Tapping into Available Capacity in Existing Infrastructure to Create Water Supply and Water Quality Solutions. Los Angeles Area Chamber of Commerce

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1 Tapping into Available Capacity in Existing Infrastructure to Create Water Supply and Water Quality Solutions Los Angeles Area Chamber of Commerce May 29, 2018 David Pedersen, P.E. General Manager The White Paper Purpose: Explore opportunity to leverage available capacity in existing WWTPs to produce multiple benefits. Drivers: Need to develop a strategy for areas of County that do not support infiltration. Recognition that conservation has contributed to available capacity at existing WWTPs. Interest of water and wastewater agencies to participate on a collaborative and complimentary solution. Advancement of potable reuse. 1

2 Land Area Overlying GW Basins 28% of the Los Angeles Basin s land area directly overlies an unconfined aquifer Volume of Water (AF) Conserved by LACFCD- Operated Spreading Grounds 2

3 Future Water Supply Development Costs Stormwater Capture Costs 3

4 Conservation and Wastewater Flows 4

5 Overlapping Infrastructure The Approach 5

6 Conclusions Only 28-percent of the Los Angeles Basin is available for groundwater augmentation through stormwater infiltration. Within the County, there are approximately 21,000 miles of sewers and 3,300 miles of storm drains with thousands of miles of additional city-owned sewer and drainage systems. A comparison of pre- versus post-drought flows show a 103,000 AFY reduction in influent sewer flows. Potentially available collection and/or treatment plant capacity presents an opportunity to maximize the use of this infrastructure for the co-equal benefits of water quality and water supply, through the introduction of stormwater under controlled conditions. Of the current wastewater flows treated, approximately 231,000 AFY is reused for both potable and non-potable uses. Within the next 10 years, planned reuse project will more than double the current reuse flow rate. Conclusions (con t) There are 47 LFDs within Los Angeles County that handle dry-weather flows only. LFDs are designed to capture dry-weather flow and provide water quality benefits but are typically not considered a source of water supply. Construction of more LFDs and/or expansion of existing LFDs to accept some of the wet-weather flows should be tested by developing pilotstudies. Controlled diversion of urban runoff/stormwater from the storm drain system can help to address MS4 requirements, while generating the potential for more recycled water to help meet future demands. Potential diversions should be analyzed on a case-by-case basis to ensure permissive integration of the storm drain and wastewater systems. Maximizingthe use of existing infrastructure can provide a more cost-effective solution. 6

7 Recommendations 1. Elevate the concept of leveraging the investment of the County s residents in existing infrastructure to provide water supply and water quality solutions in a costeffective and environmentally beneficial manner. 2. Provide incentives for cities, water agencies and wastewater treatment providers to jointly utilize available capacity in their respective infrastructure to produce water supply and water quality benefits. 3. Designate up to 10% of the Regional Program funding for the following purposes: Modeling, real-time data collection, pilot testing and regulatory compliance analysis of permissive diversion of dry-weather runoff and first flush stormwater to the sanitary sewer system and/or directly to the influent of the treatment plant, in collaboration with wastewater agencies; and Construction, operation and maintenance of facilities to permissively divert dry-weather runoff and first flush stormwater to the sanitary sewer system and for improvement of downstream collection, conveyance, treatment and water recycling facilities. 7