Laserfiche WebLink
3.3. Subsurface Soil Conditions <br /> GeoEngineers' understanding of subsurface conditions is based on review of geologic maps, previous site <br /> explorations, and the current borings drilled for this project. The approximate locations of the borings are <br /> presented in Figure 2. Subsurface soil conditions generally consist of shallow surficial fill soils overlying <br /> dense to very dense glacial till.These units are described separately below: <br /> ■ Pavement Section:The asphalt surfacing observed in the recently completed borings ranged from 3 to <br /> 6 inches-thick and is underlain by 2 to 3 inches of crushed rock base course. Previous borings <br /> completed in the south area of the site encountered 7 inches of asphalt concrete overlying a thin layer <br /> of silty sand fill or dense native soils. <br /> ■ Fill: Fill was encountered in boring B-3 on the northeast side of the property in the vicinity of the <br /> proposed new stormwater vault. The fill consists of medium dense to dense silty sand with occasional <br /> gravel.The fill was approximately 7 feet deep at the boring and overlies dense to very dense glacial till. <br /> We anticipate the fill is at least 10 feet thick in the vicinity of the existing 66-inch-diameter storm pipe <br /> located along the north side of the proposed new vault. <br /> ■ Glacial Till: Glacial till was encountered below the surficial pavement or below the fill where <br /> encountered.The glacial till consists of dense to very dense/hard silty sand and sandy silt with variable <br /> gravel content. Glacial till was observed to the depths explored in each of the borings. Perched <br /> groundwater was observed within the glacial till in boring B-3 as discussed below. <br /> 3.4. Groundwater Conditions <br /> Perched groundwater was observed at 71/2 feet and 141/2 feet during drilling in boring B-3. A seasonally <br /> perched groundwater condition is common above and within glacial deposits as seepage from precipitation <br /> and surface runoff infiltrates through the upper weathered soil, fill, and more permeable layers of glacial <br /> till and moves laterally on the underlying glacial till.Groundwater levels are anticipated to vary as a function <br /> of location, precipitation, season and other factors. <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the results of our explorations and our engineering analysis, we conclude that the Casino Road <br /> Renovation project can be accomplished as proposed with respect to geotechnical elements and that <br /> shallow foundation support will be suitable for the planned new entryways and new detention vault. A <br /> summary of the geotechnical considerations is provided below.The summary is presented for introductory <br /> purposes only and should be used in conjunction with the complete recommendations presented in this <br /> report. <br /> ■ Site Class C in accordance with the International Building Code (IBC) 2015 is appropriate for seismic <br /> design. Design parameters are provided in a subsequent section. <br /> ■ We recommend an allowable soil bearing pressure of 3,000 pounds per square foot (psf) be utilized <br /> for design of footings anticipated to be founded within the upper 2 feet of site grade.This value can be <br /> increased to 8,000 psf where footings are founded on very dense glacial till (founded below a depth <br /> of 21/2 feet or on controlled density fill (CDF) extending to the very dense till). We recommend the <br /> exposed subgrade be compacted following excavation. Footing subgrade should be evaluated by a <br /> representative from our firm to confirm conditions are as assumed during design. <br /> GEOENGINEERS November 14,2019 Page 3 <br /> File No.2095-019-07 <br />