Advanced Wastewater Treatment
Pebble Beach probably is the most famous golf course in the United States. On the world scale of recognition, it has to rank right behind the links at St. Andrews in Scotland, known as the home of the game. Now it has gone one up on its distant cousin across the ocean. Its greens and fairways are being watered with tertiary treated effluent pumped through a new pipeline from a wastewater plant which recently has gone through a major modernization and expansion.
Actually, eight golf courses, a golf practice range, an equestrian center, and the athletic fields at a private school are benefitting from this ambitious decade-long project. And another course currently is in the planning stages. All these facilities are located on the scenic Monterey Peninsula near the well-known tourist towns of Carmel and Monterey, a hundred miles or so down the California coast from San Francisco.
An example of a successful public-private partnership, the $34-million project involved four sponsoring entities: the Carmel Area Wastewater District (CAWD), Pebble Beach Community Services District (PBCSD), Monterey Peninsula Water Management District (MPWMD), and the privately-owned Pebble Beach Company (PBC). The first two of these, the CAWD and the PBCSD, are owner/operators of the system, and the Pebble Beach Company is a fiscal sponsor.
The new facilities were designed by Parsons Engineering Science Inc. of Alameda, California, which also handled construction management aspects of the undertaking. The system produces about 800 acre-feet of reclaimed wastewater annually, which is used to irrigate the golf courses and other recreational areas as noted. This supply is replacing an equivalent quantity of potable water that was previously applied to these grassy areas. And another consequence of diverting the high-quality effluent to a useful purpose is that about 700,00 gallons of secondary effluent does not get discharged to Carmel Bay every day.
Final approval for the project was obtained in December of 1992, but the work really began in June, 1986, when planning, financing and engineering was initiated. Construction required about 18 months, and startup and dedication took place in September of 1994. The main elements of the project were
- Construction of a tertiary treatment section on the site of the existing CAWD wastewater plant located at the southern end of the peninsula about a mile from downtown Carmel. This 1.8-mgd-capacity facility receives the secondary effluent and treats it to tertiary level with alum and polymer additions, coagulation, flocculation, filtration, chlorination and dechlorination. The finished quality is perfectly suitable for this type of irrigation use, and the practice is becoming very common in California and other states.
- Upgrade of the existing secondary plant to improve its reliability and the quality of the effluent it produces. This included the construction of an aeration basin, a diffused air system, a blower building, and an anoxic selector structure.
- Installation of about 38,000 ft (over seven miles) of an 8- to 24-in.-diam cement mortor-lined steel reclaimed water transmission pipe-line, along with a 2.5 million gallon storage tank, a high-lift pump station, and a booster pump station and interconnecting line to the local drinking water supply system for emergency backup.
- Modifications to existing irrigation systems at the user sites to separate the potable supply from the new reclaimed water network.
Why the Switch to Reclaimed Wastewater?
Rainfall is the resource upon which the Monterey Peninsula depends for its water supply needs. But since there is not sufficient surface storage capacity in the area, the peninsula is easily affected by climatic conditions in its Pacific Coast location. In what could be described as normal and wet years, the water supply exceeds demand. However, since the area is vulnerable to variations in climate which directly influence local surface water and groundwater quantities, it can be affected severely by multi-year drought conditions.
While the agency does not own or operate any water production or distribution facilities, the Monterey Peninsula Water Management District is directly involved in the drinking water supplies for the area by managing the production and distribution operations. MPWMD's service area takes in most of the peninsula.
Two raw water sources are used to supply the area. The first is the Carmel River from which surface water is withdrawn. It is stored in two reservoirs-The San Clemente and the Los Padres. And groundwater is extracted from municipal and private wells in Carmel Valley and the Seaside coastal area.
A number of the private wells are owned by the California-American Water Company (Cal-Am), which treats and delivers about 80 percent of the drinking water on the peninsula. Other producers include the Seaside Water System, small water distributers, and private owners.
Twice since 1976 the area served by the MPWMD has experienced extended mandatory water rationing: once for 18 months from '76 to '78, and again from '89 to '91 for a period that lasted for 28 months. The District concluded that additional water sources were needed to prevent future rationing incidents, and to stop continued adverse environmental effects along the Carmel River which were the result of water management practices in the past.
Since 1983 the District has been developing plans for a long-term water supply. They would involve the construction of a new dam and reservoir on the Carmel River. The project would provide water in quantities large enough to support the planned growth and buildout conditions anticipated in the service area of MPWMD, as well as ensuring an adequate flow of water for restoration of the river. In addition, near-term water supplies have been considered, and the District concluded that new production wells, seawater desalination, and additional wastewater reclamation facilities should be considered.
The New Distribution System
Figure 1 illustrates how the new pipeline stretches northward from the CAWD wastewater plant in the south to the area where the golf courses and other recipients of the reclaimed effluent are located. Not shown on the map, but familiar to the millions of people who have visited the area, is the 17-mile drive which essentially encircles all of these facilities, and is famous for its scenic views, especially on the ocean side. The northern end of the seven-mile pipeline is close to the golf course known as The Links at Spanish Bay.
Construction scheduling of the project had to take into account traffic management, since the route of the pipeline went through existing roads and road rights-of-way in Carmel, Pebble Beach, and several unincorporated areas. The reclaimed water storage tank was built adjacent to the maintenance yard of the Poppy Hills Golf Course. This 2.5 million gallon tank is 35 ft high and 115 ft in diameter, and holds enough water to serve the irrigation needs of the various users on peak demand days.
A connection between the storage tank and the drinking water distribution system will take care of an emergency situation if the wastewater plant should fail or be reduced significantly in capacity. This modification included also the construction of a potable water pumping station to handle the transfer from one system to the other.
Modifications to existing irrigation systems at the golf courses and other recreational sites permitted conversion from the potable to the reclaimed supply. These included disconnection from the drinking water main, connection to turnouts on the reclaimed water pipeline, separation of drinking water uses from the irrigation systems, and identification of all reclaimed water assets.
Upgrading the Treatment Plant
The modifications to the CAWD's wastewater plant by the Carmel River were substantial. As can be seen in the color schematic of Figure 2, the existing facility was altered and added to, while the new tertiary treatment section appears like a compact plant in its own right.
Irrigation operations using all of the tertiary-treated wastewater output from the plant occurs over an approximately eight-month period, but during the rest of the year some of the secondary effluent is discharged through the plant's ocean outfall. Regulatory requirements call for this discharge to be high quality, so sufficient toxicity reduction had to be built into the modified process train. To reduce ammonia concentrations and achieve a completely nitrified effluent, an additional aeration basin and anoxic selector unit were added. This required the construction of a blower facility and the installation in the aeration basins of a manifold system and fine bubble diffusion discs.
A side-elevation schematic of the new tertiary process train is shown in Figure 3. As can be seen, the secondary effluent can be sent to the ocean outfall and also to the first step in the process, which is flow equalization. Coagulant is added in a rapid mix tank ahead of a flocculation basin. Filtration follows in a vertical continuous self-cleaning filter, after which the stream passes to a chlorine disinfection unit and a chlorine contact basin. Before delivery to the distribution system, the reclaimed water is dechlorinated by the addition of sodium bisulfite. Water rejected by the Dynasand filter is sent through a clarifier and recycled to the flow equalization section. Sludge is pumped to the digesters on the site which handle the waste activated sludge produced in the secondary process. Figure 4 illustrates the basics of the SCADA system installed at the plant and on the pipeline and storage tank to monitor and control the operations of the facilities.
Financing and Water Allocations
Funding for the system's development was arranged through the issuance of Certificates of Participation (COPs) by the Monterey Peninsula Water Management District. In this case these are 30-year obligations which have to be paid off by the year 2022. The COPs are pre-sold private investor bonds that are being used to pay for the design, construction, financing and initial operation of the facilities. The issuance of $33.9 million for the Pebble Beach project was made in December of 1992. This amount was made up of $4.4 million for planning, $20.7 million for design and construction, and $8.8 million for financing costs.
The reclaimed wastewater produced by the Carmel treatment plant is distributed to the golf courses and other open space participants for a price. Pebble Beach Company is guaranteeing repayment of the COPs, and will pay annual operating expenses of the system over and above the revenues derived from the sale of the water. Several other financial interests also are participating in the funding aspects of the project.
As a result of this imaginative project, and as noted earlier, 800 acre-feet of reclaimed water is available yearly for irrigation of the golf courses and other recreational and open space areas in Pebble Beach. This frees up the equivalent quantity of potable water that previously was applied through irrigation systems. Of this, 380 acre-feet now can be used for future development in Pebble Beach, while the balance of 420 acre-feet is assigned to the Monterey Peninsula Water Management District. This is available for allocation to municipalites within the District's service area for new connections and/or drought reserve.
About the Author:
Ian Lisk, Editorial Director of Water Engineering & Management and Water & Wastes Digest, prepared this article from material submitted by T. G. Cole and Vinod Badani of Parsons Engineering Science, Inc., and by the office of The Pebble Beach Company.