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MEMORANDUM Review of Geotechnical Study Proposed Main Street Apartments 353 Main Street, Redwood City, California May 18, 2018 Project No. 1-1089 Page 3 of 7 materials do not identify the elevations of the adjacent waterways or a discussion of the rise and fall of the water levels in the creek. Our review of Google Earth Images of the site show that approximately half the perimeter of the Project — essentially the contiguous northerly and easterly boundaries of the Project - are directly proximal to Redwood Creek. Also, there exists a narrow "buffer zone" of approximately 20 feet horizontal distance from the edge of proposed parking lot to the creek system. There is also no meaningful discussion of the vertical separation elevations between the existing 1 proposed grade of the parking lot and the adjacent creek. It is our opinion that a small horizontal and vertical "buffer" may be inadequate to properly isolate the project from the creek. The referenced materials need to be updated with a study to confirm that the development and the operation of the proposed Project will not adversely impact the water quality, flow, or safety of Redwood Creek. This could occur from storm water surface flow and/or from groundwater infiltration and potential connection between the project site and the adjacent creek. One should also note that any negative impacts on Redwood Creek will immediately find their way into the nearby San Francisco Bay watershed. The directly adjacent Redwood Creek is a major local environmental feature. It is also interconnected with multiple major local water features beneath and just downstream of the Project site. The interconnected surface water features just downstream appear to be environmentally significant and sensitive. The ground and groundwater underlying the local area is geologically strongly interconnected with and interrelated as a function of its proximity to these waterways. Review of historic aerials and topographic maps show that the ground directly underlying the site previously contained numerous channels, fingers, and other hydrogeologic / stratigraphic features that produce potentials for intercommunication of storm water and groundwater from the Project site with and into these adjacent water bodies. Reference Nos, 1,2, 5 and 6 of the Materials do not provide any data or analysis that would allow one to draw conclusions regarding the interconnection (or prevention of such connection) between storm water and groundwater from the Project site with and into these adjacent water bodies. Accordingly, the City should be provided with adequate studies and related analysis to show how the Project site can be properly isolated from the adjacent Redwood Creek and other downstream water bodies. These studies should address site drainage and groundwater transmission, both during the construction period, and after development of the proposed Project. Reference Nos. 1 and 2 were not signed by a State of California Registered Engineering Geologist and Reference Nos. 5 and 6 were not signed by a Registered Geologist or Engineer and may therefore lack appropriate professional oversight considering that this Project site has a complex geologic sedimentary and hydrogeologic setting. Professional standards and State law require that all studies that relate to engineering, geotechnical, and water be reviewed and signed by appropriately registered and experienced persons. Accordingly, the State of Califomia professional standards may not allow these references to be considered as proper expert study and analysis for CEQA purposes. 350 Fischer Ave. Front • Costa Mesa, CA 92626 • P; 714 668 5600 • www.G3SoilWorks.com