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HomeMy WebLinkAboutHAMPSHIRE COURT FINAL SUBDIVISION - 31 92A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTT, FINAL STORM DRAINAGE REPORT. FOR HAMPSHIRE COURT SUBDIVISION Prepared for STORCK DEVELOPMENT CORPORATION Prepared by STEWART & ASSOCIATES, INC. 103 SOUTH MELDRUM FORT COLLINS, COLORADO 80521 303/482-9331 JUNE 1, 1992 i RAINFALL PERFORMANCE STANDARO.EVALUATION --------------------------------------------------- PROJECT: STANDARD FORM A COMPLETED BY: PI R DATE: ------------------------------------------------------------ DEVELOPED ERODIBILITY Asb Lsb Ssb Lb l Sb PS SUBBASIN-� ZONE-(ac)--I-(ft) i (%) .I(feet) I (%) I (%) rTAL s.0 77si 1.0 ; 7w !1.0 78 ---------------------------------------------------------------------� )I/SF-A:1989 IU ---EFFECTIVENESS-CALCULATIONS ---------------- _ PROJECT: STANDARD FORM B COMPLETED BY: P/JZ DATE: Erosion Control C-Factor P-Factor Method Value Value Comment ------------------ --------------------------- rpac�f o wdfkf Toun�ailonJ cn2. c{rlye.royf 0.01 0,0( I.Q s"i ra ✓ M�ic� 'in P°mod//. 0,0� �. 0 IhIC'1' �IIII�"Crl Ter D S Prow M✓ic -/------------------------------------------------------ O.00 1 MAJOR - PS. SUB AREA BA(SIN (o) BASIN (Ac) CALCULATIONS T I __—_� —aG-------------' � 7B7 S, O 1"ocG�� o.,� �.✓Gl�tf-- =--0. 7� drl'V61 a Loa(, s i ro Mvl GJ, U. 4- A- borr SroV^c� Z•.10 Ae TeMP Llc0.75 /+e S =J* 4-s s 0.48" ----------------------------------- -----------------------------------) HOI/SF-B:1989 to w• . CONSTRUCTION SEQUENCE PROJECT: i42ril2E�iCr coon" st/A/ STANDARD FORM C SEQUENCE. FOR 199t-y3 ONLY • COMPLETED BY: PI R DATE: 2 Indicate by use of a bar line or symbols when erosion control measures will be installed. Major modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. YEAR MONTH OVERLOT GRADING WIND EROSION CONTROL Soil Roughing-. Perimeter Barrier Additional Barriers Vegetative Methods Yards Soil Sealant Other curbs RAINFALL EROSION CONTROL STRUCTURAL: Sediment Trap/Basin- Inlet Filters Straw Barriers Silt Fence Barriers Sand Bags Bare Soil Preparation Contour Furrows Terracing Asphalt/Concrete Paving Other FoundGJions-dries VEGETATIVE: Permanent Seed Planting Mulching/Sealant Temporary Seed Planting Sod Installation IG �•K Nettings/Mats/Blankets Other TeM�oro� sf�1-�(�✓ • rMdlc%i STRUCTURES: INSTALLED BY MAINTAINED BY VEGETATION/MULCHING CONTRACTOR DATE SUBMITTED HDI/SF-C:1989 APPROVED BY CITY OF FORT COLLINS ON JA`U'.A Y 1991 8-20 DESIGN CRITERI?. lV W F- cr _ v Z Ate. _ _ _ _� o lil J 0 � a � N z 2 � LEGEND J Z w w e w � w a z � fi 4 J r u a *44"m 'Awjw Mom► i J 0 6 NUM19R5 J.N.S.AA. I CLIENT $MEET MUM =ER 4 or 7 e Final Storm Drainage Report for Hampshire Court Subdivision SITE LOCATION Hampshire Court Subdivision is located at the Northwest corner of West Drake Road and Hampshire Road. It is located in the Southeast a of Section 21, Township 7 North, Range 69 West, of the Sixth P.M. and lies within the Spring Creek Basin. EXISTING SITE The existing site is the only remaining undeveloped area in this portion of the Brown Farm. West Drake Road is on the south; Hampshire Road is on the east; the Hampshire Square residential development and a day—care facility are on the north side; and the Pleasant Valley and Lake Canal irrigation ditch is on the west side. The gross area of the site, including one—half of Drake Road and Hampshire Road, is 6.0 acres, and the net area of the site is 5.0 acres. The site is covered with natural grasses. The existing site drains from West to Northeast on a one percent (1%) slope. The Hampshire Court Subdivision is a part of the 20—acre RP zoned offsite area referred to in the Drake Crossing Shopping Center drainage report. According to this report, the 2—year developed flow of 14 c.f.s. from the 20—acre RP zoned site has been allowed for in the existing storm drain from Hampshire Road through the Shopping Center. The report indicates the detention required for the Hampshire Court Subdivision is the difference between the 100—year and 2—year developed storms. A page from Drake Crossing report which states these conclusions is included in this report. 11XVIN 0] 2:1 1=1 a I I Hampshire Court Subdivision will be developed into 18 single—family lots and an onsite detention pond tract. There should be no offsite drainage through Hampshire Court Subdivision because the Pleasant Valley and Lake Canal ditch will intercept any flow from the west, and the existing single—family development lying to the north will drain to the east. We propose to provide onsite detention for the difference between the 100—year developed 6—acre site and the 2—year historic 6—acre site. The 2—year historic release rate from the gross area of 6 acres is less than half the 2—year developed release rate proposed in the Drake Crossing report, so our release rate and detention volume are very conservative. The release will travel approximately 100 feet to the north through the Children's World drainage easement to tie into an existing storm drain pipe. The present site has historically drained to the northeast, which is into the Children's World detention pond area, and then into the Drake Crossing,Center storm pipe system. The proposed storm drainage system for the Hampshire Court Subdivision development will follow the same drainage pattern as historic runoff flows. Final Storm Drainage Report Hampshire Court Subdivision June 1, 1992 Page 2 We are unable to divert surface runoff from Drake Road and a portion of Hampshire Road into the Hampshire Court detention pond. Both of these streets are fully developed with curb, walk and pavement, and it is impractical to attempt diversion of the runoff flows. We hereby request a variance for not detaining this runoff. This development will not affect the Pleasant Valley and Lake Canal irrigation ditch adjacent to the west boundary of the subdivision, nor will it have any effect on the downstream ditch. The detention pond on Tract A of the subdivision shall be maintained by the owners of the subdivision. Release from the detention will be through a restricted opening and then piped into the Children's World detention pond. We propose to construct a concrete trickle pan across the Children's World pond, and to increase the size of the existing restricted outlet to accommodate the total release flow. The Children's World pond is within a dedicated drainage easement per Book 2300 at Page 929, but permission shall be obtained from the property owner to do this construction. EROSION CONTROL Hampshire Court Subdivision is located in a moderate wind erodibility zone, and the construction of the curbs and street will provide the minimum barrier spacing of 200 feet. Rainfall erosion control will be provided by installing a sediment filter at the outlet of the detention pond, by the construction of paved streets, by straw, mulched seeding, and by maintaining some of the existing vegetation. All of the storm drainage design and erosion control procedures shall be in compliance with the City of Fort Collins Standards. Phillip I. Robinson, P.E. & L.S. 7 Lake E St. _ _ r Dr O1 `vi Lj to t o c Fait-Knotwood Ct EveDf green er Ct c Sus aS W PR05D CT 0� 'J W La ml D m W. Lake St F - a T s holy St. m Dc. Ott C; m Coopers n. _3� / AZO t0/� o ad n WaY Cedor Loq PL. �� . v o H.. °{ d 'b2 am worth Rd. _ n Herit e c+ Q x 1�11� P Circle sumac St. Cl) ot `q si. r age ark a• Suffolk ' ° �� r DL pblYm0b00 Promenad �'..�'" -W. Stuart St W.- We : f Kin b p_�\ 7�� W. 31 Rams Cor- Ryeland Ave ;. 4. gs oo o E pt'r'd9( Gt. Pec a (-Ilant. �' �• ° Ct d R uQh Dr. t �� N 1 tGt• Cptekg n Dorset a a,� W.. Smart sr, a Q��pOdcr� s� ° _ ) I CtO._: -'a.a �`S/(�0 �irsN'- C.+ _ fir' C ''•"- � fie• -�,.�. Freedo n - �.��. 20 `r ° .� t a/e diT 6+ • 'r° e e :. ie GlenwoodDr rnf/eld �t Mir r�rmere c ... e c Sunder Dr_ a Cgswoltl 1 �\jj1,G �' Ctr.. c, , T: w Sluort st e11 C 6 �, pl rive. •. eUt Nell Dr n �bnCL Pon Ct.. ? C� �� •v Dr do / Q'" ydesdile DI cl FiDestons Dr y� coca°o ... 4 bg :" �i�Q s� a Dr. Ct.:f. Sca borough r ( ¢o ^ Nor PamPos a..., ; °4 Dr. Cry a I I r Av Germantow7 �. �'- Ave. 0 3, u Concord Qw Dr \nlroe. . vaflev o F u ro L` ° s i rasa Bluegrass Dc 6 D� o .. C/ a o�• so °mpshire 0 Ro55 N G H Ct. r O; :. H '.. �betr 1 t E c C, In Mt Royal Ct = 8 o Lodi CL L. b o (n Seccomb cS� T r Q. Haven Dr. 0 G+ E McK� S/ Q ---- S�_ / .- Ct... Glen o a �:{a .' > astin s D ovi mm yd . Cif St' V. t� o a E c �Q sP� Frrmonts C o o r °agh pr. a P c R O �� •r r. yew �K• Hull St. Ct. o s, 3 LOU �:$ �. �. n Zendt Dr. • F L �P sv NCr Falcon v 81 e, Ct. Miehner Dr. m Z.... _ •. ` . And - to o ul St. lr Hvline Dr. 72.c._- p/� I—rz4M �fZ�9 K Cr�o SSI la1 G �� '�Inis?F IMF r� storm drain flows directly to the 36-inch storm drain. Therefore, a 19 c.f.s. inflxxa is allowed for Area 4, tracts B & C and Valley Forge P.U.D. The retention for this area has been calculated using a mass flow diagram. This is shown in Appendix B and it was found that retention of 1.40 acre-feet is needed. The existing drainage swale can easily handle this retention. retention will be required in Areas 2, 3 and the RP zoned ara. The storm sewer has been designed to drain a 2-year storm for areas 1, 2 and 3 and the 2-year storm for the RP zoned area. It is impossible to drain the 10-year storm as required because of the size of the existing storm drain under Drake Road. We have been able, though, to provide adequate retention. It has been calculated that the RP zoned area will generate 14 c.f.s. during the 2-year developed flood. The letention required for this area is the difference between the 100--year and 2-year developed storms. At the time Intention is built for this area, careful design will have to be done so as not to allow more than 15 c.f.s. from entering the drain. For the present 100-year undeveloped flood of 15.5 c.f.s, the water will flow onto Hampshire Road and enter theJrain through an inlet at the low point. This inlet should have a throat opening of 8-feet. There will be a slight backup of water, but it will occur only during the 100-year undeveloped flood and be eliminated when the RP area is developed. Calculations for Area 1 show that the 100-year developed storm will generate 14.9 c.f.s. The combination of the two 8-foot inlets on either side of Hampshire Road will provide enough capacity for this drainage. Since the Time of Concentration for this area and Areas 2 and 3 are approximately 1/3 that of the fastest Time of Concentration for the RP zoned area in the developed state, water fran these areas should be out of the storm drain aid well down Spring Creek by the 'time the concentrated flows from the RP zoned area enter the storm drain. Therefore, the entire 100-year developed flood from Area 1 can be totally drained and no retention will be required. For both Areas 2 and 3, the storm drain has been designed to handle the 2-Year developed storm. Retention is greater than that 10-year developed storm, but this can be adequately provided as shown on Exhibit "C". The inlet for Area COMPUTATIONS Stewart & Associates, Inc. 163 5. /V1 ELDFUM St. '; Ft. Collins, CO 80521 (303) 482-9331 By: ELK Date���Client: Si -of G6c ��JP�a«,,�.�.,Es^ f Sheet No. ✓� of Chkd By: }} Date Project: /-ic r, n 6 G l/ r7� Subject �`-TOrr, i%cxrnoaP t,. i � I l COMPUTATIONS Stewart & Associates, Inc. I103 s,Mf.LM VM St. Ft. Collins, CO 80521 (303) 482-9331 By: El X Datee;,Z) fi Cf 2-Client:-STOr�I , I�e✓P�o/�M��� Sheet/No. Co of Chkd By: Date Project: Subject S Orl,i Drai�ase COMPUTATIONS Stewart& Associates, Inc. 103 .5, .M FLPR'VM St. ' Ft. Collins, CO 80521 (303) 482-9331 By: EZIE Date Client: Sheet No. of Chkd By: Date- Project: C"L/ r S-c- L � -7 Subject A/ 7IOAI F,0'A/p: ova 7 -7-7 c4f 7?_ �17 . 1. I . t__� ! v:_7 �7 c" i ; I -1.�✓ I J 1. 1 ELF,45E 1 ACk 3 mig 4) C_ U a r I-vi 7,i2 4 �)el 3 op, xi 7� E L F-,4 FP�Om!' I e_ LD PZ F N!5'1 U�/,Or, LP1 POND 6-71 0�,' oticr! 01 t 0< C)' - I C C '-FarL/ V--i 6�, 6� T-0 7,/4 L 1? Ptt_7,c) E 'IT -3S_ � /�.i J F JS COMPUTATIONS ` Stewart & Associates, Inc. /03 SMELDROMSt. ' Ft. Collins, CO 80521 (303) 482-9331 By: E/%-- Date S 31 2 Client: S-ko r'Gk eye1��/''M�Sheet No. 5 of Chkd By: Date Project: / Zctn i D� LOVr'1 S V. 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