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How Can Managers and Scientists Facilitate the Flow of Scientific Information?
Perspectives from The United States
William R. Mills,
Orange County Water District
While I served as General Manager of the Orange County Water District, California, the
District embarked on several new areas of water supply development that required the
input of the latest scientific information. The information was needed both to address the
public health risk and to satisfy the public’s need for information that would help gain
their acceptance of the projects. This paper describes three processes used for facilitating
the flow of scientific information. As background to these science facilitation
procedures, a brief description of the water situation and need for the projects will be
presented.
The Orange County Groundwater Basin
The Orange County Groundwater Basin is a large coastal basin located at the
southeastern end of the Los Angeles coastal plain. The surface area of the basin
encompasses about 230,000 acres (93,000 Ha) and contains 10 to 40 million acre-feet
(12,300 to 50,000 Mm3) of fresh water. While the basin extends to more than 2,000 feet
(670 m) from the surface, most of the groundwater lies below sea level. The basin is
adjacent to the Pacific Ocean but is protected from sea water intrusion by coastal faulting
except in two geologic ‘gaps’ that allow for the invasion of salt water when water levels
are below sea level. Usable storage is limited by seawater intrusion and possible
subsidence to about 1,000,000 acre-feet (1,233 Mm3). Recharge into the regional aquifer
is possible only in a small area, about 20,000 acres (8,100 Ha) in area, located in the
inland area of the basin.
There are at present about 500 large municipal wells with a capacity of nearly 400,000
acre-feet/year (490 Mm3) of annual production capacity. These facilities supply about
70% of the water needs of the 2.4 million inhabitants within the basin area. Two
seawater intrusion control facilities have been constructed to block intrusion into the
aquifer. Both projects repel seawater by developing a pressure mound in the aquifer
from the injection of water.
The basin is also situated at the lower end of the Santa Ana River watershed. The
watershed above Orange County encompasses more than 1,000,000 acres (405,000 Ha)
and is drained by the Santa Ana River. The population within the upper area is about 3.0
million. The watershed is divided into lower and upper areas, separated by non-water
bearing mountains, which are traversed by the Santa Ana River.
With future water supply deficiencies projected for Southern California, due to cutbacks
in the supply from the Colorado River and to environmental concerns regarding the
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Sacramento-San Joaquin Delta and Mono Lake, the district embarked on a plan to
develop local projects to meet future needs of the district. The conservation of increasing
Santa Ana River flows and the development of waste water reclamation projects were the
primary means of providing a reliable local water supply.
The first of these projects, Water Factory 21, was built in 1973 to provide a supply source
for a sea water intrusion control project. This advanced wastewater treatment plant
became the signature project for the District and was the first planned waste water
reclamation project for indirect potable use in the United States.
The second project dealt with the Santa Ana River. More than a dozen municipal waste
water treatment plants discharge tertiary treated (filtered, disinfected secondary
treatment water) directly in to the river above Prado Dam. Projections regarding the
base flow component of the Santa Ana River indicated that its current flow of 150,000
acre-feet/year (185 Mm3/yr) would double by the year 2010 due to a substantial increase
in discharges from wastewater treatment plants upstream resulting from population
growth. Storm flows were increasing as well, attributable to larger expanses of
impermeable surfaces in that growing urban area. Recognizing that the base flow and
storm flow components of the river could constitute a significant new water supply
source, OCWD embarked on an intensive program to expand its capability to capture the
river's full flow for basin recharge. As the natural flow of the river increased with the
advent of wastewater discharges in the upper area, the nutrient and dissolved organics
load in the river began to rise. Further, urbanization in the upper watershed, while
contributing to increases in storm water flow, resulted in an increase in the amount of
urban storm pollutants.
A third project, known as the Groundwater Replenishment System (GWRS), is a waste
water reclamation project similar to WF 21 but is much larger in scale and employ’s
more recent technologically advanced treatment systems. This project will be described
in more detail later.
Use of Scientists to do Applied Research
The Constructed Wetlands
As previously indicated, the Santa Ana River is an effluent dominated river. It was
recognized that the nutrient content in the Santa Ana River water, especially the nitrogen
content, was a potential threat to pubic health—the nutrient level in low flow periods of
the summer occasionally exceeded the drinking water standard. Further, the waste water
nature of the water provided a potential concern, especially to the California Department
of Health Services (DHS) because of the minute concentrations of organic compounds
with unknown health risks. Consequently, in 1995 the district began to investigate the
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feasibility of reconstructing some of its lands located in the reservoir area behind a flood
control facility (Prado Dam) to improve the water quality.
Prado Dam is located about 10 miles (16 km) upstream of the District’s recharge system.
Of its holdings behind the dam, about 475 acres (190 Ha) had been constructed into a
series of ponds for the purpose of duck hunting. The ponds were supported by a portion
of the Santa Ana River flow.
To ensure that the latest scientific information was incorporated into the project,
scientists at the University of California, with cutting edge knowledge of wetlands
systems used for water quality enhancement, were contracted to perform a three year
research project. The project included the construction of small ponds of varying depths,
planted with a variety of native riparian plants. Using the results of the research, the
district chose to reconstruct the duck ponds into constructed wetlands that would process
about ½ of the river’s base flow (100 cfs or 2,800 L/s). The research indicated that
wetlands, constructed to allow for both aerobic and anaerobic conditions, would be
extremely effective in removing nitrates from the river waters.
The ponds have now been in operation for several years such that the native vegetation
has fully matured. The result is that complete removal of nitrogen is accomplished
within a few days of retention in the wetland ponds. It was also found that the product
water (outflow) is vastly changed in character. The inflows, as expected, resemble
wastewater discharges, but the product water’s character resembles more that of natural
water.
Use of a Science Advisory Panel to Guide Research in the Safety of the Use of
Effluent Dominated River for Groundwater Recharge
The Health and Water Quality Investigation
Because the Santa Ana River is composed mostly of municipal wastewater during low
flow conditions and urban and dairy animal runoff during storm events, the district
embarked on a multi-disciplinary, multi-year investigation into possible health effects
related to this water supply source. For many years, the California Department of Public
Health raised concerns about the use of Santa Ana River water for recharging the regional
aquifer and the subsequent indirect potable use. The question that was posed by the
Department of Health, was, ‘Are there health impacts associated with the ingestion of
Santa Ana River water.’
To respond to this question, the District assembled a team of experts, mainly from the
universities across the United States. The expert panel members represented various
scientific fields, including hydrogeology, toxicology, epidemiology, and others. Panel
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members included scientists from several universities (Arizona, North Carolina,
California Northwestern, Oregon State and Stanford), the US Geological Survey, and
Lawrence Livermore Laboratory. It was agreed that the panel would have the
responsibility of directing the District’s research needed to respond to the question. The
investigation was conducted for a period of nearly eight years and cost about
$10,000,000. The investigation was effective in identifying residence times in the aquifer
(a key issue regarding virus survival) as well as chemical transformations (elimination of
organic compounds) that occur during recharge.
The chronic health issue was ultimately addressed through the bioassays. The panel
recommended the testing of Santa Ana River water using fish sensitive to water quality.
A laboratory was constructed to monitor changes in the endocrine systems of a small fish
(Medaka) when residing in filtered Santa Ana River water as compared to those residing
in imported water.
Use of an Advisory Panel to Define Health Risks of the Groundwater Replenishment
System
Since its inception in 1975, Water Factory 21 has injected in the coastal portion of the
basin more than 150 Mm3 of highly treated wastewater. The project, the first of its kind
in the world, uses a high lime pretreatment process and subsequent treatment by either
reverse osmosis or activated carbon filtration. The water is disinfected with chlorine
prior to basin injection. However, years of research at the project have resulted in
improved reverse osmosis membranes, using less energy, an alternative membrane based
pretreatment process, and disinfection without the use of chlorine. In concert with the
goal of developing local water supplies, the District proceeded in 1995 to investigate the
feasibility of a much larger and more advanced waste water reclamation project as a
replacement to Water Factory 21. This project, known as the Groundwater
Replenishment System, is now under construction.
The Groundwater Replenishment System (GWRS) incorporates the most recent advances
in water purification technology. This 312 ML/d (3.6 m3/s) project will use
Microfiltration as the pretreatment process prior to treatment by a 312 ML/d (3.6 M3/s)
RO system. Following the RO is a UV disinfection system that is immediately preceded
with the addition of hydrogen peroxide. About 40% of the product water, meeting all
drinking water standards, will be injected into the seawater barrier along the coast. The
remaining waters will be transported via a single pipeline extending from the treatment
facility, along the Santa Ana River, to the district’s recharge system, a distance of about
24 km. The US$500 million plant will produce, when operational in 2007, about 92
Mm3/yr of new water supplies for groundwater recharge.
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While no public health concerns had arisen regarding the injection and subsequent
domestic use of WF 21 waters, it was deemed necessary to employ the best available
assessment procedures to evaluate the health risk associated with the GWRS water.
To answer the question of relative health risk posed by the project waters, the District
once again chose to assemble an independent Advisory Committee. The Committee was
composed of health risks experts from the University of California (Berkeley and Davis
campuses) and the University of North Carolina. Additionally, several ex-officio
advisors were selected from state and local regulatory agencies.
The Advisory Panel noted that the district has been recharging the regional aquifer for
many years with waters derived from the Santa Ana River and imported waters from the
Colorado River and from the State Water Project (Northern California). Consequently,
the independent panel chose to estimate the relative risk associated with each recharge
water source for comparison with that of the GWRS water. The panel conducted their
assessment using the US Environmental Protection Agency’s guidance for risk
assessment. Analysis of each water sample revealed the constituents of potential
concern. The panel concluded that the GWRS water would be less or equal to that
associated with the other recharge waters.
Conclusions
The Orange County Water District has made important use of scientific information to
inform its water management decisions. It has successfully expedited the flow of
scientific information regarding water quality enhancements of degraded river water and
the use of waste waters form groundwater recharge. Depending on the type of decision to
be made, the District has sought information using a range of methods and sources, as
was most appropriate to the decision. The District has funded short and long-term
research projects, and has convened scientific advisory panels to draw expertise from a
range of fields. The information provided enabled the District to:
• Ensure the local, long-term availability of potable water for the region
• Ensure that the treatment options pose no significant threats to public health
• Make improvements to some treatment technologies that also save money
• Communicate to the public the safety of the decisions and obtain the public’s trust
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References
Santa Ana River Water Quality and Health Study, Orange County Water District. 2004.
EOA Inc., Groundwater Replenishment System Health Risk Assessment Report,
2000.
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Representative terms from entire chapter:
ana river
