Who'll Capture the Rain
The most recent drought again highlighted the weakness of Southern California’s reliance on imported water sources. As our population continues to grow, and our climate continues to change, so must our approach to water supply. This session will explore our failure to capitalize on capture and use provisions in our permits. Join me as we talk about challenges to capture and use and how we might take advantage of each drop in the future.
Municipal Separate Storm Sewer System (MS4) permits throughout the state define a preferred Best Management Practice (BMP) hierarchy when developing a post construction stormwater quality plan. Top tiers of the hierarchy not only address water quality and stream health issues, they provide benefit to our local water supplies.
Infiltration BMPs constitute the first tier in the hierarchy. Where it is possible, designing a BMP based on infiltration typically does not pose serious challenges and are readily accepted by developers. When soil conditions and groundwater are favorable, infiltration becomes a simple decision as it addresses water quality and hydromodification issues. Little encouragement is required for implementing infiltration BMPs.
Infiltration infeasibility is common based on geological conditions in the Southern California region. Most permits then identify onsite stormwater capture and use as a mandatory second tier option. This should be an inviting solution as it also addresses both water quality and hydromodification issues. However, my experience has shown it is rarely seriously evaluated and regulators do not enforce implementation.
The final tier is a suite a of BMPs that can be described as treat and release. While these BMPs help improve water quality, they do not enhance our water supply.
Why is capture and use recognized as an important option but regularly dismissed as a serious alternative for projects? With our rain patterns and water needs, is capture and use even a reasonable approach?
If considered part of the solution, onsite capture and use must be taken more seriously and we must address barriers limiting its application. Two common barriers include long-term storage and “cost-effective” treatment. Advances in how we can safely store water longer while avoiding vector issues and other regulatory conflicts, as well as onsite treatment options are required. These are engineering problems in an industry that is made up of engineers; given the appropriate attention, solutions should be available. Although additional capture and use is not a silver bullet, any drop of captured onsite stormwater is a drop that isn’t imported or pumped out of an aquifer.
Beyond onsite solutions, regional systems can also benefit from improved stormwater capture. Recycled water is a powerful option to address water supply issues where it is available. Stormwater should be included as an element of how we produce more recycled water. We will explore how distributed storage throughout a watershed could help address high volume, short duration Southern Californian storm events. Onsite storage may be able to increase flow to publicly owned treatment works (POTWs) during times they can actually use it while also providing a new path to MS4 permit compliance.
Finally, possible incentives and education for improved capture and use will be discussed. If truly a priority, municipalities need to find ways to encourage implementation by property owners and developers. If additional taxpayer funding is required, a public understanding of the importance of capture and use must be achieved. Further, construction and maintenance personnel will need to learn how to ensure these systems work properly.
The presentation will engage attendees to provide real world experience regarding capture and use while adding alternatives for further study – an exercise in not only connecting the drops from summit to sea but capturing and using available drops along the way.
Dave Mercier, Project Manager with Michael Baker International, received his Bachelor of Science in Civil and Environmental Engineering from the University of California – Los Angeles, and is a Registered Civil Engineer in California. He has 15 years of surface water management experience, concentrating on water quality and flood control. He and his team support client stormwater programs across a wide range of industries to meet their municipal, industrial, and construction compliance needs.