In my last Hydrowonk post, I discussed how challenges moving water through the Delta has created even more scarce water supplies in parts of the Central Valley. Despite the fact that Lakes Shasta and Oroville are at 92% and 94% capacity, (Lake Oroville is within 18 feet of the crest – a reality unimaginable just a year ago when the reservoir looked like this) a series of factors is stopping the water stored north from flowing to parched farmers and cities in southern California. Many water pundits and industry leaders have pointed out how the drought has changed people’s mindsets about water use, and it has affected how water district managers view long-term supplies. For example, many managers did not believe that the Central Valley Project would get zero allocation for 2014 and 2015, and that the State Water Project would deliver a 5% allocation in 2014. As the Golden State enters into the fifth year of drought, unreliable water supplies are causing many districts to look for alternative sources.
But each alternative to imported water supplies has its advantages and disadvantages. Desalination has become more prevalent in Southern California since the Poseidon Plant opened in San Diego County. The ocean can supply an almost limitless supply of water, but the supply comes at a price: the April 2016 water purchase agreement that the Carlsbad Municipal Water District executed with the San Diego County Water Authority to receive water from the Poseidon plant will initially cost Carlsbad approximately $2,400 per acre-foot. The cost for desalinated water is approximately $1,000 an AF higher than the $1,440 per AF that Carlsbad pays for water supplies (when available) from the Metropolitan Water District. City officials argue that imported water is unreliable. Further, the significant premium for the desalinated water will drop over time as the debt service for the plant decreases and the cost of imported water increases. At the moment however, the desalinated water supply remains more costly than imported supplies.
Desalination plants are not the only sources of water that are causing elected officials sticker shock: Earlier this year, Senator Bob Huff (R-San Dimas) convened a roundtable to discuss the $20 billion cumulative infrastructure price tag that meeting Los Angeles County’s storm water management and recharge plan (called MS4) may cost. While storm water can provide a local and sometimes plentiful supply, there are also costs associated with implementing widespread storm water capture. In this piece, I will address the pros and cons of increasing storm water capture in the context of Los Angeles County’s 20-year MS4 implementation plan.
MS4 Storm Water Permit Requirements
OK, get ready for a few acronyms. The 1972 federal Clean Water Act made it unlawful to discharge pollutants into the waters of the United States unless the discharge is in compliance with a National Pollutant Discharge Elimination System (NPDES) permit. The NPDES permit establishes limits for certain pollutants entering the waters of the US. To implement these regulations, the US EPA created two phases (the first in 1990 and the second in 1999) of the Municipal Separate Storm Sewer Systems (MS4) permit. Phase I regulated discharges from city storm drains and construction projects five acres or greater. Phase II included construction projects one acre or greater.
In California, the State Water Resources Control Board (SWRCB) adopts a general MS4 permit that regulates storm water runoff from highways and large complexes such as military bases, prisons and some large hospitals. For other types of sources including new development projects, counties will adopt individual permits to regulate storm flows. Permits are updated every five years.
The Advantages of Storm Water Capture
Despite “drought shaming” tactics in California to persuade water wasters from billionaires to Kim Kardashian to use less water, California cities in general still waste water. For example, even in the hottest part of the summer, you will rarely see the Los Angeles River completely dry. Why? Runoff from the mountains contributes some water to the river year-round. But more importantly, thousands of streets and lots also drain directly into the Los Angeles River, and the system captures the overspray when sprinklers water the sidewalks or when citizens wash their cars outside. And it is not just citizens that may waste water in the state: Last July, CBS Los Angeles found a Veterans Administration facility in Los Angeles that watered the lawn for more than two hours at a time, when the City of Los Angeles’s water conservation rules limited watering to no more than 8 minutes per day! While it is impossible to determine just how much water sprinklers in California waste, a study from the Seattle and Participating Local Water Utilities estimates that improperly calibrated sprinklers can waste 40-50% of water used.
Increased storm water capture helps cities in a few ways. First, it is a local source that is not beholden to conveyance capacity or pumping restrictions. Second, in many areas it is an underutilized resource. Los Angeles on average collects approximately 27,000 acre-feet of storm water, a pittance compared to the city’s overall water usage. The Los Angeles Department of Water and Power reported that the City of Los Angeles used about 33,600 acre-feet in February 2016, 6,600 acre-feet more than the city captures in terms of storm water in an entire year. But with proper infrastructure, the city believes that it could capture up to 100,000 more acre-feet per year in storm water flows that currently flow out to the ocean. However, this capacity comes at a cost.
The Disadvantages of Storm Water Capture
Infrastructure for storm water capture has its disadvantages as well. First, storm water infrastructure investments are a fixed cost and still must be maintained during rainy or drought periods. The systems are less cost effective the less it rains. Also, from a standpoint of public perception, it may be more difficult to get citizens interested in making storm water infrastructure investments when the infrastructure will be used for a small period of the year. Most of the rains in California occur between December and March. During the dry parts of the year, the storm water capture systems will remain dormant.
But the biggest challenge to more widespread storm water infrastructure investment is the cost associated with implementation. A July 2015 presentation from the Los Angeles County Flood Control District estimates that county-wide costs for storm water infrastructure will be $20 billion over the next 20 years, and monitoring and testing will cost upwards of $10 million per year. Increased design standards under the MS4 permit are part of the reason why costs are so high. In years past, storm drain design focused on getting as much water off of the land as quickly as possible to the ocean. However, engineers also recognized that this design philosophy deprived arid parts of California from capturing useful water supplies. New storm water design guidelines under many MS4 permits focus on capturing and treating as much water on-site to recharge local aquifers. But these designs often cost considerably more than earlier designs.
Storm water that falls on impervious services such as roads or parking lots can pick up contaminants from spilled oil or gasoline, and these contaminants must be cleaned before water can be allowed to recharge an aquifer. Developers must build bio-retention areas that use membranes and other organic materials to filter the water before it percolates into the ground. Further, some counties require new developments to capture water onsite so that it recharges the local groundwater supplies. While onsite retention can be planned for in brownfields, it presents a bigger challenge in developed areas with limited land area. Bio-retention ponds (See page 130 of Ventura County’s technical manual for an example of this) require that land be set aside where water can pool, be filtered through organic materials and percolate into the ground. This is a difficult and costly task in some developments in built-out areas with small lot sizes.
Where do we go From Here?
Storm water capture has to play a role in California’s future water supplies. We cannot dismiss the importance of this local and sometimes plentiful resource to augment imported and recycled water supplies. Storm water capture accounts for a small fraction of most cities’ water supplies, and we need to take measures to increase this figure. But we also have to do it in a cost-effective manner. The $20 billion price tag for the storm water improvements could buy the equivalent of approximately 27.5 million acre-feet of supplemental water from Metropolitan Water District (assuming the $728 per acre foot Tier 2 full service untreated volumetric cost). It is imperative that water planning agencies look at the supplies and associated costs holistically to determine the most cost-effective manner to secure necessary water supplies.