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In addition to augmenting groundwater supplies, the project was intended to: <br />• Enhance riverine habitat <br />• Provide public recreation and education opportunities <br />• Minimize flood and erosion hazards through improved flood forecasting <br />• Minimize groundwater pumping costs <br />Study Objectives <br />The project was proposed as a major step toward meeting the groundwater safe -yield <br />withdrawal goal —the emphasis of the Ground Water Code of the 1980 Arizona <br />Groundwater Management Act. Further, to use excess recharge storage capacity <br />efficiently, feasibility analyses for the project were needed to evaluate using reclaimed <br />water and Central Arizona Project (CAP) water as auxiliary water sources for recharge. <br />While hydrogeologic assessments of groundwater recharge in the Tucson basin had been <br />done, capturing stormwaters as a source of groundwater recharge augmentation had not. <br />A clear understanding of watershed yield in terms of peak flow and volumetric discharge <br />was needed to design in- channel structures to ensure structural integrity. Moreover, <br />water quality information was needed to fully understand recharge impacts on the <br />existing groundwater. Other technical considerations included assessing the quantity and <br />quality aspects associated with local hydrogeologic conditions and an evaluation of the <br />surface water system as a source of recharge water. Legal considerations included the <br />ability to appropriate streamflow and an assessment of the liabilities associated with an <br />urban artificial groundwater recharge project. Transferable technologies for the recharge <br />of stormwater in arid southwest regions were also explored and published. <br />Description <br />The project site is located on the north side of the city of Tucson, Pima County, Arizona. <br />The watershed of the Rillito Creek upstream of the proposed recharge facility encom- <br />passes approximately 871 square miles. <br />The Rillito Recharge Project proposed using an inflatable dam and fuse plugs to impound <br />water in the channel for recharge. The Spur basin and West County basins would have <br />recharged this water. A diversion structure in Alamo Wash would have captured runoff <br />and conveyed it to the West County basin. Related river park amenities would have <br />included a restroom with a constructed wetland system for additional treatment and <br />interpretive signs. Remaining areas along the south bank would have been landscaped <br />with native species to encourage wildlife use and buffer adjacent neighborhoods from the <br />project. Figure 1 shows the associated project facilities. <br />The preferred alternative was compatible with a U.S. Army Corp of Engineers' (Corps) <br />project to construct soil- cement bank stabilization and grade - control structures along <br />Rillito Creek. However, the design for the Corps' project moved the grade - control <br />structure to reduce project costs, thus jeopardizing the foundation for the inflatable dam <br />Program Summary Report Part 111 — Demonstration Project Summary Reports <br />