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HomeMy WebLinkAboutOVERLAND HILLS SUBDIVISION PRELIMINARY - 38 90 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTN h�^ PRELIMINARY DRAINAGE REPORT FOR OVERLAND HILLS JULY 1990 PREPARED BY STEWART & ASSOCIATES. INC. All- �ompvrATiorvS James H. Stewart & Assoclates, Inc. 214 N/.Howes/St. Ft. Collins, CO 8U521 (3U3)482.9331 By: e- ,4 Date 9O Client: _ /n �Sf�//�/G" Sheet No. of Chlcd By: Date Project: O`C//Id r!/—/—�� Job No. Subject j�I.8//7a'1.�G' 7"/C�i77i/1>^✓"4 -- — ;ompvrATIONS James H. Stewart & Associates, h1c. 214 N..Howes St. Ft. Collins, CO OU521 (303) 402-9331 By: ✓�G-f Date % O O Client: Sheet No. of �l Chkd By: Date Project: Job No. Subject eW G - -- _ i9 r..1 _ - G I I I '/ ... _ . 4401 I I : . — — I • l .l I I ompu'rATIO S ompuOrATIONS ,James H. Stewart & Associates, Inc. 214 N.-Howes St. Ft. Collins, CO 80521 (303) 482.9331 By: Da to /�"�'� Client:_ g0k.+s7 . Sheet No. /O of l� _ Chkd By: Date Project: ��`'�/���� .�'' Job No. _ Subject — /�/. - ✓/.� �e�3 a gg e / "'kol :7�„ppy V� / / ,Crm'� y�-f /�1.�✓�. I� � I I l • I I I � i -it ff, ' onnpuATiorvS . ,James H. Stewart & Assoclates, Inc. 214 N..HHowes St.t. Ft. Collins, CO 80521 (303) 482.9331 By: Date 7 // 90 Client: f�/` i!7 T!/.7/�" Sheet No.of — Chkd By: Date Project: __ //'�/�p d�6—�—�����" Job No. Subject % 12 9aci C' s STRIVART&ASSOCIATE' Consulting Engineers and Surveyors July 2, 1990 Mr. Rex Burns Larimer County Flood Administrator P 0 Box 1190 Fort Collins, CO 80522 Dear Rex: This is an update of the detention facility for Springfield Subdivision dated January 14, 1980. The detention pond is located in an old gravel pit at the Northwest corner of Springfield Subdivision; Sixth Filing. The subdivision contains 51.35 acres that drain to the detention pond. The site is in the Spring Creek drainage basin and the Mass Diagram method of required detention volume was used. The required detention is 5.9 acre feet and the allowable outflow rate is 7.19 cubic feet per second. The outlet pipe through the berm will be a 12 inch diameter N-12 A.D.S. pipe which will restrict the flow to the two year historic quantity of 7.19 c.f.s. The outflow will flow in an open swale Westerly to the existing Spring Creek thalweg. The swale centerline will be forty feet South of the North line. of the Northwest I of Section 33-7-69. This places the swale between the future South curb and the future South sidewalk of Horsetooth Road. The calculations of the runoff quantities and the capacity of the improvements are enclosed as a part of this report. Also, enclosed are the grading plan of the detention pond and the plan and profile of the outlet swale. If you have any questions concerning the plans or the report, please call. Richard A. Rutherford, P.E. & L.S. President lkk enclosures James H. Stewart and Associates, Inc. 214 N. Howes Street P.O. Box 429 Ft. Collins, CO80522 303/482-9331 SUBJECT .,1-P&ld1LElELD- �LXLIi�14LN� --. BYUAIE GLL3,/90 p ! tvs'��i SH, NO.-------- ---------------------- PROJECTNO.---------- Ti NtE (M/M.) Z Cf C A C.F.S. V OC UME 6V.Gf. /0 7,Z /.ZSx 0.¢s x 5/.3,7n Zo7•i IZ 4, 740 Zo S.Z ZB•BS lSb. Z /80, Z4-0 3o 218, 340 40 3-s /01• 1 Z4Z, (,40 40 Z•to 7S. 1 Z70, 3(,o 1zO q'1 9 30% (,80 /So /, OS 30.3 '�O.DOD-1 327, 240 300, o0o Zso, 000 II00,oa0 so, 000 1 29(0, 46 0 A 38,BZ6 T 10 Zo 30 40 60 10 lao TIME CM/v.) ISO ! SUBJECT `S e�LALb��E�Q-�LxSh'�C�24 BY--.k_-2L1_�•--. DAIE LLL- 10 -D-F,-TdinQ4L- SHE JO.-------- PROJECT NO.---------- AeeA : S/, 3SAc-, 14 57(/•l-0.z) 311o%z- ------------ $8 Miv, ). L /A3 a far. Q z yR = O. Z X 0.7 k s z 3S = -7, 19 c. /= S . H9sT• Q/oye = O,ZJ( 1•Z X S/,3S = /Z.3Ze•F,J. 1-irJT. Q goo pe ,_ /• zS X O, z A /, 7 n S/,3.5 = z I>eV. Q -Z 'c = Z Z, ¢ c., = S. C41-C, F90AJ JePAe4rE SASWf, ©vrLe-r PIP' E 2 tiv. w, r,, _ ¢/. Z O V ° D.& Z,rc 3z•2,x 3.9S - 9.5-7 _(r•/sec. A= � q 57 — 0,?S fEz Us6 12'' P.V.G. S W/��C SEGT/Onl CZ /. 4R X 4 0 1L�3 ltOZS XC, J KI`0.003) - �, 10 SITE LOCATION: The site is located in the Northwest a of Section 33, Township 7 North, Range 69 West of the Sixth P.M., Fort Collins, Larimer County, Colorado. The area is 4.1842 acres more or less. It is located in the Spring Creek Drainage Basin. The site is bounded on the East by the Springfield Sixth Subdivision; the South by Springfield Subdivision Fifth Filing; part of the West and North sides are undeveloped. There is a single family residence located to the Northwest of the site. EXISTING CONDITIONS: The site drains in three directions due to the South side being on top of a hill. The West 1.1 acres runoff is to the West to Spring Creek. The existing slope is .10%. The East 2.7 acres runoff is to the Springfield Sixth Filing. The existing slope is 1.7%. The North 0.3 acres runoff is to the North. The existing slope is 2.0%. There is no existing offsite runoff across the site. Total existing site runoff is Q� _ 1.79 c.f.s.; Q�0 = 3.79 c.f.s.; Q100 = 7.82 c.f.s. Basin I runoff, est 1.1 acres, is 0 = 0.92 c.f.s.; Q10 = 1.66 c.f.s.; Q100p = 3.56 c.f.s Basin II runoff, East 2.7 acres, is Q = 0.74 c.f.s.; 410 = 1.35 c.f.s.; Q100 = 2.7 c.f.s. Basin III runoff, tie North 0.3 acres, is Q2 = 0.13 c.f.s.; Q10 = 0.78 c.f.s.; Q100 = 1.56 c.f.s DEVELOPED CONDITIONS: All of Platte Court East of Platte Place and the South Half of Platte Court West of Platte Place along with lots 1, 2, 3 and 4 will runoff to the East to Platte Drive, then to the detention pond constructed on Tract "A" of the Springfield Subdivision South Filing. The area is 1.5 acres. Runoff to Platte Drive is Q2 = 1.28 c.f.s.' Q10 = 2.21 c.f.s.; and Q100 = 4.41 c.f.s. Lots 5 and 6 will runoff to the West directly to Spring Creek. the area is 1.1 acres. Runoff to Spring Creek is Q2 = 1.43 c.f.s; Q10 = 2.53 c.f.s.; and Q100 = 5.45 c.f.s. Lots 7, 8, 9, 10, all of Platte Place and the North half of Platte Court West of Platte Place will runoff to Tract "A" between lots 8 and 9. The area is 1.6 acres. Runoff to Tract "A" is Q2 = 1.6 c.f.s.; Q10 = 2.7 c.f.s.; and Q100 = 5.5 c.f.s. There will be no detention for lots 5 and 6 because of Spring Creek. The balance of the project will be detained in Tract •"A". The required detention is 14,998 c.f.s. Tract "A" has an excess storage capacity of 13,068 cubic feet. It is our proposal to raise the spillway elevation along with the top of the berm elevation by 0.1 feet. By raising the spillway 0.1 feet the pond will have a new excess storage capacity of 5,718 cubic feetafter our input. There will be no revision to the outflow Overland Hills Drainage Plan July 1990 Page 2 rate. A copy of the original Tract "A" pond report and plan are included for your review. The 100 year flood plain line has been determined for Spring Creek -over lots 5 and 6 and is shown on the drainage plan. The full development 100 year flood plain line of of Q ='1580 c.f.s. at station 403+40 (Horsetooth Road) from the Spring Creek Master Drainageway Plan completed in March, 1988 by Engineering Professionals, Inc. was used. The Spring Creek Master Drainageway Plan does not include our site, but by using their downstream flow will give us a conservative 100 year flood plain line for our site. Franklin D. Blake, P.E. & L.S. } MPU"TATIONS lances H. Stewart & Associates, Inc. 214 N..Howes St. Ft. Collins, CO 80521 (303) 482-9331 3y:Date S 9D Client: ��zelaor' // Sheet No.of ll ;Irkd ray: Date Project:/ ���'f_'rl7 ��Y/Zz: .� Job No. ;(Object i i i e ` C MPUTATIONS lames H. Stewart & Associates, Inc. 214 N..Howes St. Ft. Collins, CO 80521 (303) 482-9331 3y: . �.!'G/ Date Client: S�7J21//�✓ Sheet No. of 30W By: -Date Project:_���/��'���i// -5' Job No. subject/���'"r✓/`J�'?:�c�'/G'�/Ti.o%?"'/�il� l "' `% .. I - - - :-_^ QO I (ieMPU'TATIONS lairtes H. Stewart & Associates, Inc. 214 N..HowesrSt. Ft. Collins, CO BU521 (30) 482-9331 IY: _ %^ / Date Jam' Client: Sheet No. "-3, of ;hM By: Date /7/Project:�1JG/�o��l� /�/S Job No. subject A 1.' r ( )mpu"rATIONS I4tttes��H. Stewart & Associates, Inc. 214 N..Howes St. Ft. Collins, CO BU521 (3U3) 482-9331 // ly: �.L�L— Date_ Client:_ i/."�—s�A/Y/`/ Sheet No. of ;hkd By: Date Project: �l�G//9� f7/�� Job No. subject .06 t ee- I 47 c mpurATIONS lam ' es H. Stewart & Associates, Inc. 214 N..Hovves St. Ft. Collins, CO 80521 (30 482-9331 3Y: Date Client: Sheet No. � of 'hl(d By: Date- Project:- --Job No. ;ubject woo c mpuOrATIONS amps H. Stewart & Associates, Inc. 21.4N..H-owesSt. Ft. Collins, CO80521 (303)M-9331 Y: ct Date Client: —Sheet No. G of hkd By: Date Project:-- z�Cveloov Job No. ubject