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HomeMy WebLinkAboutBRAZIL 2004 SUBDIVISION - FDP - 23-04A - REPORTS - DRAINAGE REPORTVICINITY MAP 11FSf RIJM A � m - MptIN / MOBY ARENA WEST LIZABETH STREET �-- COLORADO SITE - STATE UNIVERSITY MAIN CAMPUS SWni OQ �m I wee- s R9f PIIIW A BIRION Cf SCALE: 1" = 500' CAMPUS WEST REDEVELOPMENT 1325 WEST ELIZABETH STREET FORT COLLINS, COLORADO BEING A PORTION OF THE SOUTHEAST QUARTER OF SECTION 151 TOWNSHIP 7 NORTH, RANGE 69 WEST OF THE 6TH P.M., CITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADO EXHIBITS.. development. VIII. References: A. City of Fort Collins Storm Drainage Design Criteria and Construction Standards B. Urban Storm Drainage Criteria Manuals Volume I, II, and III C. Soil Survey of Larimer County Area, Colorado D. City of Fort Collins Master Drainage Plan E (WQCV). This will provide extend detention time for more frequently occurring runoff events thereby facilitating pollutant removal. The WQCV is approximately 2,374 cubic feet and is achieved at Elevation 5024.83 feet. The WQCV will be infiltrated through the gravel base of the stormtech chambers and be captured by a 4-inch diameter perforated HPDE underdrain. The underdrain will convey flow to a proposed manhole located approximately 41-feet northeast of the proposed Type- 13 Area Inlet. When larger storm events occur, the Type-13 Area Inlet will overtop beyond the WQCV Elevation and pass via a 15-inch HPDE storm drain into the proposed manhole. A 24-inch RCP will extend from the manhole and connect to the existing storm inlet located in West Elizabeth Street. b. The pollutant removal range of the `StormTech' system will be similar to an extended sand filter basin, which is presented in Table SQ-6 from the Urban Storm Drainage Criteria Manual, (See Appendix II). The removal of suspended solids and metals can be moderate to high, and the removal of nutrients is low to moderate. VII. Conclusions: A. Compliance with Standards 1. All drainage design conforms to the criteria and requirements of the City of Fort Collins Storm Drainage Criteria Addendum. 2. Proposed erosion control and stormwater quality measures conform to the recommendations of Volume III of the Urban Storm Drainage Criteria Manual. B. Drainage Concept 1. The drainage design for the proposed Campus West Redevelopment site is effective for the control of storinwater runoff in accordance with the City of Fort Collins's Master Drainage Plan. a. Onsite stormwater detention is not required for the site due to the proposed use being less impervious than the previous uses on the site. b. The Finished Floor Elevation of the proposed buildings will be a minimum of 18 inches above the Base Flood Elevation. All HVAC equipment will be placed a minimum of 18 inches above the Base Flood Elevation and will either be ceiling mounted in commercial instances or roof mounted in residential uses. Air conditioning condenser units will not be placed at grade. c. The historic drainage path will be retained. d. Existing and downstream facilities will not be adversely affected by this r- 3. Maintenance of all erosion control measures will remain the responsibility of the developer until the completion of the project. 4. Certain measures shall be taken in the event that high winds produce blowing dust and possible wind erosion. a. Water down open and disturbed areas with a water truck. b. Surface roughening for soils that are exposed during land disturbing activities. c. Stabilizing open and disturbed areas as soon as possible. VI. Stormwater Quality Control: A. General Concept 1. Since the site area to be disturbed is greater than 1 acre, a Colorado Department of Public Health and Environment (CDPHE) Stormwater Discharge Permit will be required. a. A Stormwater Management Plan (SWMP) is required and will be completed as part of the (CDPHE) Stormwater Discharge Permit. The SWMP will be updated as needed and kept on the site for the ready availability to the operator, and so that City, CDPHE and EPA personnel can review it during an inspection. b. A BMP maintenance folder consisting of an Erosion and Sediment Control Inspection List (ESCIL) will also be kept on -site to be completed and submitted to the City of Fort Collins Public Works Department to satisfy the report requirement stated in the Stormwater Discharge Permit. BMP's need to be inspected at least once every 2 weeks and after any significant storm event. The ES CIL shall be filled out after each inspection. B. Stormwater Quality BMPs 1. The most common associated pollutant from this type of developments is sediment, which is transported in stormwater runoff to downstream receiving waters. Emphasis will therefore be placed on improving stormwater quality by limiting and removing sediment before it leaves the site. 2. The short and long term erosion control measures previously discussed will reduce, if not eliminate, the sediment load of stormwater that exits the site. 3. The proposed `StormTech' system will also act as a Sand Filter Basin (SFB), which is considered to be a structural Best Management Practices (BMP's). a. The `StormTech' system will provide a Water Quality Capture Volume end of the building, the lowest floor at the west end of the structure is to be 5032.5. The foundation is to step down as it extends to the east and have the lowest floor elevation at the east end of the building with an elevation of 5031.5 and a BFE of 5028.0. All HVAC equipment is to be either interior ceiling mounted or roof mounted equipment. No air conditioning condenser units are to be ground mounted. None of the structures or uses to be developed on the site are `critical facilities' as designated by the City Floodplain Regulations. A Floodplain Use Permit is to be required for each structure. . A FEMA Elevation Certification is to be submitted prior to the issuance of a Certificate of Occupancy for any structure. All uses and construction shall comply with Chapter 10 of the Fort Collins City Code. V. Sediment Erosion Control: A. General Concept 1. Temporary erosion control measures will be implemented during the construction of this project to help prevent water borne sediment from being washed away from disturbed areas and being deposited onto the adjacent street and properties. These measures will include: a. Silt Fencing along the north and east sides of the property. b. Straw Wattle Inlet Filter at the proposed inlet structure. 2. Long term erosion control measures will be implemented at the final stage of construction for this project. These measures will include: a. Landscape plantings. b. Installation of landscape fabric and gravel mulch on areas disturbed by construction activities and other areas that are not designated for landscape plantings. Species type and application rates shall conform to the vegetative erosion control measures recommend by the City of Fort Collins's Stormwater Department. (A copy of these measures is included in Appendix II of this report.). c. Downspouts are to discharge onto concrete aprons and concrete chases are to be installed through sidewalks. R A. General Concept 1. During a rainfall event, stormwater will be channelized within the parking lot curb and gutters and routed to the northeast corner of the site where a storm, water inlet will be constructed. The inlet will intercept storm water and direct it to a Storm Water Quality Control device, a buried `StormTech' system. In the event that a major storm occurs, an overflow is provided to allow for the discharge to the 30-inch storm drain pipe located in West Elizabeth Street. 2. The contents in the tables, charts, and figures presented in Appendix II, come from the Urban Storm Drainage Criteria Manual and the City of Fort Collins Storm Drainage Design Criteria and Construction Standards. This data and information was used in the drainage design calculations presented in Appendix I. B. Specific Details 1. Sub -Basin `A', as designated on the Proposed Conditions Drainage Exhibit, consists of 2.03 acres that makes up the property during Phase I of the development. The peak runoff rate during the 2-year storm was calculated to be 5.20 c.f.s. and the 100-year peak runoff rate is 11.99 c.f.s. CANAL IMPORTATION FLOODPLAIN The proposed site redevelopment is to consist of the construction of a mixed use building along with the driveways, parking and site landscaping. Most of the proposed construction will occur within the Canal Importation Floodplain adjacent to the West Elizabeth Street floodway. No development is proposed within the floodway. The Base Flood Elevation for the site varies from elevation 5031.0 at the east curb line of City Park Avenue to 5028.0 at the proposed driveway entrance to the site from West Elizabeth Street. The west side of the building is to be a two story mixed use building that will face City Park Avenue. The ground floor level is to consist of restaurant and retail uses. The lowest floor level is to be the restaurant and retail portion of this building. The floor level is to be a minimum of 18 inches above the Base Flood Elevation. The southern portion of the structure is to be stepped up an additional one foot. Therefore, with a BFE of 5031.0 at the west side of the building, the lowest floor at the north end of the structure is to be 5032.5. The foundation is to step up at the break point. The structure is to be slab on grade with no open area below grade. The lowest floor elevation in the residential portion of the building is to be 5033.5. The north side of the building facing West Elizabeth Street is to be a two story mixed use building. The ground floor level is to consist of restaurant and retail uses. The floor level is to be a minimum of 18 inches above the Base Flood Elevation. The structure is to be stepped down at the changes in BFE elevation. Therefore, with a BFE of 5031.0 at the west 5 following worksheets labeled "Calculation of a Peak Runoff Using Rational Method" were used to determine the minor and major peak runoff rates. The time of concentration used for the existing conditions was the computed Tc; however, the lesser value of either the Computed Tc or the Regional Tc was used for the proposed conditions. b. Table RO-3 from the Urban Storm Drainage Criteria Manual was used for recommended imperviousness values for various land cover. c. The hydrological group `B' was used in the Urban Storm Drainage Criteria Spreadsheets for the on -site soil. 2. The 10-year and 100-year storms were analyzed in the design of the storm water management infrastructure in accordance with the City of Fort Collins Storm Drainage Design Criteria and Construction Standards. a. The minor storm interval is based on the 10-year return frequency and the major storm interval is based on a 100-year return frequency. 3. A Water Quality Capture Volume (WQCV) was incorporated into the design. D. Hydraulic Criteria 1. A stormwater quality structure was designed for the projectbased upon the requirements found in Volume III of the Urban Storm Drainage Criteria Manual. a. Sizing of structures are based on the design figures and spreadsheets provided in Volume III of the Urban Storm Drainage Criteria Manual. 2. Proposed storm drain pipes onsite are designed using smooth interior wall High Density Polyethylene (HDPE) pipe. a. A Mannings `n' value of 0.013 is to be used for all storm pipe according to Sec.4.4.2 of the City of Fort Collins Storm Drainage Design Criteria. 3. Proposed storm drain pipes within public right-of-way are designed using Reinforced Concrete Pipe(RCP) pipe. a. A Mannings `n' value of 0.015 is to be used for all storm pipe according to Sec.4.4.2 of the City of Fort Collins Storm Drainage Design Criteria. 4. Recommended Channel Design Roughness Coefficients are per Table MD-1 of the Urban Storm Drainage Criteria Manual Volume I. IV. Drainage Facility Design: 4 storm event. 3. Runoff is prevented from entering the site from other sources. a. Offsite flow is prevented from intruding onto the site from the west by the curb and gutter along City Park Avenue. b. Offsite flow during normal storm events is prevented from intruding onto the site from the north by the curb and gutter along West Elizabeth Street. Excess flow routed along West Elizabeth Street may enter the site during a major storm event. c. The neighboring property to the east slopes east and north towards West Elizabeth Street. d. The neighboring property to the south slopes east and south towards University Avenue. M. Drainage Design Criteria: A. Development Regulations 1. Design criteria from the current City of Fort Collins Storm Drainage Design Criteria and Construction Standards and the Urban Flood Control District, Urban Storm Drainage Manuals Volumes I, Il, and III were utilized. B. Development Criteria Reference and Constraints 1. The drainage pattern onsite will be affected by the development of the site in that flow will be concentrated and channelized. The development of this site will not produce any more runoff than the amount that occurred during the sites use as a movie theater and gas station. Therefore, onsite storm water detention is not required. 2. The drainage impact of this site will not adversely affect existing streets or utilities. 3. No offsite drainage traverses through the site. C. Hydrological Criteria 1. The Rainfall -Intensity -Duration curve for the City of Fort Collins was used in conjunction with the Rational Method for determining peak flows at various concentration points. a. The worksheets used to determine the peak runoff rates, (see Drainage Calculations in Appendix I of this report), come from the Urban Storm Drainage Manual. The composite imperiousness of a sub -basin was first computed using the worksheets labeled "Area -Weighting for Runoff Coefficient Calculation". The 3 approximately 21,862 square feet. The associated driveways, walks and parking is to consist of 55,884 square feet. Landscaped areas are to consist of 10,788 square feet. Access to the site will be provided from a driveway entrance to be constructed at West Elizabeth Street that enters the site near its northeast corner and from an existing driveway to be reconstructed on City Park Avenue that enters the site near its southwest corner. 11. Drainage Basins and Sub -basins: A. Major Basin Description 1. The site does not lie within a F.E.M.A. designated 100-year floodplain or floodway. The site is located within the City of Fort Collins designated Canal Importation Floodplain. (Refer to Plate 7 - "Elizabeth Street/Constitution Avenue Flow Path -100-Year Floodplain Map - Fully Developed Conditions with Existing Facilities" in the Exhibits Section of this report.) 2. The proposed development lies within the "CANAL IMPORTATION BASIN" per the City of Fort Collins Master Drainage Plan. The Canal Importation Basin is approximately 5 square miles in area. The Canal Importation Basin contains three major irrigation canals that traverse the Basin from North to South. Storm water enters and exits the Basin through these canals. a. The site is located on the downhill side East of the Larimer County Canal No. 2. The site is located approximately 1,100 feet west of Shields Street, the eastern limit of the Basin. Runoff from the area flows in a west to east direction until being routed through the Colorado State University campus. B. Sub -basin Description 1. The historic drainage basin of the property is identified on the Existing Conditions Drainage Exhibit as Sub -Basin `A'. a. Sub -Basin `A' comprises approximately 2.03 acres from the total area of the site. The sub -basin drains overland in a southwest to northeast direction. The run off from the site drains onto West Elizabeth Street. A 30-inch diameter reinforced concrete pipe storm drain is located along the south side of West Elizabeth Street. Storm drain inlets are located at the northwest and northeast corners of the site. Gutter flows are intercepted by the inlets and directed to the 30-inch storm drain. The 30-inch storm drain directs the intercepted flow easterly along West Elizabeth Street and across Shields Street to the Colorado State University campus. The 2- year and 100-year peak runoff rates for the sub -basin are 6.56 c.f.s. and 14.9 c.fs 2. The site does not receive significant offsite flows from the adjacent properties during minor storm events. The site may be affected by excess flows generated during a major 0) I. General Location and Description: A. Location 1. The Campus West Redevelopment project site is located in the Southeast Quarter of Section 15, Township 7 North, Range 69 West of the 6' P.M., Larimer County, Colorado. 2. The site is more specifically located at the southeast corner of West Elizabeth Street and City Park Avenue. Previous addresses for the businesses that were located on the site were r 1325 and 1331 West Elizabeth Street. (Refer to the included vicinity map.) 3. The area surrounding the site is substantially developed. A restaurant, liquor store and apartment complex are located on the opposite side of City Park Avenue to the west. The rectory for the John =II University Center is located on the property immediately south of the site. A car wash and the John =II University Center are located on the properties to the east of the site. Restaurants, personal service shops and retail stores are located on the opposite side of West Elizabeth Street to the north of the site. l B. Description of Property 1. The site is a rectangular shaped parcel that is currently vacant. a. The subject area consists of approximately 2.06 acres. b. The north -south dimensions of the property are approximately 275-feet and the east -west dimensions are approximately 330-feet. c. The structures and pavement associated with the businesses that were on the site have been demolished and removed. The surface of the site consists of bare earth and pavement base course. A construction fence has been placed around the perimeter of the site. 2. The "Soil Survey of Larimer County Area, Colorado" prepared by the U.S. Department of Agriculture, Soil Conservation Service, indicates that the surface soil consists of Altvan Satanta loams. a. Altvan Satanta loam is described as a nearly level soil found on terraces and high benches. It is a deep, well -drained soil that formed in mixed alluvial deposits. The "Soil Survey" identifies the runoffpotential as slow to medium and that the hazard of wind and water erosion as slight to moderate. This soil type is classified in the `B' hydrologic group. 3. The site is considered to have relatively flat slopes ranging from 0.5% to 2%. The terrain typically slopes in a southwest to northeast direction. 4. The proposed development of the property will involve the construction of a 2-story mixed residential and commercial building. The total building footprint area will be TABLE OF CONTENTS (CONTINUED) v:1 Vicinity Map Canal Importation Floodplain - Plate 7 Existing Conditions Drainage Exhibit' Proposed Conditions Drainage Exhibit Grading Plan Drainage & Erosion Control Plan Storm Drain Plan & Profile Details APPENDIX I DRAINAGE CALCULATIONS APPENDIX H CHARTS, GRAPHS, FIGURES, AND DETAILS TABLE OF CONTENTS Description LETTER OF TRANSMITTAL TABLE OF CONTENTS I. GENERAL LOCATION AND DESCRIPTION A. Location B. Description of Property II. DRAINAGE BASINS & SUB -BASINS A. Major Basin Description B. Sub -basin Description III. DRAINAGE DESIGN CRITERIA A. Development Regulations B. Development Criteria Reference and Constraints C. Hydrologic Criteria D. Hydraulic Criteria IV. DRAINAGE FACILITY DESIGN A. General Concept B. Sub -basin Description C. Canal Importation Floodplain V. SEDIMENT EROSION CONTROL A. General Concept VI. STORMWATER QUALITY CONTROL A. General Concept B. Stormwater Quality BMPs VII. CONCLUSIONS A. Compliance with Standards B. Drainage Concept VIII. REFERENCES t.. ii Page 1 1 2 3 3 3 4 5 5 5 G 7 7 Engineering, Inc. August 22, 2006 Project No. GRD - 524 - 05 Mr. Glen Schlueter City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80522-0580 Re: Drainage Investigation and Sediment Erosion Control Report for the CAMPUS WEST REDEVELOPMENT project, City of Fort Collins, Larimer County, Colorado Dear Mr. Schlueter: We are pleased to submit for your acceptance, this Drainage Investigation and Sediment Erosion I' Control Report for the CAMPUS WEST REDEVELOPMENT project, to be located at 1325 - 1331 West Elizabeth Street, Fort Collins, Colorado. This investigation was based upon the proposed site i development plan; on -site observations; available topographic information and the City of Fort Collins adopted Drainage Basin Master Plans and Flood Plains. The investigation and the recommendations within this report have been performed according to the criteria established in the City of Fort Collins' "Storm Drainage Design Criteria and Construction Standards." We sincerely appreciate your time and consideration in the review of this project. If you should have any questions, please feel free to contact this office. �\\U\\�11n Orr . Respectfully Submitted s0 .000 W MESSNER Engineering, Inc. 30.•�r;� • Cameron W. Knapp, P. E.°•,,�,FSS� •....••E' N AV B=Zs—oc I hereby state that the attached "Drainage Investigation and Sediment Erosion Control Report for the CAMPUS WEST REDEVELOPMENT project, to be located in the Southeast Quarter of Section 15, Township 7 North, Range 69 West of the 6`h P.M., City of Fort Collins, Larimer County, Colorado" was prepared by me or under my direct supervision in accordance with the provisions of the City of Fort Collins' "Storm Drainage Design Criteria and Construction Standards" for the owners thereof. �a\n`\en n Ia crX+ 11/i.,. Dennis R.-Mes* Registered Profes State of Colorado Civil Engineering Consultants�L6'•� 150 E. 29th Street, Suite 270 Loveland, Colorado 80538 (970) 663-2221 DRAINAGE INVESTIGATION SEDIMENT EROSION CONTROL REPORT for CAMPUS WEST REDEVELOPMENT Located in the Southeast Quarter of Section 15, Township 7 North, Range 69 West of the 6`n P.M. (1325 West Elizabeth Street) CITY OF FORT COLLINS, LARIMER COUNTY , COLORADO Prepared for: Kenney & Associates, LLC 209 East 4`h Street Loveland, Colorado 80537 Revised: August 2006 Project No. GRD - 524 - 05 Prepared by: MESSNER Engineering, Inc. 150 East 291hStreet, Suite 270 Loveland, Colorado 80538-2765 Telephone: (970) 663-2221