The Department continues to evaluate issues surrounding pipe strength and pipe placement designs. In general, the response to the comment on surface water management is reasonable. We may have some comments on the design and location of specific basin outfalls. Due to the downsizing of the TMA, the location and sizing of the TMA runoff basins are likely to be adjusted. The approach detailed in the TMA DMP appears to be reasonable with a few modifications.
Visual inspections are a major part of the program.
We suggest that the plan detail that inspections be made on a regular schedule , with additional inspections made when weather conditions significantly change. The plan indicates a similar weather-condition based approach with 20 mph wind speeds resulting in more frequent inspections. Please provide more information on the 20 mph inspection threshold using literature-reported threshold entrainment velocities for dry materials with similar grain size distributions as that expected for the Crandon project tailings. Since the submittal of the DMP, the design of the upper stage of each cell has been modified to incorporate a leachate drain and a P40 filter layer. Note that the use of sprayers will have to be compatible with the thin lift thickness and the properties of the P40 material.