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Restoring Local Recharge Sources The purpose of the Study is to evaluate a potential treatment method, other than desiccation, that can be used to eradicate existing quagga mussel infestations and prevent the potential spread of quagga mussels. In 2016, Trussell conducted an extensive literature review for OCWD of potential treatment technologies for the quagga mussel, including free chlorine, chloramines, ozone, ultraviolet radiation, and potassium permanganate. Proprietary molluscicides were not considered in this Study. Trussell found that the literature contains many studies examining treatment for adult mussels, but limited research on veligers. The veliger stage is the final larval stage of the quagga mussel, when they are mobile, having two ciliated flaps for swimming and feeding. Of the treatment methods examined, chlorine, chloramine and ozone were found to have promise; however, they present several challenges, such as needing quenching prior to discharge to a stream or river (chlorine, chloramine), formation of disinfection byproducts (chlorine), and high capital costs (ozone). In fact, one of the constraints that MWD faces with chlorine dosing at Lake Matthews is the formation of disinfection byproducts. An alternative method of treating for quagga mussels is EarthTec QZ, which is an EPA -registered molluscicide for prevention and control of quagga and zebra mussels. This product has been shown to be effective in eradicating quagga mussels and veligers in samples obtained from Lake Mead. Based on the Lake Mead study, an EarthTec QZ concentration of 3 mg/L, which produces a copper concentration of 0.18 mg/L, resulted in complete veliger mortality within 30 minutes. The effectiveness of EarthTec QZ and moderate cost, which is estimated at $20/acre-feet (for EarthTec QZ concentration of 3 mg/L), suggest that it has the potential be a cost-effective method to safely treat impacted sources of water, such as local reservoirs and imported water supplies; however, site -specific testing is needed to develop the proper dose required in local sources and to obtain approval by CDFW. Eventual approval by CDFW will allow for expanded use of currently infested facilities and open the use of facilities that are not currently infested, which would reduce barriers to groundwater replenishment, including the recharge of local supplies such as storm water. 3.0 Studv Description OCWD staff, along with Trussell, would conduct the Study. In general terms, the Study will test the response of quagga veligers to various doses of EarthTec QZ at five locations: Lake Matthews, OCWD's OC-28 connection in Anaheim, Lake Piru, MWD connection CenB-28, and one other location to be determined. Live veligers would be collected at each location. Subsets of the collected veligers would be exposed to different concentrations of EarthTec QZ and their response would be monitored over time. This work would be conducted in existing or temporary field labs located at or near where the veliger samples are collected. This is important to minimize the potential for veliger die -off during transport. In addition to examining the effectiveness of EarthTec QZ on quagga veligers, the Study includes an assessment of the toxicity of EarthTec QZ for aquatic species — other than quagga veligers. This work will be conducted in parallel with the dose -response veliger testing. Trussell will consult with aquatic microbiology experts, CDFW staff, review available literature, and examine regulations to evaluate the water quality impacts of EarthTec QZ.