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John Doerfer's review of W&EST, Inc.'s January 19, 1989 letter follows: <br />Sediment Pond <br />a. An excavated sump is preferred instead of a dam; <br />b. the Dlan is conceptually acceptable, but the following calculations are <br />needed: <br />i, pre-development hvdrograph; <br />ii. Phase I and Phase II hydrographs and sediment volume; <br />iii. Phase I and Phase II Dond volume and dam elevations; <br />iv. outflow calculations for the 36 inch spillway; <br />v, outflow calculations for the i00 yr., 24 hr, emergence ooillway; and, <br />vi, emergency spillway cross section and slope. <br />c, what is the final reclamation of the Dond; and, <br />d, final as-built designs of the sump or dam will require submitta'?• tc the <br />Division upon availability. , <br />Additionally, please propose some monitoring plan to determine whey the site <br />has been stabilized enough to warrant the reclamation of the settling basin. <br />8. The revised design of the upper most benches proposed by Gordon Nat he son <br />of Schnabel Engineering, dated January 20, 1989, aggresses the concerr about <br />the pit wall headcutting onto adjacent lands. However, it further indicated <br />that continued spalling of the hiahwalls is anticioate d. The Division is <br />concerned that adequate reclamation of the narrow (14 - 15 `t, w;•7e, be -ches <br />may be inhibited by the constant barrage of spaiied rock fragments from <br />adjacent highwalls. Tne lack of established vegetation on the previously <br />mined Quarry benches indicate the problems expected to arise from miring the <br />area in question. <br />Given the expected lack of vegetative ground cover on the prooeseC remaining <br />10 - 15 ft, wide benches, the Division expects that the spaiied material will <br />not be adequately stabilized and/o~ protected to effectively control erosion <br />and attendant air and water pollution. <br />