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4.5 Infiltration Basin Design R�ecommendations <br /> Design infiltration rate(s) base on the soil borings and the MPCA MN Stormwater <br /> Manual are summarized in the�ollowing table. <br /> Table 2. Desi Infiltratiorl Rates <br /> Soil e Desi Infiltration Rate* i <br /> CL,Sand Lean Qa 0.06 <br /> SM,Sil Sand 0.45 <br /> Field tests (double ring infiltror�►eter)Can be performed within the proposed basin areas <br /> to verify infiltration rates of tYle in-situ soiLs. We would be pleased to provide these <br /> services if required or requested. <br /> 4.6 Site Grading and Drainagel <br /> We recommend the site be gralded to provide positive run-off away from the existing <br /> building. We recommend land�caped areas be sloped a m;nimum of 6 inches within 10 <br /> feet of the building and slabs be sloped a minimum of 2 inches. In addition we recommend <br /> downspouts with long splash b�ocks or extensions for each house. <br /> 5.0 CONS'I"RUCTION CONSIDERATIONS <br /> 5.1 Excavation � <br /> The upper soils encountered inllthe borings mainly consist of sandy lean clay. The soiLs <br /> identified in the borings will enerally be Type B soiLs under Departrnent of I.abor <br /> Occupational Safety and He�lth Administration (OSHA) guidelines. Temporary <br /> excavations should be constru�ted at a minimum of 1 foot horizontal to every 1 foot <br /> vertical within excavations. Slqpes constructed in this manner may still exhibit surface <br /> sloughing. If site constraints do�ot allow the construction of slopes with these dimensions <br /> then temporary shoring may be required. <br /> 5.2 Observations <br /> A geotechnical engineer sho observe the excavation subgrade to evaluate if the <br /> subgrade soils are similar to tho e encountered in the borings and adequate to support the <br /> proposed construction. <br /> 5.3 Backfill and Fills <br /> Portions of the site soils that ' be excavated and reused as backfill and fill appear to be <br /> above their assumed optimum moisture content. We anticipate it will be necessary to <br /> 6 <br />