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HomeMy WebLinkAboutSWP272850(1) TAMARON POINTE APARTMENTS Renton, Washington Technical Information Report Prepared By: '`S!ONACC�' Richard Klein.) PE EXPIRES: Greg A. Diener, PE Pacific Engineering Design, Inc. Revised June 24, 1999 May 10, 1999 PEDI Job No. 98020 i i TABLE OF CONTENTS I I. PROJECT OVERVIEW ........................................................................................1-5 II. PRELIMINARY CONDITIONS SUMMARY...........................................................6-8 III. OFF-SITE ANALYSIS.............................................................................................9 ' EXISTING VERSUS PROPOSED CONDITIONS......................................................................................- 10-11 A NARRATIVEAND SUMMARY .......................................................................................................................12 100-YR,24-HR SCS METHOD CALCULATION........................... 13-19 ................................ 25-YR AND I00-YR RATIONAL CALCULATIONS......................................................................................20-21 DOWNSTREAM DRAINAGE ANALYSIS WITH MAPS AND CALCULATION.................................................... 22-28 IV. RETENTION/DETENTION ANALYSIS AND DESIGN.....................................29-34 ' V. CONVEYANCE SYSTEMS ANALYSIS AND DESIGN ....................................35-50 VI. SPECIAL REPORTS AND STUDIES...............................................................51-65 ' VII. BASIN AND COMMUNITY PLANNING AREAS...................................................66 VIII. OTHER PERMITS.................................................................................................67 ' IX. EROSION/SEDIMENTATION CONTROL DESIGN .........................................68-69 ' X. BOND QUANTITIES WORKSHEET, RETENTION/DETENTION FACILITY SUMMARY SHEET AND SKETCH, DECLARATION OF COVENANT................70 ' XI. MAINTENANCE AND OPERATIONS MANUAL...................................................71 1 1 � I. PROJECT OVERVIEW r� i i i r i i i PROJECT OVERVIEW The site is comprised of 10.68 acres of land located to the east of Lake Washington Blvd., to the west of I-405, to the south of N. 28th Street, and to the north of N. 20th Street. At present, the site is a mobile home park. About 20.4 acres of land drains toward the site from the east down a steep hill. It is proposed that the mobile home park be replaced with a multi-family apartment complex comprised of about 190 units. The existing on-site drainage system except for a small area near the Northwest corner of the site, routes the drainage southward to the southwest corner of the site along Lake Washington Blvd. Iwhere an existing drainage system conveys the flow under Lake Washington Blvd. westward through Gene Coulon Park, discharging into Lake Washington. The distance from Lake Washington Boulevard to the discharge point in the lake is approximately 410 feet. IThe proposed multi-family apartment complex will have roughly the same percentage of impervious area as the existing site. The downstream drainage system piping with the exception I of one 60-foot length of storm pipe is adequate to convey the developed flow to Lake Washington. The project is exempt from detention requirements since it discharges directly to Lake Washington, and the increase in peak rate runoff for the 100-year, 24-hour storm is less than I0.5cfs. No on-site storm detention facilities are proposed. The inadequate section of downstream piping is proposed to be upgraded from a 12-inch to 24-inch pipe. I A bio-swale is proposed to treat the 2-year, 24-hour storm event prior to discharge into the downstream drainage system. ' 2 PagQ 1 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET . C Project Owner Trammell Crow Residential "Location e Tamaron Pointe Add re SS 4010 Lake Wash Blvd NE Suite 330 Kirkland WA 98033 Phone 425-828-3003 Township 23N Project Engineer Greg Diener Range 5E Company Pacific Engineering Design I� nc Section 5 Project Size 10.68 AC Address Phone 130 Andover Park E.,Suite 300 Upstream Drainage Basin Size 20.42 AC Seattle WA 98188 206-431-7975 Q Subdivision Q DOF/G HPA Q Shoreline Management Q Short Subdivision Q CO.E 404 Q Rockory Q Grading Q DOE Dam Safety Q Structural Vaults Q Commercial Q FEMA Floodplain 0 Other i Other Site Plan Permit Application Q COE Wetlands Q HPA (Multi-Family Development) - - • r r - c II I Community �.. Kennydale IDrainage Basin Cedar River Basin I IQ River Q Floodplain Q Stream Q Wetlands Q Critical Stream Reach Q Seeps/Springs I , Q Deprossions/Swalos Q High Groundwater Table L Q Lake Q Groundwater Recharge ® Stoop Slopes East side of site Q Other IQ Lakeside/Erosion Hazard Soil Type Slopes Erosion Potential Erosive Velocities Alderwood(AmB) 0-15°! Low Low Alderwood(AkF) 25-50/ High High _ IAlderwood(AgD) 25-501 High High Q Additional Shoots Attalched 3 1�( FIGURE 1 Page 2 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 7. REFERENCE LIMITATION/SITE CONSTRAINT h 4 Downstream Analysis a 0 0 0 0 Q Additional Sheets Altatched MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION [� Sedimentation Facilities ® Stabilize Exposed Surface ® Stabilized Construction Entrance ED Remove and Restore Temporary ESC Facilities ® Perimeter Runoff Control M Clean and Remove All Silt and Debris 0 Clearing and Grading Restrictions ® Ensure Operation of Permanent Facilities E] Cover Practices Flag Limits of NGPES ® Construction Sequence Other [] Other I Grass Lined Channel Tank 0 Infiltration 1 Method of Analysis ® Pipe System [] Vault F--j Depression SBUH 100Yr-24Hr Open Channel [] Energy Dissapalor [] Flow Dispersal Compensalion/Mitigation 0 Dry Pond Wetland 0 Waiver of Eliminated Site Storage 0 Wet Pond 0 Stream 0 Regional Detention IBrief Description of System Operation The on site conveyance system will collect runoff and route to a bio-swale prior to discharge into downstream drainage system. I Facility Related Site Limitations C] Additional Sheets Attatched Referenge Facility Limitation I Drainage Easement 0 Cast in Place Vault 0 Other 0 Access Easement F-1 Retaining Wall 0 Native Growth Protection Easement 0 Rockery>4'High [] Tract 0 Structural on Steep Slope 0 Other I or a civil engineer under my supervision have visited the site. Actual silo conditions as observed were incorporated into this workshool and the ' ettatchmonts. To tho best of my knowledge the information provided hero is accurate. spy .ao��� 11'90 FIGURE I �_ SEE 596 KAP b L b HILLSIDE I H $E-l''68TH = rat _" n ti>,x, ram` - CR ►�.. $T y: - 0 tt ■.�a in PIONEER N ,E i , _ ,r a u m sr [� ♦ ( _ ,; S[ �T''� ,. vs �: ., PARK;::.$ma :aP �rN� ) �'• I r �sE72x0= �u '� � ns ! ns, Y� SIN ,p 1 Or"'r', '. M Ta a r �, C Tom}_ ^sT fuZEL�A70D r x TLST 8 \.. 30 i s s,,- PK -� �sor t I E 7 ND JPL L -SC 72ND PL sr sr '4 I ` :�•Gx �•F M v t J�' !L B st It ST d TI 129 ���♦ `ci ~ -3 `T4 .. 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AkF, Bh B 29 2 �2N KDD .AgC 42 ' —- @, KPB• ••t o n AgC I; rTC'Pin I 32 EwC JI Age t t InA •n 1■ _9 u Golf Course C) AmC A Ev6 h r KpD a 'r 25 AmB ' �� 1 3 (r I 2 I A D, M 3 AmC Ag8 •� - _ g �.. 9M Sou Mere ■ DD n� KDp Jr H . \AgC ♦ 0 EwC BM May e• KPC ra •EvC 9� BM �La eridge S,h 109 _ _ • ♦ - •�I _ OvD y� 1 Bf� AgD r , ta•iti• 3 No O AgC KPD ♦ ri K �. �. Y = J KDe _ C�. Sm �. ISouth Point Agc AN Kennydale D Agc_- •U i• \ I, (� ' • v r InC I AkF ( •� ' v z' — r r_ iti I •f (AkF AgC I t Coleman Poin .e• PY. • '-AkF p f - •I A'. 919 I 1 e B C,AgD 2 gM 1 • m n •BM• 0�.:• n t•N• '� t i• ' 11 1 + n AkF ;t4 AmB •� r- L Sm• s InC� 167 Bryn Mawr AkF L IAmI HDY L-i D_j 238 � — AgC Ur _ R TO_N i" �• �s ••o. Ire ••. J .- I•. R.4 E. R.S E. RENTON 1.9 Mi. 12'30'r (Joins sheet 1 1) RdC RENTON 1.7 MI. I Scale 1:24 000 1 �0 1/2 tQ p 1 5000 4000 3000 2000 1000 0 5000 - — Th•s map�S one or a sti or 20. � III. OFF-SITE ANALYSIS I I 1 1 I 1 1 1 � q PACIFIC ENQINEERINQ DESIQN INC. CIVIL ENGINEERING AND PLANNING CONSULTANTS SHEET NO. //�' o OF CALCULATED 9Y a.. /n DATE t�X 5 /►'I t� :� / d t /eY✓�ou5 �e► ✓I ysl 5. "cl ) 70� l S, e l •b /:o.d,o.. a.. ... -73 ...... . . . ........... ...� 7 z a . . .. .. 7015 ....v :. . . r _ _ �� - ........•fig .. . . . .. Ila 1..... +w ..... :. ...:....... .: ......... . . .. :. ... lo�r .e ._........_... ........ .. ..... ...:.... . .. .... _ .... .. ... _ _ .. ....... .............. .. . .... ..:.............. ....................._........ C� .. ... .... .... 130 ANDOVER PARK EAST, SUITE 300 SEATTLE, WASHINGTON 98188 (206) 431-7970 FAX:431-7975 PACIFIC ENQINEERINQ 1ESlQN INC. roe T�u✓�� �o����� i���--, yyfl ��r CIVIL ENGINEERING AND PLANNING CONSULTANTS SHEET NO. �/J OF CALCULATED 8V t�I✓� DATE- .. .��PGS._ _ l7r�'ll....... _ ....hn��',�t//ous _ �G'✓v/t�uS .. .. L .... ... .. ... . ... 10 6�5 0 ; .. ' . . _ hl� 2Z 5 ..... . ... ;................... .. ... .. ... .. . . ... :.. .. ......... _ . .. ... . _.. .. .. ...... ; .._. _......... .... `.... _. �'. / f I�TG..I e ryl o.V. 1�..t,7 ... ..... ...... .:...... . . .. ;.. _ ... .._.. : ._ ... e►-v�ores ............ ....... ... ...... . . _ ... ..... .. _ . ... ..._. .......... . . .... . ... ._ ...... I 130 ANDOVER PARK EAST, SUITE 300 SEATTLE, WASHINGTON 98188 (206) 431-79701 FAX:431-7975 6/24/99 2 : 14 :46 pm Pacific Engineering Design Inc page 1 TAMARON POINTE JOB NO. 98020 DRAINAGE STUDY BASIN SUMMARY BASIN ID: AA NAME : 100-YR. PRE-DEV. - ON-SITE SBUH METHODOLOGY TOTAL AREA. . . . . . . : 10 . 70 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 5 . 93 Acres 4 . 77 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1120 TcReach - Shallow L: 80 . 00 ks : 11 . 00 s : 0 . 1120 TcReach - Shallow L: 220 . 00 ks : 11 . 00 s : 0 . 1490 TcReach - Sheet L: 170 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 .4500 TcReach - Channel L: 1450 . 00 kc :42 . 00 s : 0 . 0200 PEAK RATE : 8 . 88 cfs VOL: 2 . 67 Ac-ft TIME : 470 min BASIN ID: BB NAME: 100-YR. POST-DEV. - ON-SITE SBUH METHODOLOGY TOTAL AREA. . . . . . . : 10 . 69 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 5 . 27 Acres 5 .42 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 5 . 00 min 5 . 00 min ABSTRACTION COEFF : 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr : 2 . 00 s : 0 . 1120 TcReach - Shallow L: 80 . 00 ks :11 . 00 s : 0 . 1120 TcReach - Shallow L: 220 . 00 ks : 11 . 00 s : 0 . 1490 TcReach - Sheet L: 170 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 .4500 TcReach - Channel L: 1450 . 00 kc :42 . 00 s : 0 . 0200 PEAK RATE: 9 . 10 cfs VOL: 2 . 73 Ac-ft TIME: 470 min In our calculations, to determine that peak flow leaving the site, we compared the 100-yr. SCS (SBUH) Methodology with the 25-year Rational Method and 100-year Rational Method. For the 100-year SBUH Methodology only, Since the total drainage basin to discharge is not homogeneous due to different soil types and different topography, we broke-up the basin into sub-basins and summed the hydrographs and then compared the flow rates with what they would be if the area was computed as one basin. The results are as follows: Storm Event One-Basin Combined Basin Hydrographs 100-yr. 24-hr. SBUH 10.72 cfs 13.84 cfs 25-yr. Rational 16.96 cfs -- 100-yr. Rational 20.17 cfs -- In doing our downstream analysis, an additional 7.23 acres of off-site area will contribute to the 29.53 acres being routed through our site. The peak flow used for analyzing the downstream drainage system was based on the 100-yr, 24-hr. SBUH Methodology. i i l l I 1 12 STORM DRAINAGE SYSTEM - PROPOSED I. 100-yr., 24-hr. SCS Method (Using SBUH Method) A. Areas 1. On-Site - All "Type C" Soils Area = 10.69 Acres 2. Off-Site a. Type 'A' Soils- R-8 Zoning (5-8 Units per acre; 510 x 135 / 2 _ 34,425.0 _ 0.790 510 x 160 / 2 40,800.0 0.937 490 x 335 / 2 = 82,075.0 = 1.884 (175 + 565) / 2 x 130 48,100.0 = 1.104 142 x 580 82,360.0 1.891 (610 + 530) / 2 x 145 = 82,650.0 = 1.847 555 x 260 / 2 = 72,150.0 = 1.656 560 x 135 / 2 = 37,800.0 = 0.868 460 x 130 / 2 = 29,900.0 = 0.686 Acres 11.713 Actual Density =t2.5 Units/Acre b. Type'C' Soils -R-8 Zoning(5-8 Units per acre) 70 x 50 / 2 = 1750.0 = 0.040 (70 + 150) / 2 x 175 = 19,250.0 = 0.442 270 x 70 / 2 = 9450.0 = 0.217 270 x 160 / 2 = 21,600.0 = 0.496 240 x 55 / 2 = 6600 = 0.152 Acres 1.347 Actual Density=4.45 Units/Acre —45 c. Type'C' Soils - Steep Slopes 130 x 250 = 32,500 — 0.746 (110 + 180) / 2 x 100 = 14,500.0 0.333 95 x 100 = 9500.0 = 0.218 ■ (110 + 50) / 2 x 125 = 10,000.0 = 0.230 670 x 250 / 2 = 83,750.0 = 1.923 675 x 75 / 2 = 25,312.5 = 0.581 635 x 175 / 2 = 55,562.5 = 1.276 3 i 675 x 75 / 2 = 25,312.5 = 0.581 635 x 175 / 2 = 55,562.5 = 1.276 570 x 115 / 2 = 32,775.0 = 0.752 540 x 210 / 2 = 56,700.0 = 1.302 Acres 7.361 Total Off-Site Area = 20.421 Acres B. "CN" Factors 1. On-Site Impervious = 5.43 Acres @ CN = 98 Pervious = 5.26 Acres @ CN = 86 Total Area = 10.69 Acres Portion to Downstream Impervious = 5.083 Acres @ CN = 98 Pervious = 4.025 Acres @ CN = 86 Total Area = 9.11 Acres I 2. Off-Site a. Impervious = 0.30 x 11.713 = 351 @ CN= 98 Pervious = 0.70 x 11.713 = 8.20 @ CN = 68 b. Impervious = 0.46 x 1.347= 0.62 @ CN = 98 Pervious = 0.54 x 1.347 = 0.73 @ CN = 86 I C. Pervious = 7.36 @ CN =76 I Pervious = 4.03 x 86 + 8.20 x 68 + 0.73 x 86 + 7.36 x 76 20.32 I = 20.32 @ CN = 75.11 C. Tc 1450 LF @ S = 2.00% (Pipes) - 4.07 170 LF @ S = 45% (Sheet Flow- Forest) - 11.95 220 LF @ S = 14.9% (Shallow - Grass) - 0.86 80 LF @ S = 11.2% (Shallow - Grass) - 0.36 300 LF @ S = 11.2% (Sheet- Grass) - 14.98 T = 32.22 Min. ID. P = 3.9" - 100-yr. - Renton, WA 14 5/7/99 1 : 36 : 32 pm Pacific Engineering Design Inc page 1 I TAMARON POINTE JOB NO. 98020 DRAINAGE STUDY BASIN SUMMARY BASIN ID: A NAME: 100-YR. EX. FLOW TO DISCHARGE SBUH METHODOLOGY TOTAL AREA. . . . . . . : 29 . 53 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 20 . 32 Acres 9 . 21 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 75 . 11 98 . 00 TC. . . . : 32 . 23 min 32 . 23 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1120 TcReach - Shallow L: 80 . 00 ks : 11 . 00 s : 0 . 1120 TcReach - Shallow L: 220 . 00 ks : 11 . 00 s : 0 . 1490 TcReach - Sheet L: 170 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 .4500 TcReach - Channel L: 1450 . 00 kc :42 . 00 s : 0 . 0200 PEAK RATE: 10 . 72 cfs VOL: 5 . 52 Ac-ft TIME: 480 min 5/7/99 1 : 37 : 33 pm PacificEngineering Design Inc page 1 TAMARO JOB NO. 98020 DRAINAGE STUDY ---BASIN SUMMARY BASIN ID: B NAME : 100-YR. EX. FLOW FROM ON-SITE SBUH METHODOLOGY TOTAL AREA. . . . . . . : 9 . 11 Acres BASEFLOWS : PERV0 . 00 cfs IMP RAINFALL TYPE. . . . : KC24HR PRECIPITATION. . . . : 3 . 90 inches AREA. . : 4 . 03 Acres 5 . 08 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . . 6 . 92 min 6 . 92 min ABSTRACTION COEFF : 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 0200 TcReach - Channel L: 1150 . 00 kc :42 . 00 s : 0 . 0200 PEAK RATE: 7 . 39 cfs VOL: 2 . 38 Ac-ft TIME: 480 min BASIN ID: C NAME: 100-YR. EX. FLOW FROM SLOPES SBUH METHODOLOGY TOTAL AREA. . . . . . . : 7 .36 Acres BASEFLOWS : PERV0 . 00 cfs IMP RAINFALL TYPE. . . . : KC24HR PRECIPITATION. . . . : 3 . 90 inches AREA. . : 7 . 36 Acres 98 . 00 Acres TIME INTERVAL. . . . : 10 . 00 min TC. . . . : 17 . 05 min 17 . 55 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 170 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 .4500 TcReach - Sheet L: 130 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 0200 TcReach - Channel L: 1320 . 00 kc :42 . 00 s : 0 . 0200 IPEAK RATE : 2 . 30 cfs VOL: 1 . 02 Ac-ft TIME: 480 min BASIN ID: D NAME: 100-YR. EX. FLOW TYPE-C OFF I SBUH METHODOLOGY TOTAL AREA. . . . . . . • 1 . 35 Acres BASEFLOWS: PERV00 cfs IMP RAINFALL TYPE . . . . : KC24HR PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 73 Acres 00 98 . 00. 62 Acres ITIME INTERVAL. . . . : 10 . 00 min TC. . . . : 21 . 78 min 21 . 78 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 220 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1490 TcReach - Sheet L: 80 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 . 4500 TcReach - Shallow L: 90 . 00 ks : 3 . 00 s : 0 .4500 TcReach - Channel L: 1450 . 00 kc :42 . 00 s : 0 . 0200 PEAK RATE: 0 . 84 cfs VOL: 0 . 34 Ac-ft TIME: 480 min 5/7/99 1 : 38 : 3 pm Pacific Engineering Design Inc page 1 TAMARON POINTE JOB NO. 98020 DRAINAGE STUDY ------------------------ BASIN SUMMARY BASIN ID: E NAME : 100-YR. EX. FLOW FROM TYPE-A SBUH METHODOLOGY TOTAL AREA. . . . . . . : 11 . 71 Acres BASEFLOWS : cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 8 . 20 Acres . Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 68 . 00 98 . 00 TC. . . . : 32 . 23 min 32 . 23 min ABSTRACTION COEFF : 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1120 TcReach - Shallow L: 80 . 00 ks : 11 . 00 s : 0 . 1120 TcReach - Shallow L: 220 . 00 ks : 11 . 00 s : 0 . 1490 TcReach - Sheet L: 170 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 . 4500 TcReach - Channel L: 1450 . 00 kc :42 . 00 s : 0 . 0200 PEAK RATE : 3 . 30 cfs VOL: 1 . 85 Ac-ft TIME: 480 min I I I I I 2 -7 5/7/99 1 : 56 :4 pm Pacific Engineering Design Inc page 1 TAMARON POINTE JOB NO. 98020 DRAINAGE STUDY -------------------------HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf\AcFt Acres 1 13 . 839 480 243400 cf 29 . 53 2 3 . 646 480 61437 cf 7 . 24 �� �� D) I 3 17 . 485 480 304836 cf 36 . 77 9 3 . 168 480 45140 cf 9 . 11 com bIAle 10 4 . 906 480 90839 cf 29 . 53 I f / 8 IYM1INMN\l\\\\`�•' l\1 ) �ttt� � 1 � ��' ,y t,',rnrr:wlJ:ullu t L,aL�wrrntq�.LLaa' � • \1� � ;011i \ ���''_/ ---- IblJl/t'Ip/pp •„ rIU11rJIMn NI71111 1 \ \ \ ` 4 m ♦ lilttillJ/1n11U1 1 1 binlllY1tlI11N111L1V.t\ 1 r�'`� `` � \ t VIIIlIIIn111M1� 1 1f11111M1119M1pI1N1111\,\., , \ \ q\,�F,p,\ I \ \ptI111WUPlpI\\)1111giAItiNtlNlp,g1\, `\ -, \L `\ ' i 1,,,•I•,1�,I,r,1 \,rl,�,l,`Ilt .ItiL\,\,1,` 1 11'fi I 1111 t11111 l I ` \\�\ Mill/l V II IIIL 111,1\a♦�\\\\ \� \ 1 /� ttli t�l \ L i'll•Fill' . \ , \\ \�``.`��\`=_ _ __.�-�,\; 1 1 L'o"\\`1 4� Itl IL (-Y- _� \\♦`111 V\ r' 111`1\ _ ����;��_�/F=il l'I LtLLL\\L+�M 1t� � \ // LLL,ItL C ` 1"l' \ !/ /IIII/ .'1 ;\\ - — •i//, ii� 11 1+1t�`\ \ \1Lt 1, L , 11111 i I 1 .: 1 L., , =--=2' %� L1 \\ 'i11 11\4L11♦"� / `\;� \ `LI\'L 1,.\ •Vllll +. II,< � \\..Y if IIII IIL µy♦ \ \ - Lt LLtL. l ,IitL�\,\LLtt ' ll( \LL\j1111LLI1+ N ll l l =1 \l\l l+ l Ui i+tl f _-'_ V ,♦\\' tL\\\�'l ELL \ \\\LL 1 )) i '/ ,Ilk \L t \♦�\`�'����` `�I,l11 It11\L\; ' ' `1 _ 1 \` �\����\``.`•; Il till 1\\�� t f 1 J \L\\L\ / 1 1 \.L\\•\\♦\\,\\` L1\LLLLI 1\1 �.n�� ``♦�l.`\ ! / \ 1 \ tL t. C \` �\\� ten\ ♦�\\\�.1\\\\�\\♦�- � 1 � - •� \Ilk 10, '1'llli ,L,,,, \ \, \\\ ♦ N\\\\����J•;��!t � I� .� IL 11 ' 0 1�11\ELL 1•" I ' _' 9 \...,tom- ---- - - -•-�-- _ +t`'1N�t // .r{/'rr 1 \ `\' `:`�♦ + elm t. / ' .... 111 l "`\\ E♦ `\� \ �1 STORM DRAINAGE SYSTEM - PROPOSED II. 25-yr Rational Method Total Area = 20.42 + 8.70 = 29.12 Acres P = 3.40" "C" Factor On-Site - 4.85 Ac @ C = 0.90 } 8.70 C - 0.612 I 3.85 Ac @ C = 0.25 Off-Site - 3.51 Ac @ C = 0.90 8.20 Ac @ C = 0.25 0.62 Ac @ C = 0.90 20.42 0.73 Ac @ C = 0.25 7.36Ac@C = 0.15 I C = 8.98 x 0.90 + 12.78 x 0.25 + 7.36 x 0.15 29.12 C = 0.425 ITc = 18.33 Min. (from pipe sizing calcs) I iR= (aR) (Tc)-(bR) = 2.66 (18.33)-0.65 IR = 0.402, IR = 3.4x0.402 = 1.37 f Q = CIA = 0.425x1.37x29.12 = 16.96cfs I III. 100-yr Rational Method - Using Entire Basin A = 29.12 Tc = 18.33 IC = 0.425 iR = (aR) (Tc)-roR> = 2.61 (18.33)-0.63 I iR = 0.418 IR = P (LR) = 3.90 x 0.418 = 1.63 Q = CIA = 0.425 x 1.63 x 29.12 = 20.17 cfs I 20 1 •,,dtl,,dld 'j�'�y,.;:.'�,`� la.-+.1x ., /> ';`\\ vim'. \ \\ _ — �,;;./,utalumuw,tlat�oJ.rtu1\,�(a„t� \ : 1• F� '_— � µ dIYD•Inllul 1Nv \ \�4�'1�, \ �— VIA \ lIII/IMlllllllll 1YIIII,IhINl1NN110\N, �{N '\\ I, \ Ih..11:llf7tUlYA , \mnnulnnxlll t IeuplMtNnnnwn\„o,. ,` � �,\��y 1 \aNtpl4Ulgl11\\;1111111�111RIPNIIIp,q`\\ \ "'\`I1 � ` i t 1 I l l l 111 ` � 1 �6 t„11,,0I,111\11\`l \'\.qa�\\\!!• \ t 1 1 pU,,\� \ 1 ill', il'i`\`\"``y�\:`�\��•��°���-;--_��-`.\ � \ � = 2; vmo,\ -� \\\,111,\ r'•/ ,1 tt,11`t"\\ `--' iS:i:--iF==j jll,t1 \\\ \+\\M1 ♦I1//ll\\>:,: 1t1 illlllt,l\ \\_��!�-��-,'� _ /„Ii 111 \\ Iif \ ...... `\ ..... it 11'11,`Il,yl,ll\�'� \\�♦t11\\\1 \ •: , ."♦\\\\�:-�'�?='-� __�_�- ,11 1 , 1 Iljll l\I�� I 1 \ \ - 11 ,1 � •\ \\`\\t\\.\.\`� \_7 1 \.\�:�•'�_❑ �S \♦\\\N\\\\\ \' / \\`_-=�--'" �i i,�t- .\`�\\\"�\`'•`:'•==_: \ , II1 it ``\.�\��\\•.`��-=_�->C�\\ '\\111 j1�111�111 1111 __�,1 t / L' \\`\l' , Its\1'\\.:: c:'t ``_`O♦\♦�:``=___�\`� \ 11`tji`\\11111 � 111 / -_:^^-, � / \ ! Il"t -- \ \\'\'11 1 1�l 1 1 _' I ,\11,, _ ►_./\\\`���� ,0 fit`\\`--'\`�\\\�`\\11�11 1 111 / If 1 ( 1 ! /!'/ •/ ` f '\�\\qt tI b. \:::•\��W\\• \• \�\\t�\�t1��tl\11111! 1 1 1 '� �-- �; �•• 'I' lo lk\ 10 \ t\ Jay _`� _— — — \1 I it 5 , ,wi' i \ \ ♦`♦♦\ \1 �` 1 __ __ \ 11,11' \l 1 1 ICI ,".� ♦\\ �� .``♦�\ i DOWNSTREAM DRAINAGE ANALYSIS IThe entire site comprising 10.69 acres with the exception of 1.59 acres in the northwest corner and west side will drain southward to the southwest corner of the site. The total off-site area Idraining through the site to the same point is 20.42 acres. After being routed through the biofiltration swale the discharge will go into a downstream I manhole labeled as 1. The peak flow from the site into this manhole is 13.84 cfs using the 100- yr., 24-hour SBUH Methodology. An additional 7.23 acres of off-site area from the east enters the same manhole 1 from a catch basin labeled as IA. This peak flow is 3.65 cfs using the same 100-vr, 24-hour SBUH Methodology, for a total flow into manhole 1 of 17.49 cfs. IPassing this flow through the downstream drainage system all the way to Lake Washington reveals that all of the pipes except for the section between 1 and 2 will be adequate to convey the I flow. We will replace this existing section of pipe with a 24-inch pipe which will be more than adequate to handle the flow. The distance from manhole to the discharge point in the lake is about 470 feet. I (See attached map on page 23) I I I I I 22 I mamanamanuman a man (7 WEND 36" CMP INTO LAKE WASHINGTON IE= 16.5' 11 11 11 ' 11 w .� � 11 �� �. ��s �,, 11 � � � r`®--- 11 4:E, ���: 11 � � m � _.. 11 J,_-SPNH 48 -AN GR 6 48 TOP 24" CMP VERT. PIPE 23.4' FILLED WITH WATER NO W D 24" CP OTHER PIPES VISIBLE DER RR TRACKS'*4' W D DER= 3 I XE= 3 2�.8' ........... E END 24" CP I E= 33.5' Defoid jo; peon aq ol WEND 48" L x 22.50 H BO CULVERT DOI aAIJP /JjU9 6U1.461 UNDER LAKE WASHINGTON VD N IE= 43.2' vn a Ail U: r, CA o DJ Duo f� { / \ / ' // ---AOJ'24'24" 25 9.55' tv- %o- ---------- -------- -- 0 C7' Ic (2 P/V r VFW i 71V/1 (9-L 2 7 7 -V9LI7 yo 1 A- Y168-5;. 09d X I i el�,\i�j Z t 0 Si OP, NE, S U L v ,? FT/=I' Y 1 C 8 6 1 16 SF V C p11R,, T T A L F jCk tC, C,C. Peat CULVERT q� A x 2, 5 A Ld \ \`\\ � \,..)� ,.� l,;\D >� �t,;ttlil li,llllt 11,11 ` 1 _._( ".• r^1 , • ,.\ . ,1, \tt1,111t,r tltllllt 111 \ \t1'\ 1 11 \ 111'.Ill,lt 41i1t1�111 � ;;.• �1 , \ \ i dl � , ,1141j1'1't,l,ll/rli i / ��•,�. � � 1 11 1 �, \Itt`I`tl'Iiphllltl t l I � I y1 1 1 \" 11„II,1 �\1110,'Nt 1 1 t1t I\\t 1\ Ill,llltO n ,1t 11 1110111 \` O C/� Ilil,h�liall�I�� \\'\\ll 11ri11. ` t t,yl,l'{111�",����.:` \.\\\\ I•I 11 '\\1 11 1 \\111\`�-�\`•.�\\•• \\1•y ,•,,\\,i, \., .!`\\t �1\\ \ �1 N \ V,1 \`I ,,•\f71 J,\. \ ' \1 tl. „\ 1 1 ) 1 Ittt1 \\\\'� ill\``�'.'�0.�\ ����\` _\\Il,ilt`°1�ti•�\�\\`�.�����i�\`fit\I, 1/ _.. _L_ / pl -- ,\ I\5t1 �X\\\h \ , ♦ \.\.•.` `. _,t\lilill'\\t.i.��\`;���\�\\\`.•.�\ 1 i' I!I 1V \ 11 ,1, '0.`\ \ .,\ •. ,��\�\•-\111it\\11 „�;�\ -.,�, ,.\ \'•\\ y `\ � /' / \II, .•, ` •11 t !r,! / I l 1 1\ \ 5t\\\\,♦,.,1\ 11t 1,11 1101 tltl,l`\ `,`♦\"�"\\�-\\\\, i •h y.'. t11t1 1li'!i^�'__i/ 1 I 1 /!/t/ ! 111 11 tl\\ \\\,. -\,\t ,•.\\` � _;2� ..\. 41� \ J///�/ rr '__ _ 1 I 1 r 1 11 1 I I 1 111\,\\.,\ \\-\, \\\\i ♦`` \\' 11 I / I i t 111 1 1 1 1 1 111t�1\\1111 ,\\�\• t;It\,.IIIIII 51 \:�� \„-,-� `` \♦\\ \ III \\ \1 ,', u,t,ltl l\ I //� 1 i 11 1 11 5 \\_,,;` �•,\. , t `1\1111 UI'1\ ` 1` 1 1 i 1��5:,!��= J I {1,,It,11,! I t '�-•_ �__. \\\\0.,-`. \\\1 t1I! , 1\1111I11 / \\"��.'-�'•\ \, \ \1t ':'�t\1�� �`,rlr!!i/"'i / /-_.'-��_. / lillhllllr �----•:-::� \���.,\\i\ 1 lltli 111 t1\\ tl\t\11i:•-- - i=- \��♦ 1 :\• \ \`,`�i\�\Y`\\,� I'11t11, �,'�'_..`q\\. yl 1 \ � _�•',/i 1,q 1,11,,,,! ` \\ _- �` \1ttu1 ' - 7• � i rl ` y 'tll I! Jrl 11/r/ I \ 1 \\It111 \.• � yl\1y,II1/\_- „S..tllt\111 Q r Iyl},i\,11,1`t�<_ / -"" Y•y.1 111lt,t \ 1\I1,':;�' \\\.\-,` ,\ •\��`��` \\fill 11/!\` , ,duo � , \`\ � � \:_ `\ 4:,•,\t`\`\\\\\itlir 1111 tln,Iitl 1 1't\'1\, \\�t\\\\11,\I'\\ \ 11►Il�t i11' ,`\\ t;it __—, 7 `,�,thlP �\, \ �\\\ \,I j 11 1111111 ,1 l l i111 \\ ♦ i I t' I 11 - ,I``h,,1\\, �! ,\ \ `\\1\\! 1 Iillllllll� II11,11}j !I\\`y I,11�1I�_ `F@;N't?.\ �'. \ ' •, \\, t Iltlrllil IIIIII , '�` 1,11 �• - _ _� `• �1}�� \ �+ \\\wptl!alu!N:IhInG\vummm�um\ y trmsvara ��^ >\� \`� \w`�,i`, � \ \ \ \ \ulnnnuall;;,p,alpA1 1 nuanwnn+(n t •. rrglmn,alna —:•, ,\1_ F \ 111i411�N11gN1„Ippp I I/llnlllnlrnllllr , `ngNunnunlAtM -, "' '' '`utu;U11VY,Nlylkpnl lfffnlrlNllplifil \rrl, 1\Ilse �)\y, (j,• \\ '`^ 'II\n\nugaNwW!n'r1,I.:...A!%n,Mr nlcluca"I' nnumnianlrr. 'n ,lt\;vaus9arn \ 119VINAA' a99npp!n/tn r . + n 1 !fir wuAAt it .�,-�� hP � \ �,� \I .\.a1'aAA�rv'nAr ,/!, ``• \\ \4)t' \ \ 1t111 .\\\\I'A.HMHAW r AA`. A71AA 9A1 �,.c \ �fi`1! \ \. r r A!p/iii/i,tahq�al\P•�Ik`�`Nrr�V \\ `,� •\\ � � �� iN�irrJ �` !4i//i Illlll/rjlrl l�' Ilrt7hl' \ °' `��\ - ,!�,/Ip ,"/%q%Yi;,i!a� S'':y�iG_%/i•//(Ir �IA/A„Ip � ., •1,\4\< �r- _ __ � , v� .�.�-�I!/i.;i�%i%ii!/<; :'�'t�r�•eY��SS>.!r pl�lt41PAli --- -- \�`a "\\\ s - li%'�S� � r�/ /�/y/-.-'y.w�S�/i�i,�.��3F'iJNPhF•'h♦ \ n�:.; __/ter�.`� �'y1 /7/„ / 4/�,i//r � 0/+/.t'Yld( '4hIr \ � •.�� rih 1 'll 11111111111,1i1ft,1,11111111\jltl(\ 1!i \ \�I�t -t).• `. \ ` Ill I I Ill piq\\\, ,U�d\\,\1(111.! 1 I, r I)11 r\11 1 I l / --_ \ r\ `\ - \ \ �..\\\11111 „11'I ,11, 1\\\\d'�'`•AI/I ! ! !! `\ � , 1 \\ - � \ :\, ,p 1'l lqul P\. :5a•�\,tc, >khYarrinln! Ir!/! •\� \ .\ \-,. \ Lf4� �!C 1t'1�I,II I r It N, ,\\\\,\tARI,14An!/Ill!!( /�I I I/ cFd"4, 1Ildl rl,gmPIT --- `\ -\` � 1�, \' /•��� /�! 'J C'� %%I !/! .. I 1 11I I I I ---- ____ � 1 /Illlillit �1,111111111IIIIII' .;;i����,• yt¢y;_.5��-"^ �t"�\ , ! •inY ;MW�,r/i�1r.� \ \\Y\\,111gJ,uM�IF -- -- _ -.� ��.,`=t\ •I.< �� �� d r {�lfr .Ih14t`� �r t `„tlallld'll\ \ 1 'y/ ; •%rr 'Ak' III 9 '{, II �i•�j �t,C\-.'i'!.`1 5/7/99 2 : 48 : 31 pm Pacific Engineering Design Inc page 1 TAMARON POINTE JOB NO. 98020 DRAINAGE STUDY BASIN SUMMARY BASIN ID: OF-1 NAME : OFF-SITE FLOW TO DOWNSTREAM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 7 . 23 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 5 . 14 Acres 2 . 09 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 77 . 73 98 . 00 TC. . . . : 27 . 98 min 27 . 98 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 . 2530 TcReach - Shallow L: 280 . 00 ks : 3 . 00 s : 0 . 3500 TcReach - Shallow L: 440 . 00 ks : 27 . 00 s : 0 . 0489 TcReach - Channel L: 140 . 00 kc:42 . 00 s : 0 . 0178 PEAK RATE : 2 . 95 cfs VOL: 1 .40 Ac-ft TIME: 480 min rBASIN ID: OF-2 NAME : OFF-SITE FLOW TO DOWNSTREAM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 25 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 4 . 25 Acres 0 . 00 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 76 . 00 98 . 00 TC. . . . : 27 . 98 min 27 . 98 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 .4000 p2yr: 2 . 00 s : 0 . 2530 TcReach - Shallow L: 280 . 00 ks : 3 . 00 s : 0 . 3500 TcReach - Shallow L: 440 . 00 ks : 27 . 00 s : 0 . 0489 TcReach - Channel L: 140 . 00 kc :42 . 00 s : 0 . 0178 PEAK RATE : 1 . 10 cfs VOL: 0 . 59 Ac-ft TIME: 480 min BASIN ID: OF-3 NAME: OFF-SITE FLOW TO DOWNSTREAM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 2 . 98 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : KC24HR PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 89 Acres 2 . 09 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00 TC. . . . : 5 . 00 min 5 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 300 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 0488 TcReach - Shallow L: 140 . 00 ks : 27 . 00 s : 0 . 0488 TcReach - Channel L: 140 . 00 kc :42 . 00 s : 0 . 0179 PEAK RATE : 2 . 74 cfs VOL: 0 . 82 Ac-ft TIME : 470 min 27 5/7/99 2 :48 : 31 pm Pacific Engineering Design Inc page 2 TAMARON POINTE JOB NO. 98020 DRAINAGE STUDY HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf\AcFt Acres Qioo �v Blo- �� 1 13 . 839 480 243400 cf 29 . 53 2 3 . 646 480 61437 cf 7 . 24 or_ 2 0r-3 ' 3 17 .485 480 304836 cf 36 . 77 f/YP 9 3 . 168 480 45140 cf 9 . 11 10 4 . 906 480 90839 cf 29 . 53 Z (Lh r ��o - swAle 75- Q T � Bi o - 5wG je 28 i i IV. RETENTION/DETENTION I ANALYSIS & DESIGN I I I I The project is exempt from detention requirements since it discharges directly to Lake ' Washington, and the increase in the peak rate runoff for the 100-year, 24-hour storm is less than 0.5cfs. Since no storm detention facilities are proposed, this section shall not apply. However, we will use the space for design of the bio-filtration swale. Bio-Filtration Swale Design Q2 = 3.17 cfs - On-site only (see attached calcs) Assume depth of flow= 8" (wetlands plants) B = 9.64' Total Width= (2' +2' + 9.64)x 200 = 17.6 155 B* = 17.6 - 2 - 2 = 13.6 Qioo = 13.84 cfs - Total Drainage Basin - 100-yr flow V = 3.07'/sec (See attached calcs), Y = 0.31' Bio-swale= 155 LF, B* = 13.6 Side Slopes= 3:1, S = 2.0% V. CONVEYANCE SYSTEM ANALYSIS & � DESIGN r r 3s PACIFIC ENQINEERINQ DESIQN INC. '108 a �� CIVIL ENGINEERING AND PLANNING CONSULTANTS SHEET NO. OF 9 CALCULATED 6Y "` -/ /L%l r2 DATE 7-0 c� i -She Lg- c !� p' / /4 r ¢a . _ . .a o, 2 z .. 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