San Fernando Valley, California
Human Impact on the Environment
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Water Quality

The growth of Los Angeles had always forced the City to be concerned with the adequacy of its supply, and consequently its attention had always been directed outward in its search.  The new emphasis on managing the water resource brought protection of water quality to the forefront as the primary goal of good management.

Today, Los Angeles is the second largest city in the nation.  In December 1995, Los Angeles joined the "Partnership For Safe Water Program" in an agreement with the U.S. Environmental Protection Agency to self-assess and potentially implement additional drinking water safeguards and treatments. Los Angeles met Partnership eligibility requirements because of its good standing under current regulations and a commitment to undertake various phases of the program.

There are three sources for Los Angeles’ water: approximately 60% comes from the Eastern Sierra via the Los Angeles Aqueduct system, 15% from the San Fernando groundwater basin, and 25% from the Metropolitan Water District’s Colorado and Feather River supplies.

Water from the Owens River watershed is protected from industrial and agricultural contamination by DWP land management practices.  However, some turbidity arises as water from the watersheds travels through unlined channels in a natural rural setting before being diverted into the two aqueducts for its journey to the City.

The DWP determined that a filtration plant would be necessary to reduce this turbidity and in 1986 Los Angeles completed its first filtration plant.  Using ozone and rapid rate deep bed filters, the $146 million Los Angeles Filtration Plant treats up to 600 million gallons of water each day.  It is the largest direct filtration plant in the U.S. and the second largest ozone plant in the world.

One benefit resulting from the use of ozonation as a disinfectant process is the reduction in formation of trihalomethanes (THMs).  These chemical compounds are formed when chlorine combines with naturally occurring organic material in the water.  By using ozone as a disinfectant in the initial treatment process instead of chlorine, the City is able to reduce THMs by as much as 50%.  New operations, commencing in 1999, have allowed the plant to convert to biologically active filtration, or biofiltration.  Ozone plays an important role in growing harmless bacteria on the filters to remove a wider range of disinfection byproducts now being regulated.

In August of 1999, Los Angeles began to fluoridate its water at the Los Angeles Aqueduct Filtration Plant.  Natural background levels of fluoride are boosted to optimal levels that help prevent tooth decay.  Additional fluoridation facilities have already, or will soon, come on line at groundwater treatment sites and at MWD service connections.

The next 25% of the City’s water comes from MWD.  As Arizona begins to exercise its increased rights on the Colorado River, the MWD will need to rely more on northern California water supplied through the State Water Project.  When water from the State Water Project flows through the Sacramento-San Joaquin Delta it picks up organic material from the riverbeds.

With increased use of water containing a greater amount of organic material, higher levels of THMs in the MWD supply would have been likely.  However, by using chloramines, a combination of chlorine and ammonia, as a primary disinfectant, the MWD has taken steps to reduce this problem.

The San Fernando groundwater basin not only supplies 15% of Los Angeles’ domestic needs, but it also acts as a vast underground reservoir where water accumulates during years of abundant rainfall and is stored for use in the future.

In 1980, newly available sensitive monitoring equipment detected trace amounts of trichloroethylene (TCE) and perchloroethylene (PCE), as well as smaller amounts of other industrial chemicals in the San Fernando groundwater supply.

The concentration of these contaminants is very small, measured in parts per billion (a part per billion is equivalent to a few drops in a swimming pool).  There is concern, however, that a lifetime of exposure to even very low levels of these contaminants could have a negative health effect.  Both the State and federal government have, therefore, established very demanding standards for the amount of these contaminants that are allowed in a water supply. The City’s groundwater supply meets all of these standards at all times.

Some of the contaminated wells have been abandoned. The loss of production from the abandoned wells, has been made up by developing new well field such as Tujunga Well Field (12 new wells) which is located up gradient of the significant contaminant plumes.

The San Fernando Groundwater Quality Management Plan was issued in July 1983. The objective of this effort is to protect and upgrade the quality of the stored water in the Basin.  Special emphasis is placed on monitoring and removing the organic contaminants TCE and PCE found in the groundwater.  The Plan recommends systematic installation of sanitary sewers in designated areas through the San Fernando Valley in order to eliminate existing commercial and industrial Private Sewage Disposal Systems and their discharge of wastewater to the groundwater basin.  The State-mandated Underground Storage Tank Program headed by the City of Los Angeles Fire Department focuses on the monitoring and removal of gasoline, and their related constituents from the soils, in order to prevent contamination of the underlying groundwater.

The North Hollywood Aeration Facility removes and treats the contaminated groundwater in the upper zone of the aquifer and prevents the migration of the contaminants downward into the San Fernando groundwater basin. The water from seven contaminated shallow wells is pumped to the top of the aeration tower. As the water flows downward an upward air blower, flows counter-current through the water. Volatile gases trapped in the water then vaporize and join the air stream.  This air stream is filtered through activated carbon to be sure none of the contaminants are released to the atmosphere.

The DWP is participating in several research projects aimed at developing new technologies that will assist in the removal and destruction of source water contaminants.  One such technology, known as advanced oxidation, uses ozone and hydrogen peroxide to oxidize groundwater contaminants into harmless by-products such as chloride and carbon dioxide.  The Department of Water and Power continually monitors the purity and quality of its water supply.  More than 60,000 laboratory and field analyses are made yearly, 15,000 for bacteriological control and the balance for chemical, physical, and radiological inspections.  Sampling occurs at all sources; watershed, reservoirs, distribution mains, and consumer taps.  Water carrying and storage facilities are also checked.

DWP is required by State and Federal law to regularly test City water.  Monitoring of over 90 regulated chemicals and bacteriological contaminants is required at varying frequencies based on the type of constituent and the type of source water.  There are constituents found in drinking water that are not yet regulated.  Some of these “unregulated constituents” are monitored because they could be candidates for future regulations or are of interest to our customers.  The DWP has a crew of field and laboratory personnel who sample and test City water every day of the year, including weekends and holidays.  The distribution system water samples are collected from secured water sampling taps installed throughout the city.  Regular water samples are also collected from watersheds, reservoirs, groundwater supply wells, storage facilities and other locations.  There are over 170 different constituents which DWP tests for in the water.

The people of Los Angeles today enjoy safe drinking water from high quality sources that meets or exceeds all standards set by state and federal agencies.  The Los Angeles Department of Water and Power is constantly working to assure that this continues into the future.

The San Fernando Valley today still has some of its own water sources. Approximately 20 miles out of the valley, the San Gabriel Mountains serve as the major stream source of the Pacoima, the Little Tujunga, and the Big Tujunga. At the opposite west end of the valley, Bell Creek flows from Simi Hills and the Santa Susana Mountain Range. However, aside from these, the waters moving through the valley are intermittent at best, and are normally seen only after a rare wet cycle. Land developers have covered up most small creeks with eroded mountain sediments of rock, sand, gravel, or clay, in an effort to sell real estate property. When the wet cycle comes inevitably in the winter, uninformed and unsuspecting homeowners have to deal with foundation cracks and flood conditions, dumfounded that five months prior they were being warned to conserve water amidst the summer drought.

The San Fernando Valley, rectangular in shape and surrounded by ever eroding mountains, slopes towards the southeast into “The Narrows.”This is a one mile wide opening through which the eroded mountain materials travel in the river. However, more sediment remains in the old inland sea than is carried out to the ocean. The resulting porous nature of the valley ground absorbs this silt and water underground, creating a reservoir that inch towards The Narrows. The result is a slow flowing underground river that is pressurized, because only so much material can physically pass through The Narrows at once under natural conditions. This is what is known as the source of the Los Angeles River, and this is why the Valley was so important to the City of Los Angeles in the beginning years of the twentieth century. 

The Los Angeles River is the heart of an 871-square mile watershed. The watershed encompasses the Santa Susanna Mountains to the west, the San Gabriel Mountains to the north and east, and the Santa Monica Mountains and Los Angeles coastal plain to the south.

The Los Angeles River Watershed has diverse patterns of land use. Forest or open space covers the upper half of the watershed, while the remaining watershed is highly urbanized with commercial, industrial, or residential uses. There are 22 lakes within its boundaries. In addition, there are a number of spreading grounds in the watershed including sites at Dominguez Gap, the Headworks, Hansen Dam, Lopez Dam, and Pacoima Dam. The Los Angeles River is hydraulically connected to the San Gabriel River through the Rio Hondo, although this occurs primarily during large storm events.

Many people don't even realize there is a river in Los Angeles. It's usually remembered as the cement channel where two Terminators had a high-speed chase in the movie T2, or the staging ground for a giant ant invasion in Them!. But our river is more than a backdrop for movies and traffic. It is presently a shadow of it's former self, but areas of great beauty still exist.

The Los Angeles River is not like other rivers in the United States. At only 52 miles long, the L.A. River is 45 times shorter than the Mississippi, but drops 795 feet in elevation from the headwaters in the San Fernando Valley to its end in Long Beach. That's 150 feet more than the Mississippi drops in its entire 2350 miles, meaning our river is short but steep.

In times of peak flow, the river carries 183,000 cubic feet of water per second out to the Pacific Ocean (the equivalent of 40 million garden hoses going full blast) - 14 times the flow of NY's Hudson River. The LA River has no "average" flow, varying widely from a bare trickle in drought years to a raging torrent in years of heavy rain.

The Los Angeles River Watershed has impaired water quality in the middle and lower portions of the basin due to runoff from dense clusters of commercial, industrial, residential, and other urban activities. The impairments include pH, ammonia, metals, coliform, trash, algae, oil, pesticides, and volatile organics.

Of course, one of the most different things about the LA River is the fact that much of it is encased in concrete. Confining the river to a concrete channel began in 1938, as an effort to control the devastating floods that periodically swept through the city. It took 30 years and 3.5 million barrels of concrete to channelize the river and its tributaries, and when it was done, it wasn't called a river anymore. It was renamed the Los Angeles River Flood Control Channel.

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PROBLEMATIC POLLUTION

Control of pollution is one area in which Los Angeles has achieved moderate improvement. The city’s notorious smog—produced mainly by exhaust emissions from millions of trucks, diesel buses, and automobiles, and trapped by the Santa Monica and San Gabriel mountains—is still among the worst in the United States. It is linked to a wide range of health problems, most noticeably to an alarming increase in asthma among children. It reached its worst levels in the 1970s, but strict vehicle emission standards imposed by the federal Environmental Protection Agency have had a marked effect. Federal and state officials are working to impose new measures, such as conversion of buses from diesel to natural gas and lower emission levels from automobile manufacturers.

Another major environmental problem has been the pollution of the Santa Monica Bay. Millions of gallons of untreated runoff from streets and lawns flow into the bay through storm sewers, especially during the winter rainy seasons. Dangerous levels of bacteria are regularly found at many of the beaches. City planners have attempted to have storm drain runoff diverted into treatment plants.

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Hansen Dam

Hansen Dam is an essential element for flood control in the Los Angeles County Drainage Area (LACDA). In conjunction with Sepulveda Dam and Lopez Dam, it is vital for the flood control protection of the lower portions of the San Fernando Valley and the City of Los Angeles. The project was built by the Corps of Engineers, Los Angeles District between September 1939 and September 1940. The project is located near the northern edge of the San Fernando Valley on Tujunga Wash, about one mile below the confluence of the Big Tujunga Wash and the Little Tujunga Wash, and about four miles southeast of the City of San Fernando. Hansen Dam is approximately 3.5 miles northwest of Lopez Dam.

Hansen Dam was authorized by the Flood Control Act, approved 22 June 1936 (Public Law 738, 74th Congress) and extended and amended by subsequent Flood Control Acts of 1937, 1938, 1941, 1944, and 1946. The plan for construction, in accordance with the recommendations contained in the report dated 11 April 1940 by the Chief of Engineers, and submitted in House Document 838, 76th Congress, 3rd session, was authorized by the Flood Control Act, approved 18 August 1941.

WORKS CITED:

Falzanno, Johanna. The Development of the San Fernando Valley: A History of Natural Resource Issues and Prospects for the Future. February 15, 2003.Pepperdine University

Microsoft Encarta Encyclopedia 1993-2003 Microsoft Corporation

The River Project: Know Your Watershed Official Homepage. http://www.theriverproject.org/lariver.html

United States Environmental Protection Agency. San Fernando Valley (Area 4) Report. http://yosemite.epa.gov/r9/sfund/r9sfdocw.nsf/a64b5c0640bfb79e88256f0000092947/5385870e7c6b8d9b88257007005e946d!OpenDocument

US Army Corps of Engineers Los Angeles District Reservoir Regulation Section. Hansen Dam http://www.spl.usace.army.mil/resreg/htdocs/hnsn.html

http://wsoweb.ladwp.com/Aqueduct/historyoflaa/waterquality.htm