Agenda - Council - 04/09/2018 - Laserfiche WebLink

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The Auto Ranch site is adjacent to a City stormwater pond. It was rejected because part of the infiltration would have been in the 10 year capture zone. The B & A Cylinder site was evaluated and then rejected because the site was contaminated by a previous user and infiltration is not permitted on contaminated sites. Part of the site may also be needed for the grade separation improvements for Ramsey Boulevard and the BNSF tracks. The selected site is in the southeast corner of the COR, south of the Medical Examiner's office between Rhinestone Street and Ramsey Boulevard. This site was selected due to its close proximity to the existing stormwater retention pond, and because a majority of the site is currently encumbered by drainage and utility easements and because of the odd shape of the lot which makes the lot less desirable for development. 2.3 Scope City of Ramsey Improvement Project 18-09 proposes to construct an infiltration basin in the southeast corner of the COR between Rhinestone Street and Ramsey Boulevard, north of the existing pond and south of the Midwest Medical Examiners building. The proposed site will utilize a drainage and utility easement reserved with the Ramsey Town Center project over ,property now owned by PSD, LLC. It will require acquisition of approximately 0.82 Acres of property outside of the easement from PSD, LLC. The proposed acquisition will square up the southern boundary of the PSD site which is more desirable for development. Staff has provided the acquisition map to PSD, LLC as a prelude to acquisition discussions. The bottom of infiltration basins must be three (3) feet above ground water elevation per design guidelines. The basin will be divided into an east basin and a west basin to bridge an existing large diameter stoiui sewer line that follows the proposed alignment of Peridot Street. The divided basin will provide cover over the existing stormsewer pipe. The system will utilize a stormwater lift station to pump water out of the existing pond up to the basin to provide the minimum recommended vertical separation. The lift station will be set up to pump the required infiltration volume for the 1" storm, then shutoff for 24 hours or until the next rain event, whichever is longest. The lift station will be taken out of service during the winter months to prevent freezing of the pipes. The infiltration basin will have a small amount of additional capacity that could be sold to developers outside of the COR that cannot infiltrate on site due to soil conditions or other constraints. The infiltration basin will be planted with native vegetation that can tolerate periodic inundation. The plans show a future street connection along the north side of the basin between Rhinestone Street and Ramsey Boulevard. The connection to Ramsey Boulevard will be right -in, right -out only, in conformance with the Anoka County Highway Management Plan. This will be constructed as a future project when development warrants. Staff is working with Anoka County to verify that this connection will be allowed as proposed. Feasibility Report COR Infiltration Basin City of Ramsey Project No. 18-09 Page 3