditions) Flow Control ❑ inton Slandard (Exisling Site Conditions) •/�}'aj ), Flow Control Our don Standard(Forested Condlians) Flood Probiem Flaw UninCorporaled IGng County Flow Cantroi Standards Renton City Limits L _ PotenEal Annexation Area it 4F �t ry .990 - RIMOZA—A 1 SI 167 '�,.,. .. rut „{ salt i s . -,�,� �► ,aC�: SL..... ..�,;e;a:�.a-�•-._.fir A �� ;��if,►:�� brie �: 7. OF i r OP Flow Control Application Map Date: 01;0912014 N 4 r 0 1 2 _a�.�� R s• 3Niles b Reference 11-B z Wellfield Capture Zones Aquifer Protection Area Zones One Year Capture Zone ,Zone 1 Five Year Capture Zone Zone Modified Ten Year Captum Zone Zone 2 .� Cedar Valley Sole Source Network Structure Aquifer Project Review Area Productlon weal 5{ -- Sireamflow Source Area Sprin druoie S nn 9 P 9s Cedar Valley Sole Sou" AquFerif._ jRenton City Limits Polentfal Annexation Area Bryk c BNtn\ PR=1 ' -1-17 Groundwater Protection Areas Date: 01IDWO14 v we Q 1 2 Miles Reference 11-G qE 14M M1x F= } Renwn City U; Solt Typa — - Sh_ KPC - PITS - 5k ' _•�POWtW l4ale Wn Area AgH A 6, NPD . Pc Sm ks:Y Mill �0veatlwl>er Pra�.�On Ane BWndlly AGS - iL [ . i '.:: •.+ `1 Awl., Plolation Mea Z.- 1 Pgn ..... FrC hp P, Tu ,y yi4q /�.g hx -,- lvee Zanel RWdfiW ._: .. AkF FKO Nk ---Lk qVB .�ACIAkrPmtec-0on EwC ... - H. .`Py RdC w AIC InA RdE An MG 0¢ Re SOD KpO ow sh NC %C ! NDi . rt I51;. E,l'. MC . r� In s 1 NU f % K" Tl ts It � p,, - BIbK oec j �� ✓ � �/ ...� `, l e« • r'�l1iE S � M t, F.0 ; J Ri5 �. / Y ' vD '4€ A MB.. LS S S 34'h ix i � ISYIt 4 31 Sl j MgAt 77 ' ^.Fi iL4,lfikb� aS5 l, Ally. .. Es rai 4a ':, Mo .nl n nrs' 'P„G roc s W.i �P rw Aa F, M R NB W 9i} MB ry RT` - 1qC U ; • . W U A?U AC e a u r a6? 2'jS p. Ib A&- nwe M�' Soil Survey Date: 0VOW201� Mises WATER QUALITY TREATMENT Wetpool Sizing Calculations Per 2009 King County Stormwater Management Manual Project Name: 2820 Park Avenue North Plat Project Number: Frontage & Access road treatment Facility Description: Water Quality Sizing 01/30/2015 Step 1: Identify required wetpool volume factor (f). f = 3 Per KCSWDM 6.4.1.1 Step 2: Determine rainfall (R) for the mean annual storm. R = 0.47 Per KCSWDM Fig. 6.4.1.A Step 3: Calculate runoff from the mean annual storm (V,) for the developed site. V,=(0.9A;+0.25At9+0.10Att+0.01A,)x(RI12) where_ A; = Impervious Surface Area = 16,723 s.f. At4 = Till Grass Area = 59,597 s.f. Atf = Till Forest Area = 0 s.f. A, = Qutwash Area = 0 s.f. V, = 1,173 c.f. Step 4: Calculate required wetpool volume (Vb). Vb=fxVr Vb = 3,519 c.f. Section 5: Conveyance System Analysis and Design A backwater analysis and a Nomograph evaluation were performed on the existing 6" concrete pipe. In both cases, the 6" concrete pipe has adequate slope and capacity to convey the "peak flow rate" discharge from the stormwater vault. Q LL_ O O H ry W � Q Z D 0. 0 d] C3 �_ Q t� .` A 4# AIR w�� f +fat fi Ld ■ zez ■I ti 1 ■ 1 • ---------- .. ------- ■. 1 � 1 x ■ I f . 1 �► j ■ — —#-'�� s•r-r-E�1 rw�-ski rF��3 � lr t ar r � r ■ srl.r�•r+��rrrrrrw■ HLWN X[hMV yWd 1 § LL k a # m k k all 00 S L U LU CA q % k -j> g 2 U c $ q2 0 E CCD C)�mkq /22¢k 4 r -I S 7 j 0 0 2 CD CD 00 a m 0 7 ? 00 �-i OD\ 2\�R6 §ka/ 7 t CL I 0 k dd $ > % q ƒk(n0) S J 2/ co " Ln � ¢ cq �L/M/ \ o n � L& � /� >da 0 / / G fa o § 0 0 § LU Z d a ?«Lƒ � g ■ _ \� ƒC> u 4t m� E EE £# § LL k a # k k all \ S L U 7 CA q % S 7 j 0 0 2 00 a m 0 7 ? 00 ƒ §� 7 t CL I 0 k « S J 2/ co 1P 3 3 q \ o n * - L& � 2 t 0 / fa o § 0 0 § LU Z d a § LL k a # 4.2.1 PIPE SYSTEMS —METMODSOFANALYSIS FIGURE 4.2.1.1 BACKWATER CALCULATION SHEET NOTES Column (1) Msign flow to be conveyed by pipe segment, Column (2) Length of pipe segment. Column (3) Pipe Size; indicate pipe diameter or span x rise. Column (4) Mannings "n" value. Column (5) Outlet Elevation of pipe segment. Column (6) Inlet Elevation of pipe segment. Column (7) Barrel Area; this is the full cross-sectional area of the pipe. Column (8) Barrel Velocity; this is the full velocity in the pipe as determined by: V = QIA or Col.(8) = Col_(1)/Col.(7) Column (9) Barrel Velocity Head = 02g or (Col.(8);/2g where g = 32.2 ft/see (acceleration due to gravity) Column (10) Tailwater (TW) Elevation; this is the water surface elevation at the outlet of the pipe segment. If the pipe's outlet is not submerged by the TW and the TW depth is less than (D+d )J2, set TW equal to (D+d)12 to keep the analysis simple and still obtain reasonable results (D = pipe barrel height and d = critical depth, both in feet. See Figure 4.3. LF (p. 4-49) for determination of d.). Column (11) Friction Loss = Sfx L [or Sfx Col (2)] where Sf is the friction slope or head loss per linear foot of pipe as determined by Manning's equation expressed in the form: Sf = (nk)'12.22 R" Column (l2) Ilydrautic Grade Line (HGL) Elevation just inside the entrance of the pipe barrel; this is determined by adding the &fiction loss to the TW c€evatiom Col.(12)= Col _(11)+Col.(10) if this elevation falls below the pipe's inlet crown, it no longer represents the true HGL when computed in this manner. The true HGL will fall somewhere between the pipe's crown and either normal flow depth or critical flow depth, whichever is greater. To keep the analysis simple and still obtain reasonable results (i.e„ erring on the conservative side), set the HGL elevation equal to the crown elevation. Column (13) Entrance dead Loss = K, x P'/2g [or Ke x CoL(9)] where K, = Entrance boss Coefficient (from Table 4.3.1.B, p. 4-42). This is the head lost due to flow contractions at the pipe entrance_ Column (14) Exit Head Loss = 1.0 x ling or 1.0 x Col.(9) This is the velocity head lost or transferred downstream. Column(15) Outlet Control Elevation — Col.(12)+Col.(]3)+Col.(]4) This is the maximum headwater elevation assuming the pipe's barrel and inlet/outlet characteristics are controlling capacity. It does not include structure losses or approach velocity considerations. Column (16) Inlet Control Elevation (see Section 4.3.1.2, page 4-39, for computation of inlet control on culverts); this is the maximum headwater elevation assuming the pipe's inlet is controlling capacity_ it does not include structure losses or approach velocity considerations. Column (17) Approach Velocity Head; this is the amount of head/energy being supplied by the discharge from an upstream pipe or channel section, which serves to reduce the headwater elevation. If the discharge is from a pipe, the approach velocity head is equal to the barrel velocity head computed for the upstream pipe. If the upstream pipe outlet is significantly higher in elevation (as in a drop manhole) or lower in elevation such that its discharge energy would be dissipated, an approach velocity head of zero should be assumed. Column (] 8) Bend Head Loss = Kb x V12g [or KA x Col.(]7)] where Ka = Bend Loss Coefficient (from Figure 4.2.1.F, p. 4-27). This is the loss of head/energy required to change direction of flow in an access structure. Column (19) Junction Head Loss, This is the loss in head energy that results from the turbulence created when two or more streams are merged into one within the access structure. Figure 4.2.1.E (p. 4-28) maybe used to determine this loss, or it maybe computed using the following equations derived from Figure 4.2.1.L. Junction Head Loss — K; x V'12g [or K; x Col.(17)] where Kf is the Junction Loss Coefficient determined by K, = (Q3/Qi)/(1.18+0.63(Q3/Q,)) Column (20) - Headwater (HW) F.ievation, this is determined by combining the energy heads in Columns 17, 18, and 19 with the highest control elevation in either Column 15 or 16, as follows: Col.(20) = Cai.(15or16)-Col.(]7)+Col. (18)+Col.(19) 2009 Surface Water Design Manual 1/9/2009 4-25 SECTION 4.2 PIPES, OU ITALLS, AND PUMPS 1/ _ 1.49 X2/3 v2 (4-1) n or use the continuity equation, Q = AV, such that: 1.49 2n u2 (4-2) Q = —AR S n where Q = discharge (cfs) V = velocity (fps) A = area (sf) n = Manning's roughness coefficient; see Table 4.2.1.D below R – hydraulic radius = area/wetted perimeter (ft) S – slope of the energy grade line (ft/ft) For pipes flowing partially full, the actual velocity may be estimated from the hydraulic properties shown in Figure 4.2.1.E by calculating QA11 and Vfull and using the ratio to find V and d (depth of flow). Table 4.2. LD provides the recommended Manning's "n" values for preliminary design using the Uniform Flow Analysis method for pipe systems. Note: The "n" values for this method are 15% higher in order to account for entrance, exit, junction, and bend head losses. TABLE 4.2.1.D MANNING'S "n" VALUES FOR PWES Type of Pipe Material Analysis Method Uniform Flow Backwater Flow (Preliminary (Capacity design) Verification) A. Concrete pipe and LCPE pipe 0.014 0.012 B. Annular Corrugated Metal Pipe or Pipe Arch: 1. 2-2/3" x 1/2" corrugation (riveted): a. plain or fully coated 0.028 0.024 b. paved invert (40% of circumference paved): 1) flow at full depth 0.021 0.018 2) flow at 80% full depth 0.018 0.016 3) flow at 60% full depth 0.015 0.013 c. treatment 5 0.015 0.013 2. 3" x 1" corrugation 0.031 0.027 3. 6" x 2" corrugation (field bolted) 0.035 0.030 C. Helical 2-213" x'12" corrugation and CPE pipe 0.028 0.024 D. Spiral rib metal pipe and PVC pipe 0.013 0.011 E. Ductile iron pipe cement lined 0.014 0.012 F. SWPE pipe (butt fused only) 0.009 0.009 1/9/2009 2009 Surface Water Design Manual 4-20 4.3.1 CULVERTS---METHODSOFAArALYSIS 4.3.1.2 METHODS OF ANALYSIS This section presents the methods of analysis for designing new or evaluating existing culverts for compliance with the conveyance capacity requirements set forth in Section 1.2.4, "Core Requirement #4: Conveyance System." ❑ DESIGN FLOWS Design flows for sizing or assessing the capacity of culverts shall be determined using the hydrologic analysis methods described in Chapter 3. ❑ CONVEYANCE CAPACITY The theoretical analysis of culvert capacity can be extremely complex because of the wide range of possible flow conditions that can occur due to various combinations of inlet and outlet submergence and flow regime within the culvert barrel. An exact analysis usually involves detailed backwater calculations, energy and momentum balance, and application of the results of hydraulic model studies. However, simple procedures have been developed where the various flow conditions are classified and analyzed on the basis of a control section. A control section is a location where there is a unique relationship between the flow rate and the upstream water surface elevation. Many different flow conditions exist over time, but at any given time the flow is either governed by the culvert's inlet geometry (inlet control) or by a combination of inlet geometry, barrel characteristics, and tailwater elevation (outlet control). Figure 4.3.1.A (p. 4-44) illustrates typical conditions of inlet and outlet control. The procedures presented in this section provide for the analysis of both inlet and outlet control conditions to determine which governs. Inlet Control Analysis Nomographs such as those provided in Figure 4.3. LB (p. 4-45) and Figure 4.3. LC (p. 4-46) may be used to determine the inlet control headwater depth at design flow for various types of culverts and inlet configurations. 'These nomographs were originally developed by the Bureau of Public Roads—now the Federal Highway Administration (FHWA)---based on their studies of culvert hydraulics. These and other nomographs can be found in the FH WA publication Hydraulic Design of Highway Culverts, HDS No. #5 (Report No. FHWA-IP-85-15), September 1985; or the WSDOT Hydraulic Manual. Also available in the FHWA publication, are the design equations used to develop the inlet control nomographs. These equations are presented below. For unsubmerged inlet conditions (defined by QIAD05 < 3.5); Form I*: HWID = HID + K(QIAD0.5),u - 0.5S** (4-3) 7, � I ` Form 2*: HWI.D = K(Q/ALP 5)" (4-4) For submerged inlet conditions (defined by Q/AD05 ? 4.0); 1 ^ HW/D = c(QIADr1 )z } Y- O.SS** r ' l (4`5) _ 'll where HW = headwater depth above inlet invert(ft) L f D = interior height of culvert barrel (ft) H, = specific head (ft) at critical depth (dc + Fc2l2g) Q – flow (efs) % 7 A = full cross-sectional area of culvert barrel (sly 2009 Surface Water Design Manual 1/9/24109 4-39 n,Gt�l4 SECTION 4.3 CULVERTS AND BRIDGES S = culvert barrel slope (ft/ft) I,M, e, Y = constants from Table 4.3.1.A. The specified head H, is determined by the following equation: 2 He = d, + V, /2g (4-6) where d, = critical depth (ft); see Figure 4.3.1.F (p. 4-49) V, = flow velocity at critical depth (fps) g = acceleration due to gravity (32.2 ft/See). * The appropriate equation form for various inlet types is specified in Table 4.3. LA (p. 4-40 * For mitered inlets, use +0.7S instead of -0.5S. Note: Between the unsubmerged and submerged conditions, there is a transition zone (3.5 < QIAD0.5 < 4.0) for which there is only limited hydraulic study information. The transition zone is defined empirically by drawing a curve between and tangent to the curves defined by the unsubmerged and submerged equations_ In most cases, the transition zone is short and the curve is easily constructed. TABLE 4.3.1.A CONSTANTS FOR INLET CONTROL EQUATIONS* Unsubmerged Submerged Shape and Material Inlet Edge Description Equation Forth X M c Y Circular Concrete Square edge with headwall 1 0.0098 2.0 0.0398 0.67 Groove end with headwall 0.0078 2.0 0.0292 0.74 Groove end projecting 0.0045 2.0 0.0317 0.69 Circular CMP Headwall 1 0.0078 2.0 0.0379 0.69 Mitered to slope 0.0210 1.33 0.0463 0.75 Projecting 0.0340 1.50 0.0553 0.54 Rectangular Box 300 to 750 wingwall flares 1 0.026 1.0 0.0385 0.81 900 and 150 wingwall flares 0.061 0.75 0.0400 0.80 0° wingwall flares 0.061 0.75 0.0423 0.82 CM Boxes 900 headwall 1 0.0083 2.0 0.0379 0.69 Thick wall projecting 0.0145 1.75 0.0419 0.64 Thin wall projecting 0.0340 1.5 0.0496 0.57 Arch CMP 90° headwall 1 0.0083 2.0 0.0496 0.57 Mitered to slope 0.0300 1.0 0.0463 0.75 Projecting 0.0340 1.5 0.0496 0.53 Bottomless Arch 900 headwall 1 0.0083 2.0 0.0379 0.69 CMP Mitered to slope 0.0300 2.0 0.0463 0.75 Thin wall projecting 0.0340 1.5 0.0496 0.57 Circular with Smooth tapered inlet throat 2 0.534 0.333 0.0196 0.89 Tapered Inlet Rough tapered inlet throat 0.519 1 0.64 0.0289 0.90 . Source: FHWA HDS No. 5 1/9/2009 4-40 2409 Surface Water Design Manual SECTION 4.3 CULVERTS AND BRIDGES TABLE 4.3.1.B ENTRANCE LOSS COEFFICIENTS Type of Structure and Design Entrance Coefficient, K, Pie Concrete PVC Spiral Rib DI and LOPE Projecting from fill, socket (bell) end 0.2 Projecting from fill, square cut end 0.5 Headwall, or headwall and wingwalls Socket end of pipe (groove -end) 0.2 Square -edge 0.5 Rounded (radius = 11120) 0.2 Mitered to conform to fill slope 0.7 End section conforming to fill slope" 0.5 Beveled edges, 33.70 or 450 bevels 0.2 Side- or slope -tapered inlet 0.2 Pipe, or Pipe -Arch, Corrugated Metal and Other [Von -Concrete or 0.1 Projecting from fill (no headwall) 0.9 Headwall, or headwall and wingwalls (square -edge) 0.5 Mitered to conform to fill slope (paved or unpaved slope) 0.7 End section conforming to fill slope" 0.5 Beveled edges, 33.70 or 450 bevels 0.2 Side- or slope -tapered inlet 0.2 Box, Reinforced Concrete Headwall parallel to embankment (no wingwalls) Square -edged on 3 edges 0.5 Rounded on 3 edges to radius of 1112 barrel dimension or beveled 0.2 edges on 3 sides Wngwalls at 30" to 750 to barrel Square -edged at crown 0A Crown edge rounded to radius of 1112 barrel dimension or beveled top 0.2 edge Vlfngwall at 100 to 250 to barrel Square -edged at crown 0.5 Wingwalls parallel (extension of sides) Square -edged at crown 0.7 Side- or slope -tapered inlet 0.2 " Note. End section conforming to fill slope" are the sections commonly available from manufacturers. From limited hydraulic tests they are equivalent in operation to a headwall in both inlet and outlet control. Some end sections incorporating a closed taper in their design have a superior hydraulic performance. V9/2009 4-42 2009 Surface Water Design Manual SECTION 4,2 PIPES, OUTFALLS, AND PUMPS FIGURE4.2.1.F !NOMOGRAPH FOR SIZING CIRCULAR DRAINS FLOWING FULL 1,000 900 800 .00171 700 —2.0 600 .0002 500 0003 Minimum 400 .0004 Allowable .0001 _0005 Velocity 300 1200.000496�i .0006 (Flowing 3.0 0008 0002 Full) 108 o DDI _0003 o 90 $4 .002 .0006 4.0 —78 72 O .403 .0008 —66 LU A04 �1 5 0 100 0 O .006 n -90 54 Cn .008 .002 c Z-- 80 70 0 48 .01 .003 c ui 6.0 42 004 - cr 'r- ? 36 .02 006 O a_ 7.0 z 33 ..005 .03 aa8 a_ w 0 � 20 .04 .010 O w uj .05 c�'n 9.0 0 21 .08 _020 10.0 [20 10 c 0 LU 18_040 _030 0 w w a o.0801 15 .05 12 .100 10 9 10 8 S PLE USE 7 8 24° dia. CMP @ 2% slope yields 20.0 Z. 6 17cfs @ 5.4 fps velocity 5 (n=0.024) 4 Values per Manning's equation Q= ( 1.49 ) AR'/3 S0112 3 n 30.0 This table can be converted to other "n" values by applying 2 4 formula: 40.0 Q1 = n2 Q2 n 1l J, 1/9/2009 2009 Surface Water Design Manual f 4-22 [ Section 6: Special Reports and Studies Geotechnical Study attached Robert M. Pride, LLC Consulting Engineer November 7, 2014 Mr. Darrell Offe Offe Engineers 13932 SE 159th Place Renton, WA 98058 Re: Geotechnical Recommendations Proposed Residential Development 2800 Park Avenue North Renton, Washington Dear Mr. Offe, This report provides recommendations for onsite storm water infiltration on this proposed nine lot subdivision located on the northeast corner of Park Avenue and North 28th Street in Renton. It is understood that a detention tank is also being proposed for contaminated water storage on the west side of the project site. Site and Subsurface Conditions This rectangular property covers nearly two acres of land that has a gentle slope from the east to west side. An existing residence is situated on this property near the south end that will be removed as part of this new development. A new roadway will extend toward the north end of this development to provide access to these new residences. Geologic research of mapping by Booth in 2007 shows this area of Renton is underlain by recessional deposits consisting of silty sands, sands and gravels (Qvr). Field exploration consisted of excavating four exploratory test pits and documenting subsoil conditions in an open excavation located south of Lot #1. Summary logs of these test pits are described below and their locations are shown on Drawing No. 1: TP -1 Located on Lot 2 at the west end o.o to t.oft Topsoil — Silty Sand; dark brown, moist, loose; 1.0 to 3.5ft Silty Sand; light brown, moist, medium dense; 3.5 to 8.oft Sand with gravel; light brown, moist, medium dense; no groundwater encountered; TP -2 Located at south end of Lot 3 0.0 to 1.3ft Topsoil — Silty Sand; dark brown, moist, loose; 1.3 t05.0ft Sandy Gravel; light brown, moist, medium dense to dense; no groundwater encountered; TP -3 Located on Lot 2 at the east end 0.o to o.gft Topsoil — Silty Sand; dark brown, moist, loose; 0.9 to 3 -Oft Silty Sand; light brown, moist, medium dense; 3.0 to 7.5ft Sandy Gravel; light brown, moist, dense; no seepage; Robert M. Pride, LLC page 1 13203 Holmes Point Drive NE Kirkland, WA 98034 TP -4 Located on property south of Lot 1 as an open excavation o.o to Loft Topsoil —Silty Sand; dark brown, moist, loose, 1.0 to 4.oft Gravelly Sand; light brown, moist, medium dense; 4.0 to 9.0ft Sand; light brown, moist, medium dense; no groundwater seepage encountered; Based on my site investigation and geologic research the native soils below the topsoil layer consist of silty sands, sands and sandy gravels that will perform adequately for storm water discharge into these granular sediments. I have classified these upper soils as "medium sand" and the lower sandy gravels as "coarse sands or cobbles" in accordance with the King County Design Manual — Table 4.5.2. Maximum infiltration rates range from 7.5 min/inch for the fine sands, and 3 min/inch for the coarse sandy gravels. Please call if there are any questions. Respectfully, a .0 16 71 GIS-Ti,�p \ '"LN/oNAL EAG Robert M. Pride, P. E. Principal Geotechnical Engineer dist: (1) Addressee encl: Drawing No. x — Site Plan rmp: Offe28thResidl rnu rrrm nui�i — irr Robert M. Pride, LLC page 2 13203 Holmes Point Drive NE Kirkland, WA 98034 . SsNH 34" SH.".LL_dW RIM=212.00 - "SE EX. L ` SEVr,_,Z FOR LWT t , R1�ocxr-_ Ex. raErE;� /r 3 1 '1 %T4 :s,N"'k111E STRIP -� -rte � � � � � `� / -• . _ l\�'� J� I �. �. \+ � Ii ry 6.3 I _ .I .. T ( i u L i I :: <' E.I. WATCP omen z SSIAI-' --4' SHALLOW, I ' z IE -204.^6: F' NEW '=IRE HYDRANT ••--• '�', -- -- _ �I ---=20C.64, ?2" — , RIM=204.2�—�,.1 -`w �• II - RIM=209.0~ I ). 13VW- -P MAIN � To 4YDR�JT 6 rrpE i21 �9 I - V 1 R051H :Rth V; -�a- SITE PLAN Proposed Residences --- Project No. 28o0 Park Avenue North Renton, Washington Dra"ingNo. 1 Robert M. Pride, LLC Consulting Geotechnical Engineer Section 7: Other Permits None applicable at this time Section 8: CSWPPP Analysis and Design The proposed development consists of 1.44 acres of property. The proposal is to minimize the amount of area needed to install the required improvements. However, the overall development including the construction of the new houses will disturb over one acre of property. A NPDES permit will be required from the State Department of Ecology together with an approved erosion control plan from the City of Renton. The retention of the existing vegetation during construction should reduce the amount of construction runoff in the wet seasons. An erosion control plan will be provided as part of the civil construction plans submitted to the City of Renton for the utility permit. a Section 9: Bond Quantities, Facility Summaries, and Declaration of Covenant A Declaration of Covenant (Operation, maintenance, and restrictions) will be provided at the final civil engineering construction plans submittal to the City. Bond Quantity forms will be provided at time of Civil Engineering Plans Section 10: Operation and Maintenance Manual The Operation and Maintenance of the proposed BMP's provided will be included within the Declaration of Covenant from Section 9. These documents will be provided for review on as part of the utility permit submittal.