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Draft 14. Subregional Planning Element additional water supply, treatment, conveyance, storage, and groundwater recharge and extraction facilities. In addition, over the next 20 years, Zone 7 plans to replace or improve its existing system. Providing adequate, sustainable water for planned growth is a major Subregional issue that requires continuing planning coordination, growth management, and cooperative efforts to obtain additional supplies that will meet future agricultural, urban, and environmental needs. Wastewater Treatment and Disposal The Dublin San Ramon Services District and the City of Livermore provide wastewater treatment and disposal in the Tri-Valley area. The Livermore-Amador Valley Water Management Agenry (LAVWMA) exports treated wastewater by way of its pipeline from the Tri-Valley area to San Francisco Bay.. A LAVWMA expansion project has now been completed. Pleasanton, the Dublin- San Ramon Services District, and Livermore plan to share the allocated expansion increment among them, which should accommodate their wet-weather flows for many future years. See the Wastewater section of the Water Element for additional discussion of regional wastewater issues. Hydrology and Water Quality The Tri-Valley area lies within the greater Alameda Creek watershed mainly within the Zone 7 service area. Three major east-west arroyos -Arroyo las Positas, Arroyo Mocho (which includes water from Tassajaxa Creek), and Arroyo del Valle -encompass the general drainage pattern of the watershed. These arroyos join Arroyo de la Laguna in Pleasanton which then drains the Tri Valley in a southerly direction to San Francisco Bay via Niles Canyon and Alameda Creek. The Tri-Valley area does not contain any natural ]akes: both the Del Valle and San Antonio reservoirs axe human made as are the former sand-and-gravel pits comprising Shadow Cliffs and the Chain of Lake. Alameda County developed the "Chain-of-Lakes" concept in the 1970s. Zone 7 plans to establish the Chain of Lakes fox flood control, sediment diversion, and recreation. The Chain of Lakes are located between the cities of Livermore and Pleasanton and, when complete, will consist of a series of abandoned sand-and-gravel quarry pits converted into nine lakes, linked in a series, plus Cope Lake. Thus far Zone 7 has established four of these lakes, which all contribute to groundwater recharge, plus Cope Lake, which does not contribute. The remainder of these lakes will be available in the next 10 to 30 years after they have been mined and reclaimed. For additional discussion of the Chain of Lakes, see Stortnwater and Water Resources in the Water Element and see Sand and Gravel, Water Management and Recreation, and Soil Resources in the Conservation and Open Space Element. With implementation of its Sham Management Master Plan, Zone 7 would mitigate Subregional flooding with the Chain of Lakes, and would reduce streambed siltation and erosion with projects on several areas of local arroyos. Subregional Planning 060507, clean 14-9 City Council 6/5/2007