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Home My WebLink AboutSite Certifications - 04/23/2008-~---- 1 t 2008 April 17, 2008 ~ Mr. Jay Barber J-R ENGINEERING City of Fort Collins Storm Water Utility 700 Wood Street Fort Collins, CO 80521 A Westrian Company Re : D rainage Ce rtification for Preston Center Fourth Filing Harmony One JR Project: 39494.00 Dear Mr. Barber, We are submitting for your review and approval an overall site certification and an as constructed survey of the drainage facilities for Preston Center Fourth Filing Harmony One based on a record survey conducted by King Surveying in April of 2008 and JR Engineering's field inspection on April 14, 2008. The following is a summary of our findings: As the design proposed, by the previously approved drainage report for the Preston Center Fourth Filing explained, the existing detention pond constructed for the Preston Center Third Filing project provided adequate detention for the development with no additional grading. Survey as-built information for the existing pond was accepted by the city at the time of the completion in 2001 . The design for Preston Center Fourth Filing was required to improve the pond's existing outlet structure by adding a water quality structure connected to the existing concrete. Per our field inspection the additional water quality structure is determined to be in general conformance with the approved plans and specifications. Using the survey information provided to JR Engineering, a storm system as -built drawing was also completed and is attached. The plan indicates that invert elevations of the storm pipes varied slightly however·, the variations are small and are not expected to have a negative effect on the anticipated drainage patterns. All pipes appeared to maintain positive drainage based on observed slopes. Additionally, the rip -rap has been installed according to plan. In addition to the underground storm system , King Survey also provided as-built spot elevations for the parking lots. Our review of their elevations revealed that finished grade elevations are in general conformance with the designed grades (see the attached record grading plan). While onsite JR inspected the temporary erosion control measures such as silt fence and inlet protection which all appeared to be in good condition. Stabilizing surfaces including asphalt and concrete had been established at the time of inspection. Sod for most the proposed landscaping area has been placed. 2620 East Prospect Road, Sui te 190, Fort Collins, CO 80525 970-491-9888 • Fax: 970-491-9984 • www.jrengineering.com Mr. Jay Barber, April 2008 Page 2 of 2 In conclusion, based on King Survey's record survey and JR Engineering 's field inspection, the drainage facilities for Preston Center Fourth Filing or Harmony One have been constructed in general conformance to the approved plans. I find that the storm system , as built, should operate as designed in the approved final drainage report. If you have any questions or comments , please contact me at 970.491.9888 . Attached are the following supporting documents: • The standard "Drainage Certification Form " used by the City of Fort Collins that pro vides a list of the various drainage items checked. • A grading exhibit showing the proposed spot elev ations vs. the as -built spot elevations. • As-built drawings noting the variations from the proposed design for the storm system and outlet structures. Respectfully submitted, Prepared by: ~-~~~ Justin Fecteau Design Engineer Re viewed By: Michael S. Brake PE , PLS Principal , Vice President X :\3940000.all\3949400\Word\Letters\As-built Pond Cert .doc DRAINAGE CERTIFICATION FORM Please fi l l out all applicable items in this certification form for single family, multi-family and commercial properties . Write "OK" for items checked or actual number checked in field. Use "N/An for items that are not applicable to the property that is being certified . A. Drainage facilities certification 1 . Pond Certification -volume verification -tDMPc.£Te l.O:t"'fl-1 ~{.TI>~ ~TI;.(2 1If -?DOI a .topographic records and volume · b.cross -s ections and spot elevations -positive fall to pan -side slopes -invert elevation -spillway elevation -placement and size of riprap -side slopes -grading -orifice plate installation and size -compaction of berm -structural integrity of pond~-.:;:-=-==-~~C:\~;c.-~ 2. Swales -NA -location (are they within easement) NA -dimensions and cross-section verification~A -longitudinal slopes and side slopes ~A -s pot elevations NA -permanent erosion control measures (drop structures, riprap, etc .... ) -+-IA--F"z?ie 1,~. -tie -in to pipes, pans, curbs, etc .... ~A -weir size (elevations , size, opening, etc . )tJ A -available freeboardi\.!A -landscaping infringement on swales ~A 3 . Pipes -size and type OK ~slopes (as-built and comparison to minimum 0 .4 % slope) oK -pipe capacity calculations if slopes are significantly altered -z:>~ -invert elevations 0/( -installation and backfill materia1-A6~~ 0 ~ -cover-A~~ t)K. -encasement and clearance from other utility lines c l ose by -IJ!,6 u.rn&IO o~ 4 . Concrete Pan Channels/\/~ -size tJA -slope NA -super elevation Nft -cross .section t\Jt-1- -thickness tJ(.} -elevations INA- 5 . Inlets -size and type OI< -size of opening (or name of standard used) 7yP£ !lo coml:30 -grate elevation O,i::.. -invert elevation 0/{ -box size {)~ 6 . Cross pans /.JA -size N~ -type t-lA -grade tJA -e l evation NA -cross -sectional depth~~ -tie -in to curb and gutter ~IA- 7 . Culverts ,v/-r -size NA -type ~A -invert elevationN~ -headwalls t\lA 8 . Underdrains .size~ -type~ -cover t\lA -backfill t',lA -geotextiles t..1~ -cleanouts r,J~ 9 . Curb cuts -size oft.. -tie in to swale, pipe , etc ... ()/( B. Certification of Grade Elevations Adjacent to Drainage Facilities: • -minimum opening elevations ol( -top of foundation elevations 6~ -comparison to 100 year WS EL 's (Freeboard bK_ requirements and floodpla i n issues) C. Certification of Erosion Control Measures: 1 . Perm a nent Measures : -Permanent vegetation (6" bare spots and weeds under contro l ) C>/( -riprap OI< -riprap bedding()/( -drop sections f.lf.+ -sediment basins/water quality ponds{)/< -netting mats/blankets tJtr -mulch i ng -::,c;O AND /?.()~K /f}IAtvH !,,ANO&CA-Pe -C><. 2 . Temporary Measures : -mulching -inlet filter installation OI( -check bale dams -DI( -seeding and temporary vegetation o/( -silt fence Ok D . Site Cleanup After Construction -construction clean up 6/{ -s mooth i ng of ruts O 1< -reseeding DI< E. Statement of Compliance This certification is signed and stamped and by signing thi s form the engineer(s) attest s that they have inspected . : ' ,-, ) I the site and to the best of their knowledge the as-built conditions of the drainage facilities are as described in the above form and in the redlined plans enclosed. Failure to properly disclose all known information could result in the rejection of this certification and prevent the release of any Stormwater Uti l ity holds on Bu i lding Permits and/or Certificates of Occupancy . F. Signature and Stamp by a Colorado Registered Professional Engineer.