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MEMORANDUM <br />Review of Geotechnical Study <br />Proposed Main Street Apartments <br />353 Main Street, Redwood City, California <br />May 18, 2018 <br />Project No. 1-1089 <br />Page 4 of 7 <br />• Water Chemistry Surface, Creek, and Groundwater — Lack of Study <br />An adequate study and analysis of the site water chemistry should be completed to <br />determine whetherthere will be a significant environmental impact related to water quality. <br />Items 1, 2 and 6 of the referenced materials do not provide any meaningful discussion of <br />water chemistry, actual existing water quality, and other considerations with regard to <br />water character. The referenced materials have not adequately distinguished whether the <br />water is fresh or saline, let alone any chemical I contaminant considerations. Our cursory <br />internet search identified numerous studies related to the water quality of the Redwood <br />Creek. Reference E provides significant information about the water quality of the creek; <br />information which is conspicuously absent in the consultant reports. A detailed meaningful <br />evaluation of these waters that includes chemical analytical evaluation and <br />characterization, along with identification of associated hazards and risks relative to the <br />proposed Project should be considered necessary to comply with CEQA. <br />Groundwater—Lack of Study <br />There is no meaningful discussion and information provided in the referenced materials <br />regarding groundwater, and thus conclusions concerning potentially significant <br />environmental impact to groundwater, the adjacent creek, or adjacent properties cannot <br />be assessed. Items 1, 2, and 6 of the referenced materials do not contain any data or <br />analysis of groundwater to adequately to adequately assess and mitigate environmental <br />impact, as appropriate. The consultants did not perform direct studies to quantify <br />groundwater with regard to its nature, elevation — including upper/ lower bounds and tidal <br />influences, transmissivity, inherent chemistry, and relation to existing and proposed <br />surface conditions. Impact on the foundation and slab construction from groundwater <br />cannot not be determined in the absence of this study. This study should include potential <br />groundwater fluctuations over time to determine potential impact to foundations, slab on <br />grade, remedial grading, deep foundation construction, and other site improvements and <br />remedial efforts. <br />The SHZR Report by the State of California indicates that groundwater elevations are less <br />than 10 feet. This SHZR Report suggests much less than 10 -feet, and considering the <br />inferred interconnectivity and proximity of the creek system and tidal effects of the Bay, <br />may fluctuate significantly and be higher than implied in the referenced materials that the <br />City has relied on to consider the impact of groundwater. Significant additional study is <br />warranted to ferret out these considerations, starting with actual groundwater evaluation <br />under the supervision of an appropriately experienced Engineering Geologist 1 <br />Hydrogeologist. This may include groundwater monitoring wells to properly assess <br />groundwater nature and water levels over time, water chemistry, and groundwater flow 1 <br />storage and related engineering characters — in particular, how groundwater will interact <br />with and influence the proposed work and adjacent properties and waterways. <br />350 Fischer Ave. Front • Costa Mesa. CA 92626 • P: 714 668 5600 • www.G3SoilWorks.com <br />