ENFORCE24478 - Laserfiche WebLink

Home Browse Search

Technical Revision 86-1 Adequacy Response lc. Provide a plan for sediment control from the newly topsoiled area above the Homestead Ditch per Rule 2.05.6 (3)(b). This issue was originally brought up during the permitting process and Stipulation No. 15 of the Findings document requested development of a mitigation plan. Correspondence from CYCC to the Division on July 15, 1986, on this matter focused on the effectiveness of the operator's soil stabilization practices for the small area exemption. We were under the impression that this correspondence referred exclusively to the previously reclaimed area above the Homestead Ditch. At this time. the Division grants that this revegetated area may justifiably be designated as a small area exemption. However, as the newly topsoiled forty (40)+ acre tract with a twenty (20)+ percent slope is at considerable erosional risk, we would like you to present a design to route this water through a sedimentation ponds. Response: In order to provide a sediment control for the newly topsoiled 27 acres above the Homestead ditch, CYCC proposes to install a filter fabric fence. However, this requires a request for an additional small area exemption. The fence would be installed just above the Homestead ditch along the contour and would extend the entire length of the new topsoil and 100 feet on either side of the new topsoil. The filter fabric fence is 3 feet high and would be buried 6 inches to a foot in the ground. This would leave 2-2 lit feet above ground to trap sediment. CYCC will monitor and maintain the fence semi annually (prior to major snowfall and following spring run off) until the site is vegetatively stabilized. As discussed with CMLRD, this seems like a reasonable alternative given the difficulty of trying to collect the water and culvert it across the Homestead ditch and then having to put it in a rock channel to get it off the slope. In addition to the filter fabric fence the soil sta bill za to practices used on the above approved 18 acre small area exemption will be utilized. 3a. In calculating the discharge through the primary dewatering device the Division utilizes a factor of 1.0 for the entrance head loss (Ke) after Barfield, Warner and Haan, page 232. Please justify your use of 0.5 for this value. Describe the source ~of the term for frictional head loss (Kc). The staff assumes that the outlet pipe is made of corrugated metal (CMP) and that it has Manning's n of 0.025. Table 4.1 of Barfield, Warner and Haan shows a Kc of 0.1990 for an 8-inch CMP and 0.1157 for a 12-inch CMP. Response: CYCC agrees with the above and has utilized the revised factors to recalculate outlet work and emergency spillway designs. In all cases the only changes which have occurred are an increase in detention times and a very minor increase in spillway flow depth of a 25 year event. Exhibit 3-30 11/19/86