NorthBay biz reports on the practice of rainwater harvesting, which, although still in its infancy in California, is gaining momentum with businesses and homeowners alike.

Look closer. Where the parking lot slopes a bit, there’s a drain inlet, a hole in the ground covered by a metal grid. That’s for drainage, so the lot doesn’t flood. Well, there must be a drain pipe connected to that hole, and the water must run off somewhere. It might connect to an underground storm water collection system, or it might just run off into a nearby seasonal creek. Either way, it ends up in a river somewhere, and it could be carrying pollutants in the form of oil, grease or sediment.

That’s right, the stuff on your tires can end up in the water supply. Yuck!

Now say goodbye to that old-school parking lot, and start thinking about rainwater retention and management. In fact, let your imagination run wild. Imagine an underground modular structure, a big plastic catacomb that captures the rain from a storm and stores it, to be gradually released later or even used for irrigation. Imagine parking on top of that big three-dimensional grid, separated by a layer of asphalt.

A North Bay company is pioneering this unique idea of managing rainwater underground. Cudo Stormwater Products, a Sonoma County firm that specializes in storm water management products, was founded by Doug Allard, who also founded a separate company, KriStar Enterprises, Inc. in 1993. The Cudo cube comes in plastic or concrete and can be stacked underground in a variety of configurations.

From above, the parking lot doesn’t look any different. The runoff from a rainstorm is still directed to a drain inlet, which connects to an underground grid, a matrix of stacked Cudo Cubes. The cubes are designed to lock together and form a rigid structure that can support the load of a parking lot or similar use.

Cudo Cubes, two feet per side, are manufactured of 100 percent recycled polypropylene plastic in a plant in Southern California and inventoried in Sonoma County. Concrete Cudo Cubes are made in Santa Rosa; they’re four feet per side, weigh about 3,500 pounds each, and can be used for shallower applications, where the weight of vehicles needs to be supported partly by the structure of the Cudos themselves.

Various plugs and connectors allow Cudos to be interconnected or to control water flow. The outside of the grid can be sealed, so the water stays inside, or it can be permeable, so the water gradually seeps out into the soil. The Cudo system also allows for the use of filters and pumps. Filters can be used to make sure grease and oil from parking lots don’t end up in groundwater. Pumps can be inserted so water can be pumped out and used for irrigation.

According to Allard, new regulations regarding “low impact development” are driving this type of innovation. “We’re starting to see increased demand for water storage on construction sites,” Allard says. “If you create a paved parking lot, you might be required to replicate the amount of runoff that existed prior to your development. It’s known as the ‘predevelopment hydrology.’”

Low impact development

The California Regional Water Quality Control Board, North Coast Region, is paying a lot of attention to low impact development (LID) standards. In an April 2009 memo to the Town of Windsor, the water board states: “The Regional Water Boards, the Department of Fish and Game and the California Coastal Commission are actively advancing LID implementation in California.”

The Water Board memo encourages Windsor to stay on top of best practices in storm water management. It further states: “A combination of aggressive use of LID techniques, best conventional techniques to manage high flows, land use actions to preserve sensitive areas (wetlands and riparian zones) and effective pollutant control through outreach and education are necessary to reduce pollutants in storm water to the maximum extent practicable and to preserve water quality.”

What does it all mean? Simply stated, you can’t allow pollutants generated on your project to run off onto someone else’s property, or into public water supplies. That seems simple, but it’s not always. Underground water tables don’t respect property lines, and neither do historic drainage patterns. New development is, in fact, held to a higher standard than before, but it’s the only way to comply with new regulations.

Containment

A common technique for storing storm water is the detention basin, a low spot where water collects during what water experts call “a rain event.” In Healdsburg, a detention basin was built after its downtown area flooded a few times in the 1990s. The basin catches storm runoff at the headwaters of Foss Creek and slows down the creek flow, theoretically preventing flooding. It worked fine until last winter, when a new development along the creek changed the local water flow patterns and Healdsburg’s downtown flooded again (city leaders say it won’t happen again).

Detention basins differ somewhat from retention basins. Detention basins, like the one in Healdsburg, go dry when there’s no rain. Retention basins typically have a permanent pool that expands and contracts. Both types of basins control water flow, cut down on erosion and usually reduce urban flooding. (A selling point of the aforementioned Cudo system is that it can eliminate the need for a basin by storing water underground, which might be an advantage in urban infill projects.)

What happens to storm water after it’s retained, detained or otherwise stashed?

It’s not unusual for the water to simply seep into the ground. In fact, the Cudo system functions best, according to Allard, when it can empty within 24 hours after it fills. Basin storage typically holds water for longer periods.

In either scenario, the primary goal is to slow the water down and let it infiltrate, and also collect some for later use. Fast moving water in creeks and streams can accumulate and transport large amounts of sediment, which can damage wildlife habitat, and it can flood developed areas, which usually isn’t too good for human habitat or agricultural uses.

And, it accumulates other stuff. As explained by John Guardino, an agricultural scientist with the Southern Sonoma County Resource Conservation District, “Once rain falls and begins to run along the ground, it can pick up and transport pollutants.”

Rainwater collection and management can also play a role in water conservation, an issue of increasing importance. Guardino notes, “Rainwater harvesting and reuse offsets potable water use.” If rainwater can be stored and used for nonpotable uses such as irrigation, then fresh water supplies can be conserved and used more efficiently and effectively.

Irrigation

Commercial and residential irrigation is the “low-hanging fruit” in the rainwater harvesting story, meaning it’s the fastest and easiest way to use stored rainwater—but it has to be done correctly, because the water has to be stored and kept clean and free of bacteria and mosquitoes, often for months. After all, if it’s raining hard enough to let you capture and store water, you probably don’t need to irrigate right away.

Mother Nature has been storing rainwater forever. Entire ecosystems have evolved around the cycle of rain and drought. The African watering hole is one of the best examples. Rain collects in low areas of the geography during torrential rains. Wildlife migration and feeding patterns are based on accessibility to water.

In more developed areas, farmers and ranchers collect and use rainwater in a similar fashion. A natural collection point for water is enhanced with berms or riprap, and water is pumped or channeled back out when it’s needed.

Wineries use this method, and many are recycling water as well. Shafer Vineyards in the Napa Valley has two ponds. One was constructed by Shafer to store and aerate winery water: Instead of going to a leach field or running off into a creek, the water that’s used to clean tanks, equipment and floors is diverted into the pond, where it’s aerated and naturally treated before being reused for irrigation.

The second pond (known as “Jake’s Lake” after a winery pooch who used it for swimming) captures rainwater from the nearby hills. It has a capacity of 30 acre-feet, fills during a typical rainy season, and supplies a lot of the winery’s summer irrigation needs.

According to Doug Shafer, the winery has cut its use of groundwater to 1 percent of its total water use. “Essentially, our whole focus is to harvest rainwater and reuse and recycle it,” he says. “After it’s done double duty on our property, it enters the watershed in the same pristine condition as when it arrived.”

Small commercial projects here and there are also harvesting rainwater. The Lagunitas School District in Marin County has a project at its San Geronimo campus. According to district staffer Donna Henderson, a roofed lunch shelter now has a rainwater catchment system that fills a cistern. “We use it for irrigation of the school garden.”

Rainwater harvesting, storage and reuse for irrigation is gaining support from local governments and water agencies that are struggling to meet increasing municipal water demands. The Sonoma County Water Agency funded the development of the Sonoma Valley Groundwater Management Program, which was developed by a coalition of government, business, dairy, agriculture and environmental groups.

According to Guardino, an important component of the effort is to develop a resource guide for landowners, and water harvesting will play a significant role in the future of Sonoma Valley. Guardino says “groundwater use is projected to increase in this area, and the immediate question is: How do we create a sustainable plan for future groundwater use?”

Guardino says the Sonoma Valley plan will look at roof catchment systems as well as how to manage storm water that falls on the land. “Storm water traditionally has been seen as a nuisance,” he says. “We’re helping to educate the public to recognize it as a valuable asset.”

Guardino goes on to explain that a recent United States Geological Service study suggests the Sonoma Valley aquifer is under stress (an aquifer is defined as any geological formation that contains or conducts groundwater, particularly those that supply water to wells and springs). He mentions there are many potential techniques that could help enhance aquifer recharge where appropriate.

He also stresses that there are opportunities to offset potable water use by “banking” water. “The future could involve water banking, storing potable water in a healthy aquifer in the winter when it’s plentiful, then pumping it out at a sustainable rate in the summer.”

Marin Municipal Water District is also funding a rain harvesting program. The district issued a request for proposal (RFP) this fall (not yet awarded at press time) for a rainwater harvesting consultant to launch a pilot program in Marin County. The district wants to hire a consultant who will spend 2010 educating commercial and residential water district customers about rainwater harvesting, and to actually install and manage pilot systems at homes and businesses.

California behind other areas

According to experts, California has a lot to learn when it comes to rainwater harvesting and reuse. Aaron Avila of National Storage Tank, based in Santa Rosa, says, “California is really behind on this issue. Texas is the leading state, it’s enacted ordinances that mandate rain harvesting. California is just coming up to speed.” He also cites Australia and its dry climate as an international leader in technology for rainwater harvesting.

Avila and his firm are supplying tanks and expertise to wineries that have an interest in capturing free water from the sky. Large barrel rooms, case storage facilities and bottling lines can be under thousands of square feet of roof, and channeling that runoff into storage tanks makes sense.

Avila notes, “one of the biggest issues is when debris comes off the roof. You have to be able to filter it.” Filtration tends to be in stages—the initial goal is to keep leaves and other large debris out of the tanks, but finer filters are employed as well, especially if the water will be pumped into a drip irrigation system that could clog with minute particles.

Avila and other experts say there are lots of commercial projects that plan to collect and store rainwater, but a sluggish economy is slowing development. “Everyone is moving toward it,” Avila says.

Bill Wilson agrees. An engineer with the Santa Rosa firm of Carlile Macy, Wilson says he knows of “shopping centers and big housing projects that could collect hundreds of thousands of gallons” of rainwater per year. “There are some really great projects on the drawing boards,” he says.

One of the largest projects being considered is at Sonoma Mountain Village, the former Agilent campus that’s being converted by Codding Enterprises into a sustainable community. According to Geof Syphers, chief sustainability officer for Codding, a large-scale system is being contemplated for the site—up to 6 million gallons of storage—but it’s at least two years away in the planning process.

Residential programs growing

The idea of capturing rainwater from the roof of your home is becoming more popular than ever, especially in the last few years of low rainfall. The city of Santa Rosa actually has a rebate program that will pay homeowners $0.25 per gallon of rainwater storage. Dan Muelrath, the Water Conservation Program Coordinator for Santa Rosa, says the rebates are based on the city’s water costs.

Muelrath, who says rainwater storage rebates coordinate with city programs that encourage homeowners to replace thirsty lawns with landscaping that uses less water and programs that educate water customers about conservation, asks, “Is it more cost-effective (for the city) to buy water from the Sonoma County Water Agency or is it cheaper to save it with these programs? This is the driver behind most conservation programs.”

Looking ahead

Wilson believes rainwater harvesting is part of a movement toward a new attitude about water and points to new regulations that have a “start at the source” philosophy about water management. “The old model was to have a detention basin, prone to nuisance problems and maintenance issues. The current trend is toward smaller systems that can be easily monitored.”

If Wilson is correct, it could spell the end of the massive public works projects—the “end of the pipe” approaches—of the 20th century. If every home and business captures rainwater, uses it efficiently and recycles some of its wastewater through irrigation or toilet flushing, we become more self-reliant, and multi-million dollar municipal treatment projects can be downsized or even eliminated. “We may eventually move to a system of decentralized, recycled water,” he says.

Low Impact Development

From a California Regional Water Quality Control Board fact sheet:

LID [low impact development] is an alternative method of land development that seeks to maintain the natural hydrologic character of the site or region. The natural hydrology, or movement of water through a watershed, is shaped over centuries under location-specific conditions to form a balanced and efficient system. When hardened surfaces such as roads, parking lots and rooftops are constructed, the movement of water is altered; in particular, the amount of runoff increases and infiltration decreases. This results in increased peak flow rate and volume, and pollution levels in stormwater runoff. LID designs with nature in mind: working with the natural landscape and hydrology to minimize these changes. LID accomplishes this through source control, retaining more water on the site where it falls, rather than using traditional methods of funneling water via pipes into local waterways. Both improved site design and specific management measures are used in LID designs. LID has been applied to government, residential and commercial development and redevelopment, and has proven to be a cost-efficient and effective method for managing runoff and protecting the environment.