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HomeMy WebLinkAboutSite Certifications - 10/17/2003BEYOND ENGINEERING October 17, 2006 Mr. Basil Hamdan,'' City of Fort Collins Stormwater 700 Wood Street P.O. Box 580 Fort Collins, Colorado 80521 SUBJECT: Larimer County Corrections Center Phase 2.Upper Detention.Pond Dear Basil: Hensel Phelps Construction Co has finished constructing the "Upper Pond" as described further in the Larimer County Community Corrections Drainage & Erosion Control Study, Phase 2 — Correction Center Addition by Nolte Associates Inc., dated March 28, 2006. Larimer County Corrections Center is referred to herein as LCCC. This Certification Letter and the attached exhibit present a summary of the survey data performed on 10/06/2006 of the Upper Pond only, it does not serve as a general grading or utility certification for the LCCC addition. Also, the "Lower Pond" and "Parking Lot Pond" were not surveyed as they were not to be re -graded as part of the LCCC addition improvements. The table below summarizes the design volume and survey volume of the detention pond system at elevation 4907.68. ° 0 Detention Pond Volume _ (per Design) Volume (per Survey) ft3 ac-ft ft3 ! ac-ft Upper Detention Pond (in Basin 101c) 6,503 0.149 6,070 0.139 Lower Detention Pond (in Basin 102) 11,500 0.264 Not Surveyed use design data Parking Lot Detention Pond (in Basin 100) 3,966 0.091 Total: 21,969 0.50 21,536 0.49 NOLTE ASSOCIATES, INC. 1901 SHARP POINT DRIVE, SUITE A FORT COLLINS, CO 80525.4429 970.221.2400 TEL 970.221.2415 FAX WWW.NOLTE.COM �.in. 7 06 pu�CeniS Based on the survey, the as -constructed detention pond volume is 0.01 acre-feet less than the design detention storage volume which is in substantial conformance with the design. Per survey, the concrete pan is located generally as shown on the design plans, although it is significantly flatter in several areas than design indicates. The culvert underneath the sidewalk was increased to a 15" RCP per design. The upstream end of the 15" RCP was lowered from 4905.72 to 4905.61. The downstream invert was not checked. The pond berm along the sidewalk was also lowered by up to approximately 0.40' in several locations, but it was still slightly higher than the 100-year water surface elevation of 4907.68. The following are photos of the pond taken on October 11, 2006, looking westerly (left) and If you have questions, please contact me at (970) 419-1338. Sincerely, Nolte Asso ' , Inc. Michele White, P.E. Associate Engineer N:\FCO2590minage\Word\Drainage_ Certifimion_Hamdan_20061017 Am NOLTE ASSOCIATES, INC. ©-,I1 tl an,epe, me —1h 1009 1 �.., 0, a 0 0 10' 20' 40, 1 inch = 20 ft. w � 9 ` I 00 PAN CL �_--_--- PROPOSED 100 YEA I ` I 490B 4WATER 907 68 SURFACE ELEV. INVERT 4905.61 O 0 4909.DO - 0.00 4?97�\ DATE: 10/10/06 TIME: 2:57:46 PM SERVER: FCSO LAYOUT: Larout2 PATH: N:\FCO259\CADD\CP\EXHIBIT DRAWNG NAME: ET-POND-AS-BUILT.DWG PAGE SETUP: ---- MGR: NCqmTE B E Y O N D E N 0 1 N E E R I N 0 N01 111" PONT OIOVE. MIT A FORT COULK CO 0002b 0102212400 TEL 07UM410 FAX --__ - MJWTECON CORRECTIONS FACILITY- PHASE 2 SHEET NUMBER POND GRADING AS -BUILT 1 PREPARED FOR: LARIMER COUNTY OF 1 SHEETS DATE SUBMITTED: 04/04/2006 JOB NUMBER FCO259