b'LT ENGINEERINGCATALOGSIZINGrises over the bypass weir and is discharged via the outletUnder the Storm Water Phase II Final Rule, urbanizedof the control manhole to the MS4. Trash is collected in theareas where construction disturbs one acre or morecontrol manhole debris screen. must develop water quality controls. The Final Rule requires a water quality system design that will reduce Treated Stormwater: As water enters the treatmenttotal suspended solids (TSS) loadings by an average ofchamber of the interceptor, trash and light debris are80 percent annually. A professional engineer must develop filtered through a screen; heavy oils immediately rise to thea Best Management Practice Plan (BMP) to obtain a surface, Total Suspended Solids (TSS) sink to the bottom.NPDES number from permitting authorities. Typically,The remaining oily water mixture flows through the seconda designer utilizes site specific runoff coefficients and chamber. Both the smaller oil droplets and the finer TSSrainfall intensity rates to develop the hydrology calculations are progressively separated. Coalescing media is used toand structural control systems that become a Storm Water separate significant concentrations of hydrocarbons. InQuality Management Plan (SWQMP) or BMP. the final stage, effluent is discharged at the bottom of the interceptor preventing collected pollutants from enteringUsing the First Flush Principle has become the acceptable the outlet piping. Collected oils and solids will remain in themeans of determining treated stormwater flow rates.interceptor until removal. The initial runoff flow will be more polluted than the stormwater that runs off later, after the rainfall has DESIGN CONSIDERATIONS cleansed the catchment area. The stormwater containing this high initial pollutant load will be treated with the The separator tank is designed to conform to ASTM C913StormTrooper Stormwater Interceptor. Most studies have Standard Specification for Precast Concrete Water andfound that significant concentration pollutant loads are Wastewater Structures, the weight of the soil above shallretained when at least 90 percent of the storm eventsbe capable of withstanding a live load equal to an AASHTOare treated.HS-20 or HL93 highway loading using full impact load or 300 psf applied to the top slab. To determine the treated flow rate required of the stormwater interceptor, the flow rate of the first flush All exterior walls of the tank shall be designed for anis estimated. An accepted practice is to calculate the equivalent fluid pressure of 85 lbs/ft2.Structure shall bedrainage using the Rational Method for estimating design designed to resist buoyant uplift forces with a factor ofpeak discharge from a small watershed or the total safety of not less than 1.10.The top of the pressure diagramacreage of a development. shall be assumed to originate at finished ground level.Additional lateral pressure from approaching truck wheelsThe StormTrooper System should be located downstream and/or 300 psf surcharge shall be considered in accordanceof stormwater runoff for maximum performance, typically with AASHTO Standard Specification for Highway Bridges. the final conveyance before stormwater exits the property. The stormwater interceptor is usually buried allowing MAINTENANCE for gravity flow of the runoff. The interceptor should be The frequency of cleaning at any given installation willinstalled and located so that it will be easily accessible for vary depending on use. The StormTrooper stormwaterinspection, cleaning, and removal of separated pollutants. interceptor should be cleaned (or pumped out) routinelyThere should be an adequate number of interceptor access to prevent the escape of appreciable quantities ofopenings to permit cleaning of all compartments.detained pollutants. Sediment should be removed beforeAll access manholes should extend to grade.accumulations effectively reduce storage capacity andThe StormTrooper interceptor is designed for stormwater detention time of the interceptor. Hydrocarbon- absorbingrunoff from typical commercial applications where light pillows, when used, should be properly disposed of andamounts of oil & contaminants are found (e.g., parking lots). replaced when full. A professional pumping companyFor Industrial applications where excessive pollutants are familiar with regulations regarding proper disposal shouldpresent, the StormTrooper EX Extra-Duty (over 1000 ppm) pump out the interceptor. is recommended.80 [email protected]|888-611-7275|WWW.PARKUSA.COM'