2006-02-23_AgendaPacket - Laserfiche WebLink

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I 3.3 Preferred Alternative 3.3.1 Roadway and Trail -1 The preferred roadway and trail alignment is shown on Figure 4. This design includes the avoidance and minimization measures described in Section 3.2.1 above. This minimizes wetland impacts to the isolated basin to 914 square feet. ' 3.3.2 Water Quality Improvements Although realignment of the roadway further minimized opportunities to ~? provide pretreatment of runoff in the area south of South Owasso Boulevard, it provided the opportunity to provide pretreatment in the area of the vacated road bed. This allows upland area for a pond that will be of sufficient size and orientation to provide pretreatment of runoff from the majority of the :'' contributing watershed area. The large contributing area and the distance and grades between the three primary discharge points necessitates construction -! of secondary treatment ponds to provide effective pretreatment prior to _' discharge into the wetland area. As described in Section 2 above, the proposed project includes construction of three ponds or cells as shown on Figure 4. Cell 1 is located on the bed of _ the existing roadway, outside of the wetland area. Cell 1 will provide pre- treatment of runoff from the 104-acre portion of the 126-acre contributing area to the south. prior to discharge into the other proposed treatment cell and the adjacent wetland area. Pretreatment in this upland area also minimizes the area of wetland impact from the proposed secondary treatment cells. Treated runoff from Cell 1 overflows into Cell 2, which also receives runoff from the 10 acres of residential area west of Farrington Street (Figure 3) and outflow from the stormwater pond to the north on South Owasso Boulevard. This existing discharge at Famngton Street will be directed into the western end of Cell 2. The majority of the area of Cell 2 is excavated within the wetland area and will impact 0.63 acres of wetland. However, wetland impacts have been minimized by locating the pond in the area of the existing excavated channel to the greatest extent possible. Outflow from Cell 2 will be directed over the northern edge of the excavated cell into the adjacent wetland, by sheet flow, instead of continuing the more discrete flow of the existing channel to Lake Owasso. Cell 3 will receive runoff from the 12 acres of residential area that currently J discharges into the wetland at .Marion Street. This third cell is located completely within the wetland area and will impact 0.28 acres of wetland. _ However, wetland impacts have been minimized by locating the pond in the area of the existing excavated channel, as shown on Figure 4, to minimize impacts to the adjacent, vegetated areas of the wetland. 4.0 Wetlands Wetlands are defined jointly by the U.S. Army Corps of Engineers (USAGE) and the U:S. Environmental Protection Agency (EPA) as follows: "Those areas that are inundated or saturated by surface or ground water at a - frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for Wetland Permit Application A-ROSEV0501.00 - South Owasso Boulevard Water Quality Improvements Page 12