2024-053 - Final Supplemental for The Related Bristol Specific Plan Project

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Facts in Support of Findings: Construction Pollutants of concern during construction activities generally include sediments, trash, petroleum products, concrete waste (dry and wet), sanitary waste, and chemicals. Each of these pollutants on its own or in combination with other pollutants can have a detrimental effect on water quality. In addition, chemicals, liquid products, petroleum products (such as paints, solvents, and fuels), and concrete -related waste may be spilled or leaked during construction, which would have the potential to be transported via storm runoff into nearby receiving waters and eventually may affect surface or groundwater quality. During construction activities, excavated soil would be exposed, thereby increasing the potential for soil erosion and sedimentation to occur compared to existing conditions. In addition, during construction, vehicles and equipment are prone to tracking soil and,/or spoil from work areas to paved roadways, which is another form of erosion that could affect water quality. However, the use of BMPs during construction implemented as part of a SWPPP as required by the NPDES General Construction Permit and included as PPP WQ-1 would serve to ensure that Project impacts related to construction activities resulting in a degradation of water quality would be less than significant. As detailed in the Preliminary Geotechnical Investigation Report (Included as Appendix G to the Draft Supplemental EIR), the historic highest groundwater at the site has been mapped at a depth of about 5 feet bgs and groundwater in 2022 was encountered between depths of 12 feet and 16 feet bgs. If contaminated, release of dewatered groundwater to surface waters can introduce total dissolved solids to surface waters. If groundwater or perched groundwater is encountered during construction and groundwater dewatering is necessary, it would be completed in compliance with the Groundwater Discharge Permit, as specified PPP WQ-2. Compliance with the requirements of the Groundwater Discharge Permit would ensure impacts related to waste discharge requirements and water quality standards would be less than significant during dewatering activities, and no mitigation would be required (Draft Supplemental EIR at pp. 5.7-10 through 5.7-1 1). Operation The proposed Project includes operation of retail and restaurant commercial and multi -family residential uses. Potential pollutants associated with the proposed uses include various chemicals from cleaners, pathogens from pet wastes, nutrients from fertilizer, pesticides and sediment from landscaping, trash and debris, and oil and grease from vehicles. If these pollutants discharge into surface waters, it could result in degradation of water quality. The Newport Back Bay, to which the Project site ultimately drains, is currently listed as impaired on the USEPA's 303(d) list for various pollutants. Therefore, additional pollutant discharge could create new or exacerbate existing impairments within these waterbodies, which could result in a significant impact related to water quality. However, operation of the proposed Project would be required to comply with the requirements of the Santa Ana Regional MS4 Permit and Orange County DAMP to develop of a project -specific WQMP (included as PPP WQ-3) that would describe implementation of LID infrastructure and non- structural, structural, and source control and treatment control BMPs to protect surface water quality.