Agenda - Public Works Committee - 01/19/2010

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AECOM Mr. Jankowski December 8, 2008 3 if necessary to facilitate drainage to western portions of the pond, excavate shallow trenches (i.e., approximately six inches deep) to direct water flow towards the pump in the west end of the pond. Additional sumps can be established for pumping water from other low areas that may be exposed as the pond water is removed. Install temporary 2-inch diameter polyvinyl chloride (PVC) piping from the pump to BNSF property north of the railroad tracks as follows: - Manually place a section of PVC piping under the railroad tracks (i.e., through ballast rock, beneath the rails, and between the ties) in a manner that does not disrupt railroad operations. - Connect 2-inch diameter flexible hose to the PVC piping, where it extends north of the outer rail, and extend the hose west for approximately 300 feet along the gravel access road on BNSF R.O.W. north of the railroad tracks. - Discharge Pond Water through perforated hose to minimize potential for excessive ponding and wash-out in the discharge area on BNSF R.O.W. Pond Water removal activities will begin approximately two weeks before soil excavation activities are initiated. Removing the Pond Water in advance of excavating will allow the base materials targeted for removal to dry out and also allow time for the discharge to adequately evaporate and infiltrate into the subsurface of the BNSF R.O.W. The discharge area will be monitored to ensure no excessive ponding or washouts are occurring on the BNSF R.O.W. Storm Water Runoff If precipitation events occur during pond excavation activities, storm water runoff will be intercepted, to the extent practical, before entering the pond in an effort to minimize additional accumulations of standing water. To prepare for potential precipitation events, storm water runoff will need to be managed at the following three locations: • East Swale -Drainage swale into east end of the pond. Located between the Burger King parking areas and Ramsey Boulevard. • East Inlet -Constructed concrete inlet to eastern portions of the pond. Storm water runoff flows to the inlet from eastern and southern portions of the paved parking areas surrounding the Burger King building. The majority of storm water runoff in the pond enters via the East Inlet. West Inlet -Inlet into southwest end of the pond at the drainage swale located between the Burger King parking areas and the Anoka West Pet Hospital property. Storm water runoff flows to this inlet from western portions of the paved parking areas surrounding the Burger King building and from a paved parking area on the Anoka West Pet Hospital property. The following is a generalized description of methods that will be used to manage potential storm water runoff during excavation of Pond Base materials: Construct a temporary berm across the storm water retention pond in a north-south direction to separate the pond into two general areas (i.e., east and west work zones). This will allow storm water runoff that enters the pond to be directed away from work zones as needed. Construct a storm water retention box at the East Inlet (i.e., end of concrete) to divert incoming storm water flow to areas within the pond located away from the work zone. The retention box will be constructed with outlets through the west and north sides, where PVC overflow pipe extensions will be installed to direct runoff to western or eastern portions of the pond, as needed, N:ProjectW/BNSF/2000/2983 Ramsey/Correspondence/Other/09 Dec City Ltr