9931 19TH AVE SE 2018-01-02 MF Import

Barghausen Consulting Engineers JN 6413 X April 10, 1997 Page 2 geotechnical engineering study of November 26, 1996, notably on pages a and 9 therein. Acknowledging the likelihood that the native soil underlying the proposed wall footing area is glacial till, we have recommended that the wall be founded entirely upon the competent native till. We strongly recommend that the presence of the till and its suitability for this purpose be confirmed by the geotechnical engineer prior to placement of the wall. Reiterating comments from the engineering report, all wall backfill should be accomplished in a manner to prevent the buildup of excess lateral soil pressures. This can be accomplished by placing wall backfill in 8-inch loose lifts using small hand operated compactors. Drainage system recommendations provided on page 9 of the report should be implemented to minimize hydrostatic pressures behind the wall. With respect to permeability of the Keystone wall, we are not aware of any studies which have been conducted to show permeability of Keystone wall sections in an application such as this. In the overall assessment, this detail appears to be irrelevant to the extent that the water balance for the wet cell pond is not dependent upon the permeability of the wall, but rather is controlled by the permeability of the soils into which the pond and the wall are constructed. That conclusion is intuitively reinforced by the plan detail showing the floor of the pond founded upon the native soils. Through common sense, it follows that we would not expect a significant variation in permeability between soils behind the wall and those underlying the cell area. We appreciate the opportunity to be of service in addressing these small details, and trust that the information will be of value in your planning and design activities. If you have questions, please do not hesitate to call. Respectfully submitted, nc r, MSO.SCcIA.T, EPS., INC. qi7 G., Encl. ENVIR0MMOr 1IL AS80CIATEB, INC.