RES 231363 - Laserfiche WebLink

AUGUSTIN BERNAL MOUNTAIN BIKE TRAIL PROJECT DRAFT INITIAL STUDY 12956 DUDEK 54 April 2022 iv) Landslides? Landslides are downslope movements of materials including rock, soil, artificial fill, or combinations of such materials. The size and distance of landslide movements can greatly vary. The City of Pleasanton has identified areas within the City as higher risk areas for landslides and this includes the northeastern side of Pleasanton Ridge, which includes the project site. Recognizing this hazard, the General Plan designates the majority of the land on Pleasanton Ridge as Agricultural and Grazing and Parks and Recreation. The proposed project would construct a mountain bike trail to replace an unofficial user-created trail. The project would not introduce a new use to the Augustin Bernal Community Park, would not construct any new structures, and would not substantially increase trail use activity within the park. Thus, the proposed project is consistent with the General Plan in relation to minimizing exposure of people to risks associated with landslides. Additionally, project construction would require minor grading, with grading cuts generally at a maximum of 0.5 feet in depth and a total of approximately 68 cubic yards of earthwork. All grading would be completed in accordance with the current CBC and City’s grading and erosion prevention ordinance which would ensure that project grading does not create unstable slopes or increased risks of landslides. Thus, there would be less-than-significant impacts related to the risk of loss, injury, or death involving landslides. b) Would the project result in substantial soil erosion or the loss of topsoil? Grading and construction would be completed in accordance with the CBC and in compliance with the National Pollutant Discharge Elimination System Waste Discharge Requirements from Small Municipal Separate Storm Sewer Systems (MS4s). BMPs implemented as part of the project would include measures to stabilize work areas including fiber wattles, silt fencing, concrete washout areas, soil stabilizers, revegetation, or other appropriate measures. These measures would ensure that soil erosion during grading and construction is prevented. The trail design plans also identify BMPs to be installed at the site during construction to provide long-term post-construction erosion control. Site stabilization and pollution prevention measures are noted on Sheets N-1 and N-2 of the trail design plans provided in Appendix A. In addition, implementation of MM-GEO-1 and BMPs would ensure that erosion is minimized through long-term drainage control, placement of erosion control mats, and seeding following construction. Therefore, impacts would be less than significant with mitigation incorporated. c) Would the project be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the project, and potentially result in on- or off-site landslide, lateral spreading, subsidence, liquefaction or collapse? As discussed in response a) above, risks of seismic activity, landslide and liquefaction are known concerns for the project site. As previously discussed, all grading and construction would be completed in accordance with the CBC and the Pleasanton Municipal Code which would ensure that project grading would not create additional geologic and soil stability concerns. Further, the proposed project would not construct any structures or alter or substantially increase use of the Augustin Bernal Community Park and thus would not substantially increase exposure of people to