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City of Pleasanton Recycled Water Project CEQA Addendum 2.3 Original Proposed Project Description As originally described in the June 2014 Draft IS/MND and the September 2014 Final IS/MND (collectively referred to as the IS/MND), the Proposed Project would primarily consist of the upgrade and expansion of the Dublin San Ramon Services District's (DSRSD) existing wastewater treatment plant (WWTP) to provide a recycled water supply of approximately 2,500 acre-feet per year (afy) to meet recycled water demand in the City's service area and offset deliveries from the City's groundwater supplies and water supply purchases from Zone 7. All of the WWTP plant upgrades will be included within DSRSD's existing WWTP location and within existing facilities that were previously designed, sized, and constructed for this potential upgrade and expansion. All of the recycled water will be produced by the City of Livermore Waste Water Treatment Facility and/or the Dublin San Ramon Services District/East Bay Municipal District (DERWA) Recycled Water Treatment Facility. The Proposed Project/Action also includes the construction of up to approximately 22-miles (115,200 linear feet)of pipeline ranging in diameter from 6-inches to 18-inches. In addition, the Proposed Project/Action will also include approximately 3.2 miles (16,500feet) of existing pipeline that will be repurposed from abandoned or existing potable pipelines. Table 1 provides a summary of the pipeline segments by construction phase. The pipeline facilities would be located primarily in existing roadways. In addition, the Proposed Project/Action will also include the conversion of the existing 8 million gallon (MG) Tassajara Reservoir to a recycled water storage facility. 2.3.1 Construction Considerations Construction of the Proposed Project/Action facilities is expected to begin in the summer of 2014 and will likely continue into the summer of 2019. Construction work will typically be done within normal working hours, weekdays between the hours of 8 a.m. and 8 p.m., and possibly on Saturdays between the hours of 10 a.m. and 6 p.m. The Proposed Project/Action would be constructed primarily within existing roadways and any damages occurring during construction will be returned to the pre-construction condition or better. Detailed below is a summary of the construction techniques and activities. • The upgrades to the tertiary filtration system would involve installing parallel filter cells in existing facilities within DSRSD's existing WWTP (see DERWA EIR for Recycled Water). • Each customer location will require some level of work due to possible meter location changes and pressure differences affecting overspray requirements. On-site plumbing changes may be required to comply with cross connection requirements. • The majority of the pipelines would be installed in existing roadways using conventional cut and cover construction techniques and installing pipe in open trenches. It is assumed that up to a 50- foot wide construction corridor would be used to help maximize the efficiency during construction. However, in most places a 25-foot construction corridor could be realized, especially for the smaller diameter pipelines. It is anticipated that excavation would range from 2-5 feet wide and would typically be no more than 6-feet deep. • Any local creek or drainage crossings would be constructed using trenchless techniques and will be done in the dry season and will not occur during inclement weather or between October 15 and April 1. Specifically, the pipeline crossing the Arroyo Mocho will either be hung on the existing road bridge or cross under the creek channel using directional drilling methods. • Dewatering of the pipeline as a result of hydrostatic testing during construction as well as any dewatering as a result of operations and maintenance activities shall be discharged to land and/or December 2014 2-2