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The beachside community of Malibu, CA, which on a good traffic day is a 45-minute drive from downtown Los Angeles, is home to some 13,000 residents, some of whom are lucky enough to live directly on the sand, the rest scattered in the canyons and foothills of the Santa Monica Mountains that form Malibu’s backdoor. Wastewater disposal is via some 6,300 commercial and residential onsite treatment systems citywide.
In addition to 27 miles of coastline, which turns to enclose the northwest boundary of Santa Monica Bay and includes internationally famous Surfrider Beach, Malibu is also home to two regionally significant aquatic resources, Malibu Creek, the only stream that runs the width of the mountains, draining 109 square miles of watershed, and Malibu Lagoon, one of two significant remaining freshwater estuaries in southern California. Both the creek and lagoon have been identified as impaired for bacteria and nutrients under section 303 (d) of the Clean Water Act. Surfrider Beach routinely receives failing grades for bacteria in Santa Monica--based Heal the Bay’s annual “Report Card” of California beaches.
The Los Angeles District of the California Water Quality Control Board, which is responsible for regulating waste discharge throughout the state (there are nine districts statewide), has long hypothesized that onsite wastewater treatment systems (OWTS) in proximity to Malibu’s water resources may be among the factors contributing to poor water quality. Malibu residents, on the other hand, have complained about urban stormwater runoff from upstream communities and tertiary treated effluent for a wastewater reclamation facility located farther north up the creek. For years surfers who come to Malibu for the break just south of where Malibu Lagoon empties into the Pacific have complained of rashes and flu-like symptoms. On another front, two years ago, the California Coastal Conservancy, in conjunction with the California Department of Parks and Recreation and Heal the Bay, announced a plan to restore the 16-acre lagoon, improving the flow in and out of the much-studied body of water as habitat for the tidewater goby, an endangered species, and habitat for resident and migrating waterfowl.
The Mess in Malibu
The city of Malibu is located within the boundaries of the Santa Monica Mountains National Recreation Area, which receives over 30 million visitors a year, a large percentage of whom head for the beach. The city itself is completely surrounded by protected public land, and residents consider themselves environmentally aware. Formerly governed by the Los Angeles County Board of Supervisors, which mandated a conventional community-wide sewer system to manage the area’s wastewater, residents voted to incorporate in 1991, in part to forestall the sewers, which they considered would facilitate unwanted growth.
Because of Malibu’s natural resources and given concerns about public health, the city has attracted the attention of a variety of environmental groups including Heal the Bay, Santa Monica Baykeeper, Natural Resources Defense Council, and the Surfrider Foundation, which have variously called upon Malibu to clean up its wastewater act. Other outside stakeholders include the Malibu Creek Advisory Council, California Department of Parks and Recreation, Los Angeles County Environmental Health Division, California Department of Health Services, Surfrider International, the California Coastal Commission, and the Santa Monica Bay Restoration Commission.
In all, 395 onsite wastewater treatment systems serve what is locally known as the Malibu Civic Center. In consideration of its proximity to the creek and lagoon this approximately 2,500-acre subportion of the Malibu Creek watershed has been the object of a range of scientific studies undertaken by private consulting firms on contract to the city as well as academic researchers. Because these efforts have not been coordinated in regard to intent or methodology, the result has been a hodgepodge of nonintegrated and often conflicting data that feeds a continuing stream of rumor and innuendo about what should be done to manage the area’s wastewater, at what cost, and under whose auspice. A post-incorporation Specific Plan for development of Civic Center property recommended a self-contained wastewater treatment facility for the area, but the plan was not adopted by the City Council, and virtually all commercial, multi-family, and single family properties remain dependent on onsite systems.
Recently, however, a number of factors have converged to cause the city to review its management of its onsite wastewater treatment systems citywide. One result was Malibu Ordinance 242, which outlines a management plan requiring renewable operating permits for all commercial and multifamily OWTS; secondary treatment plus disinfection for commercial and multifamily occupancies undergoing repair, renovation, and new construction; renewable operating permits for all residential systems that undergo repair, renovation, and new construction; and a training and licensing program for OWTS. Yet to be approved is a point of sale inspection program for commercial occupancies.
Coincidentally, the EPA, and subsequently the Los Angeles Regional Water Quality Control Board (LARWQCB), developed Total Maximum Daily Loads (TMDLs) for Malibu Creek and Malibu Lagoon as a means of decreasing nutrient and pathogen loading in compliance with the 1972 Clean Water Act. The EPA action was a result of a 1999 suit brought by a coalition of environmental groups including Heal the Bay, which were concerned that the agency wasn’t doing enough to protect the region’s aquatic resources. Once the EPA’s TMDLs were released, LARWQCB announced its intention to continue development of its own standards and has in fact gone on to do so.
Assessing the Risks
Concurrent with these developments, the City of Malibu committed to what project co-director Bruce Douglas of Questa Engineering Corp. in Santa Barbara, CA, describes as a focused, risk-based analysis aimed at determining the effect of Civic Center onsite treatment systems on water quality in the creek, lagoon, and surf zone and to suggest alternatives for a decentralized system for the area. The study, which was undertaken by Stone Environmental Inc. in Montpelier, VT, was funded with bond money from the California Coastal Protection Act of 2000 administered through the Santa Monica Bay Restoration Commission and the California State Coastal Conservancy. During the course of the risk assessment study, Malibu contracted with Questa Engineering for a preliminary conceptual design study to identify potential wastewater management solutions that could aid the City Council in initiating better management of Civic Center OWTS.
Based on the results of the risk assessment study and the conceptual design studies, a detailed feasibility study to evaluate site-specific management options was undertaken and is in the final stages of completion. The next step will be a facilities plan to flesh out the specifics of the recommended alternatives, including a more detailed evaluation of the economics of water reuse, which will be critical to establishing a decentralized system in the Civic Center. If research and funding approvals stay on schedule, Douglas estimates the city could have a system in place by 2010.
Craig George, deputy building official for the City of Malibu, summarizes the confluence that has brought the community to this crossroad. “Means have been identified for cleaning up the creek and lagoon,” says George. “Moneys are available that weren’t available previously. And there are mandates to do so.”
Groundwater Flow Mystery
“The big unknown was where the groundwater in the Civic Center was going,” says Mary Clark, project manager for the risk assessment study. “The city wanted to know how much of the groundwater was actually flowing directly toward the ocean and how much was going toward the creek and lagoon, and they wanted to know what the bacteria and nitrogen load was from the onsite systems. They wanted the science to develop the most appropriate management strategies, and they wanted to be able to show other communities that wastewater can be handled with decentralized systems if they’re appropriately sited and designed and maintained.”
Malibu City Manager Katie Lichtig concurs. “Groundwater flow was critical, but the connectivity between the onsite wastewater treatment systems and the groundwater was also important so we could identify our highest risk areas.”
“Assumptions had been made,” says Douglas, “that groundwater flow patterns were consistent with surface flow patterns. But we didn’t know that. Additionally, analysis undertaken to develop the TMDLs for these waters maintained that onsite treatment systems in the Civic Center were failing, but no one could point to which systems these were.”
According to both Clark and Douglas, the goal was to provide Malibu with a “fact-based, outcome-driven approach” for Civic Center OTWS management. “Although historically decentralized and onsite systems received little or no management,” says Clark, “these systems must be managed if the goal is to provide for water quality and environmental and health protection. What we’re looking for is a level of management for individual systems that is appropriate to the level of risk. Risk-based assessment requires a thorough evaluation of the facts before developing a management program. This means scientific investigation.”
“You can’t impose onsite system management on a community that doesn’t recognize its importance,” says Douglas, who was involved in the initial 2003 Questa Engineering scoping study as well as the risk assessment and feasibility studies. “We needed some common, agreed-upon facts and commonly agreed-upon outcomes shared by city management, Malibu residents, LARWQCB and environmental groups. The benefit of a risk assessment study is that you have a strategy about how you’re going to develop data and make decisions that everyone can look at.”
Clark expresses it differently. “To be effective, community-level risk assessment requires stakeholder and public involvement, first to build understanding of the facts and relevant issues. And second, to build ownership and responsibility for implementing resulting outcomes.”
“It’s important to note that you have to deal with stakeholder issues differently in every community,” says Douglas. “In Malibu the stakeholder process took a lot longer than we had anticipated. Community meetings are easy to schedule. It’s harder to work behind the scenes and build trust and respect with people. This is where the Malibu city staff was critical. They sat down with people face-to-face and explained there was not an angle here, that this was an objective and scientific study. Stone Environmental had done similar work on Martha’s Vineyard, which helped Malibu residents understand that the approach of looking at groundwater quality and sensitivity to resources is tried and proven. On Martha’s Vineyard, the town’s goal was to protect its shellfish beds. In Malibu it was a combination of ecological habitat, water quality elements, and pubic health risk.”
Three Conclusions
Together the risk assessment and feasibility studies produced three conclusions that are critical for Malibu’s handling of its onsite systems: 1) groundwater in the civic center does not necessarily follow surface flow, meaning that the creek, lagoon, and surf zone are not equally at risk from nitrogen and bacteria, a finding that helped prioritize areas for implementation of management strategies; 2) hydrogeological characteristics of the Civic Center limit options for onsite systems management; and 3) an integrated approach involving wastewater and stormwater management will best serve the city’s objectives for the creek, lagoon, and surf zone.
The Malibu Civic Center consists of a low-lying plain along Santa Monica Bay, plus adjacent steep uplands that rise from sea level to 100 feet, with additional upland areas that rise 500 feet into the foothills to the Santa Monica Mountains. The area contains some undeveloped parcels but sustains the largest commercial development in the city along with multi-family and single-family residences that include The Malibu Colony, a dense subdivision where houses are built close together directly on the beach. The Los Angeles County courthouse and library, the county fire department and county sheriff’s offices are also located in this area, which effectively functions as Malibu’s town center. Contemporary development is built on what was naturally an estuary-lagoon and wetlands established within an alluvial plain at the mouth of Malibu Creek. Generally the water table is 3 to 36 feet below ground surface and depths fluctuate with tidal and season hydrology variations. In the vicinity of the existing leach fields, the water table is generally greater than 5 feet below ground surface.
The risk assessment study Stone Environmental developed for Malibu focused on the water table aquifer as the receiver of treated effluent from the area’s onsite systems, which it delivers directly to surface waters. Because prime TMDL targets are bacteria and nutrients, the study focused on these two wastewater components, the level of risk for bacteria being dependent on subsurface conditions (specifically the vertical separation between the infiltrative surface of the dispersal system and water table plus the horizontal time of travel from source to receiving waters), and the risk for nitrogen impact dependent on the mass loading of nitrogen and the degree of degradation likely between source and receiving waters.
To begin with, existing records regarding hydrogeology and geology of the Civic Center and OTWS were reviewed (locations of OTWS, design flows vs. water use data and soil borings) along with data regarding existing monitoring well construction, depth to groundwater, and groundwater quality. The information was entered into a Geographic Information System (GIS) database along with data from 84 monitoring wells. This was used to develop a Malibu-specific conceptual hydrogeological model. What resulted was a 3D numerical modeling tool that aided researchers in evaluating the impacts of onsite systems on groundwater quality and in delineating the direction of groundwater flow from major wastewater dispersal areas. Manual observations of surface water elevations were made at surveyed reference points, along with automated observations of surface water elevations, and the study team collected water-level measurements and water quality samples from 40 existing monitoring wells, including 12 privately owned wells. The water quality sampling program also included 16 new wells. Twenty monitoring wells were sampled on a monthly basis between April 2003 and March 2004, with sampling constituents developed to match prior and on-going studies, including total coliform, fecal coliform, Enterococcus, ammonia-N, nitrate-N, nitrite-N, and total Kjeldahl nitrogen and chloride.
The groundwater computer modeling was conducted by McDonald Morrissey Associates using a 3D model (MODFLOW) developed by the US Geological Survey. Results from the flow modeling were used to evaluate the direction of groundwater flow, and travel times and capture zones for the lagoon and ocean. The purpose of the solute transport modeling analysis was to estimate nutrient loading; transport modeling simulated changes of miscible contaminants in groundwater.
Amassing the Data
“Information management is a problem for many communities,” says Clark. “Existing information is available, but in paper files that are scattered in different locations.” In an effort to make it easily available to project team members, including the Malibu city staff, Stone Environmental assembled the amassed data into a Web-based information wastewater management system (IWIMS) that included information on parcels, structures on a property, ownership, OTWS permits, final approval drawings, and monitoring well sample and analytic data. Stone researchers envisioned the database as an ongoing resource for the city, and Deputy Building Official George agrees that it will be critical to implementing OTWS management associated with ordinance 242.
“IWIMS is going to be extremely useful to the city for maintaining and managing notification, reporting, and tracking operating permits,” says George. “If we had to do this manually, it would probably take five or six people. With IWIMS we’re estimating we can do it with one and a half.”
IWIMS also factored in the development of a precedent-setting Memorandum of Understanding (MOU) between the City of Malibu and LARWQCB. With IWIMS inspiring a level of confidence in the city’s data management and control capabilities, the board delegated its authority to permit residential OTWS to Malibu, using the MOU to specify practices the city is responsible for in managing these permits. The Malibu-LARWQCB agreement was the first negotiated in the state, and the board has used it as a model for other communities under its jurisdiction.
Results of the risk assessment study indicate that the area contributing groundwater to Malibu Lagoon is much smaller than had previously been assumed. The study identified 70 OWTS overlaying the alluvial aquifer that are contributing nitrogen to Malibu Creek and Lagoon; 17 are commercial or multifamily. There are approximately 161 systems that are potentially in the bacteria contributing area, five of which are commercial or multifamily. An additional eight systems, all residential, are located in both contributing areas. Civic Center groundwater appears to be vulnerable to nitrogen loading, with overall estimated nitrogen levels generally consistent with previous studies. Total nitrogen concentration in approximately 30% of the monitoring wells exceeds the standard of 10mg/L, and total nitrogen concentrations in 40% of the monitoring wells appeared to be elevated above background levels. Bacteria was present in groundwater in areas with and without OWTS, and the study found shallow groundwater appeared to be significantly influenced by bacteria from sources other than onsite systems. And although many of the onsite systems in the Civic Center area are providing adequate bacteria reduction, some don’t appear to meet targeted standards.
Surprising Flow Rates
One of the most unanticipated study findings was the variation in groundwater flow rates from OTWS to the receiving waters, which ranged from half a year to 50 years. In consideration of this information, researchers concluded systems within six months travel time to surface waters, or with inadequate separation to groundwater, or excessive wastewater loading rates pose the greatest risk to water quality and should be considered a high priority for whatever area-wide management is selected.
“The most important information accruing from the risk assessment study,” says Douglas, “was definition of the boundaries of the areas that contribute groundwater to the lower Malibu Creek subwatershed. The risk assessment study determined that the creek and lagoon are at risk for nutrients but not bacteria from onsite systems, which suggests that one management option would be to focus on the commercial systems within the contributing areas and on nutrients. The properties on the beach within six months travel time for bacteria would be the next high priority area.”
A total of 216,000 gallons per day (gpd) of wastewater flow is produced in Civic Center subareas ranked high priority for community wastewater management. To develop potential management options, the MODFLOW groundwater flow model used in the risk assessment study was modified to assess the potential water quality implications of various combinations of options for wastewater collection, treatment, and dispersal, including sites that might require onsite nitrogen removal.
As feasibility study consultants, Questa Engineering has assumed that the treatment plant would be a state-of-the-art facility designed to produce tertiary quality water suitable for unrestricted recycling in accordance with Title 22 of the California Code of Regulations; also that it would provide a high level of nitrogen removal to meet a maximum standard of 10 mg/L with an average concentration of approximately 5 mg/L.
“Dispersal and recycling capacity can be provided for a community wastewater system within the Civic Center for a service area with average wastewater flows up to approximately at least 200,000 gpd,” says Douglas, “and in a way that would provide compliance with the bacteria and anticipated nitrate TMDL for Malibu Creek and Lagoon.”
Collection Selection
For collection, conventional gravity sewers with sanitary lift stations were eliminated as poorly suited to the generally flat terrain and high groundwater conditions in areas of the Civic Center, and a septic tank effluent pump system (STEP) was instead recommended. “Because there’s not a lot of topographical relief here,” says Douglas, “it makes sense to utilize the onsite septic tanks to separate out solids and collect only the liquid wastewater. There’s less solids to deal with at the reclamation facility, and because you’re pumping clear effluent you can use small-diameter pipe. Also, the definition of decentralized is to have your generation, treatment, and dispersal in reasonably close proximity to each other. The proposed collection system does this.”
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MAP: STONE ENVIRONMENTAL INC. |
| The Study Area is outlined in red. |
Recommended treatment options include a sequencing batch reaction (SBR) and a membrane batch reactor (MBR). Both have good records to indicate that either could meet Malibu’s treatment objectives and neither requires a large area. Both could be easily enclosed for visual screening and to control noise and odor. Although the study did not determine a strong preference between SBR and MBR technology, researchers did suggest that SBR would be less costly and would allow more design flexibility. In addition, two types of constructed wetlands were evaluated: a subsurface flow constructed wetland (SFCW) and a Tidal Flow Constructed Wetland (TFCW). The former appears limited in its potential for nitrogen removal and by its relatively higher land use requirement when compared to other technologies. TFCW is a closed system that alternates water levels to provide alternating saturated and unsaturated conditions suitable for nitrogen removal. However, TFCW would not provide tertiary water quality and would need to be followed by a polishing process similar to a membrane reactor.
The third component of the proposed management system, dispersal of the treated effluent, will provide managers their thorniest challenge. “Everything is limited by the dispersal of what we’re going to produce,” says George.
“The goal would be for commercial development and multi-family housing to take back their treated wastewater ,while effluent from single family homes would be dispersed to designated sites,” Douglas explains. Potential disposal sites in the Civic Center that have significant capacity for dispersal via the two methods of plant uptake and percolation to groundwater were identified. Next a detailed water balance of the area was conducted using El Niño conditions in the 1997--98 water year, the idea being to determine potential plant uptake under conservative conditions. (Malibu typically receives 14 inches of rainfall a year, which falls mostly during the winter months.)
“There’s a finite capacity here dictated by the soils and the climate,” says Douglas. “We’re working with a hydraulic limitation in that the geology here is very complex. Because we have limited capacity at dedicated dispersal sites, we will insist that properties maximize their evapotranspiration potential. The Civic Center has approximately 35 acres potentially available for irrigation disposal in three sites, for a combined capacity of approximately 163,000 gpd. So it will be very important that existing development be able to take back what it generates, to the extent possible, and any new development will have to take back all its wastewater, with the capacity to reuse 75% of design flows via irrigation and indoor reuse, while providing capacity to percolate 100% of the water in the ground on the site.” This requirement, Douglas points, out satisfies two other community concerns: the system conserves water and is “growth neutral.”
As one problem was addressed, another fundamental remained. The risk assessment study had indicated OTWS were not the sole source of bacteria in the Civic Center groundwater, and this forced researchers to consider management of other contributers if the city’s goal is to really clean up the lagoon. “In this particular setting,” says Douglas, “stormwater has more bacteria impact and wastewater has more nutrient impact. So if you do one and not the other, you’ve only addressed half the question. And although the city has been planning a stormwater treatment facility for the area, because of land availability it was sized for dry weather flows. We looked at what would happen if we had more land available. We modeled groundwater impacts from a range of distributed reclaimed water reuse and percolation alternatives at the same time we modeled the hydrology of the area feeding into the Civic Center, looking at different kinds of storm events. The goal was to not use land for wastewater management that could be better used for stormwater management. The primary focus of a combined wastewater/stormwater approach for Malibu is the possible development of wetlands, stormwater retention, and other water features, and increased riparian habitat, which Malibu residents are enthusiastic about.”
Looking Ahead
What’s the reaction among stakeholders to the results of the risk assessment and subsequent feasibility study? Still to come is determination of who foots the $50 million bill for the project, which includes the cost of purchasing land for a treatment plant and designated dispersal and stormwater management sites. Craig says the staff is considering various options including grants, a bond measure and individual property assessments. Whatever choice is made, it will have to pass muster with residents.
“I definitely think that we have had success with the Regional Water Quality Control Board, and with groups such as Heal the Bay and Santa Monica Baykeeper,” says City Manager Lichtig. “The board and the Santa Monica Bay Restoration Commission were critical stakeholders in developing the scientific protocols we used. To me this is a journey, and all these steps along this journey are helping us achieve a better tomorrow for Malibu and for the beachgoers the city welcomes every year.”
Dr. Mark Gold, executive director of Heal the Bay, says his organization is working hard with the City of Malibu to accomplish the studies’ recommendations, including the centralized treatment plant, stormwater treatment plan, and what Gold described as a true water use program. “This is one of the few times in the last decade,” said Gold, “where the city and Heal the Bay have been on the same page. We’re going to do everything we can to help pull this off.”
Journalist PENELOPE GRENOBLE O'MALLEY is a frequent contributor to environmental publications.
Ed. Note: Onsite Water Treatment will continue to monitor Malibu’s progress managing its OTWS and will keep our readers informed.
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