9311 18TH AVE W A,B 2018-01-02 MF Import

COME RAIN, WE SHINE:" STORMWATE�^ ( MANAOEMENT INC. Lilly's Court- Stormwater Treatment System Size and Cost Estimate Everett, Washington Information provided: • Total contributing area = 0.62 acres • Impervious area = 0.33 acres • Voiume of detention = 324 cubic feet • Volume of runoff = 1,082 cubic feet • Depth in detention = 5 feet • Detention release rate = 0.01 cfs • Flow Rate per Cartridge = 7.5 gpm • Presiding agency = City of Everett Assum inn� • Media = ZPG cartridges • Dead storage is provided • Credit from detention = 2890 • Event Mean Concentration = 100 mg/I � Drop required from inlet to outlet = 2.3' minimum Size and cost estimates: The StormFilter is a flow-based system, and [herefore, is sized by calculating the peak water quality flow rate associated with the design storm. However, when the StormFilter is placed downstream of detention the flow rate generated at the water quality storm is not always representative of the total volume of water that will go through the system or type of pollutant-loading the system may experience in one year. Stormwater Management recommends using a 72" precast manhole StermFilter with 4 cartridges. The estimated cost of this unit is $15,840, complete and delivered to the job site. This estimate assumes that the manlioie is 6 feet deep. The final system cost will depend on the actual depth of the units and whether extras like doors rather than castings are specified. The contractor is responsible for setting the manhole StorrnFilter and all external plumbing. Typically, we recommend annual maintenance for the StormFilter treatment system, but the maintenance cycle will ultimately depend on the rainfall conditions and actual pollutant Ioading. Please contact Stormwater Management, Inc. for more information about maintenance costs. SMI ENGR:.lOER 1/18/06 /•�'� �;�