5.6. A-D. SR 01-16-2007 - Laserfiche WebLink

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A 78-stall parking lot is proposed on the west side of the building with an 8-foot wide sidewalk connecting the lot to the building. Per discussions with the City, required parking numbers should be based upon 1 stall per 1,000 square feet of building. The City will allow the Applicant to state their required parking needs with the remainder of the parking being shown as proof of parking. The site plan as designed proposes 78 constructed parking stalls with an additional 113 proof of parking spaces shown. A 30-foot wide bituminous road with B612 concrete curb and gutter will provide access around the building. GradinglUtilities/Stormwater Ponds Stormwater requirements are met by way of three detention/retention basins located in the northern and southern portions of the site. Each of these ponds will contribute to infiltrating stormwater runoff into the granular soils prevalent in this region. Two relatively small detention basins are proposed in the southwest and southeast portions of the site to collect regional stormwater runoff from the parking lot and access drives as well as roof drainage. A portion of the stormwater runoff volume at the southern ponds will be retained to allow infiltration to occur. For significant rainfall events when stormwater runoff would fill the southern ponds above a depth of five feet, discharge to the larger northern pond would commence via storm sewers on both the east and west sides of the building. These storm sewers serve a dual purpose, as they also collect local stormwater runoff in the access drives and parking lot. Per City requirements, the site stormwater management system is sized to retain two 100-year back-to-back storm events. The northern pond is proposed exclusively as a retention/infiltration basin. The ultimate emergency overflow for the site would consist of two high level outlet structures at the north side ofthe northern pond, each with pipe outlets connecting to existing storm sewer stubs located in the Business Center Drive right-of-way. Proposed stormwater runoff from the constructed site will be less than the existing conditions. Sanitary sewer and watermain utility services are provided through connections to existing municipal mains located in the utility easement along the south side of the site. There is currently a lO-inch watermain and a 12-inch sanitary sewer main located within the easement. An 8-inch watermain service loop is proposed around the building along withsix fire hydrants and isolation valves placed at appropriate intervals. A 6-inch water service for the building is shown at the southwesterly portion of the building. Two 6-inch sanitary sewer services are proposed at the south side of the building, with an anticipated connection to an 8-inch lateral sanitary sewer that would outlet to an existing sanitary manhole. Due to the excessive depth of the existing sanitary sewer, construction of an exterior drop structure is planned at the proposed manhole connection. A deep, 8-inch sanitary service is proposed at the east side of the building as required to collect discharge water (used in an internal cooling process) via gravity flow. This sanitary service will connect to the existing manhole south of the southeasterly pond near the manhole bottom grade. Watertight pipe/manhole joints will be constructed at all proposed manhole connections. New concrete inverts will be constructed to blend with the existing manhole. If necessary, dewatering will be done to allow the deep sanitary sewer work to be constructed per City Engineers Association of Minnesota (CEAM) specifications. The site grading will commence by first meeting all erosion control requirements as stipulated in the National Pollutant Discharge Elimination System (NPDES) permitting process. Conformance with the NPDES permit will continue throughout the term of the site construction project. After required erosion control measures are installed, topsoil and any other organic materials will be stripped from all proposed fill areas and stockpiled. In cut areas, topsoil will be salvaged for ultimate re-spread. At this stage, concurrent engineered fill placement at the building pad site and pavement areas will be done with suitable granular materials excavated from the three pond sites. The grading plan has been prepared to provide sufficient excavated materials from the pond sites to construct the building pad and the subgrade for all bituminous and concrete pavement areas. Project Narrative United Health Group Next Technology Center RLK Incorporated Project No. 2006-S01-M November 27, 2006 Page 2 of 5