Laserfiche WebLink
<br /> <br />Mr. Dan Hernandez <br />October 21, 1989 <br />Page Two <br />Recommendation 3. Tho new silt retention facility near the ol~i scale <br />area in phase I and the proposed amendment III facility needs 1:o be <br />designed for a 100 .year storm event. There ere several reasoni~ <br />for this oars conservative design approach. Storms which <br />occur at that elevation ere intense, with the exact rainfall <br />amounts unknown. There ie not a corresponding hietoricsl base for <br />comparisons. Previous correspondence speaks to the gullying end <br />erosion of intense storms, reference the January 15, 1985, letter <br />from Merk Heifner to Philip Saletta, concerning peat inspections. <br />The mine has operated in the pest end is projected to operate i.n the <br />future for time spans exceeding 25 years. <br />Concern 2. The operator has indicated a need for "sanding chiF~s" for <br />use along the access road. large tonnages appear to be in place along <br />the road. Tho operator has not~indiceted that these chips ere swept or <br />recycled for use. It is not believed the operator owns or employe e <br />street sweeper. It appears that these chips ere left to wash into the <br />drainage ways. <br />Recommendation 4. We recommend stockpiling these Banding chips <br />within the exiating permit area et the mine site. We also recommend <br />cleaning up the roads after the need is over, within a schedule normal <br />to other users; i. e., city and state street departments. <br />Concern 3. There ere still unknowns with regards to the factors of <br />safety for elope stability et areas one and four. the CAP plan <br />ie beeed upon a computer generated model which requires assumptions <br />es pert of the input data. The program also would require e <br />homogeneous soil strata end absence of water seepage within the <br />soil strata. Our voile within the strata are not homogeneous but <br />very. Above the bedrock referenced in the CAP exists a zone of <br />decomposed bedrock or native clays, next an organic layer of a few <br />inches, next any surface vegetation that was not removed prior to fill <br />work end then finally a variable fill. The fill would vary in <br />description as to source, moisture content, density, and other <br />engineering properties of a technical nature. Also the karat <br />geology ie seepage prone. The CAP recommends a horizontal elope <br />of three to one vertical if water ie present. Surface drainage <br />improvements along the road cannot address a seepage condition <br />occurring below the roadway adjacent to the fills. <br />1 <br />