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HomeMy WebLinkAboutBUCKINGHAM PLACE, SECOND FILING - PDP/FDP - FDP150001 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTAAAApex pex EEEEnnnnggggiiiinnnneeeeeeeerrrriiiinnnngggg 908 Laporte Avenue ■ Fort Collins, Colorado 80521 ■ 970.219.2834 May 4, 2013 Mr. Glen Schleuter Stormwater Department City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80521 RE: Final Drainage and Erosion Control Letter Buckingham Place, Second Filing APEX Project #45-104 Dear Glen, We have prepared this final drainage letter for Buckingham Place, Second Filing for your review and approval. The existing property is an undeveloped 12,529 square-foot lot on the east side of Third Street approximately 200 lf north of Lincoln Avenue. It is located in the Dry Creek Master Drainage Basin. This project proposes to develop to single family residential lots on the property. The following is a summary of the impacts to the drainage systems on and off the site. In addition, supporting calculations and a drainage exhibit have been attached. Runoff The existing site (Basin EX) drains to the east and has 0.02 cfs and 0.78 cfs of runoff leaving the site in the 2-year and 100-year storms, respectively. In the developed condition, approximately 0.17 acres drains to the west and 0.12 acres drains to the east. The area draining to the west is defined as Basin A and will have 0.13 cfs and 0.87 cfs of runoff leaving the site in the 2-year and 100-year storms, respectively. The area draining to the east is defined as Basin B and will have 0.02 cfs and 0.41 cfs of runoff leaving the site in the 2-year and 100-year storms, respectively. Detention Storage The entire site is estimated to be approximately 50% to 60% impervious when built out. The Dry Creek Master Drainage plan estimated this area at 90% impervious. Due to the reduction in the planned imperviousness, the size of the site, and the difficulty in providing detention we are not proposing any detention storage with this project. Water Quality The small site, location of the Coy Ditch, and proximity to adjacent storm sewer make it very difficult to provide typical water quality. The residential site will have an area of non paved surfaces at the front and rear of the lot. These areas will intercept the stormwater runoff that comes from the roof, driveway, and patio areas and provide some water quality via “disconnected impervious areas”. This is the extent of water quality that we are proposing. Erosion Control Erosion and Sediment Control devices will be implemented on the site as needed. It is anticipated that onsite runoff will be contained by straw wattles or silt fence surrounding the site. Inlet protection will be placed adjacent to the inlet approximately 100’ south of this site on 3rd Street. A separate Erosion Control Report has been attached as Appendix C. Summary Due to the size of this small site, the proposed development of the site will have minimal impact to the stormwater. The runoff from the site is less than what was originally planned for in the Master Drainage Plan, therefore no on site detention or downstream improvements are included with this project. I appreciate your time and consideration in reviewing this submittal. Please contact me at 970- 217-7420 or seliason@bluesky-engineer.com if you have any questions. Sincerely, Samuel M. Eliason, P.E. APEX Engineering Attachments: • Appendix A - Calculation of Peak Runoffs (EX 2-yr, EX 100-yr, A 2-yr, A-100 yr, B 2-yr, B 100-yr) • Appendix B - Drainage Exhibit • Appendix C - Erosion Control Report • Appendix D – Grading and Erosion Plan and Details Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Appendix A Calculation of Peak Runoff Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Appendix B Drainage Exhibit Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Appendix C Erosion Control Report Buckingham Place, Second Filing Fort Collins, Colorado Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing A. Site Description 1. Construction Activity Description Construction activity includes installation of BMP’s, grading, utility (sanitary sewer, and waterline) construction, removal and replacement of asphalt and concrete in 3rd Street, on site concrete and wall construction, and building construction. 2. Proposed Sequence for Major Activities The project is expected to be constructed in one phase with this initial development. The ultimate improvements of 3rd Street, which include reconstruction of the street, new curb & gutter, sidewalk, and potential relocation of the Coy Ditch are not included in this sequence of activities. The developer will be escrowing funds for that future construction and the extent, scope, and timing of that future construction project is totally unknown. The anticipated sequence for major construction activities is follows: • Installation of erosion control • Removals in 3rd Street for installation of utilities • Installation of utilities • Patching in 3rd Street • Clearing, excavation, and removal of existing items • Installation of building foundation • Site grading including installation of walls. • Construction of building • Final landscaping. Construction is estimated to begin sometime in 2013 and be fully completed within one year. 3. Area Estimates The site area as defined by the property boundaries is approximately12,529 square- feet which is also the area that will undergo clearing and grading activities. The total project area including offsite utilities and paving is approximately 17,000 square-feet. The site areas do not include any additional offsite areas (for staging, material storage, overburden stockpiles of dirt, borrow areas, etc) other than that mentioned above. 4. Soil Description Earth Engineering Consultants completed the soils investigations for the project site and presented the results in the Soil Description and Limitation Report, 3rd Street Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Pavement Section Design, Buckingham Place, Second Filing, Fort Collins, Colorado. According to this report, the surficial soils are mainly clay loam identified specifically as Loveland clay loam and Table Mountain loam. These soils exhibit low strength and shrink/swell potential and are unstable surficial soils. 5. Existing Vegetation The existing site is undeveloped with approximately 60% vegetative cover. The vegetative cover consists of native grasses and bushes. There is a large amount of bare dirt on the property that appears to be driven on regularly. 6. Location and Description of Other Potential Pollution Sources Potential pollutant sources include sediment, uncovered soil, construction machinery, building materials, and fertilizers. It is anticipated that any storage of materials or machinery will be on site and surrounded by silt fence or straw wattles. 7. Non-Stormwater Components of Discharge According to the Preliminary Geotechnical Evaluation, 3rd Street and Buckingham, Fort Collins, Colorado by Earth Engineering Consultants: Free water was observed at depths on the order of 11 to 14 feet below present site grades at the time of drilling. Those depths are on the order of 4 feet or less below the apparent surface of the native soils At these depths, it is expected that groundwater will be encountered during the construction of utilities. If groundwater is encountered, a temporary sediment/retention basin should be constructed to store pumped dewatering flows. The other non-storm water components of discharge include water line flushing, irrigation to establish seeding, washing out concrete trucks, and watering for dust mitigation and compaction. It is important for the contractor to manage the runoff from these items utilizing the BMP’s mentioned in this report (ie silt fence and straw waddles) 8. Receiving Waters This site is located in the Dry Creek Drainage Basin of Fort Collins, Colorado. Runoff from the west side will drain to the west, to the Coy Ditch in the iterim and to 3rd Street when the ultimate Street improvements are installed in the future. Runoff from the east portion of the site drains to the east side of the site and to the property to the east. In both cases, the stormwater eventually makes it to Lincoln street and drains to the east through a series of sewers and swales before it enters Dry Creek. Dry Creek outlets to the Cache La Poudre River south of Mulberry Street and before it crosses underneath Timberline Road. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing B. Stormwater Management Controls 1. SWMP Administrator The SWMP Administrator is currently: Mr. Charles Meserlian 700 N. College Avenue Fort Collins, CO 80524 Phone: 970-490-1251 Fax: 970-484-6695 2. Identification of Potential Pollutant Sources This section focuses on the identification of the potential pollutant sources and briefly discusses the Best Management Practices (BMPs) that will be used. More information on the BMP’s utilized on this site is included in the next section “3. Best Management Practices”. A. All disturbed and stored soils; It is expected that there will be stockpiles of dirt on the site from the utility installations and the foundation excavation. Silt Fence or Straw wattles should be placed around the outer boundary of the site to contain the runoff from the stockpiles. B. Vehicle tracking of sediments The construction is so limited on this site that a vehicle tracking control pad has not been shown on the erosion control plan. It is important that the contractor is aware of vehicle tracking of sediments though. At the end of each workday, the Contractor shall sweep or scrape 3rd Street to dispose of debris that may have accumulated during the workday. It is also important that inlet protection be in place for the inlet on the west side of 3rd Street, that is approximately 100’ south of the site. C. Management of contaminated soils There are not any known contaminated soils on the site. However, if the contractor encounters contaminated soils during the construction process they should stop construction immediately and notify the appropriate government authorities in accordance with good construction safety and practice. D. Loading and Unloading operations Loading and unloading will take place on the site or along 3rd Street. BMP’s should be in place to keep sediment from the street and Coy Ditch. E. Outdoor storage activities (building materials, fertilizers, chemicals, etc.) Storage of onsite materials including building materials, fertilizers, waterline, sanitary sewer, and storm sewer will be covered and placed on pallets to prevent direct contact with the ground and potential surface runoff. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing F. Vehicle and equipment maintenance Vehicle and equipment maintenance should be performed offsite or onsite within the perimeter silt fence or straw wattles. Vehicle and equipment maintenance shall not happen along 3rd Street. At a minimum all vehicle and equipment maintenance shall be performed on the hard surface or gravel areas at least 50’ from any stormwater feature (ie inlet, storm sewer, concentrated runoff, swale, etc.) G. Significant dust or particulate generating processes The Contractor shall comply with applicable air pollution control requirements of the City. The Contractor shall take appropriate actions to minimize atmospheric pollution and take reasonable precautions which shall include, but not be limited to: 1. The use of water for control of dusts for construction processes such as demolition, grading, or the clearing of land. 2. Covering, at all times when in motion, open-bodied trucks transporting materials likely to give rise to airborne dusts. H. Routine maintenance activities involving fertilizers, pesticides, detergents, fuels, solvents, oils, etc; Chemicals, fuels, lubricants, and paints typical with building construction stored on-site will be in water tight containers and covered as necessary and stored in a bermed area, a storage building, or within a vehicle to act as secondary containment. I. On-site waste management practices (waste piles, liquid wastes, dumpsters, etc.); Waste piles should be covered or surrounded by silt fence or straw wattles. Liquid wastes should be collected and stored in covered containers and disposed of properly. Solid waste materials, including disposable materials incidental to the major construction activities, will be collected in on site dumpsters. The containers will be emptied periodically and trucked away from the site. Dumpsters should have covers. J. Concrete truck / equipment washing, including the concrete truck chute and associated fixtures and equipment; A dedicated concrete washout area is not anticipated to be necessary for this project. The contractor shall clean out equipment away so that runoff is not allowed to leave site and enter 3rd Street, the Coy Ditch, or neighboring properties. K. Dedicated asphalt and concrete batch plants; There will not be dedicated asphalt or concrete batch plants on this site. L. Non-industrial waste sources such as worker trash and portable toilets Worker’s trash shall be disposed of in an onsite dumpster. The site should be free of trash at the end of each working day. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Portable toilets shall be utilized by construction personnel and serviced regularly by a commercial operator. They shall be located a minimum of 5 feet from the curb or 50 feet from inlets and must be anchored. If sanitary facilities are located on a paved surface, a secondary containment BMP will need to be constructed. M. Other areas or procedures where potential spills can occur. BMP’s such as tarps and drip pans should be used for painting, stucco, dry-wall etc. operations 3. Best Management Practices (BMP’s) Once construction activity begins, Best Management Practices (BMP’s) intended to contain sediment onsite must be constructed, inspected and repaired as necessary. Such controls must be functional before upslope land disturbance takes place. The BMP’s will be installed as shown on the Grading and Erosion Control plan shown in Appendix D. They must be supplemented as on-site experience proves necessary in order to control sediment, pollutant discharge, and insure public safety. The following temporary and permanent BMP’s will be installed and maintained to control on-site erosion and prevent sediment from traveling off-site during construction. The descriptions below provide some information about each BMP, but further information can be found in Urban Storm Drainage Criteria Manual, Volume 3 – Best Management Practices by Urban Drainage and Flood Control District. Temporary BMP’s • Construction Fence is a temporary BMP. The contractor is to place construction fencing around development as needed to limit access by construction equipment and personal vehicles to designated areas of ingress and egress. Since the majority of site will soon be surrounded by a permanent fence, there will be limited construction fence needed on this project. • Inlet Protection is a temporary BMP that helps prevent soil and debris from the site from entering the storm drain inlets and usually consists of a sediment filter around or upstream of the storm drain inlet. Inlet protection allows storm water to flow into the drain but only after excess sediment has been filtered out. Inlet protection will be used on existing and proposed storm inlets and will be installed at such time as construction of the storm sewer system occurs. Inlet protection for this site will consist of wattles, which are meshed netting “tubes” filled with straw, excelsior, or coconut fiber placed around grated inlets and curb inlets. Wattles require proper installation and maintenance to ensure their performance. Sizing shall be per manufacturer’s recommendation. • Regular Meetings is a temporary and non-structural BMP. Regular meetings with on-site workers including builders, suppliers, landscape personnel, etc. should be conducted so that they are kept up to date with site standard operating procedures. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing • Silt Fence is a woven synthetic permeable fabric that filters runoff. Silt fence is a temporary barrier that is installed prior to earthmoving activities and is placed downstream of areas where runoff from construction activities is expected to occur, especially along the site perimeter to allow sediment to settle from runoff before water leaves the construction site. Silt fences will be installed per manufacturer’s recommendations. Silt fence encourages sheet flow and is not intended to be used in areas of concentrated flow. If concentrated flow is encountered during the placement of the fence, an alternative BMP shall be used and the SWMP should be updated to reflect this change. • Straw Wattles are a temporary BMP that are used for a variety of purposes. They are used for inlet protection, curbside check dams, swale protection, at the bottom of slopes, or the limits of property boundaries. The straw wattles, which are meshed netting “tubes” filled with straw, excelsior, or coconut fiber. Wattles for swale protection should be installed following rough grading of channel areas. Wattles require proper installation and maintenance to ensure their performance. • Street Sweeping and Vacuuming removes sediment that has been tracked onto roadways to reduce sediment transport into storm drain systems or a surface waterway. This practice should be used on the adjacent paved road to the construction site. Paved roads should be inspected on a daily basis and more frequently as needed. • Temporary Seeding is the establishment of a temporary vegetative cover on a graded area that will be exposed for longer 30 days. Temporary seeding can be used on areas requiring temporary protection that will eventually need permanent vegetation at the completion of the construction or it can be used for areas that will be re-disturbed after a period of inactivity. • Wind Borne Sediment and Dust Control measures will be provided during the construction process to control wind borne sediment. During grading activities, water will be applied to the disturbed soils for the purpose of maintaining cohesion with clay type soils and also to meet moisture requirements for compaction of disturbed soils. Other measures of mitigation for wind erosion may include the timely installation of seed and mulch following the establishment of final grade, and the timely installation of pavement following completion of utility trenching operations and curb construction. Open areas should be kept in a roughened condition. Permanent BMP’s • Permanent Seeding and Planting is the establishment of a permanent perennial vegetation such as trees, shrubs, vines, grasses/sod, or legumes on exposed areas for final permanent stabilization in order to provide stabilization of the soil by holding soil particles in place. It also reduces storm water runoff velocity, maintains sheet flow, protects the soil surface from erosion, promotes infiltration of runoff, and improves wildlife habitat. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing • Preservation of Existing Vegetation should occur where no construction activity is expected to occur. Preservation of natural vegetation is generally a permanent BMP and is applicable to construction sites with pre-existing vegetation. Only land needed for building activities and vehicle traffic needs to be cleared. C. Erosion Control Sequencing The erosion control sequencing for construction is as follows: Prior to Construction Silt Fence or Straw Wattles – Before construction commencement, silt fence will be placed around the boundary of the site. Inlet Protection – Inlet protection should be in place on the inlet that is on the west side of 3rd Street, approximately 100’ north of the site. These erosion control devices shall be in place, functional, and maintained during and following the construction operations. During Construction Street Sweeping and Cleaning – The adjacent streets and parking lots shall be swept and cleaned on a daily basis to ensure sediment is not being tracked away from the construction site. Wind Borne Sediment and Dust Control – Wind borne sediment and dust control measures should be implemented during grading activities. Permanent Seeding – Permanent seeding or landscaping shall be placed immediately in areas that are final graded and where little future disturbance is expected. In particular, permanent seeding should be included on the side slopes of the detention pond. Temporary Seeding – The majority of the landscaped areas will be permanently seeded/planted. However, if any of the areas are left disturbed without permanent stabilization 30 days after grading, temporary seeding will be required. Post Construction BMP’s shall be maintained until final site stabilization. D. Final Stabilization and Long-term Stormwater Quality Final stabilization is reached when all soil disturbing activities at the site have been completed and vegetative cover has been established with a density of at least 70 percent of pre-disturbance levels or when equivalent permanent erosion reduction methods have been utilized. Upon final stabilization, temporary BMP’s may be removed. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Water quality will be provided through established landscaping and pervious areas on the site. E. Inspection and Maintenance Procedures Appropriate measures shall be taken to inspect and maintain existing erosion control features, as described herein or per manufacturers specifications (whichever is more stringent) and install new erosion control elements as needed. The temporary BMP’s will be inspected and documented at a minimum of once every 14 days and after each precipitation or snowmelt event. Records should include complete inspection reports for each inspection, maintenance and/or repair. A record-keeping system is recommended in managing inspection and maintenance reports and should include all maintenance records, spill response, weather conditions, training, correspondence, etc. Preventative maintenance also involves the regular inspection and testing of equipment, timely maintenance of the equipment, and complete records of the maintenance and inspections of the equipment. The maintenance and inspection records should be kept on site and made available upon request. Inspections must include the observation of the construction site perimeter, runoff discharge points, disturbed areas, staging areas (including concrete washout areas and fueling areas), erosion and sediment control measures identified, and any other structural BMP’s that may require maintenance. The inspection must determine if there is evidence of or potential for pollutants to enter the drainage system and if they should be modified, replaced, or added to. The following list includes some recommended maintenance procedures: • Erosion and sediment control measures determined, upon inspection, to be in need of repair shall be maintained before the next anticipated storm event or as necessary to maintain continued effectiveness of erosion and sediment control measures. If it is impractical to maintain erosion and sediment control measures before the next storm event, maintenance should be accomplished as soon as practical. • Locations where vehicles enter or exit the site shall be inspected for evidence of sediment being tracked off-site by construction traffic. Such sediment shall be removed before it can be conveyed to the receiving storm drains or creeks. • Seeded areas will be checked to see that grass coverage is maintained. Areas will be watered, fertilized and reseeded as needed. • It is the responsibility of the Operator to maintain effective pollutant discharge controls. Actual physical site conditions or contractor practices could make it necessary to install more control than are shown on the Erosion Control Plan. For example, localized concentrations of surface runoff or unusually steep areas could require additional erosion control devices. Assessing the need for, and implementing additional controls will be a continuing aspect of the SWMP until final stabilization. This plan intends to control water-borne and liquid pollutant discharges by some combination of interception, filtration, and containment. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Parties implementing this plan must remain alert to the need to periodically refine and update the plan in order to accomplish the intended goals. • Sediment that has escaped the construction site must be removed at a frequency sufficient to minimize off-site impacts. F. Erosion Control Surety Calculations An Engineer’s opinion of probable cost for the erosion/sediment control measures has not been included because the minimum $1500 will cover this small site. Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Appendix D Grading and Erosion Control Plan and Details Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing Final Drainage and Erosion Control Report Attachments Buckingham Place, Second Filing