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HomeMy WebLinkAboutDrainage Reports - 03/29/1988TMItC Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226-4955 February 29, 1988 Ms. Susan Hayes Storm Drainage Department City of Fort Collins P.O. Box 570 Fort Collins, Colorado 80522 RE: AMENDED FINAL DRAINAGE REPORT FOR THE SIXTH FILING AND PARCEL "U" OF THE CENTRE FOR ADVANCED TECHNOLOGY The Sixth Filing and Parcel "U" to the Centre for Advanced Tech- nology is located south of the Third Filing, north of the Fourth Filing, west of Research Boulevard and east of the New Mercer Ditch (see following vicinity map). More specifically this site is located near the middle of the south half of Section 23, Township 7 North, Range 69 West of the 6th Principal Meridian. This development site is, as is most of the Center site, covered with natural grasses. The ground slopes to the southeast at about 0.5%. The only recent change to the existing ground is that during the construction of Third Filing, a detention pond was constructed on the northern part of this site. The detention pond is only temporary until the development of this site. Development of this site will occur in phases. Sixth filing con- struction will likely begin soon after City approval, while Par- cel "U" construction will occur at a later date, after final City approval of the Parcel "U" Final Utility Plans. This phasing will require the construction of a temporary detention pond on the Parcel "U" site. This temporary pond will detain the com- bined runoff from the Sixth and Third Filings. The existing tem- porary pond which services the Third Filing will be obiliterated by the Sixth Filing Grading. Design calculations for this tem- poary pond are attached. When Parcel "U" is developed flows from the site will be combined with the developed flows from the Sixth and Third Filings. These flows will accumulate in a permanent detention pond located in the central or main parking lot. This pond will be facilitated by the use of six area inlets (see Drainage and Grading Plan) and Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado 303/574-3504 a series of concrete pans. The maximum water surface for this pond will be at elevation 5037.8 which is 1.4 feet above the flow line of the inlets. The pond will have a maximum 100 year design storage.volume of 1.687 ac.-ft. which compares to a required volume of 1.675 ac.-ft. (see following calculations). A 5 inch orifice plate will be placed at the invert -out of the most easterly inlet. This will be done to restrict the developed flows from this site and the Third Filing to their two year his- toric level. This easterly inlet will then be connected to the storm drain system in Research Boulevard which was master planned as Basin A3 from the Drainage Report for the Centre for Advanced Technology Special Improvement District, by RBD, Inc. Engineering Consultants, Feb. 1987 and the Amended Addendum dated February 1988. Any emergency overflow from this pond would flow east to a 5' type "R" inlet in Research Boulevard (see Drainage and Grading Plan). The flow will be via the most southerly entrance. This project was designed according to the City of Fort Collins Drainage Specifications to promote safe and positive drainage through this site. Sincerely, RBD, Inc. Stan A. Myers, P.E. Project Manager cc: 035-050 VICINITY MAP E0. N�W o % n z 3 ITE LOCATION NO SCALE' DATE: __. _ 2/ BJ PROJECT: CENTRE 6TH FILING JOB NUMBER: 035--051 Dfi''::1:Ghl ENGINEER: SAM I&SIN DESIGNATION = 3RD & 6TH COMBINED DETERMINE EX19TING 0 FOR 2 YEAR STORM HISTORIC RUNOFF COEFFICIENT .2 BASIN SLOPE- .;a - PERCENT BASIN LENGTH 770 FEET' AREA: 3.66 ACRES HIST TC = 1.87*(1.1-( 1 .2 ))*SORROOT 770 i)/ .S 58.62643 MINUTES HISTORIC RAINFALL INTENSITYt .9558166 INCHES/HOUR HISTORIC OUTFALL: .6996592 CUBIC FEET PER SECOND DETERMINATION OF DETENTION FOND VOLUME FOR DEVELOPED CONDITIONS DEVELOPED STORM: 100 YEAR STORM DEVELOPED RUNOFF COEFFICIENT .693 CCFAC .693 1.25 ?.6f�l = _ti. 170475 DURATION GROSS VOL. OUTFLOW VOL.. DETENTION VOL. MIN CU. FT. CU. FT. CU. FT 5 8674.42 209.8978 8464.521 1t) 13354.04 419.7956 12934.25 15 17006.43 629.6933 16376. 74 30 23512.24 24 1259.387 22252.86 45 28248.93 1.889.08 26359.85 60 29789.78 2518.77.3 27271.01 to 32166.66 7778.16 22408.5 120 12671.49 5037.546 27633.94 18'7 35610.77 7536.32 28054.45 % 31719.71. 15112.64 24607.07 REMUTRED DETENTION VOLUME. IS 28408„5 CU. FT. OR .6521695 ACRE FEET INC Engineering Consultants CLIENT SVM7"1- JOB NO.O$ S' OS PROJECT O&OVE %� 0 V� CALCULATIONS FOR 7EW, 'Wr F P V; MADE BY DATE ___CHECKED BY_ DATE -SHEET- OF 34.0 O - a�as ' 3�.0 12G90 l 9 SAS 87,C 259� �8� 2.b Ae-Fr- ?e4C)e REa IC. CSRIFJC'E SMING CXXFFA6. IzhTE ! 0;?, ©,7efis h= 3.0 CLIENT C' V&--_ITT JOB NO.O3S'06/ IiJC PROJECT Ct"Tx �+£� CALCULATIONS FOR /.U.CET Ni9PACIT/ES Engineering Consultants MADE BY:'J1'^OATE 7 CHECKED BY -DATE -SHEET-OF ALC PAtG�/.vG /NCtTS <//t'JE�AAfE �/sl67LJS/Ot�S: 7. S SQ /N = /, SS /i /,- C? /rY ///<t`T /S 4M14'TJ 7t/E MPAOTY = 9, /st' X. $ = 7 32Q4s al,3�e7'z C/i?PA41/7'Y /S AVA/1/A0/(6, /F Tf/fj le- -/,4/E Pe-IrP/!74-7:� 6077,:U600 7f/E eAFAC'/TY /6 13,5X 7,UE r1Ec�'a CAPAee7Y DATE: 1-22-88 PROJECT: CAT 6TH JOB NUMBER: 035-050 DESIGN ENGINEER: BC BASIN DESIGNATION = ALL DETERMINE EXISTING 0 FOR 2 YEAR STORM ------___------------.----aaass---axxaaxsassa HISTORIC RUNOFF COEFFICIENT BASIN SLOPE: .5 BASIN LENGTH lOC!0 AREA: 9.303001 ACRES HIST TC = 1.87*(1.1-•( 1 ))*50RROOT 1000 1/3 HISTORIC RAINFALL. INTENSITY: HISTORIC OU'TFAL.L: 1.6'a8681 .2 PERCENT FEET * .2 ))/ 5 67.03894 MINUTES .8807274 INCHES/HOUR CUBIC FEET PER SECOND DETERMINATION OF DETENTION POND VOLUME FOR DEVELOPED CONDITIONS DEVELOPED STORM: 1()o DEVELOPED RUNOFF COEFFICIENT' C C F A C == 693 9. 3 !30i: 1 = 8. 058725 DURATION GROSS VOL. MIN CU. FT. 5 22048.67 1 i ! 33943.35 35 15 4;.227 3C) 59763.5 45 71603.23 60 75719.77 90 81812.16 120 8.3552.85 180 90515.59 36() 100959.7 R.EOUIR'ED DETENTION VOLUME IS I.675i)07 ACRE FEET YEAR STORM .693 G C oMPoS.1 F LgbEG C7N �j ATE LA'COVT 1.23 OUTFLOW VOL. CU. FT. 491.6045 983. 2089 1474.813 2949. 62'7 4424.44 5899.254 8848.88 11798.51 17697.76 35395.52 72963.28 28 DETENTION VOL. CU. FT 21557.07 32960.14 41752.18 56813.87 67378. 78 69820.52 72963.26 71754.35 72817.83 65564.18 CU. FT. OR ORIFICE DESIGN w AIEZ - TI; �0 Z7 ) t�• = 3�.8--�z.�l-O.z1b8=4,'a�1z :.Q=06I(Q.1So3> z(32.z�(4,�lIZ'j=1.62c�s