pf_02867 - Laserfiche WebLink

Home

Erosion and sedimentation control measures will be implemented prior to grading and maintained in a functionable condition during construction. The control measures will remain in-place until the project area has been resurfaced and revegetated. Installing and maintaining temporary erosion protection and sedimentation control will be the responsibility of contractors working in the project area in strict conformance with approved erosion control plans. 18. Water Quality - Surface Water Runoff a. Compare the quantity and quality of site runoff before and after the project. Describe methods used to manage and/or treat runoff. Response: The proposed project would reduce storm water runoff over the 126 acres of development parcels and public roadway areas by 2.31 acre-feet nom 39.27 acre-feet to 36.96 acre feet during a 10 year, 24 hour event. The proposed project would reduce storm water runoff over the 126 acres of development parcels and public roadway areas by 3.25 acre-feet nom 55.17 acre-feet to 51.92 acre feet during a 100 year, 24 hour event. The above runoff estimates are based on an average impervious coverage ratio of 90% currently and 80% under the proposed conditions. The majority of existing development consists of trucking facilities that include bituminous surfacing over 90 - 100% of parcel areas, and office, dispatching, and loading buildings. New development will be governed by zoning ordinances that require approximately 20% of a parcel to be pervious, landscaped surface. The quality of site runoff will be improved due to connection of redeveloped parcels and proposed roadways to storm water treatment basins located adjacent to the project area. The basins will intercept site runoff and remove pollutants and sediment prior to discharging into receiving waters. No ponding of site runoff occurs under the existing conditions. Vehicle related pollutants consist of Copper, Lead, Zinc and Phosphorus. A study conducted by the U.S. Environmental Protection Agency (EPA) titled, Results of the Nationwide Urban RunoffProl!l'alTl, dated December 1983, have identified the above pollutants as the predominant constituents in highway runoff. Other common pollutants are Total Suspended Solids (TSS) and Chloride. TSS and Chloride are introduced into the roadway runoff primarily nom winter de-icing practices and the amounts vary depending upon the application rates and the number of ice/snowfall events in a given year. An effective means of reducing the amount of pollutants discharged into the receiving stream/water body is to provide sedimentation ponds at the outfall of the storm sewers. b. Identify the route(s) and receiving water bodies for runoff nom the site. Estimate the impact of the runoff on the quality of receiving waters. (If the runoff may affect a lake, consult EA W Guidelines about whether a nutrient budget analysis is needed.) Response: The proposed project lies within the jurisdiction of the Rice Creek Watershed District. Runoff nom the site areas west will be routed through storm water treatment ponds prior to discharging into natural water bodies. The ponds provide pollutant removal and will reduce peak discharge rates to be less than the pre-existing peak runoff rates into receiving #24397 13