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5 – Effects Found Not To Be Significant Draft Environmental Impact Report February 2021 14800 W. Schulte Road Logistics Center 5-11 be implemented, and must demonstrate that the combination of BMPs selected are adequate to meet the discharge prohibitions, effluent standards, and receiving water limitations contained in the Construction General Permit. As such, through compliance with the Construction General Permit, the Project would not adversely affect water quality. Therefore, short-term construction impacts associated with water quality would be less than significant. With respect to Project operation, future uses on site that could contribute pollutants to stormwater runoff in the long term include uncovered parking areas (through small fuel and/or fluid leaks), uncovered refuse storage/management areas, landscape/open space areas (if pesticides/herbicides and fertilizers are improperly applied), and general litter/debris. During storm events, the first few hours of moderate to heavy rainfall could wash a majority of pollutants from the paved areas where, without proper stormwater controls and BMPs, those pollutants could enter the municipal storm drain system before eventually being discharged to adjacent waterways. The majority of pollutants entering the storm drain system in this manner would be dust, litter, and poss ibly residual petroleum products (e.g., motor oil, gasoline, diesel fuel). Certain metals, along with nutrients and pesticides from landscape areas, can also be present in stormwater runoff. Between periods of rainfall, surface pollutants tend to accumulate, and runoff from the first significant storm of the year (“first flush”) would likely have the largest concentration of pollutants. Stormwater quality in San Joaquin County is regulated by the Stormwater Quality Control Criteria Plan (SWQCCP), which sets forth standards that apply to all new developments and significant redevelopment projects falling under the priority project categories, of which the Project site is one. The primary strategy employed by the SWQCCP is to require development to manage and treat stormwater flows to the maximum extent practicable to control pollutants, pollutant loads, and runoff volume by minimizing the impervious surface area and implementing source control measures, controlling runoff from impervious surfaces using structural BMPs (e.g., infiltration, bioretention, and/or rainfall harvest and re-use), and ensuring all structural BMPs are monitored and maintained for the life of the development. These measures are often referred to as low-impact development principles (City of Stockton and County of San Joaquin 2009). As part of the Project, a new engineered stormwater drainage system would be constructed on the Project site to collect and treat on-site stormwater. After development, a majority of stormwater from the Project site would drain into three below-grade, open, earthen infiltration basins within the north portion of the site. Stormwater flows would be conveyed via sheet flows away from buildings, and where possible, through below-grade, landscaped areas prior to entering the nearest catch basin and subsequently being conveyed to the three earthen detention basins. The landscaped areas would act as the first filter for detaining suspended solids in stormwater flows. The detention basins would be planted with native grasses and erosion control vegetation along their side banks. Stormwater flows collected by the detention basins would be allowed to infiltrate into the soils, recharging the underlying groundwater basin (San Joaquin Valley Basin). The Project and its new stormwater drainage system would be sized to capture and treat all on -site stormwater generated by two consecutive 10 -year, 24-hour storm events, as required by the County. The detention basins would feature an earthen bottom that would allow flows collec ted by the detention basins to infiltrate into the soil and recharge the underlying groundwater basin. The Project’s stormwater capture and treatment system would be designed to meet the requirements of the SWQCCP, ensuring that the Project would not violate water quality standards or waste discharge requirements or otherwise substantially degrade surface water or groundwater quality.