Water Resources Strategic Memos for California Water Foundation

The work principally involves selecting the appropriate benefits that stormwater retention BMPs create, applying the applicable methods, and performing the calculations necessary for benefit cost analysis within the MS4 permit compliance context. "Within the MS4 permit compliance context" is a very important point to consider, and helps more narrowly define the universe of benefits that can be realized and reasonably monetized, or quantified in some manner to some degree using an understandable metric. A first task is to identify the universe of benefits ascribed to stormwater retention BMPs within the ms4 permit context, and then further categorize them into those that can be monetized and those that cannot. As a first cut example, some benefits that have been attributed to stormwater retention BMPs simply do not apply in the southern California context, such as "avoid combined sewer overflow." Others are trickier (habitat creation and the "value" of that habitat, for whatever may be living that habitat) and will need to be objectively evaluated. Also, the "valuation" of stormwater reaches further than MS4 compliance, and there are several efforts underway currently beyond the reach, if you will, of the MS4 system. Mixing benefits between or among other valuation efforts with the MS4 context will confound the work unless it is accounted for early. There are Case Studies upon which to build the cost (and benefits realized) information base and a significant amount of data exist, and the Case Study hydrologic and engineering features are known generally at this point yet need some further definition in July and early August. The necessary hydrologic sizing information is based on guidance documents used to support the Orange County and San Diego MS4 programs, and applying this information to case study scenario analysis is extensive in and of itself. And, San Diego County is developing Water Quality Equivalency calculations that any Alternative Compliance project would need to use to determine the "offset" volume, and we have to account for this process (and necessary calculations) in our case study development.