Development in the coastal zone must conform to the policies and standards of the California Coastal Act and, if applicable, the Commission-certified Local Coastal Program (LCP) of the government with jurisdiction in the area of the proposed development. The Coastal Commission reviews projects on a case-by-case basis and considers the environmental benefits and coastal zone impacts of all projects. The following types of potential coastal zone impacts should be considered and addressed for desalination plants:
These impacts, related Coastal Act policies, and potential mitigation measures are discussed below.
Construction activities could result in the following types of coastal zone impacts: air emissions; disturbance of dune, surf zone, and seafloor ecology; disturbance to seabirds, marine mammals, other land and marine species, and their habitats; disturbance to archaeological and paleontological resources; erosion; interference with public access and recreation; noise; nonpoint source pollution; and obstruction of views by machinery, piping, or tall structures.
Significant construction impacts may also occur away from the desalination plant site if long pipelines are needed for seawater intake or for distribution of the product water, or if power transmission lines or distribution facilities must be built. Pipeline routes may have adverse impacts on benthic habitats such as surfgrass and rocky tidepools. Streambed or lagoon ecosystems along proposed power transmission line routes would be of particular concern. Any proposed diking, filling, or dredging activities in open coastal waters, wetlands, or estuaries must be in compliance with Section 30233 and other sections of the Coastal Act.
- Minimize the numbers and lengths of pipelines and power transmission lines;
- Site pipeline routes to minimize impacts to sensitive areas;
- Site plants in locations where existing intake or outfall structures may be used or minimize the size of new seawater intake and outfall structures; and
- Incorporate mitigation measures commonly required for construction activities (e.g., construction schedules that minimize impacts on public access and recreation, visual screening, noise buffers, siting away from high resource areas, limited construction zones and corridors, etc.).
Desalination plants require significant amounts of energy for their operation. For example, the Santa Barbara RO desalination plant was using about 6,600 kWh of electricity per acre-foot of water produced before the plant shut down operations. In most cases, RO plants are less energy intensive than distillation plants.
Section 30253(4) of the Coastal Act requires that new development minimize energy consumption. Consequently, the Commission will review desalination plant proposals to determine if a project incorporates means to conserve energy or reduce energy use. The Commission should also consider the secondary impacts resulting from the increase in power production needed for the desalination plants. These impacts include higher levels of air emissions, increased entrainment and impingement of fish from intake of cooling water, higher levels of cooling water discharges to the ocean, and effects from additional transportation of oil and gas.
Cogeneration is a process in which exhaust steam from electricity generating plants is used for another purpose. If a desalination plant uses cogeneration to supply part of its energy needs, the plant could reduce both its demand for power and the associated environmental impacts of power generation.
For example, a distillation plant can use the heat in a power plant's exhaust steam to evaporate feedwater. A cogeneration power plant that operates with a distillation plant, however, must be specially designed for that purpose. A distillation plant that is dependent on a power plant's exhaust steam for its operation would not be able to operate when the power plant is not operating. (The capacity factor for most thermal power plants is not more than 75%.)
An RO plant may also use exhaust steam from a power plant to heat feedwater slightly (too high temperatures can damage the RO membranes). In this application, the RO plant depends on electricity to power its high pressure pumps; the thermal heat from the power plant improves the production of the desalination process but does not power the plant. Therefore, RO plants can operate with or without the heat from the power plant, and the power plant does not have to be specially designed to fit with the desalination plant. Cogeneration can also be used in RO plants by using exhaust steam in a steam turbine to power the pressure pumps. (Figure 3.)
A third option for cogeneration is in a hybrid plant that uses both RO and distillation (e.g., MSF) technologies. Existing power stations can and have been "retrofitted" in the evaporators and RO units to achieve a hybrid plant, thus eliminating the need to construct a new desalination facility. The MSF plant draws waste steam from a thermal power station and uses the energy in the steam to preheat seawater which is then distilled in the MSF unit. The RO unit uses electricity from the power station and operates during periods of reduced power demand, thus optimizing the overall efficiency of the entire operation. Advantages of the hybrid design include: reduced energy costs (the distillation portion would have energy savings from cogeneration, while the RO portion could use electricity from the grid to produce water when the power plant is not in operation) and reduced capital and operating costs from reuse of cooling water, feedwater or steam.
Although distillation plants usually have higher overall energy requirements than RO plants, the potential energy savings from cogeneration are greater for distillation plants. According to one estimate, use of cogeneration at an RO plant that produces 15,000 AF/yr could reduce electricity consumption by about 7%. (Source: Southern California Gas Company, 1991.) According to another estimate, for an RO plant that produces 50,000 to 60,000 AF/yr of water and that uses the exhaust steam from a power plant to heat the feedwater 20°F, the electricity demand could be reduced 10 to 15%; for a distillation plant of the same capacity that uses cogeneration, the reduction in demand for additional energy sources could be 20 to 25%. (Source: pers. comm. with Mark Skowronski, SCE, 1991.)
One option being considered is to design and build a new power plant to operate in conjunction with a desalination facility. A power plant designed specifically for cogeneration with a desalination plant could produce lower air emissions than existing power plants if the new plant is fired with natural gas and uses the latest air emission control technologies. However, construction and operation of a new power plant could have a number of adverse impacts including air emissions, impacts on marine resources, degradation of visual and recreational opportunities, disturbance of sensitive habitat areas, and increased growth in coastal communities.
One method for reducing energy use in all types of desalination plants is by employing energy recovery. In the case of distillation, heat in the brine and fresh water leaving the plant is used to preheat the feedwater. In RO, energy is recovered by converting hydraulic pressure in the brine to electricity or by transferring this energy to the feedwater.
Solar energy could also be used to heat the water for a small distillation plant. Solar energy is expensive compared to other desalination technologies and may require a larger area for the solar energy gathering and conversion devices; however, this technology would not produce toxic air emissions and would not consume exhaustible resources.
Ocean Thermal Energy Conversion (OTEC) is an offshore technology for producing electricity where the difference in the temperatures of deep ocean water and warm surface water is used to vaporize liquid ammonia for turning a turbine. The turbine drives a generator that provides power for the water pumping system. Warm surface water is evaporated in a partial vacuum and the condensed fresh water is shipped back to land in a tanker from the offshore location (e.g., a floating production platform). OTEC was evaluated by various federal agencies in the 1960s and 1970s and was found to be commercially viable, though expensive. One company has recently developed a proposal to use OTEC, but so far none of the municipalities or companies that are planning desalination plants have decided to use this technology. OTEC would not produce toxic air emissions and would not consume exhaustible resources, other than from the tankers used to ship the water.
Figure 3. Cogeneration options.
- Preference for desalination technologies and plant designs that reduce energy consumption;
- Use of renewable energy resources, when feasible; and
- Siting of the proposed plants near to power plants capable of cogeneration.
Section 30253(3) of the Coastal Act requires that new development be consistent with requirements imposed by an air pollution control district or the State Air Resources Control Board as to each particular development. In general, desalination plant air emissions consist only of discharges of nitrogen and oxygen from distillation plants that use deaeration processes to reduce corrosion, discharge of the air ejector system (thermal plants), or discharge of the degassifier (RO plants).
The production of energy for use in desalination plants, however, will increase air emissions. In addition, substantial increases in air emissions could occur if a new power plant or cogeneration facility is built for a desalination project. Some of the proposed plants would be built in areas where air quality violations already exist; consequently, the plant designs should include consideration of measures to offset air emissions from energy production.
- Compliance with local Air Pollution Control District and State Air Resources Board standards;
- Preference for reduced energy use, as discussed above; and
- Use of alternative energy sources to minimize air emissions.
Marine resources in the vicinity of a desalination plant can be affected by the constituents present in the waste discharges, by the waste discharge method used, and by the process of feedwater intake. Coastal Act Sections 30230 and 30231 provide for the maintenance, enhancement, and restoration of marine resources and biological productivity. Specifically, Section 30230 provides:
"Marine Resources shall be maintained, enhanced, and where feasible restored. Special protection shall be given to areas of special biological or economic significance. Uses of the marine environment shall be carried out in a manner that will sustain the biological productivity of coastal waters and that will maintain healthy populations of all species of marine organisms adequate for long-term commercial, recreational, scientific, and educational purposes."
Section 30231 states in part:
"The biological productivity and the quality of coastal waters, streams, wetlands, estuaries, and lakes appropriate to maintain optimum populations of marine organisms and for the protection of human health shall be maintained and, where feasible, restored through, among other means, minimizing adverse effects of waste water discharges and entrainment...."
In addition to these Coastal Act policies, Section 307(f) of the Federal Coastal Zone Management Act (CZMA) provides that for purposes of the Commission's exercise of its consistency review authority under CZMA Section 307(c), federal, state, and local provisions established pursuant to the Clean Water Act (CWA) shall be incorporated into state coastal management programs and shall be the water pollution control requirements applicable to such program. Consequently, a number of the general policies and objectives of the California Ocean Plan are incorporated directly into the California Coastal Management Plan (CCMP). In addition, Coastal Act Section 30412(a) specifies that the provisions set forth in Section 13124.5 of the State Water Code shall apply to the Commission, while Coastal Act Section 30412(b) states that the SWRCB and the RWQCBs are the state agencies with primary responsibility for the coordination and control of water quality.
The constituents of water discharged from desalination plants depend in part on: the desalination technology used; the quality of the intake water; the quality of water produced; and the pretreatment, cleaning, and RO membrane storage methods used.
All desalination plants use chlorine or other biocides, which are hazardous to marine resources, to clean pipes and other equipment and sometimes to pretreat the feedwater. The State RWQCBs do not permit chlorine or other biocides to be discharged directly into the ocean. Consequently, these chemicals would have to be neutralized before discharge.
Alternative treatment processes and technologies that eliminate the need for biocides can also be used. For example, ultraviolet light may be used instead of biocides to remove biological organisms. Ultraviolet light is more expensive than biocides but is an effective method. Similarly, the disc tube RO technology, which has been used primarily in Europe, does not require use of pretreatment chemicals to remove particles and organisms. This technology, unlike the more common spiral wound RO technology, does not have a mesh net between layers of the RO membranes (the net catches particles and biological organisms and can clog the membranes). The disc tube technology, however, is more expensive than the spiral wound technology and, according to one source, is unproven on seawater desalination. (Source: Dick Sudak, Separation Processes, 1992.) The need for pretreatment chemicals and processes can also be eliminated or reduced substantially if feedwater is taken in from beach wells or infiltration galleries, which serve as natural filters. (An infiltration gallery has perforated pipes arranged in a radial pattern in the saturated sand onshore, and water in the sand seeps into the perforated pipes.)
Some RO plants use a coagulant (usually ferric chloride), as part of the pretreatment process to cause particles in feedwater to form larger masses that can be more easily removed with filters before the water passes through to the RO membranes. The pretreatment filters are backwashed with filtered seawater every few days, producing a sludge that contains filter coagulant chemicals. Options for disposal of coagulants, particles and sludge removed from the filters include discharge with the brine, transport to a landfill, or a combination thereof. A desalination plant would have to include a process for removal of the particles if they are to be discharged with the sludge. Ferric chloride is not toxic but may cause a discoloration of the receiving water if discharged.
Desalination plants often use anti-scalants to remove scales that form on the plant's interior. Most plants use a polyacrylic acid as an anti-scalant, which is not hazardous to marine resources. MSF distillation plants may use a small quantity, about 0.1 milligrams for each liter of water, of an antifoaming agent (similar to cooking oil) to reduce the foam produced when the water boils.
In RO plants, cleaning and storage of the membranes can produce potentially hazardous wastes. The membranes must be cleaned at intervals from three to six months depending on feedwater quality and plant operation. The membrane cleaning formulations are usually dilute alkaline or acid aqueous solutions. In addition, a chemical preservation solution (usually sodium bisulfite) must be used if the membranes are stored while a plant is shut down. These chemicals should be treated before discharge to the ocean to remove any potential toxicity.
In general, discharges from desalination plants may have the following types of potentially adverse constituents and qualities:
- Salt concentrations above those of receiving waters (seawater salt concentration is about 35,000 ppm; desalination plants discharge brine with 46,000 to 80,000 ppm). Salt concentrations may be reduced by mixing desalination plant discharges with other discharges, such as wastewater;
- Temperatures above those of receiving waters (about 5° F increase at the point of discharge) for discharges from distillation plants; (Source: Baum, 1991.)
- Turbidity levels above those of receiving waters;
- Oxygen levels below those of receiving waters from deaeration to reduce corrosion (distillation plants only);
- Chemicals from pretreatment of the feedwater (these may include biocides, sulfur dioxide, coagulants (e.g., ferric chloride), carbon dioxide, polyelectrolytes, anti-scalants (e.g., polyacrylic acid), sodium bisulfite, antifoam agents, and polymers);
- Chemicals used in flushing the pipelines and cleaning the membranes in RO plants (these may include sodium compounds, hydrochloric acid, citric acid, alkalines, polyphosphate, biocides, copper sulfate, and acrolein);
- Chemicals used to preserve the RO membranes (e.g., propylene glycol, glycerine, or sodium bisulfite);
- Organics and metals that are contained in the feedwater and concentrated in the desalination process; and
- Metals that are picked up by the brine in contact with plant components and pipelines.
Concern over the potential adverse effects to marine resources of desalination plant discharges is tempered by the following factors: the total volume of brine being released; the constituents of the brine discharge; and the amount of dilution prior to release. For example, the potential for environmental damage from small amounts of brine discharge (less than 1 MGD) may differ considerably from the potential impacts associated with discharges greater than this amount. Discharge of concentrated brine in large amounts requires more careful consideration of potential environmental impacts than do smaller brine discharge volumes. (Source: Dr. Phillip McGillivary, NOAA, 1992.)
The constituents of discharges of particular concern for marine organisms include biocides, high metal concentrations, and low oxygen levels. Not all desalination plant discharges contain these constituents; however, where detected, these constituents should be removed or neutralized to acceptable levels before discharge or else adequately diluted in the ocean in accordance with RWQCB NPDES permit requirements for compliance with the California Ocean Plan and Regional Basin Plans.
The high salt concentration of the discharge water and fluctuations in salinity levels may kill organisms near the outfall that can not tolerate either high salinity levels or fluctuations in the levels (similarly, if a temporary desalination plant is shut down, the organisms that have become accustomed to high salinity levels and/or salinity fluctuations may be killed). In addition, discharges from desalination plants will be more dense than seawater and could sink to the bottom, potentially causing adverse impacts to benthic communities. These effects may be significantly reduced if desalination plant discharges are combined with sewage treatment plant discharges (which are less dense than seawater) or are diluted by mixing with power plant cooling water discharges. At this time, there is considerable uncertainty about how well desalination plant discharges, either alone or combined with other discharges, will be diluted in seawater. The metals may become concentrated in the upper few micrometers of the ocean (the microlayer), which would be toxic to fish eggs, plankton, and larvae that are located there. Toxic constituents of the plume could be driven by wind or currents to become concentrated in the intertidal zone. (Source: pers. comm. with Dr. Phillip McGillivary, NOAA, 1991.)
Discharge of brine water with high salt concentration, particularly if combined with sewage effluent, may also cause sewage contaminants and other particulates to aggregate in particles of different sizes than they would otherwise. This effect influences rates of sedimentation, and is highly important for determining the well-being of benthic organisms that may be buried or burdened by an increase in deposition of unstable and/or finely suspended materials. If the particles are smaller and stay in suspension, they could interfere with transference of light in the ocean, which would diminish the productivity of kelp beds and phytoplankton. In addition, redistribution of trace metals (e.g., iron, nitrogen, and phosphorus) could change the phytoplankton community to one that is unappetizing to fish and may also be toxic (for example, by increasing the possibility or prolonging the occurrence of a "red tide" condition). Larval fish that feed on the phytoplankton could be forced beyond nearshore waters, where they may not survive. (Source: pers. comm. with Dr. Phillip McGillivary, NOAA, 1991.)
Changes in salinity and/or temperature from the brine discharges may also affect migration patterns of fish along the coast. If some fish species sense a change in salinity or temperature, they may avoid the area of the plume and move further offshore. As a result, the fish would be forced to swim a longer distance, they would leave the areas of highest food concentrations, and they would have increased exposure to predators. The potential impacts of this nature are uncertain because of limited knowledge about fish migration along the coast and uncertainty about how large the plume would have to be to cause this effect.
The brine from desalination plants can be discharged directly into the ocean or combined with power plant cooling water or post-treatment sewage plant discharges. Mixing the discharges with power plant cooling water would most likely be desirable, because the brine solution discharged would be considerably less concentrated. Mixing with sewage treatment discharges may also be preferable to direct discharge to the ocean. Brine discharge from desalination plants is more dense than seawater and could remain or fall to the ocean bottom, depending on the outfall location. Treated sewage effluent has a relatively low level of total dissolved solids, and blended brine/wastewater effluent has the potential to be closer to ambient ocean concentrations, so dispersion may be enhanced beyond a brine-only discharge. The addition of brine discharge to wastewater effluent reduces the biological oxygen demand (BOD) of the sewage effluent and has the potential to reduce the temperature of the sewage effluent. (For more information, see Woodward-Clyde Consultants, EIR for the City of Santa Barbara and Ionics, Inc.'s Temporary Emergency Desalination Project, March 1991.) On the other hand, blending the brine discharge with sewage discharges may have some undesirable side-effects, which are discussed below under Marine Resource Impacts.
Difficulties in enforcement may arise if desalination wastes are mixed with other waste streams. If the recipient of the desalination waste stream is the only party responsible for compliance with the regulatory requirements, this discharger would have to request the desalination plant operator to make changes if problems with compliance develop. If a proposed desalination plant incorporates combined discharges, the project description must identify the party or parties responsible for meeting the discharge requirements in order to avoid enforcement problems.
Intake of water directly from the ocean usually results in loss of marine species as a result of impingement and entrainment. Impingement is when species collide with screens at the intake; entrainment occurs when species are taken into the plant with the feedwater and killed during plant processes. The intake of feedwater can also affect marine resources by altering natural currents in the area of the intake structure.
The use of beach wells or infiltration galleries eliminates these impacts; however, these intake methods have not been used extensively in California, and the maximum capacity of a plant that could draw feedwater effectively from these sources is unknown. Beach wells should only be used in areas where the impact on aquifers has been studied and saltwater intrusion of freshwater aquifers will not occur. Infiltration galleries are constructed by digging into sand on the beach, which could result in the disturbance of sand dunes.
Very little information is available on the impacts of desalination plants on the marine environment. For example, few if any monitoring studies have been conducted on the marine resource impacts of discharges from plants operating in the Middle East, Saipan, the Virgin Islands, and Cuba. Although a number of brackish water desalination plants are operating in Florida, these plants are not permitted to discharge directly to the ocean because the ocean waters are shallow out to about 10 to 15 miles from shore and do not dilute the discharges adequately. The brine is discharged either into deep, confined aquifers or to saline streams or lakes that discharge to estuaries.
An extensive analysis was conducted of the impacts of ocean discharges from a MSF desalination plant that operated in Key West, Florida during the 1960s and mid-1970s. The following studies were done to characterize dispersion of the effluent: 1) measurements of the concentration of metals in marine sediments; 2) dye observations and in situ diver observations; 3) temperature inversion analysis; and 4) semiweekly analysis of water conditions, including temperature, salinity, copper, alkalinity, pH, and oxygen. In addition, the following studies were conducted to determine impacts on the biological community:
1) analysis of foraminifera, small shelled protozoans;
2) wooden settlement panels that collected organisms over known exposure times and on substrates that were uniform in size and material;
3) surveys of organisms within transects;
4) laboratory bioassays;
5) surveys of organisms within one-meter square quadrats at twenty monitoring stations;
6) transplants of selected species into particular effluent regimes to study their survival and growth;
7) analysis of biomass samples;
8) collection of benthic diatoms and protozoans in glass microscopic slides in special racks (diatometers);
9) analysis of plankton tows; and
10) Carbon 14 measurements of photosynthesis.
The studies found that the effluent mixed turbulently with ambient water at the point of discharge. The density of this mixture was greater than that of the ambient water in the harbor where the effluent was discharged, so the mixture sank to the harbor bottom, filled up the harbor basin which was deeper than the surrounding waters, and then flowed into more shallow water. The temperature of the effluent averaged about 0.5 to 0.9°F above ambient temperatures and the effluent salinity was 0.2 to 0.5% above ambient salinity. The analyses found that the changes in temperature and salinity did not by themselves cause damage to marine organisms, but did result in lower mixing rates for copper in the effluent. Copper concentrations, which were often 5 to 10 times ambient levels, were found to be toxic to marine organisms. The studies also found that effluent discharged following startup of the plant after maintenance procedures had higher copper concentrations and caused more biological damage than effluent discharged during normal operations. (The high levels of copper detected may have due to a copper grating that was later replaced, not to the desalination process itself. The internal components of many modern desalination plants are composed of titanium rather than copper.) A variety of organisms were adversely affected by the effluent. For example, sea squirts, various species of algae, bryozoans, and sabellid worms were excluded from the harbor during at least a portion of the study; no live lamellibranchs were found by the end of the study; many dead shells of various clams and oysters were found; and echinoids were killed in the shallower waters near the harbor. Two or three of the species that survived well in the area near the effluent did so because they were able to avoid the peaks associated with start-up and were able to tolerate the steady-state effluent conditions. (Source: Chesher, 1975.)
In California, discharges from the desalination unit at the Chevron Gaviota Oil and Gas Processing Plant have been monitored in accordance with the plant's NPDES permit since January 1987. The discharges have been relatively small, because the unit has been operating at reduced capacity. Discharge constituents monitored include: dissolved oxygen, copper, iron, nickel, pH, temperature, total chlorine residual, toxicity concentration in marine organisms (bioassays), arsenic, cadmium, lead, hexavalient chromium, mercury, silver, zinc, cyanide, suspended solids, particulates, grease and oil, settleable solids, flow rate, and turbidity. A plume trajectory study was not conducted, because the computer models used by the RWQCB at the time could not be applied to plumes with salinity levels greater than that of the ocean. (New computer models have since been developed.) The monitoring results to date show no violations of the permit except for high levels of zinc. (The high levels may have been a result of high levels at the intake.) Recent monitoring has shown zinc levels within permitted standards.
The Marin Municipal Water District built a pilot plant and conducted some studies of the impacts of discharges from this plant on San Francisco Bay. Bioassay studies were conducted on two waste streams - the concentrate discharged directly to San Francisco Bay, and the concentrate mixed with effluent from the Central Marin Sanitation Agency (CMSA). The studies performed for each waste stream were the 7-day chronic Menidia beryllina test, the 96-hour Skeletonema costatum growth test, the 48-hour bivalve larvae test, and the 96-hour acute Citharichthys stigmaeus test. The studies found that to achieve the No Observable Effect Concentration (NOEC) for these organisms, the dilution ratio for Bay water to effluent would have to be 23:1 for unmixed concentrate and 20:1 for concentrate mixed with the CMSA effluent. The study also found that the quality of the CMSA effluent was improved by mixing it with the pilot plant discharges, because the salinity increased and the buoyancy was reduced. (Source: Boyle Engineering Corp. for the Marin Municipal Water District, 1991.)
The Southern California Coastal Water Research Project (SCCWRP) Toxicology Laboratory recently completed a study of potential effects resulting from the discharge of effluent from the City of Santa Barbara desalination plant. The research was conducted for use in an EIR for the City's Long-Term Water Supply Program. The SCCWRP conducted experiments to measure the effect of elevated salinity on sensitive marine species likely to be found in the vicinity of the Santa Barbara discharge to determine if salinity stress affected an organism's sensitivity to sewage toxicity, and to document the level of toxicity in brine resulting from chemicals added during the desalination process. According to the SCCWRP, the experiments indicated that a salinity of 36.5 g/kg (the maximum expected to occur at the Santa Barbara discharge site) did not produce measurable effects on amphipod survival or giant kelp growth; however, an inhibition of sea urchin embryo development at this salinity was measured. Additional studies are needed to confirm the data and determine their applicability to other discharge situations. (Source: SCCWRP, Coastal Currents, Vol. 2, No. 1, Summer 1993.)
Other existing desalination plants in California have been operating only for only a short time or are very small, so the impacts of discharges from these plants cannot be compared with potential impacts from larger plants. The Santa Catalina Plant, which began operating in June 1991, is located near Areas of Special Biological Significance (ASBS), as designated by the SWRCB. The results of monitoring studies for this plant should be reviewed closely by the Commission staff to determine whether any adverse impacts have occurred and whether the staff should recommend that any changes be made to mitigation and monitoring requirements in the plant's NPDES permit.
The following types of pre-operational baseline information would be useful for the Coastal Commission to have in evaluating the marine resource effects of desalination plant discharges.
- Studies of the effects of discharges from a pilot plant built where a final plant will be located;
- Measurements of dispersion rates to determine how readily brine will disperse in the ocean;
- Laboratory studies to determine the effect on particle size of mixing brine and sewage water;
- Laboratory studies to determine the dispersion of metals;
- Tracer studies using small quantities of nonradioactive isotopes of metals to determine the quantity of metals that end up in the ocean microlayer;
- An inventory of marine organisms in the area of the outfall; and
- A long-term inventory of marine organisms in the microlayer.
(Sources: Post-operational monitoring recommendations from Woodward-Clyde Consultants, 1991; pers. comm. with Dr. Phillip McGillivary, NOAA, 1991; pers. comm. with Sorrel Davis, RWQCB, Central Coast Region, 1991.)
- Secchi Disk Depth Test to measure how much light is penetrating the water column (to determine whether there may be an impact on the benthos);
- Measurements of impacts on habitat in the microlayer;
- Measurements of impacts on fish in the water column;
- Plume trajectory evaluation of depth, temperature, salinity, and density;
- Nontoxic dye tests to measure dilution;
- Sampling of sediments; and
- Measurements of salinity at various offshore sampling locations.
(Sources: Woodward-Clyde Consultants, 1991; pers. comm. with Dr. Phillip McGillivary, NOAA, 1991.)
- Intake and outfall siting and design to avoid sensitive locations;
- Low flow velocities at intake channels and through intake structures to minimize entrainment and impingement of marine species and to reduce the need for pretreatment;
- Intake design to reduce the potential for entrainment and impingement (e.g., screens at the intake to reduce entrainment);
- Use of onshore intake wells or infiltration galleries to eliminate entrainment of marine species;
- Outfall siting and design to ensure an adequate mixing rate and dilution volume to minimize adverse impacts;
- Outfalls to the open ocean, not to estuaries or other areas with limited water circulation;
- Use of pretreatment techniques that minimize or eliminate the need for hazardous chemicals;
- Removal of hazardous constituents in the brine waste stream prior to discharge;
- Evaluation of whether landfill disposal would have more or less impacts than ocean disposal;
- Mixing with sewage treatment plant or power plant cooling water discharges (when mixing of discharge streams is intended, ensure that a desirable proportion of each discharge is maintained to enhance dilution);
- Use of pipes that minimize the corrosion of hazardous substances (polyethylene or titanium is preferable to copper nickel); and
- Timing of operations to minimize impacts (e.g., intermittent operations to minimize discharges at times during the lunar month when fish migrations are highest; or operation only during the winter season when the ocean is more turbulent, and discharges would be more readily diluted).
Section 30250(a) of the Coastal Act requires that new development be located within or next to existing developed areas able to accommodate such development, or in other areas with adequate public services. Section 30254 provides that new public works facilities be "designed and limited to accommodate needs generated by development or uses permitted consistent with the provisions of this division." If applicable, new development must also conform to the policies and standards contained in the Commission-certified LCP of the local government with jurisdiction in the area of the proposed development. Such policies may relate to the allocation of limited water resources or to other regional water and growth management goals.
The construction of desalination plants to meet water supply needs in the state may result in growth-inducing impacts. Limited water is often the major constraint to development in many parts of the coast. Therefore, new desalination projects in coastal areas could lead directly to new development and a resulting increase in population migration to coastal areas. New development served by the plant could in turn interfere with long-term regional goals for growth control. For example, desalination plants built in rural areas could lead to growth in these areas rather than within existing urban boundaries; desalination plants built in urban areas may also change the character of these areas.
The Coastal Act mandates that certain types of development receive priority over other development. These higher priority developments include: lower cost visitor and recreation facilities (Section 30213); visitor-serving commercial recreational facilities designed to enhance public opportunities for coastal recreation (Section 30222); aquaculture facilities (Section 30222.5); facilities serving the commercial fishing and recreational boating industries (Section 30234); and coastal-dependent development (Section 30255). The most effective way to ensure proper implementation of these and other Coastal Act or LCP development priorities in areas where desalinated water may need to be produced is to achieve these development priorities through zoning and other standard land use regulatory devices. Because public ownership and operation of desalination plants can also be expected to assist in ensuring that water allocations will occur in a manner that is consistent with the foregoing development priorities, the Commission may need to consider special or additional conditions in connection with any approvals it may grant for privately-owned desalination plants.
Potential growth-inducing impacts should be considered for those communities that receive the water, as well as those where the desalination plants will be located. The Commission and local governments should consider, on a regional scale, the pros and cons of building a number of small plants versus a few larger ones. Growth-inducing impacts may be more significant for projects that operate for many years, as compared to those that are short-term projects for drought relief. The Commission should consider the potential long-term impacts of extending the life of projects that are presently intended for short-term use.
- Strong, community-wide water conservation and reclamation measures to reduce the need for new water projects;
- Siting of plants near existing seawater intake facilities (e.g., intake pipelines or seawater wells);
- Siting of plants near existing energy sources and distribution systems;
- Siting of plants near existing fresh water distribution mains to distribute the product water;
- Sizing of plant capacity to be commensurate with the planned level of development authorized by the certified LCP for the area;
- Assessment of the long-term growth-inducing impacts of proposals for long-term projects and for projects that are intended to be temporary, but may become permanent in the future; and
- Coordination of project approval with regional growth management goals.
The following potential coastal zone impacts should be considered in evaluating proposals for desalination plants:
- Impacts to the marine environment from accidental discharges of hazardous materials;
- Impacts to commercial fishing and navigation during construction of intakes and outfalls and during operation;
- Interference with public access and recreation from pipelines, wells or other structures;
- Visual impacts - towers for most distillation plants will be 30 to 46 feet high; RO plants are usually not more than 15 to 20 feet high;
- Impacts resulting from geologic hazards and seismic activity;
- Noise from pumps during operation;
- Impacts on the desalination process from pollution near the intake pipes (e.g., discharges from other sources, oil spills, etc.);
- Use of landfill disposal space for solid waste disposal;
- Impacts from increased chloride concentration - RO product water may have higher levels of chlorides than other water sources (using product water with high levels of chloride for irrigation may result in more water use and adverse impacts on soils; chloride levels can be reduced by employing more passes [RO plants] or by using a different process [e.g., MSF, MED, VC]); and
- Cumulative impacts of the desalination plants in the coastal zone.
- Quality control procedures and personnel training to avoid accidents;
Secondary containment for chemical feed lines and provisions for
leak detection;
- Notification of commercial fishing interests and the U.S. Coast
Guard prior to construction;
Placement of navigational buoys on any new intakes and outfalls;
- Provisions for public access and timing of construction to avoid peak recreational periods;
- Architectural design and natural buffers to reduce visual impacts;
- Preliminary siting studies of potential geologic hazards conducted by geologists or engineering geologists licensed in the state of California;
- Equipment enclosures to reduce noise levels;
- Siting to avoid pollutants near the intake; and
- Recycling or reuse of solid wastes.
Return to previous chapter,
Chapter 2: Coastal Desalination Projects in California
Go to next chapter, Chapter 4: Regulatory Authority and Legislative Issues Related to Desalination Plants
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in California Table of Contents
Go to Seawater Desalination
in California Glossary
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