02/09/2004 Council Packet - Laserfiche WebLink

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areas into the design of the many parking lot vegetated islands on the site. It is unclear from the document if this low impact development practice is currently part of the proposal. By constructing depressed rather than raised islands and surrounding the islands with curb cuts or concrete edges that slope to the interior of the islands, runoff from the parking areas can be muted into these vegetated areas, then through a piped overflow into the underground chambers. In this fashion the first flush of runoff events can be retained in the bio- infiltration areas, maximizing the efficiency of the rest of the runoff treatment train. Item 10 — Land Cover and Item 25 — Nearby Resources. The proposal includes a high percentage of impervious surfaces that will cover 30 acres if the project is implemented as proposed. To preserve water quality in the adjacent regional park stormwater runoff from the development will need to be managed in an ecologically sensitive manner. Portions of the site are identified as regionally important in the joint Metropolitan Council and Minnesota Department of Natural Resources Regional Natural Resources Inventory and Assessment (NRI/A). The EAW should acknowledge this designation. Areas of particular concern include: • proposed reductions in wooded/forested land cover abutting the regional park; • potential loss of the island of oak woods in the southwest/central part of the site; • use of native vegetation in the proposed urban/suburban landscaping where there are development transitions to the regional park's natural areas. Item 19 Geologic Hazards and Soil Conditions This item states that "excessively drained soils and relatively high ground water table creates a potential for ground water contamination." The sanitary waste issue is addressed through the municipal sanitary treatment off site. It is recommend that this information also be considered when managing stormwater runoff. Deep stormwater ponds would have the potential to directly contaminate ground water with oils, road salt, and other contaminates associated with roads and parking lots. Item 21— Traffic The EAW states that year 2020 traffic volumes for full build -out of the site will be part of a simulation program that is being developed. It further states that results of the traffic simulation as it relates to the regional transportation system will be shared and discussed with Minnesota Department of Transportation (MnDOT) and the Anoka County Highway department. The results of the traffic simulation model should also be shared and discussed with the Metropolitan Council. There is currently no transit service to the proposed development. However, Routes 250 and 262 do operate local service in the area, and Route 250 travels past the site on Lake Drive on its "deadhead" routing to and from St. Joseph's Church Park & Ride lot. Metro Transit and Metro Transit Services can consider rerouting one or both of these routes to offer residents service to both downtown Minneapolis and downtown St. Paul. In 2 2 3 4 5 6 RESPONSE 2 The majority of the interior parking lot islands do not have sufficient area to treat and store the amount of runoff that will be generated from the proposed development, but these islands will consist of a pervious surface that will provide some infiltration. Detention ponds and underground infiltration chambers will be utilized to treat and store runoff from the site. Where applicable, a drop curb design will be used to provide access to infiltration ponds. Currently, the site plan includes four onsite ponds that will receive runoff from impervious areas through a drop curb design. 3 At the time the EAW was written, the City was not aware of the Regional Natural Resources Inventory and Assessment (NRI /A) and that the MNDNR and Metropolitan Council had identified a portion of the site in the assessment. The Metropolitan Council was contacted, and a copy of the NRI /A map was attained. Preservation efforts have been incorporated into the site plan that will reduce impacts on a grove of mature trees located on the eastern side of the site (adjacent to the park). Furthermore, the proposed development includes natural open space areas and vegetative buffers between the development and the park boundary. 4 Suitable separation (3 to 4 feet) will be maintained between the bottom of detention ponds /infiltration chambers and groundwater to minimize the potential for contamination.