AgdaPkt 2016-02-22 Closed and Interview and Joint SA PFA

Browse Search

City of Redwood City, Public Works Division Initial Study & Mitigated Negative Declaration Document Date: October 15, 2015 Revision Date: January 25, 2016 Page 43 Blankinship & Associates, Inc. the lower contribution of copper pesticides to surface water concentrations is the aquatic pesticide general permit which requires an Aquatic Pesticides Application Plan describing management practices to mitigate effects to water quality resulting from pesticide application (TDC Environmental, 2004). These requirements serve as control measures to limit copper algaecide discharges from lagoons and sloughs to San Francisco Bay. Applications of copper-based aquatic herbicides according to label direction typically require concentrations of copper between 500 and 1,000 µg/L (equivalent to 0.5 to 1.0 mg/L). Within the Lower & South San Francisco Bay, site specific objectives (SSOs) are in place for copper limiting the maximum average concentration allowed for copper within the Lagoon and connected waterways (CRWQCB, 2013). These SSOs are enforceable water quality objectives limiting the 1-hr average copper concentration (Criteria Maximum Concentration) to 10.8 ug/L and the 4-day average concentrate (Criteria Continuous Concentration) to 6.9 ug/L. These water quality criteria may be exceeded within the treatment area, shortly after application, and downstream of the point of aquatic herbicide use (i.e., outside of the treatment area or in “receiving waters”) when applied at labeled rates. Accordingly, because label application rates may exceed the SSOs, the City is obtaining a SIP exception. As a result of both dilution and uptake, copper-containing aquatic herbicides, as they will be applied in the Lagoon, rapidly dissipate and/or become permanently insoluble and as a result are not bioavailable shortly after application (CDFA 2002; Trumbo 1997, 1998; WA DOE 2004). When copper is applied according to label direction, its half-life is between 3 and 19 hours due to a combination of precipitation, absorption by biota, adsorption by particulate matter, and adsorption or complexation with organic matter. When used according to label directions by qualified personnel, impacts of copper-containing aquatic herbicides have no significant impact. The City or contractor will implement the following mitigation measure for applications of copper to reduce any potentially significant impacts to less than a significant level: These mitigation measures for applications of copper are: HWQ-1. As required by the SIP and the SWRCB general permit for the application of aquatic herbicides, the City or contractor will execute the Aquatic Pesticide Application Plan (APAP). The APAP calls for surfacewater sampling and analysis before, during, and after aquatic herbicide application to assess the impact, if any, that the Project may have on beneficial uses of water. Additionally, consistent with SIP exception requirements, the City will arrange for a qualified biologist to assess impacts to receiving water beneficial uses. Item b): No Impact. The Project will not involve any construction activities or require the use of groundwater and therefore there is no impact on groundwater recharge or supplies. Items c), d), & e): No Impact. The Project will not involve construction of any structures that would alter drainage patterns or increase storm water runoff. The Project will not increase erosion or siltation on- or off-site. No streambeds will be altered. No increase in drainage capacity of local storm sewers will be required. Item f): See response to item a). 6.3.A. - Page 51