202 ALDER ST Geotech Report 2018-01-02 MF Import

' ' Proposed LSrw R�dge Subsurfare Exploraion, Geologic Hazards, /nfilvaion Potential, Elementarv Srhool Rep(acement and Preliminary Geotechnica!6ngineenng Report £reren Wathington Preliminary Design Recommendarions , restore planned elevations. Reuse of on-site soils for structural fill may require aeration and drying to reduce moisture contents at the time of construction. Reuse of on-site soils for , structural fill is only allowed if specitically addressed in the project plans and specifications. Below areas of planned paving, it would be possible to leave existing fill in place with some ' remedial preparation. We recommend that paving areas be stripped of existing topsoil, and proof-rolled and compacted as described later in this report for prepazation of paving 1 subgrades. If the resulting surface is firen and unyielding and compacted to 95 percent or more of the modified Proctor maximum dry densiry, no further preparation is required. If the subgrade is wet or yielding, we recommend that a portion of the existing fill be removed and ' replaced with material that is capable of being compacted under field conditions that are present at the time the work is completed. Decisions on appropriate preparation procedures should be made in the field at the time of construction when site, soil, and weather conditions ' are known. A typical scenario might include replacement of the upper 2 feet of existing fill with new svuctural fill. During wet site or weather conditions, selec[ fill may be needed for this application. It should be noted that leaving existing fill in place below• planned paving ' carries some risks of future settlement. Such risks are offset by a substantial saving in initial construction costs. We are available to answer questions regarding cost savings and risks ' associated with leaving the existing fill in place below planned paving. 9.l Construction Site Drainage and Surface Water Control ' The site should be graded to prevent water from ponding in construction areas and/or flowing into excavations. Exposed grades should be crowned, sloped, and smooth-drum rolled at the ' end of each day to facilitate drainage. Accumulated water must be removed from subgrades and work areas immediately prior to performi.�g further work in the area. Equipment access may be lunited, and the amount of soil rendered unfit for use as structura] fill may be greatly , increased if drainage efforts are not accomplished in a timety sequence. If an effective drainage system is not utilized, project delays and increased costs could be incurred due ro the greater quantities of wet and unsuitable fill, or poor access and unstable conditions. tWe anticipate that perched ground water could be encountered in excavations completed during ' construction. We do not anticipate the need for extensive dewatering in advance of excavations. The contractor should be prepared to intercept any ground water seepage entering the excavations and route it to a suitable discharge location. Uepending on grading plans, the ' use of cutoff drains might be warranted where grades will slope toward pavement edges or buildings. If curoff drains are planned, they should be installed early in the site work phase to enhance drainage for the remainder of the project. Drainage recommendations are included in •' Section 11.1 of this report. ' Septeml�er 21, 20/0 ASSOC/ATED EARTH SGENCFS, INC. BwGkb-KE/00255A2-Pro�msi10100235�KE1WF Page 13 '