52 Franklin Avenue Project

52 Franklin Avenue Project

The Project consists of the construction and operation of a residence. The lot slopes uphill from Franklin Avenue. A building footprint is shown on the front two-thirds of the lot. Because the site is limited in developable area, due to the debris capture area and associated 8-foot-wide access path (discussed below), it is anticipated that the Project could require setback variances. The estimated construction schedule is provided in Table 1 of the IS/MND. As discussed previously, geotechnical engineering and engineering geologic investigations carried out between 1989 and 2025 concluded that the potential for another debris flow exists, derived from susceptible soils on the steeper, upper portions of the property and the hillside above the rear property line. The potential hazard for a new house built on the property, associated with potential future debris flows, would be similar to the 1982 debris flow unless mitigative measures are undertaken (Michelucci & Associates, Inc., 2023). Geotechnical mitigation measures on the site included as Project design and peer reviewed by Cotton Shires Associates (CSA) as part of this environmental review would consist of constructing a “U” shaped debris barrier, consisting of retaining walls, to form a basin that would capture and enclose a potential debris flow onto the Project site (see Project Description Figure 3 of the IS/MND). The debris flow capture capacity is currently estimated at 543 cubic yards, above the recommendation of 500 cubic yards by the Applicant’s geotechnical consultants (Michelucci and Associates and Earth Systems) and confirmed by the City’s geotechnical consultant, CSA. An 8-foot-wide setback along the western property line would allow access to the debris capture area for equipment to remove debris captured within the basin, as needed.

South San Francisco

San Mateo

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San Mateo