02/23/2005 Env Bd Packet - Laserfiche WebLink

Home Search

• • • Further treatment and volume retention may be achievable by minimizing or eliminating the pipe from the infiltration area to the lake. This could be a final treatment opportunity. The soils for this area are very sandy. Water in this swale should infiltrate very well. An additional swale may be constructed from the North to the South where the pipe daylights to the lake. This would give another 400 feet of infiltration capacity to the treatment train. Adding an organic base to this swale as per "Infiltration Area Planting Detail ", and planting as a linear rain garden would have an additional filtration benefit. Suggest that all houses direct runoff from impervious to pervious grass areas, through the directional use of downspouts. Suggest that the developer prepare a brochure for new homeowners. The brochure should discuss the importance of water treatment and that some areas may be a bit wet after a storm. Other information should include Shoreland Overlay district restrictions on vegetation removal. The 30 % required open space for a shoreland area project should be protected from compaction as much as possible. Restoration to pre - development soil compaction densities should be accomplished with a ripper or tiller. All water treatment areas should be protected with fence after initial grading. Grading should be done with low- impact equipment. The yellow area shown on Attachment 2 is the area within 200 feet of surface water where the slope is greater than 3:1. NPDES requires that this area have a minimum of 7 days that exposed soils can remain unstable. This site must have temporary erosion protection or permanent cover within 7 days. The NPDES lists action steps that must be taken to ensure erosion control. The permit must be on site at all times. The developer should indicate an area where their permit information and inspection reports are available for inspection. All treatment areas should be planted with native, deep- rooted, plants (the city specifications). Areas between or behind houses that are acting as swale areas should be planted with approved low- profile native plants. These plants should be low profile, transitional -type plants. All areas seeded with a quick -grow erosion - control requirement that includes a native seed spec requirement should be seeded at the same time. A highly recommended BMP for erosion control assurance is to place a temporary sediment basin on the site. This might be accomplished by simply digging a hole on the SE lot, and creating a drainage swale to it on the East Side of the Proposal. When designed surface -water treatment features on the rest of the site are stable, then the hole can be filled in. Env. Bd. Mtg. 1/26/05 Page 2 Item 5B