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Mr. Steve Glass December 9, 1998 Page 3 Conditional Use Permit Application The CUP application describes the proposed mineral extraction and portable concrete mix plant operations. A site plan showing the existing and proposed finished grade elevations was submitted with the application. A road cross section of the Underdahl Drive restoration to serve the property was also provided. The road cross section shows 12 inches of crushed stone base, 5 inches of bituminous, and 3-foot wide gravel shoulders. This detail is adequate for the trucks expected to use this road. It is important that poor soils be undercut in the subgrade and be filled with breaker run as stated in the detail's notes. The soils in this area are naturally high in organic material and the Town should plan on inspecting construction of the road to ensure compliance with the construction detail. The site plan shows a 240 foot by 360 foot area with a gravel parking area, material storage, and a portable concrete plant approximately 320.feet south of the CTH AB road right-of-way. An erosion control berm is shown along the east side of the property to protect the wetlands east of the construction area from sedimentation. At the November 4, 1998, Town of Blooming Grove Plan Commission meeting, Mr. Cattell stated he planned to construct a berm along the north boundary of the property and plant it with various pine trees to form a visual barrier for traffic on CTH AB. This is not shown on the site plan. Erosion control provisions should be provided to prevent soil loss into the drainage ditch running west to east across the northern boundary during construction of the berm. A storm water detention basin should be included to control the quantity and quality of runoff from the parking, material storage and mix plant area. The application states that washing operations are not expected at this time but may occur in the future. Any agreement to allow the CUP should specify that properly sized settling basin be installed and maintained for wash water. The following comments address the restoration plan for the site submitted by the owner. Regarding slopes, the final contours matching the remaining half of the drumlin appear to be 3 feet horizontal to 1 foot vertical, which is very steep and makes erosion control problematic. A shallower matching slope would be more appropriate. The gentle slope towards the east will help in capturing precipitation and enhance the infiltration if the proper vegetation is used. To enhance infiltration, the proposed mixture of exotic grasses should not be used. These shallow rooted grasses have poor long term performance for erosion control, have minimal habitat value, and are relatively ineffective in promoting infiltration and groundwater recharge. They are also weeds that have caused widespread damage to native vegetation because of their constant use and promotion on development projects. Instead, we recommend that you require the owner to seed native vegetation over the entire site. Use hydro seeding with a tackifier and water-absorbent emulsion to stabilize the steeper slopes and require at least 18 inches of rapidly-permeable material from the drumlin be spread over the site before top soiling and seeding. These measures could be ensured through a permanent easement. We have enclosed specifications for hydro seeding and native prairie seeding. B33A042\B33-98A