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Home My WebLink AboutDrainage Reports - 12/14/1989NC Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226-4955 December 14, 1989 Ms. Susan Hayes City of Fort Collins P.O. Box 580 Fort Collins, CO 80522 RE: AMENDED ESAB FINAL DRAINAGE REPORT Dear Susan: We are pleased to submit to you this Amended Final Drainage Report for the ESAB site. Please call if you have questions. Respectfully, RBD, Inc.L� �,rtJIO�C Cort Nickel, P.E. cc: 033-014 YJ250 f 4 Other Offices: Vail, Colorado 303/476-6340 9 Colorado Springs, Colorado (719) 598-4107 r Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226-4955 December 14, 1989 Ms. Susan Hayes City of Fort Collins P.O. Box 580 Fort Collins, Colorado 80522 RE: AMENDED FINAL DRAINAGE REPORT FOR ESAB AT OAKRIDGE BUSINESS PARK, FOURTEENTH FILING Dear Susan: The ESAB site is located at the northeast corner of the Oakridge development. The ESAB site is bounded on the north by Harmony Road (State Highway No. 68), the east by the Union Pacific Rail- road and is bounded on the southwest corner by Innovation Drive. The site is located within the McClellands Major Basin of South Fort Collins, Colorado. The attached vicinity map shows the project site. The site is currently covered with natural grasses and slopes to the Southeast at approximately 1% where it is redirected south by the Union Pacific Railroad embankment; which runs north to south. It is then detained by a regional ponding facility located in the southeast corner of the Oakridge development. This regional pond is sized for selected sites within the development as more fully explained in the "Master Drainage Study for the Oakridge Business Park", by RBD Inc., September 27. 1989. This report specifies that storm flows on the ESAB site shall be detained by use of on - site storm drainage detention facilities and shall release at a l/ rate not greater than 0.5 cfs/acre for the 100 year storm condi- tion and 0.2 cfs/acre for the 10 year storm condition. The ESAB site is divided into two drainage basins; as shown on the attached drainage plan. In general, Basin "A" includes the northwest quarter of the building extended to Harmony Road along with the western parking lot, while Basin "B" includes the remaining roof area, the South and East parking lots and all other areas, bounded by Harmony Road on the North and the Union Pacific Railroad on the east. Offsite flows from Harmony Road will be prevented from entering the site by the required Harmony Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado (719) 598-4107 Road berming as shown on the plans. Flows from the area west of this site will be negligible and no flows are anticipated from the south or east. The above described sites were measured for total area, impervious area and pervious area. Once determined, a composite runoff coefficient was calculated. The following table more fully explains those calculations. Basin Total Pervious Impervious Composite C100 = Area Area Area/ C Cx1.25 (acres) (acres) (acres) A 2.84 .79 2.05 (.79x.2)+(2.05x.95) = 0.741 0.927 B 6.41 2.73 3.68 (2.73x.2)+(3.68x.95)= 0.631 0.788 6.41 Using the information above, and maximum allowable release rates of 0.5 cfs/acre and 0.2 cfs/acre, the required pond volumes were determined using the Mass Diagram Method. A staged release rate for the initial 10 year storm will be accommodated for each_of the Pon areas. The staged release for Pond A will be b�l. facilitated by future offsite improvements as required upon 111044 completion of the Oakridge Business Park Master Drainage Plan. 1AM The staged release for Pond B will be constructed with the pond �p through the designed outlet structure. YYY Computer printouts of the Mass Diagram Method are enclosed in the Appendix for your reference. As shown, Pond "A" and Pond "B" require 19,640 ft3 and 36,095 ft3 of storage for the 100 year storm; respectively. For the 10 year storm, the storage volume for Pond A was not computed because of the above mentioned reason; the storage volume for Pond B was computed to be 25711 ft3 Each detention pond has been graded to achieve these volumes (reference calculations in Appendix). Pond "A" utilizes the western parking lot to achieve this volume and drains into an ex- isting storm drain system in Innovation Drive. Pond "B" utilizes the undeveloped tract on the South side of the site and drains into an existing drainageway on the eastern edge of the Oakridge Development. The discharge from these systems drains into the regional detention pond mentioned earlier. The grading results in a parking lot depth of 1.33 ft. for Pond "A" and a depth of 2.90 ft. in Pond "B". (Reference calculations in the Appendix). If the depth in either pond should rise slightly greater than the depths shown above, the ponds will overflow to the south and dis- charge will be carried by sheet flows in the direction of the regional pond. A summary table displaying the results and analysis follows this report. Erosion control measures have been incorporated into the accom- panying drainage plans to reduce adverse impacts related to offsite discharge. ESAB's operations do not adversely effect water quality. Waste from their operations are filtered and monitored and outfall into the sanitary sewer system. For these reasons no need is measures. seen for special water quality filtration When the recommendations from this report are.implemented, along with the City of Fort Collins drainage criteria, this site will drain stormwater in a safe and controlled manner. If you have any questions or comments, please feel free to call. Sincerely, RBBD, Inc. t dZ 44'Cort Ni el, P.E. Project Engineer cc: 035-012 HORSETOOTH ROAD!:.. L r. Sri < '. �� `�. 1 n- v; non warrenPaiki i / I ;COUNTY ROAD 40 0 • N • .. r cc NCollindate I '\ v , . NOV �. \ • , , <u `�I ;� •_•ho`dott .Course s L eke ozr Ul LA. 32 (114 Virat;w Park, I, ��.•�.. \ 1 i Vf ; 11 I Trait Park i \I _ � I ' 1 � - �I. • _I' � II � \1 `.I . � ! I �— it ` `�. HARMONY ROAD`_-: /., • c_vsl ��: i. • ...'i— i a: �J" Il:u,nry,./ I�•.•'�a-'.�..�W.y,.�-`� til COUNTY ROAD 38 "'t i c��✓ % I o Z i • . 'mac•., �: // 1 I ' . t d/� ~� << • a �.: -' JEGT,SIfE I / rye_ .�QEE J \) REGIONALr DETENTION �; ) 10 r' \� a U is VICINITY MAP NO SCALE BSAB - 100 YEAR STORM FLOW CONDITION MAX DETENTION DETENTION BASIN RELEASE RATE ORIFICE POND VOLUME DEPTH AREA 0.5 cfs/ac DIAMETER A 19,640 cf 1.33 ft 2.84 ac 1.42 cfs 5.25 in B 36,095 cf 2.90 ft 6.41 ac 3.20 cfs =34.0 in = Weir length around proposed standpipe. BSAB - 10 YBAR STORM FLOW CONDITION MAX DETENTION DETENTION BASIN RELEASE RATE ORIFICE POND VOLUME DEPTH AREA 0.2 cfs/ac DIAMETER A 13,820 cf 1.20 ft 2.84 ac 0.57 cfs =: B 25,711 cf 2.56 ft 6.41 ac 1.28 cfs 5.5 in :: Future facilities will accoo®odate this flow APPEND 2 X MASS DIAGRAM METHOD +o DETENTION VOLUMES PROJECT: ESAB SITE COMA NTS:BASIN A MAXIMUM ALLOWABLE RELEASE (C S) = 1.42 RATIONAL EQUATION: O = CIA c,c«» 0.927 A(area) ® 2.84 TIME of CONCENTRATION = TIME CA (min) s 2.6326B 10 2.6326G 15 2.6326B 20 2.6 68 25 2.63268 30 2.6326e 35 2.63268 40 2.6326B 45 2.63269 50 2.6326e 55 2.63268 60 2.63269 70 2.63268 BO 2.63268 90 2.63268 100 2.63268 110 2.63268 120 2.63268 I INFLOW OUTFLOW STORAGE (in/hr) (ca ft) ccu !t) (cu !t) (ac ft) 9 7108.236 426 66e 6 i \ \ 7.3 11531.17, 852 10679.13 0.245159 6 14216.47 1278 12938.47 0.297026 5.2 16427.92 1704 1.4723.92 0.338014 4.6 19165.49 2130 16035.49 0.368124 4.15 19666.11 2556 1711.0.11 0.392794 3.8 2I008.7e 2992 18026.7a 0.41sese 3.5 22114.51 340e 18706.s1 0.429442 23101.76 3834 19267.76 0.4427,27 3 23694.12 4260 19434.12 0.446146 2.8 24325.96 4&g6 19639.96 0.450e71 2.6 24641.GB 5l12 19529.9e 0.448344 2.3 25431.68 5964 19467.63 0.446916 2.05 25905.57 6816 19089.57 0.438236 1.85 2630o.47 7666 18632.47 0,427742 1.7 26853.33 8520 18333.33l 0.420875 1.55 26932.31 9372 17560.31 0.407,129 1.45 27485.17 10224 17261.17 0.396262 MASS DIAGRAM METHOD for DETENTION VOLUMES PROJECT: ESAB SITE COMMENTS:BASIN B MAXIMUM ALLOWABLE RELEASE (CFS) _ RATIONAL EQUATION: 0 = CIA C*Cf= 0.788 A (area) _ TIME OF CONCENTRATION = TIME CA (min) 5 5.051C.)8 10 5.051OG 15 5.05108 20 5.05108 25 5.05108 30 5.05108 5 5.05108 40 5.05108 45 5.05108 50 5.05108 55 5.05108 60 5. c_?5108 70 5.05108 80 5.05108 90 5.05108 100 5.05108 110 5.0511?G 120 5.05108 3.205 6.41 I INFLOW OUTFLOW STORAGE (in/hr) (cU ft) (c)_) ft) (ciI ft) (ac ft) 9 13637.91 961.5 12676. 4.1 0. 291 i )1 C ) 7.3 2212'.7, 1923 20200.73 0.46'744 6 27275.83 2884.5 24.391.33 0.559947 5.2 31518.73 3946 27672.73 0.63-5278 4.6 34852.45 4807.5 30044.95 0.689737 4. 15 3,7731 . 56 5769 31962.56 0. 7:=59 3.8 40307. 61 6730.5 33577.11 0.770924 3.5 42429.07 7692 34737.07 0.797453. 3.25 44•323.22 8653.5 35669.72 0.818864 3 45459.72 9615 35844.72 0.822881 2.9 46671.97 10576.5 .36095. 47. 0. 8286� 8 2.6 47278.10 115.38 35740.1'0 0.82048 2.3 4B793.43 13461 35332.43 0.811121 2.05 49702.62 15384 34318.62 0.787847 1.85 50460.28 177-07 33153..2b 0.761094 1.7 51521.01 .19230 32291.ol 0.741299 1.55 51672. 54 21153 3- 0519. 54 0.700632 1.45 52733.27 23076 29657.27 o.6EO937 DATE: 12/12/89 PROJECT: ESAB JOB NUMBER: 033=014 DESIGN ENGINEER: TMO BASIN DESIGNATION = BASIN B DETERMINE EXISTING 0 FOR l0 YEAR STORM HISTORIC RUNOFF COEFFICIENT .2 BASIN SLOPE: .96 PERCENT BASIN LENGTH 800 FEET AREA: 6.41 ACRES HIST TC = 1.871(1.1-( 1 } .2 ))*SQRROOT 800 ))/ .96 1/3 = 49.25395 MINUTES HISTORIC OUTFLOW IS SUPERCEDED BY: 1.3 CUBIC FEET PER SECOND DETERMINATION OF DETENTION POND VOLUME FOR DEVELOPED CONDITIONS DEVELOPED STORM: 10 YEAR STORM DEVELOPED RUNOFF COEFFICIENT .78B CCFAC _ .789 + 1 } 6.41 = 5.05108 DURATION GROSS VOL. OUTFLOW VOL. DETENTION VOL. MIN CU. FT. CU. FT. CU. FT 5 8546.427 390 8156.427 10 13274.24 780 12494.24 15 16911.02 1170 15741.02 30 23457.21 2340 21117.21 45 27275.83 3510 23765.83 60 29639.73 4680 24959.73 90 32731 7020 25711 120 33822.03 9360 24462.03 IGO 36549.61 14040 22509.61 360 41459.26 29080 13379.26 REQUIRED DETENTION VOLUME IS 25711 CU. FT. OR .5902433 ACRE FEET DATE: 12-12-09 PROJECT: BSAB JOB NUMBER: 033-014 DESIGN ENGINEER: TKO BASIN DESIGNATION = BASIN A DETERMINE RIISTING Q FOR 10 TEAR STORM --------------------------------------------------------------------- --------------------------------------------------------------------- HISTORIC RUNOFF COEFFICIENT .2 BASIN SLOPE: 1.6 PERCENT BASIN LENGTH 180 FEET AREA: 2.84 ACRES MIST TC = 1.87t(1.1-( 1 t .2 )1tSQRR00T ISO W 1.6 1/3 19.3085 MINUTES HISTORIC OUTFLON IS SUPBRCRDRD BY: .6 CUBIC FEET PER SECOND DETERMINATION OF DETENTION POND VOLUME FOR DEVELOPED CONDITIONS DEVELOPED STORM: 10 YEAR STORK DEVELOPED RUNOFF COEFFICIENT .927 CCFAC = .927 t 1 2.84 = 2.63268 DURATION GROSS V06. OUTFLON VOL. MIN CU. FT. CU. FT. 5 4454.495 180 10 6918.683 360 15 8814.212 540 30 12226.17 1080 45 14216.47 1620 60 15448.57 2160 90 17059.77 3240 120 17628.42 4320 180 19050.07 6480 360 21609.04 12960 REQUIRED DETENTION VOLUME IS 13819.77 .3172582 ACRB FEET DETENTION VOL. CU. 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