Agenda - Council - 09/14/2021 - Laserfiche WebLink

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Field tests (double ring infiltrometer) can be performed within the proposed infiltration basin area to verify infiltration rates of the in -situ soils. We would be pleased to provide these services if required or requested. 5.0 CONSTRUCTION CONSIDERATIONS 5.1 Excavation The soils encountered in the borings consisted of predominantly of sandy soils consisting of poorly graded sand, poorly graded sand with silt and silty sand corresponding to the ASTM classifications of SP, SP-SM and SM. These soils will generally be Type C soils under Department of Labor Occupational Safety and Health Administration (OSHA) guidelines. The borings also encountered clayey sand and silty clay that mostly had a soft consistency. For that reason, the clayey sand and silty clay will also generally be Type C soils under OASHA guidelines. Temporary excavations in Type C soils should be constructed at a minimum of 1 1/2 foot horizontal to every 1-foot vertical within excavations. Slopes constructed in this manner may still exhibit surface sloughing. If site constraints do not allow the construction of slopes with these dimensions, then temporary shoring may be required. 5.2 Observations A geotechnical engineer or a qualified engineering technician should observe the excavation subgrade to evaluate if the subgrade soils are similar to those encountered in the borings and adequate to support the proposed construction. 5.3 Backfill and Fills We recommend moisture conditioning all soils that will be used as fill or backfill in accordance with Section 4.3 above. We recommend that fill and backfill be placed in lifts not exceeding 4 to 12 inches, depending on the size of the compactor and materials used. 5.4 Testing We recommend density tests of backfill and fills placed for the proposed building foundations. Samples of the proposed materials should be submitted to our laboratory prior to placement for evaluation of their suitability and to determine their optimum moisture content and maximum dry density (Standard Proctor). 5.5 Winter Construction If site grading and construction is anticipated to proceed during cold weather, all snow and ice should be removed from cut and fill areas prior to additional grading and placement of fill. No fill should be placed on frozen soil and no frozen soil should be used as fill or backfill. 13