01/31/2007 Env Bd Packet - Laserfiche WebLink

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• Any importing of soil onto the site should be reviewed and approved by the City Engineer prior to placement on the site. All soils compacted by construction should be loosened to preconstruction conditions. • Surface Water Surface water is ultimately tributary to Baldwin Lake. The project proposes three wet detention ponds and several small infiltration areas (rain gardens). Stormwater is proposed to be routed to the existing municipal stormsewer system located in the southwest corner of the site. The system will need to satisfy the City's discharge rate requirements (no net increase) as well as Rice Creek Watershed District infiltration requirements. Impervious parking areas should be kept to the minimum allowed under our City code. The pervious nature of the existing soils does allow opportunities for increased infiltration on the site. However, the high ground water level on the site may pose some limitations. All infiltration areas must have a minimum three feet of separation between the bottom of ponds and the ordinary high ground water level. The developer must demonstrate that this separation will exist. All ponds designs should include the use of for -bays to pretreat water entering ponds and allow for more efficient maintenance. There does appear to be opportunities for a significant portion of the surface water running off of the parking lots could be infiltrated with the use of stormwater bmp's such as the use of pervious pavers, pervious asphalt, and other periphery bmp's such as drainage swales, and rain gardens. Access to all surface water treatment areas must be provided for and indicated on the plat proposal. A storm water maintenance agreement will be required to insure proper maintenance of the systems. Storm Water Pollution Prevention Plan The developer has submitted a Storm Water Pollution Prevention Plan (SWPPP). The SWPPP must be approved and implemented prior to the commencement of a grading permit. A number of modifications to the SWPPP have been identified and will need be incorporated into the final plan as identified in the attached SWPPP memo. Tree Preservation A Tree Inventory was submitted by the developer. 11 trees were found and idenfitied on the inventory as specimen trees. A "Specimen Tree" is defined as a healthy hardwood tree measuring equal to or greater than thirty (30) inches in diameter and /or a coniferous tree measuring fifty (50) feet in height. Five of the trees are located either off site or in the proposed Hodgson Road right -of -way.