25C - AGMT - OCWD CENTENNIAL PARK

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Section 5 Total Impervious Surface Addition or Replacement — 3.1'77 S, The total impervious surface improvements do not total 5,000 SF or more, which would be the threshold for a Priority Project Significant Redevelopment, Therefore, the Proposed Project would be considered a Non- Priority Project and would need to prepare a Non-Priority Project Water Quality Plan (NPP). Treatment control BMP's are not required for NPPs. However, the Proposed Project would incorporate 2,045 SF of pervious pavement as a site design feature for a new sidewalk between the Centennial Park parking lot and Shared Recreation/Communication Structure 1, near the Soccer Field complex. The pervious sidewalk would have the capacity to infiltrate the Design Capture Volume (80% Capture Efficiency DCV = 84.1 cu-ft) of the proposed 3,177 SF of impervious area improvements. The soil properties in this area are favorable for infiltration and would be an ideal location for LID BMP implementation. At a design infiltration rate of 0.3 inches/hour and an aggregate base depth of 0.5 feet, a minimum surface area of approximately 481 SF of pervious pavement would be needed (Note. the surface area of pervious pavement is reduced as the aggregate base depth is increased). In this case, there is more pervious sidewalk area than what Would be needed to treat the Design Capture Volume. The Non-Priority Project Water Quality Plan prepared for the Mid Basin Centennial Park Injection Well Project is included in Appendix G. The Water Quality Plan identifies infiltration strategies and storm water control measures to minimize adverse long term storm water management water quality impacts. With the implementation of Mitigation Measure HWQ-2 potential adverse long term storm water runoff management water quality impacts would be reduced to a less than significant level. Alternative 3: Reduced Intensity Alternative Under Alternative 3, one less injection well would be constructed. Compared to the Proposed Project there would be less construction activity and less potential for degraded surface water runoff impacts to occur- Similar to the Proposed Project, a SWPPP Would be prepared and implemented to minimize degraded construction storm water runoff impacts. With the implementation of Mitigation Measure GEO-1 potential degraded surface water runoff impacts would be reduced to a less than significant level. Because one less injection Well Would be constructed there would be a slight reduction in the amount of new and/or replaced impervious surfaces. A total of 2,917 square feet of impervious surfaces would be introduced and /or replaced at the project site. The total impervious surface improvements do not total 5,000 SF or rnore, which would be the threshold for a Priority Project Significant Mid Basin Centennial Park Are_rlki Project Final EIP 5-130