section 5 water supply

5-1 City of Manhattan Beach R:rpts\Manhattan Beach\Water Master Plan Water Master Plan

SECTION 5

WATER SUPPLY 5-1 Sources of Supply The City’s existing potable water supply consists of imported water from Metropolitan Water District of Southern California (MWD) and groundwater from the City’s two (2) wells. Historically, the City has imported an average of 5,664 AFY and pumped 1,024 AFY from the groundwater basin. Eighty five percent of the City’s source water is imported. Detailed purchase and production data is shown in Table 4-1.

5-2 Imported Water Supply Water is imported into Southern California through two major water supply systems:

1. The Colorado River Aqueduct, constructed and operated by MWD, transports water from the Colorado River to MWD’s service area

2. The State Water Project, owned and operated by the State of California Department of Water Resources (DWR), transports water from the Sacramento-San Joaquin Delta through the California Aqueduct

5-2.1 Metropolitan Water District and West Basin Municipal Water District

MWD is the purveyor of imported water for most of Southern California. It provides supplemental water to 26 member public agencies through a regional distribution network of canals, pipelines, reservoirs, treatment plants, pump stations, hydropower plants and other appurtenances. The MWD service area is illustrated on Figure 5-1.

West Basin Municipal Water District (WBMWD) is the MWD member agency that provides imported water to agencies in the South Bay portion of Los Angeles County. WBMWD provides imported water to the City of Manhattan Beach at connection WB-04, located at the intersection of Manhattan Beach Boulevard and Redondo Avenue. The WBMWD service area is shown on Figure 5-2. Los Angeles, Orange, and Ventura Counties are encompassed within MWD’s Central Pool service area that accounts for more than 60 percent of MWD’s total demand for supplemental water. The Central Pool service area is served by three MWD water treatment plants: the Jensen Plant in Granada Hills, the Weymouth Plant in La Verne, and the Diemer Plant in Yorba Linda. Each of these plants serves a localized exclusive area as well as a portion of a common area of the Central Pool, known as the ‘Common Pool’. As shown on Figure 5-3, the City of Manhattan Beach is encompassed within the Common Pool service area.

The City’s water system has one MWD connection, WB-04. WB-04 Connection is located at the intersection of Manhattan Beach Boulevard and Redondo Avenue. The ground elevation is approximately 80-feet amsl at this location. The City has an existing 18-inch pipeline connected to the MWD’s 45-inch West Basin Feeder, which enters the City from the east in Manhattan Beach Boulevard. MWD assures that it can deliver 15 cubic feet per second (cfs) at a minimum pressure of 83.5 pounds per square inch (psi) at the outlet of their meter. The SCADA records for the MWD connection between June 2, 2009 and June 14, 2009 show an average discharge pressure of 98 psi. The minimum and maximum pressures were 87 psi and 104 psi, respectively.

PROJECT NO: 1640901.20DATE: April 2010

CITY OF MANHATTAN BEACHWATER MASTER PLAN

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PROJECT NO: 1640901.20DATE: April 2010

CITY OF MANHATTAN BEACHWATER MASTER PLAN

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SECTION 5 WATER SUPPLY


The SCADA records showed an average flow rate of 4.34 cfs from the MWD connection. The minimum and maximum flow rates were 2.26 cfs and 10.36 cfs, respectively. From the MWD connection, flow is conveyed directly to the Block 35 Facility and the Peck Facility. An existing 18-inch pipe extends from the connection, south along Redondo Avenue and west on 8th Street to the Block 35 Facility. An existing 14-inch pipe extends from the connection, west along Manhattan Beach Boulevard to Herrin Avenue and north through Polliwog Park to the Peck Facility. The Metropolitan Water District of Southern California prepared an Integrated Water Resources Plan in 1997. This plan estimated that the demands of the Common Pool area would exceed the treated water capacity available by the summer of 2013. Additional treated water capacity would be needed in the Common Pool area due to limitations in MWD treatment plant capacity and conveyance facilities. The additional amount of treated water needed was estimated to be 286 cfs by the year 2020. In order to mitigate this projected deficiency, the Integrated Water Resources Plan recommended the Central Pool Augmentation Project consisting of a new outlet structure at Lake Matthews, a new treatment plant in Eagle Valley with a first stage capacity of 400 cfs, and an 18 mile long tunnel and pipeline system to deliver the treated water to the Orange County section of the Central Pool. This project would supply the needs of south Orange County, and reduce the demand on the Diemer Plant. The capacity relieved at the Diemer Plant would then be available for the remainder of the Central Pool. However, the increase in demands has been lower than projected by the original Integrated Water Resources Plan. Metropolitan prepared the 2003 Integrated Water Resources Plan Update, which was adopted on July 13, 2004. The updated plan includes refinements to the regional supply development targets based on identified changed conditions, and provides a long term resources plan to 2025. The supply planning includes a 10 percent buffer, which sets resource development targets above forecasted demands. The purpose of the buffer is to provide flexibility in implementation plans for the uncertainties in demands, water quality impacts, new supply implementation risks, and potential loss of existing regional supply. It is currently anticipated that the Central Pool Augmentation Project will not be implemented until after 2018, and there will be sufficient supplies for Metropolitan’s service area through 2025.

5-3 Groundwater Supply 5-3.1 West Coast Basin The City of Manhattan Beach has two (2) active Wells (Well 11A and Well 15) that extract water from the West Coast Basin, which underlies the southwestern portion of the Los Angeles Coastal Plain. It is bounded by the Ballona Escarpment to the north, the Newport-Inglewood Uplift to the east, the Santa Monica Bay to the west, and San Pedro Bay and the Palos Verdes Hills to the south. The location of the groundwater basin is illustrated on Figure 5-4. For many years, groundwater from the West Coast Basin was over extracted. The groundwater level dropped below sea level and the coastal regions of the West Coast Basin were contaminated by seawater. This sparked many important events in the history of the basin that has led it to the condition we find it in today, which is much improved from the early 1900’s:

� 1946 - West Basin Water Association was formed to provide supplemental source of water for major producers, limit groundwater extractions, and create exchange pool



Insert Figure 5-4 West Coast and Central Groundwater Basin



� 1946 - Superior Court asked Department of Water Resources (DWR) to determine the boundaries and geohydrologic characteristics of the West Coast Basin

� 1947 - West Basin Municipal Water District (WBMWD) was formed to distribute imported water from the Colorado River which helped regulate the water supply

� 1948 - WBMWD annexed to the Metropolitan Water District of Southern California (MWD) and Colorado River water started flowing into West Coast Basin later that year

� 1955 - Court approved Interim Agreement drafted by the pumpers to reduce groundwater extractions

� 1959 - Water Replenishment District of Southern California (WRD) formed to manage, regulate and replenish the basin each year.

� 1961 - West Coast Basin Judgment signed. DWR was appointed as Watermaster to account for all water rights and groundwater extraction amounts each year.

The adjudication limits the allowable annual extraction of groundwater per water rights within the basin in order to prevent seawater intrusion and an unhealthy groundwater level. The Watermaster provides the following services:

� Administers the controls prescribed by the judgments.

� Reports annually to the Court and the parties to the judgment on significant groundwater related events that take place in the basin.

� Each month, computes the amounts pumped during the current fiscal year (based on monthly party reports of amount pumped) and the amount that can legally be pumped the remainder of the year

� Mails monthly water extraction reports to all parties

� Administers an exchange pool

� Schedules tests to determine the accuracy of the water meter on every active well at least once every two years

� Conducts static groundwater level measurements in about 130 wells in the fall and spring of each year and prepares contours of groundwater elevations

� Works with advisory/management boards in the basin to review activities such as delinquent accounts, drought responses, and proposed amendments to the judgments

� Records water rights sales and leases between parties and maintains successor lists

The annual report includes water management activities that affect the use of groundwater, such as in-lieu replenishment, sea water intrusion barriers, desalter projects, and water recycling programs.

5-3.2 West Coast Basin Groundwater Recharge and Protection

Natural Replenishment

Natural replenishment of the groundwater basin occurs as underflow from the Central Basin. Some of the water that is spread in the Central Basin crosses the Newport-Inglewood Uplift into the West Coast Basin. The effectiveness of recharge is limited to the space available in Central Basin for spreading facilities, and the ability of the West Coast Basin to accept the water.



Recharge of Central Basin occurs through local runoff; artificial recharge of recycled water produced at the Whittier Narrows, San Jose, and Pomona Water Reclamation Plants; and artificial recharge of untreated MWD water. The Water Replenishment District of Southern California, formed in 1959, is responsible for securing the supplies for artificial recharge of Central Basin at the Montebello Forebay. In Fiscal Year 2008-2009, the total recharge water spread in Central Basin was 80,623 acre-feet.

Replenishment of the West Coast Groundwater Basin also occurs through infiltration of surface flow in the Los Angeles and San Gabriel Rivers, and return irrigation water. In-lieu Replenishment

The Water Replenishment District of Southern California (WRD) began the in-lieu replenishment water program in 1966. Under this program, any customer with access to supplemental water may use in-lieu replenishment water instead of groundwater. The in-lieu replenishment water program can be used to alter pumping patterns within a basin, replenish areas of low transmissivity where conventional recharge techniques are ineffective, heighten the effect of injection water by reducing nearby extractions, reduce the quantity of replenishment water purchased, and reduce the annual groundwater extractions from the West Coast Groundwater Basin.

Seawater Barrier Improvement Program

The West Coast Basin Barrier Project and the Dominguez Gap Barrier Project prevent further seawater intrusion and serve as the primary means of replenishing the West Coast Basin. The Los Angeles County Department of Public Works (LACDPW) owns and operates the barriers, while WRD procures imported water and recycled water that is used for injection. Both agencies work cooperatively to maintain and improve the barriers’ effectiveness.

The West Coast Barrier Project consists of 153 injection wells and 302 observation wells, which span approximately nine (9) miles along the coastline from Los Angeles International Airport to the Palos Verdes Hills. Imported water and recycled water is injected to create a pressure ridge that prevents the inland movement of sea water within the 200-Foot Sand, the Silverado, and the Lower San Pedro Aquifers. The recycled water is first treated to secondary levels at the Hyperion wastewater treatment plant and then receives tertiary treatment, microfiltration, and reverse osmosis at WBMWD’s Edward C. Little Water Recycling Facility. The treated water is blended with imported MWD water, provided from connection WB-28. The blending facility is located on El Segundo Boulevard, west of Nash Street in the City of El Segundo. Currently, the barrier is supplied with 75 percent recycled water and 25 percent imported water. An agreement was recently signed between WBMWD and the WRD to supply 100 percent of the West Coast Barrier with recycled water after the Phase V expansion of the Edward C. Little Water Recycling Facility.

The Dominguez Gap Barrier Project includes 94 injection wells and 221 observation wells, which impede sea water intrusion along San Pedro Bay. Imported and recycled water is injected into the 200-Foot Sand-Gaspur, 400-Foot Gravel, and Gaspur Aquifers.

5-3.3 Administration of the West Coast Basin Judgment

The West Coast Basin Judgment contains provisions for the Parties to obtain additional pumping rights, to exceed their entitled extractions, or otherwise to make variations in their annual pumping. There is a voluntary Exchange Pool that any party can be a part of. Recipients of Exchange Pool water may pump the



amounts released to them in addition to their Adjudicated Right. The amounts that parties may release are limited by the Judgement.

Adjudicated Rights may also be transferred through a lease or sale agreement. The Watermaster maintains a list of parties who are interested in buying, selling, or leasing water rights. This is a courtesy service provided by the Watermaster to assist parties in resolving problems regarding an excess or deficiency of water rights.

5-3.4 Groundwater Rights

Currently, the adjudicated water right of the West Coast Basin is approximately 64,468 acre feet per year. The City of Manhattan Beach’s adjudicated water right is 1,131 acre feet per year. This does not include any leased water or any surplus water from the previous years. In the 2008-2009 fiscal year, the City leased an additional 461 AF of groundwater from the City of El Segundo. When combined with the adjudicated right, the City had an allowable extraction of approximately 1,592 AF. In the future, the allowable extractions from the City of El Segundo will be leased by Manhattan Beach. Aside from surplus water which varies from year-to-year, the City will lease El Segundo’s adjudicated right of 953 AF, which will provide an allowable extraction of approximately 2,084 acre-feet per year.

5-3.5 Groundwater Level

Central Basin groundwater levels decreased up to 15 feet in FY 2007-2008. This was primarily due to the lack of replenishment water and pumping overdraft. The water level in West Coast Basin has remained relatively stable due to recharge. Groundwater storage decreased over 44,000 AF basin-wide, but mostly in the Central Basin.

5-3.6 Groundwater Quality

The groundwater quality and replenishment is actively monitored by the Water Replenishment District of Southern California (WRD). The WRD has created the Regional Groundwater Monitoring Program to track the water quality in the Central and West Coast Basins (CWCB). With over 50 locations and nearly 250 monitoring wells, WDR takes approximately 500 groundwater samples annually. The samples are tested for over 100 water quality constituents to monitor the water quality in the basins.

The groundwater is currently pumped to the Block 35 ground level reservoir, where it is blended with imported water from MWD. The City has experienced high manganese levels in its groundwater. To comply with the Environmental Protection Agency (EPA) and the State of California Department of Health Services secondary drinking water standards, the City must blend its groundwater with imported water to limit the manganese level to 50 mg/l. Currently, the City adjusts the amount of MWD water such that the blended water has a final concentration of 45 mg/l. The water from the wells and MWD are chlorinated and mixed directly at the point of

entrance to the reservoir and discharged into the center of the reservoir to assure a thorough mix. The water is then pumped out of the reservoir where it is again chlorinated and directly mixed with the supply line from MWD before entering the distribution system. The system is generally chlorinated to bring the residuals up to 2.5 parts per million (ppm).

section 5 water supply

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