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will be protected with turf reinforcement mats. Any potential high flows from offsite will be mitigated as they
<br />enter the construction site. Measures may include the use of high flow silt fence, checkdams, biologs, and/or
<br />stilling basins. Disturbed areas will be seeded and stabilized as soon as possible after construction. A fiber blanket
<br />or hydraulic seed stabilizer may also be used. Erosion control is also discussed in Item 12 of this EAW.
<br />The ~najority of excavated soil will be returned to the construction trench at,er placement of the pipe. Any excess
<br />soil will be disposed of in upland areas where sediment will not impact water resources or other sensitive areas.
<br />Soil erosion control practices will be implemented to minimize impacts to wetlands and other surface waters in the
<br />vicinity of the project. Best management practices will be implemented. Construction practices will be managed to
<br />limit the duration of exposed soil to wind and rain.
<br />Detailed temporary and permanent sediment and erosion control plans must be prepared in accordance with the
<br />MPCA National Pollutant Discharge Elimination System (NPDES) General Stormwater Construction Permit. A
<br />Storm Water Pollution Prevention Plan (SWPPP) will be submitted for review and approval. Erosion control
<br />measures will be implemented prior to the start of any construction activities and will remain in place until site
<br />stabilization has been achieved. Specific measures may include silt fence, rock construction entrance,
<br />sedimentation basins, check dams, erosion control blankets, and prompt re-vegetation of disturbed areas via.seeding
<br />and ,nulch. Regular inspection will ensure that measures implemented remain effective.
<br />There are highly credible soils and steep slopes on the trunk sewer alignment. According to the Soil Survey of
<br />Anoka County, soils on the alignment are NrD (Nymore loamy coarse sand, 12 to 25 percent slopes); NyA, NyB,
<br />NyC (Nymore loamy sand, 0 to 2 percent slopes, 2 to 6 percent slopes, 6 to 12 percent slopes, respectively); Ma
<br />(Markey muck)'; ZmA, ZmB, ZmC, ZmD (Zimmerman fine sand, 0 to 2 percent slopes, 2 to 6 percent slopes, 6 to
<br />12 percent slopes, 12 to 24 percent slopes, respectively); HuA, HuB, HuC (Hubbard coarse sand, 0 to 2 percent
<br />slopes, 2 to 6 percent slopes, 6 to 12 percent slopes, respectively); Is (Isan sandy loam); Iw (Isanti find sandy
<br />loam); Mc (Histosols); Me (Meehan sand); Rf (Rifle mucky peat); AnA, AnC (Anoka loamy fine sand, 0 to 2
<br />percent slopes, 6 to 12 percent slopes, respectively); LnA (Line loamy fine sand, 0 to 4 percent slopes); DiA; Bm
<br />(Blomfbrd loamy fine sand); Bx (Brickton silt loam); DnB (Dickman sandy loam, 2 to 6 percent slopes); Kr
<br />(Kratka loamy fine sand); and DIA (Dalbo silt loam, 1 to 5 percent slopes). The distribution of these soil types is
<br />shown in Figure 4.
<br />NrD is highly credible soil. ZmD is a potentially highly erodible soil that is considered highly credible, based on
<br />typical slope percentages and lengths for determinations made in the NRCS office. NyC, AnC, and DIA are
<br />potentially highly credible, but are considered not highly erodible based on typical slope percentages and length for
<br />determinations made in the NRCS office.
<br />NrD and ZmD have slopes greater than 12 percent, and are therefore considered steep slopes.
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<br />a. Compare the quantity and quality of site runoff before and after the project. Describe
<br /> permanent controls to manage or treat runoff. Describe any stormwater pollution
<br /> prevention plans.
<br /> Because the sewer pipe will be buffed, the quantity and quality ofrunoffbefore and after the project will not
<br /> change. Discharge from dewatering activities during excavation is discussed in Item 13 and will be conducted as
<br /> stipulated in applicable permits and approvals (see Items 8, 12, 13 and 16).
<br /> With increases in impervious surface areas associated with development, increases in stormwater runoffvolumes
<br /> and rates are possible. Stormwater runoff volume and rate increases fi:om enabled deVelopment will be managed
<br /> through the application of the City's stormwater management plan to the area where development occurs.
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<br />b. Identify routes and receiving water bodies for runoff from the site; include major
<br /> downstream water bodies as well as the immediate;-receiving waters. Estimate impact
<br /> runoff on the quality'of receiving waters.
<br /> Receiving water bodies in the ,)icinity of the proposed p~ojec't include wetlan'ds, Trott Brook, the Rum River, and
<br /> ultimately the Mississippi River. As discussed in Item 16, appropriate erosion and sediment control measures will
<br /> be implemented during construction, and runoff fm,m the site will be minimized. Because the sewer pipe will be
<br /> placed below grade, and because the disturbance caused by construction of the pipe will be temporary, permanent
<br /> significant impacts to receiving water bodies are not anticipated.
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