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Home My WebLink AboutGATEWAY AT HARMONY PUD, LOT 3, MAKEN II - AMENDED FINAL - 1-88J - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT I DRAINAGE INVESTIGATION FOR MAKEN II - P.U.D. CITY OF FORT COLLINS, LAR.IlVIER COUNTY, COLORADO I Prepared for Maken Partnership 750 17th Street Boulder;Colorado 80302 I • I November 1996 I Project No. G RD-228-96 I I 1 IPrepared By 111 NIMelkilER Ef ►r$alnq Associates 150 E.29th Street,#238 Loveland,Colorado 80538 Zhlephone: (970)663-2221 1 III ilEngineering Associates Ill - November 22, 1996 Project No. GRD - 228 - 96 II Mr. Basil Y. Hamdan Stormwater Utility 235 Mathews II P. O. Box 580 Fort Collins, Colorado 80522-0580 Dear Mr Hamdan, 1111 The enclosed report represents the results of the drainage investigation for the proposed "Maken II - P.U.D." to be located on Lot 3 of"The Gateway At Harmony Road P.U.D. Third Filing" in the City of Fort Collins, Larimer County, Colorado. ilThis investigation was based upon the proposed site development plan; proposed site grading plan; on-site observations; and available topographic information. The investigation was performed in accordance with the criteria established in the City of Fort Collins "Storm Drainage Design Criteria and Construction. Specification Standards" manual. llIf you should have any questions, please feel free to contact this office. Respectfully Submitted, IllMESSNER gineering Associates 0.//7_,_L....,, UDennis R. Messner, P.E. DRM/mkm • `.00,, % 1 2Er f 4 .�. 2.10 ifyi II Enclosures A��. V e ••,•�ole` �-- cc: Maken Partnership I III • Civil and Environmental Engineering Co nsultants II150 E. 29th Street, Suite 238 Loveland, Colorado 80538 Telephone: (970) 663-2221 111 TABLE OF CONTENTS • Letter of TransmittalMil i Table of Contents i Scope 1 Site Description 1 "Historic" Conditions 1 Proposed Development 2 Erosion Control Measures 2 Conclusions and Recommendations 3 References 4 Drainage Summary IIErosion Control Cost Estimate letter EXHIBITS Vicinity Map "Historic" Conditions Exhibit UProposed Conditions Exhibit Calculations U I I I, Nii U I I SCOPE I The following report represents the results of a drainage investigation for a proposed commercial development to be located in the Southeast Quarter of Section 35, Township 7 North, Range 69 West of the 6th P.M.in the City of Fort Collins, Larimer County, 111 Colorado. The investigation was performed for the project developer, Maken Partnership. The purpose of this investigation is to determine the effects of the proposed development on the area's existing drainage conditions and to determine the 111 improvements, if any, and the appropriate sizing for the proposed improvements so that it may be incorporated with the construction of the project. The conclusions and recommendations presented in this report are based upon the proposed site II development plan; proposed building construction plans; on-site observations; and the available topographic information. The analysis was performed in accordance with the City of Fort Collins "Storm Drainage Design Criteria and Construction Standards", - manual. SITE DESCRIPTION IThe site is considered to be somewhat rectangular and contains approximately 0.853 acres. The site's East-West dimension is approximately 262 feet, its North-South I dimension at the West boundary is- approximately 160 feet and its North-South dimension at the East boundary is approximately 115 feet. The site abuts the westerly right-of-way of College Avenue. The site is located in the MCCLELLANDS/MAIL CREEK DRAINAGE BASIN. "HISTORIC" CONDITIONS I The site is vacant and is surrounded by streets or existing development. The ground surface has been roughly graded and is bare of vegetation. The site slopes are considered to be moderate and range from 1 % to 3 %. The "historic" direction that the I site 'slopes is from North to South toward Mail Creek. The major portion of the site slopes from Northwest to Southeast and drains toward College Avenue. The run-off generated in the area to the West of College Avenue is directed into a 42 inch diameter storm drain that is situated along the westerly side of College Avenue. The storm drain discharges into Mail Creek. I The area to the South of the site is a McDonald's restaurant. The site improvements for the restaurant have been designed to to direct the surface run-off to a detention pond located at the East side of the site. No run-off from the South contributes to the drainage on site. The area to the West is an internal access drive and parking lot. The site improvements for the parking lot have been designed to to direct the surface run-off to a detention pond located at the North side of the site. A small amount of run-off from the West contributes to the drainage on site. The area to the North is a Jiffy Lube andI . car wash. The site improvements for the Jiffy Lube and car wash have been designed to to direct the surface run-off to detention ponds located at the East side of the site. A small amount of run-off from the North contributes to the drainage on site. The area to the East is College Avenue. The street improvements for College Avenue are much lower than the site and therefore does not contribute to the drainage on site. 1 I I I PROPOSED DEVELOPMENT OS The proposed development is to consist of an 11,685 square foot commercial structure to be located in the northwest corner of the site. The proposed access drives and parking are to be situated along the West, South and East sides of the structure. IAs previously stated the run-off from the site flows onto College Avenue. There are no other drainage facilities available to accept run-off from the site. _ The current City policies require that the difference between the historic rate of run-off and the developed rate of run-off be detained onsite. The release rate is to be no greater than the 2 Year Storm historic rate. The drainage plan and report for The Gateway at Harmony Road P.U.D. has established the detention requirement for the site at the difference between the allowed run-off rate, 0.5 c.f.siacre and the 100 Year storm event. The proposed detention facilities will outfall to the 42 inch storm drain located along College Avenue. 111 The City's policies normally require that the adjacent street flows be incorporated with m ntsF This po licy applies most efficiently when the street the onsite detention require e � P y PP construction and onsite detention are performed concurrently. In this instance, it is s 111 not physically feasible to combine the two;flows since the flow generated on the streets can not be intercepted and directed into an on-site detention facility and then routed back into the curb and gutter. The area within the westerly half of the College.Avenue right-of-way has been considered as tributary to the detention facilities for sizing 111 purposes. The existing detention facilities located to the West and North of the site outfall through a storm drain pipe that is located on the proposed Maken II - P.U.D. site. The existing pipe is situated under a portion of the proposed structure. Therefore the storm drain pipe will need to be relocated in order to avoid conflict with the structure. EROSION CONTROL MEASURES Erosion control considerations are based upon the short term activities that occur during construction and the long term measures that are to be placed for the life of the facility. The long term measures are the proposed methods and materials to be used to provide surface treatments for the driveways, parking areas, walkways and the landscape materials and plantings in the open areas that will provide a combination of ground covers to deter erosion. The anticipated construction schedule should have the site grading completed, within one (1) week after commencing construction. The schedule for construction activities is anticipated to be: March 1 - March 7, perform site grading; March 7 - March 14, construct drainage related facilities; March 15 - March 21, install building foundation. and water and sewer service lines; March 22 - May 30, construct structure; April 15 - April 21, construct curb, gutter and sidewalks; April 28 - May 1, place pavement; May 15 - May 25 install landscaping. 2 I I IThe recommended short term erosion control methods to be incorporated with the construction activities consist of the following: prior to commencing construction a "Silt Fence" is to be placed along the eastern boundary of the site in order to control and contain mud and debris onsite; upon completion of grading operations and at the time that the drainage inlets are installed a "Straw Bale Filter" is to be placed at each inlet; 111 and tracked mud to be cleaned up as required. Wind erosion measures are to consist of water application and roughening of exposed surfaces. CONCLUSIONS AND RECOMMENDATIONS 1. The proposed development will retain the "historic" drainage patterns. 111 2. The site is located in the MCCLELLANDS/MAIL CREEK DRAINAGE BASIN. The site is not located within a defined floodway or flood plain. ® 3. All development is to be performed in accordance with City of Fort Collins criteria. A variance to the'Crty's`policies is requested from detention of adjacent:streetflows''due''to.physical'impracticality 4. Onsite detention of storm water is required by the City of Fort Collins. The volume of run-off to be detained is estimated to be 10,836 cu. ft. The detention volume has been determined based upon the calculated volume of run-off generated by a 100 Year Storm. The entire site, one-half of the adjacent College Avenue, and the adjacent drive at the West side of the site have been considered as the tributary area to determine the volume of the detention pond. The calculated volume generated from the tributary area is to be released at a controlled rate determined by the sum of the `historic' rate of run-off from the site for a 2 Year Storm plus the rate of run-off for the drive to the West of the site. The calculated release rate is 0.43 c.f.s. 5. The City of Fort Collins Standards for temporary erosion control measures are to be incorporated with the construction activities. Specifically, the following are to be incorporated in the site construction activities: a. A "Silt Fence" is to be placed along the easterly border of the site. b. "Straw Bale Filters" are to be placed at each inlet. c. Water application is to be made to prevent dust during the site development phase of the project. d. Roughening of the exposed earth surfaces shall take place during the site development phase of the project. 3 111' I REFERENCES 1. City of Fort Collins, STORM DRAINAGE DESIGN CRITERIA AND CONSTRUCTION STANDARDS, May 1984 with subsequent revisions and additions. 2. Final Drainage Report for The Gateway at Harmony Road P.U.D., prepared by Stewart and Associates, Inc., Fort Collins, Colorado, May 1, 1989. 3. Drainage and Erosion Control Report for The Gateway at Harmony Road P.U.D. Third Filing, prepared by WESTEC, Fort Collins, Colorado, July 19, 1995. I 4. Drainage and Erosion Control Report for Taco Cabana P.U.D. Third Filing, prepared by WESTEC, Fort Collins, Colorado, July 19, 1995. I I MI I I I I I 4 I I I STORM WATER DETENTION SUMMARY I SITE DRAINS TO "McCLELLANDS / MAIL CREEK" DRAINAGE BASIN 111 GROSS SITE AREA (includes 1/2 of College Ave.) =46,401 Sq. Ft. = 1.07 Ac.± NET SITE AREA = 37,157 Sq.Ft. = 0.853 Ac.± HISTORIC "C" = 0.20 DEVELOPED "C" _ 0.85 HISTORIC "Q2" = 0.54 c.f.s. CRITERIA BASED DETENTION VOLUME = 7,200 Cu.Ft. ± PLAN DETENTION VOLUME = 7,342 Cu.Ft. MAXIMUM DEPTH OF DETAINED WATER = 0.7 Ft. @ Elevation 5034.50 PEAK DISCHARGE FROM DETENTION, Q = "HISTORIC" Q2+ QOFFSITE = 1.72 c.f.s. ± I I I I I I I Engineering Associates November 22, 1996 Project No. GRD - 228 - 96 Mr. Basil Hamdan Stormwater Utility City of Fort Collins 235 Mathews R O. Box 580 Fort Collins, Colorado 80522 - 0580 111 Re: Maken II - P.U.D., Fort Collins, Colorado Dear Mr. Hamdan, The estimated cost for erosion control devices for the subject site has been estimated to be: 1. Silt Fence 190 1.f. @ $2.50/ft. _ $475.00 111 2. Straw Bale Filter 2 Each @ $75.00/Ea. = $150.00 Total $625.00 ® Cost Q 150% = 1.5 x$625.00 = $937.50 The cost to the 37,157 square foot site at$0.0298/sq.ft. = $1,107.28 150% of the re-seeding cost = 1.5 x$1,107.28 = $1,660.92 ® Therefore, the subject project's estimated erosion control security amount is determined to be $1,660.92. This amount is to be included as surety for the erosion control guarantee along with any other surety requirements that may be a part of the 111 City's "Developer's Agreement" requirements. If you should have any questions or desire additional information, please feel free to Icontact this office. Respectfully,Submitted, MESSNE gineering Associates 'AA% cA4(\ -, :Dennis R. 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