Loading...
HomeMy WebLinkAboutTIMBERLINE INTERNATIONAL MIXED USE - PDP200007 - SUBMITTAL DOCUMENTS - ROUND 1 - STORMWATER MANAGEMENT PLANStormwater Management Plan for Timberline-International Preliminary Development Plan Fort Collins, Colorado March 3, 2020 Prepared for: FR Holdings, LLC Devin Ferrey 125 S. Howes Street; 2nd Floor Fort Collins, CO 80521 Prepared by: 11582 Colony Row Broomfield, Colorado 80021 Phone: (720)259-0965, Fax: (720)259-1519 Project Number: 1805.00 - TIM I hereby certify that this Stormwater Management Plan for the Timberline- International PDP was prepared under my direct supervision in accordance with the State of Colorado storm drainage design and technical criteria, for the Owners thereof. _____________________________________ 03/03/2020 Mary B. Wohnrade, P.E. Registered Professional Engineer State of Colorado No. 30325 TABLE OF CONTENTS VICINITY MAP Page I. SITE DESCRIPTION 1.1 Introduction 1 1.2 Site Location and Description 1 1.3 Construction Documents 1 1.4 Proposed Site Improvements 1 1.5 Sequence of Construction Activities 2 1.6 Area of Site and Disturbed Area 2 1.7 Soils/Runoff Information 2 1.8 Existing Vegetation/Ground Cover 3 1.9 Potential Pollution Sources 3 1.10 Non-Stormwater Components of Discharge 5 1.11 Receiving Water 5 II. BMPs FOR STORMWATER POLLUTION PREVENTION 2.1 Site Map 6 2.2 BMP’s Before and During Construction 6 2.3 Post Construction BMP's 8 2.4 Materials Handling and Spill Prevention 8 III. FINAL STABILIZATION AND LONG-TERM STORMWATER MANAGEMENT 3.1 Measures to Achieve Final Stabilization 9 IV. INSPECTION AND MAINTENANCE PROCEDURES 4.1 Inspection Procedures 9 4.2 Maintenance Procedures 10 4.3 Record keeping 10 4.4 Revising BMP’s and the SWMP 11 V. AIR QUALITY STATIONARY SOURCE PERMITTING 5.1 Regulations 11 5.2 APEN - Application for Construction Permit 11 5.3 Fugitive Dust Control Plan for Land Development 11 REFERENCES 12 APPENDICES Appendix A Erosion and Sediment Control Inspection List Erosion and Sediment Control Escrow Calculations Construction Sequence Chart CDPHE Stormwater Discharge Permit PLANS Sheet 1 Stormwater Management Plan (SWMP) Pre-Disturbance Plan Sheet 2 Stormwater Management Plan (SWMP) Interim Plan Sheet 3 Stormwater Management Plan (SWMP) Final Stabilization Plan Stormwater Management Plan for Timberline-International FDP Fort Collins, Colorado I. SITE DESCRIPTION 1.1 Introduction This Stormwater Management Plan (SWMP) has been prepared in compliance with the Colorado Discharge Permit System (CDPS) for stormwater discharges associated with construction activities, from the Colorado Department of Public Health and Environment, Water Quality Control Division (Division). A copy of this SWMP must be kept onsite, in order to be readily available to the contractor, and to facilitate its review by the City of Fort Collins staff during an inspection. The objective of this SWMP is to identify Best Management Practices (BMPs), which when implemented, will meet the terms and conditions of the CDPS. The SWMP Administrator for this Stormwater Management Plan will be Andrew Rauch of FR Corp., who will be the project manager during construction. 1.2 Site Location and Description The site is located in the southwest quarter of Section 8, Township 7 North, Range 68 West of the 6th Principal Meridian, County of Larimer, Colorado. The property is bounded by Timberline Road on the east, International Boulevard on the south, Lake Canal on the west, and an existing commercial property on the north (See Vicinity Map). The property site is approximately 1.39 acres, located in a commercial area and is currently being annexed into the City of Fort Collins. The site is currently undeveloped and contains an existing ditch access road, a fill pile, and some existing utilities. 1.3 Construction Documents The Grading and Erosion Control Plan that accompanies this Stormwater Management Plan (SWMP) is contained in the construction plans entitled, Timberline-International, which have been prepared by Wohnrade Civil Engineers, Inc. 1.4 Proposed Site Improvements Proposed improvements to the site consist of the following: • Construction of an approximately 8,000 sf commercial building; • Installation of utilities including: a new sanitary sewer service line; new water service line; gas, telephone line, and underground electric lines; • Construction of new paved parking areas, and drives; • Construction of a new stormwater detention and water quality facility. 1.5 Sequence of Major Activities Construction activities are expected to commence during the first week in December, Timberline-International Stormwater Management Plan March 3, 2020 Page 2 2018. The sequence of major activities includes: 1. Mobilization of crews and equipment, and pre-disturbance site access; 2. Site clearing and grubbing; 3. Utility and infrastructure installation; 4. Building construction; 5. Site grading; 6. Final stabilization Site demolition will include asphalt patching, the removal of existing sanitary sewer line and removal of existing headwall and wingwalls. Site activities continue with the installation of underground utilities, followed by construction of the new single-story building, site grading, construction of the parking areas and drives, and finally site stabilization with landscaping. Upon completion of construction, all disturbed areas will be stabilized with permanent vegetation, bark mulch, thermal bluegrass, and cobbles. Disturbed areas will be seeded with a native seed mix as specified on the Landscape Plan, which is contained in the project construction plans. 1.6 Area of Site and Disturbed Area The total area of the Timberline-International site is approximately 1.39 acres. Roughly 1.39 acres of the site are expected to be disturbed as part of this project. There will be a minor amount offsite disturbance as part of the new storm sewer installation along Timberline Road, and proposed street and drainage improvements at the northwest corner of Timberline Road and International Boulevard. 1.7 Runoff Information Soils information was obtained from the soils report for the Lot 1 Industrial Business Park, International PUD project, dated October 1, 2018 (See Reference 1). Four exploratory test holes were placed within the approximate limits of the proposed site improvements. The subsurface conditions encountered generally consisted of 2 to 3 feet of sand and clay fill overlying 2 to 7 feet of clayey sand over sand and gravel. Groundwater was encountered during drilling at depths ranging from 11.5 to 13 feet. A Construction Dewatering permit from the State of Colorado may be required if groundwater is encountered during the installation of water and/or sewer utilities. Stormwater runoff calculations have been performed as part of this project, and developed coefficients have been derived. The 100-yr developed runoff coefficients vary from 0.49 to 0.76. Soil erosion potential prior to development is moderate due to existing vegetation on the project site. Soil erosion during construction will be high due to site disturbance as a Timberline-International Stormwater Management Plan March 3, 2020 Page 3 result of construction activities. The potential for soil erosion subsequent to development is moderate as a result of site stabilization by re-vegetation and new paved surfaces. Re-vegetation will include a native grass seed mix, rain garden growing media, and other vegetation, as shown on the project Landscape Plan. Specifications and procedures for final site stabilization, including the native grass seed mix and soil amendments, can be found on the project Landscape Plan. 1.8 Existing Vegetation/Ground Cover Roughly 70% of the existing site is vegetated with native grasses, weeds and trees. The density of the existing vegetation is estimated to be roughly 60%. 1.9 Potential Pollution Sources Potential pollution sources include the following: 1. Disturbed and Stored Soils: Disturbed soils will be stabilized at the completion of construction as per the project Landscape Plan. Existing vegetation will be preserved whenever possible, and stabilized as soon as practical. Disturbed soils will be prevented from migrating offsite through the use of inlet protection, and outlet protection. 2. Vehicle Tracking of Sediment: The tracking of sediment onto adjacent streets will be controlled using a vehicle tracking control pad. The tracking control pad will help reduce the amount of sediment that is tracked onto adjacent streets. Any sediment that enters the street will be removed by street sweeping, either manually or, using a street sweeping vehicle. 3. Management of contaminated soils: Contaminated soils may be generated onsite during construction, and may include soils surrounding the concrete washout area, portable toilets, or near the hazardous waste disposal area. Contaminated soils will be removed at the conclusion of construction, and disposed of as required. 4. Loading and Unloading Operations: A stabilized staging/outdoor storage area will be designated by the site superintendent and is likely to change as the project progresses due to the site’s tight constraints. This area will be stabilized to provide storage of construction materials, and for the loading and unloading of construction vehicles. The area will be secured using 6-foot high chain link construction fencing. The loading of trucks for exporting excavated material will be at a minimum, as a result of an earthwork balance. Timberline-International Stormwater Management Plan March 3, 2020 Page 4 5. Outdoor Storage Activities: Outdoor storage of building materials will be enclosed by perimeter chain link fencing that will not require secondary BMPs. There will be no onsite storage of fertilizers or chemicals. 6. Equipment Maintenance and Fueling: The fueling and possible maintenance of equipment will take place onsite in a designated fueling/maintenance area, the location of which will be determined by the project superintendent. The fueling and maintenance area should be located away from adjacent streets, drainage facilities, and watercourses. 7. Significant Dust or Particulate Generation: Dust control measures will be used onsite when dust poses a problem to air quality. Disturbed areas will be sprinkled with water (until wet) using a water truck to prevent wind blown sediment transport. 8. Routine Maintenance Activities: Routine maintenance activities involving fertilizers, pesticides, detergents, fuels, solvents, and oils include the regular inspection of hazardous waste containers, and secondary containers. Ensure that secondary containment is provided for hazardous materials, and ensure that all containers are labeled property and no leaks are present. 9. On-site Waste Management: Waste materials that are generated onsite will be disposed of immediately, or will be placed in an onsite designated trash and bulk waste collection area. Hazardous materials will be segregated in a designated onsite hazardous waste collection area, and placed in secondary containment. The contractor shall clean up litter and debris on a regular basis. Waste collection areas will be located away from streets, gutters, watercourses and storm sewers. 10. Concrete Washing: A concrete washout area has been delineated on the Interim Erosion Control Plan. The designated washout area will be identified using signage, which must be kept in good condition. 11. Dedicated asphalt or concrete batch plants: No batch plant onsite. 12. Non-industrial waste sources (worker trash and portable toilets): Waste generated onsite will be contained in an appropriate waste management container in a designated onsite waste collection area located a minimum of 50-feet from any storm inlet structure or watercourse. Portable toilets will be located adjacent to the job trailer, as shown on the Timberline-International Stormwater Management Plan March 3, 2020 Page 5 Interim Plan, and will be maintained on a regular basis. Tie-downs will also be provided for portable toilets to prevent a spill due to high winds. Toilets will be located a minimum of 50-feet from any storm inlet structure or watercourse. 13. Other potential spills: None. 1.10 Non-Stormwater Components of Discharge There are no known springs or irrigation return flows which would contribute to non- stormwater components of discharge from the site. The potential for dewatering during construction is moderate based on information contained in the soils report, which indicates that groundwater was encountered at depths ranging from 11.5' to 13'. Should groundwater be encountered, the contractor shall obtain a Construction Dewatering permit from the Colorado Department of Public Health and Environment. 1.11 Receiving Water The existing site drains generally from northeast to southwest to the adjacent Lake Canal that flows along the west and south property line. The ultimate receiving water for all stormwater runoff from the Lot 1 Industrial Park International PUD site is the Cache La Poudre River. Under post-project conditions, stormwater will be detained and released through a pond outlet pipe that conveys stormwater runoff to Lake Canal which eventually is then conveyed to the existing storm sewer. The storm sewer then conveys runoff to the Cache La Poudre River, which is located approximately 0.85 miles to the south. II. BMP’S FOR STORMWATER POLLUTION PREVENTION 2.1 Site Map Three Site Maps have been prepared for the Initial, Interim, and Final stages of the project. The Pre-disturbance Site Map includes temporary erosion control measures to be installed prior to earth moving activities. This map has been prepared by the design engineer, and has been included in this Stormwater Management Plan. The Interim Site Map includes structural and non-structural BMP’s to be installed during site grading, and construction of site improvements including: the building; parking areas and drives, and onsite detention/water quality pond. This plan has been prepared by the design engineer, and has been included in this Stormwater Management Plan. The Final Stabilization Map has been prepared by the design engineer, and includes Timberline-International Stormwater Management Plan March 3, 2020 Page 6 permanent stormwater quality measures for final stabilization of the site. This plan has been included in this Stormwater Management Plan. Construction details for structural BMP’s can be found on the General Details sheets of the civil construction plans for the proposed project. 2.2 BMPs Before and During Construction Construction activities inherently produce several kinds of pollutants which may lead to stormwater contamination. The primary concern at construction sites is sediment transport. Best Management Practices (BMPs) describe a wide range of management procedures, schedules of activities, prohibitions on practices, and other management practices. BMPs include operating procedures, treatment requirements, and practices to control site runoff, and drainage from materials storage. BMPs are also designed to prevent or control stormwater pollutants before it has a chance to affect receiving streams. There are two basic types of BMPs, structural and non-structural. Structural BMPs are generally intended to minimize erosion and sediment transport, and include physical processes. Non-Structural BMPs are mainly definitions of operational or managerial techniques, and generally address temporary and permanent vegetative stabilization, and preservation of existing mature vegetation. Structural BMPs that will be implemented prior to construction activities include the following: Vehicular Tracking Control Construction equipment and vehicles will be allowed to enter the site only at the designated entrance, which will be equipped with a stone stabilized pad. This will act as a control measure, and minimize potential transport of mud by vehicles or runoff. The location of the tracking pad is identified on the Stormwater Management Plan (SWMP) Pre-Disturbance Plan (Sheet 1 of 3, attached). The contractor will also be required to remove any sediment that is transported onto Timberline Road using either manual or vehicular street sweeping. Silt Fence Silt fencing is a temporary measure used to control sediment transport, and as a perimeter control measure. Silt fencing will be installed in the location shown on the Stormwater Management Plan (SWMP) Pre-Disturbance Plan (Sheet 1 of 3, attached). Silt fencing is used in small drainage areas to retain sediment, and is most effective in situations where there is overland flow. Silt fences can also be used to capture wind blown sediment. Rock Sock Rock socks are intended to trap sediment contained in stormwater runoff that flows into roadways as a result of construction activities. Rock socks will be placed Timberline-International Stormwater Management Plan March 3, 2020 Page 7 at regular intervals in the curb flowline to help reduce sediment loading to adjacent storm sewer inlets. Rock socks are located in the gutter flowline near the existing curb inlets located on the north side of International Boulevard. Since nearly the entire property drains to an existing box culvert in the southwest corner of the site, the proposed rock socks are an added measure of protection. Sediment Control Logs Sediment control logs or, straw wattles, are used as a sediment barrier to intercept sheet flow runoff from disturbed areas. Sediment control logs will be installed along the north property line. Non-Structural BMPs that will be implemented during construction activities include the following: Dust Suppression Wind erodes soil and transports sediment offsite where it may be washed into receiving water during the next rainstorm. Disturbed areas will be sprinkled with water until wet, as required, to prevent sediment transport. Preservation of Natural Vegetation This practice is used as a permanent control measure, and provides a natural buffer zone. The contractor should ensure that existing vegetation is preserved where possible, and that disturbed areas are stabilized as soon as practical. Structural BMP's that will be implemented during construction activities include the following: Concrete Washout Equipment and vehicles used to handle concrete will be cleaned at a designated area selected by the construction superintendent. This area will be clearly marked and maintained by the contractor. Once the concrete washout area is retired, all dried concrete will be removed and hauled offsite for disposal. One concrete washout area have been designated in the Stormwater Management Plan (SWMP) Interim Plan (Sheet 2 of 3, attached). Inlet Protection Storm drain inlet protection is a filtering measure placed around any inlet or culvert to trap sediment, and prevents sediment from entering inlet structures and existing storm sewers. Four cubic yards of pea gravel will be placed at the upstream end of the pond outlet structure to prevent sediment from exiting the site through the pond outlet pipe, and into the existing canal. Rock sock inlet protection will also be placed in the guttter line along International Boulevard. The above structural and non-structural BMP’s are shown on the Stormwater Management Plan (SWMP) Interim Plan (Sheet 2 of 3, attached). Timberline-International Stormwater Management Plan March 3, 2020 Page 8 2.3 Post Construction BMPs Stabilization measures will be initiated as soon as practicable in portions of the site where construction activities have ceased. The following BMPs will be used after construction is complete: Outlet Protection Scour Stop transition mats will be provided at the outlet of the valley pan, at the pond overflow weir to dissipate the velocity of concentrated stormwater flows and prevent scour, and at the downstream end of the new access driveway curb and gutter return transition to existing edge of pavement along Timberline Road. Seed/Sod/Erosion Control Blankets Areas which have been disturbed by construction will be revegetated using a native seed mix as specified on the Landscape Plan. Permanent seeding has been specified in the areas throughout the site, including cut slopes and the detention/water quality pond. A Landscape Plan has been prepared for the project, and includes landscape areas surrounding the building, and adjacent to the public right-of-way. The above post construction BMPs are shown on the Stormwater Management Plan (SWMP) Final Stabilization Plan (Sheet 3 of 3, attached). 2.4 Materials Handling and Spill Prevention There will be moderate use of chemicals, fuels and other similar materials, as it relates to construction activities at the site. Substantial amounts of hazardous materials are not expected to be stored onsite. Proper precautions to be followed for spill containment are outlined in the Urban Drainage Criteria Manual, Volume 3, Chapter 7, Construction Best Management Practices, Section 4.4, Materials Management. III. FINAL STABILIZATION AND LONG-TERM STORMWATER MANAGEMENT 3.1 Measures to Achieve Final Stabilization Final stabilization is achieved when all soil disturbing activities at the site have been completed, and uniform vegetative cover has been established with a density of at least seventy (70) percent of pre-disturbance levels, or equivalent permanent, physical erosion reduction methods have been employed. As soon as practicable after construction activities have ceased, permanent stabilization should commence to prevent further erosion of soil from disturbed areas. All disturbed areas (with the exception of paved and building areas) should be permanently stabilized once construction activities have ceased. Timberline-International Stormwater Management Plan March 3, 2020 Page 9 Stormwater management controls to prevent or control pollution of stormwater subsequent to construction include: permanent native seeding, landscape areas, and paved surfaces. The project Landscape Plan contains all information related to soil preparation, soil type, native seed mixture, soil amendments, and mulching. All temporary erosion and sediment control measures shall be removed and disposed of within 30 days after final site stabilization is achieved, or after the temporary measures are no longer necessary. IV. INSPECTION AND MAINTENANCE PROCEDURES 4.1 Inspection Procedures Under the Term and Conditions of Section 5 of the CDPS General Permit, the permittee will perform inspections of the storm drainage system at least once every 14 calendar days, and within 24 hours of the end of any storm event, including but not limited to rain or snowmelt, which results in water or sediment being transported across the site during active construction. Inspections will occur at least once every month when all construction activities are completed. The permittee will designate a qualified person, or persons, to perform the following inspections: 1) Disturbed areas and areas used for storage of materials that are exposed to precipitation will be inspected for evidence of, or the potential for, pollutants entering the drainage system. 2) Erosion and sediment control measures identified in this SWMP will be observed to ensure that they are operating correctly. 3) Where discharge locations or points are accessible, they will be inspected to ascertain whether erosion control measures are effective in preventing significant impacts to receiving waters. 4) Locations where vehicles enter or exit the site will be inspected for evidence of off-site sediment tracking. Based on the results of the inspection, BMPs which are identified in this SWMP may be revised as required, and as soon as practicable following the inspection. The inspector will complete an Erosion and Sediment Control Inspection List (see Timberline-International Stormwater Management Plan March 3, 2020 Page 10 attachment, Appendix A) for each inspection performed. The operator will keep a record of inspections to be made available upon request by the Colorado Water Quality Control Division. The inspection reports will be kept on site and a copy of each inspection report will be provided to the local and/or state agencies as requested. 4.2 Maintenance Procedures During construction activities, every effort will be made to prevent migration of sediment from the site. Erosion and sediment control measures must be inspected regularly, as described in Section 4.1. All erosion and sediment control measures must be maintained in an effective operating condition. Damage to erosion and sediment control systems caused by construction traffic shall be repaired immediately by the contractor. The contractor is responsible for collecting and disposing of all sediment and waste materials in an appropriate manner. All maintenance activities will be performed as indicated in the manufacturer’s specifications, or other sources determined to be acceptable. 4.3 Record keeping Record keeping is an important component of the SWMP. Keeping records of spills, leaks, SWMP implementation, etc. is a requirement of the general permit. Enforcement actions, including fines, could result if records are not adequate. A logbook will be maintained at the site for inspection reports, maintenance records, spill response, BMP revisions, weather conditions, training, correspondence, or any other records pertaining to implementation of the SWMP during construction. 4.4 Revising BMP’s and the SWMP The SWMP is a “living document” that is continuously being reviewed and modified to reflect changing site conditions. The SWMP must be modified to reflect actual field conditions, and documented according to the procedure outlined in paragraph 4.3. V. AIR QUALITY STATIONARY SOURCE PERMITTING 5.1 Regulations The Colorado Department of Public Health and Environment, Air Quality Control Commission, Regulation Number 3, states the requirements for stationary source permitting, and air pollution emission notice requirements. Part A, Paragraph II.D.1. specifies exemptions from Air Pollution Emission Notice Requirements. Paragraph II.D.1.j. pertains to disturbance of surface areas for purposes of land development. Disturbance to sites which do not exceed twenty-five (25) contiguous acres, and do not exceed six months in duration are exempt for the requirements of Regulation Number 3. Information regarding the City of Fort Collins Fugitive Dust Ordinance can also be found Timberline-International Stormwater Management Plan March 3, 2020 Page 11 at http://www.fcgov.com/airquality/fugitive-dust.php. 5.2 Air Pollutant Emission Notice (APEN) - Application for Construction Permit Disturbance of surface areas for purposes of land development, that exceed twenty-five (25) contiguous acres, or exceed six months in duration will be required to complete an Air Pollution Emission Notice (APEN) and Application for Construction Permit. 5.3 Fugitive Dust Control Plan for Land Development The Colorado Department of Public Health and Environment, Air Quality Control Commission, Regulation Number 1, states the requirements for emission control for particulate matter, smoke, carbon monoxide, and sulfur oxides. Regulation 1 requires that a fugitive dust control plan be submitted by applicants whose activity results in fugitive dust emissions. Timberline-International Stormwater Management Plan March 3, 2020 Page 12 REFERENCES 1) Geotechnical Investigation Report, Proposed Commercial Development Lot 1, Industrial Business Park, Fort Collins, Colorado, prepared by CTL Thompson Inc., October 1, 2018. 2) Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, Volume 3, November, 2015. Timberline-International Stormwater Management Plan March 3, 2020 Page 13 Appendix A Timberline-International Stormwater Management Plan March 3, 2020 Page 14 Timberline-International Stormwater Management Plan March 3, 2020 Page 15 Timberline-International Stormwater Management Plan March 3, 2020 Page 16 Scale: Designed By: Reviewed By: Sheet 1 MBW JR 1"=30' Project: Date: Sheets 11582 Colony Row Broomfield, Colorado 80021 Phone: (720)259-0965 Fax: (720)259-1519 No. Revisions: By: Date: WOHNRADE CIVIL ENGINEERS, INC. TIM: 1805.00 3/2/2020 3 Scale: Designed By: Reviewed By: Sheet 2 MBW JR 1"=30' Project: Date: Sheets 11582 Colony Row Broomfield, Colorado 80021 Phone: (720)259-0965 Fax: (720)259-1519 No. Revisions: By: Date: WOHNRADE CIVIL ENGINEERS, INC. TIM: 1805.00 3/2/2020 3 Scale: Designed By: Reviewed By: Sheet 3 MBW JR 1"=30' Project: Date: Sheets 11582 Colony Row Broomfield, Colorado 80021 Phone: (720)259-0965 Fax: (720)259-1519 No. Revisions: By: Date: WOHNRADE CIVIL ENGINEERS, INC. TIM: 1805.00 3/2/2020 3