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The California Department of Health Services (CDHS) has prepared this public health assessment under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). The public health assessment is a mechanism to provide the community with information on the public health implications of specific hazardous waste sites and identify those populations for which further health actions or studies are indicated.

The Frontier Fertilizer site is located near the eastern boundary of the City of Davis, in Yolo County, California. Until recently, the land in the immediate vicinity of the 11.43-acre site has been used for farming. Currently, this land is being developed for residential, service commercial and light industrial use.

Two separate pesticide sales companies operated at the site from 1971 and 1987. Disposal of waste water and unused agricultural chemicals by these companies into an unlined basin on the property from approximately 1972 until 1983 have caused soil and groundwater contamination. In the area beneath the unlined basin, the principal contaminants of concern include dibromochloropropane (DBCP), 1,2-dichloropropane (1,2-DCP), and ethylene dibromide (EDB). Another contaminant of concern is carbon tetrachloride, however, the source of contamination is unknown.

Although much of the soil contamination was removed from the site in 1985, sampling since then indicates that substantial subsurface soil contamination still exists. An interim groundwater extraction and treatment system has been in operation at the site since January 1994. The U.S. Environmental Protection Agency placed the site on the National Priorities List in May 1994.

Residents living near the Frontier Fertilizer site have been concerned about the health hazards connected to the site; however, based on the information reviewed, this site did not and does not pose a public health hazard.

No completed exposure pathways currently exist or are expected to exist in the future. Therefore, the site currently does not pose a public health hazard. Significant future exposure to site-related contaminants is unlikely if: 1) migration of groundwater is controlled via current and future remedial actions; 2) remedial actions reduce groundwater contamination to below levels of health concern; 3) deed restrictions are adhered to, such that the subarea lying adjacent to Frontier Ferilizer and designated for industrial or service commercial uses is not used for residential development; 4) any future excavation/construction projects at the site take the necessary precautions to insure that workers are not exposed to contaminants above levels of health concern; and 5) potential exposure to carbon tetrachloride released from contaminated groundwater/soil gas is further evaluated.

However, ATSDR and CDHS conclude that the Frontier Fertilizer site posed a past public health hazard due to exposure of workers on the property to contaminants in a water supply well. Specifically, workers may have been exposed to 1,2-DCP and EDB by drinking or otherwise using water from the Labor Camp well from about the mid 1970's until 1992. 1,2-DCP and EDB were selected for follow-up because they were the only two contaminants detected at levels about health comparison values in the Labor Camp well. This was the only completed exposure pathway identified in this public health assessment. Based on rough estimates of exposure to workers from drinking water contaminated with EDB, workers may be at a moderate increased risk for both cancer (1 in 286) and possibly other adverse health effects. And for drinking water contaminated with 1,2-DCP, there is no apparent increased cancer risk (1 in 386, 997); however, there may be risk to other non-cancer adverse health effects. However, an accurate toxicological assessment of the site is not possible due to lack of data and information on actual exposure levels.

ATSDR's Health Activities Recommendation Panel (HARP) determined that primary health care providers should be made aware of past worker exposure.

ATSDR and CDHS have made recommendations to reduce and prevent exposure to contaminants related to the Frontier Fertilizer site. These recommendations include: further assessment of the area where the carbon tetrachloride plume was detected, deed restriction to restrict future development in areas of known groundwater and soil contamination. In addition to the recommendations, ATSDR and CDHS will inform health care providers of the potential for past exposure to migrant workers and provide health education for the community residing near the Property. This document is based on data and information available through June 1995. Additional evaluations by CDHS and ATSDR will be appended to the document as they are completed.


The California Department of Health Services (CDHS) has prepared this public health assessment under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). ATSDR, located in Atlanta, Georgia, is a federal agency within the United States Department of Health and Human Services. ATSDR is authorized under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980 to conduct health assessments at hazardous waste sites on the National Priorities List (NPL). This public health assessment evaluates the public health significance of the Frontier Fertilizer site and is based on a review of environmental sampling data and consultation with involved agencies and the public.


The Frontier Fertilizer site is located near the eastern boundary of the City of Davis, in Yolo County, California. The site is an 11.43-acre triangular shaped plot (referred to as Property within this report). Current activities on the Property include use of the woodworking shop and a maintenance yard for agricultural equipment. The site is bordered on the west and north by agricultural fields and to the south by Second Street (see Figure 1). The agricultural fields are currently being developed for service commercial, light industrial use, and residential (the nearest resident is located approximately 1,500 feet north of the site). Interstate I-80 runs parallel to Second Street about 200 hundred feet to the south of the site.

The Property was first operated as a farming headquarters in 1950 by the C. Bruce Mace Ranch Company (1). Grain warehouses and barns for machinery storage were the first buildings erected on the Property. A labor camp for Mexican nationals was constructed on the Property between 1952 and 1954 and was used as such until 1970, when mechanical tomato harvesters reduced the need for labor. In 1970, the Property was sold to Anderson Farms, Inc. From 1970 to 1972, the labor camp buildings were used by transient farm labor families (2). Afterwards, the labor camp buildings housed a wood shop and a machine shop. In 1972, a tomato grading station and wash rack for rinsing tomato trucks was constructed on the Property.

The Barber-Rowland Company of Davis entered into an agreement with Anderson Farms in 1972 (approximate date) to set up a fertilizer and pesticide sales business on 4-acres on the western side of the Property (1, 2). In December 1982, Barber-Rowland Company of Davis and Anderson Farms, Inc. terminated their agreement. Beginning in January 1983, the western 4-acres of the Property was leased to the Frontier Fertilizer Company, which continued the fertilizer and pesticide sales business until March 1987 (1, 2).

Barber-Rowland and Frontier Fertilizer sold fertilizers and pesticides in bulk or mixed in 500 to 1,000-gallon tank trailers for transport and application (1, 2). Returned tank trailers and other containers containing unused or residual fertilizers or pesticides were rinsed out and the rinsate was poured onto the ground or into an unlined disposal basin located near the northwest corner of the Property. Also, the exterior of the trailers were washed at a concrete pad located southwest of the pole barn (2) (see Figure 2).

In July 1983, a Frontier Fertilizer employee's dog died of pesticide poisoning after coming in contact with liquid in the disposal basin. On August 2, 1983, Yolo County Department of Public Health (YCDPH) personnel conducted a site investigation and discovered a 20-foot by 15-foot by 4-foot basin filled with approximately 1,500 gallons of dark and oily liquid (1). The Frontier Fertilizer owners were never issued a Resource Conservation and Recovery Act (RCRA) permit to treat, store, or dispose of hazardous wastes. Two days later, the YCDPH personnel returned to collect liquid samples but discovered that the basin had been pumped out. Soil samples collected at the bottom of the basin and surrounding area were analyzed and found to contain ethylene dibromide (EDB), dibromochloropropane (DBCP), 1,2-dichloropropane (1,2-DCP), and other pesticides. EDB was found at levels up to 1,056 parts EDB per million parts soil (ppm).

In September 1983, YCDPH, with concurrence from the California Department of Toxic Substances Control (DTSC)(1), determined that corrective action at the site was warranted (1). Additional soil sampling was carried out in 1984 and 1985 by Frontier Fertilizer, YCDPH, DTSC, the U.S. Environmental Protection Agency's (U.S. EPA) National Enforcement Investigation Center (NEIC), and the Federal Bureau of Investigation (FBI).

In April 1985, the Regional Water Quality Control Board (RWQCB) and DTSC authorized the removal of approximately 1,100 cubic yards of contaminated soil from the pesticide disposal basin. The removal action was performed by Frontier Fertilizer's contractor Luhdorff and Scalmanini Consulting Engineers. Soil was removed to a depth of 20 feet over a 25-foot by 45-foot area. The contaminated soil was spread out in a thin layer over a 15-acre area three miles east of the site to enable the volatile pesticides to dissipate into the air and facilitate degradation.

Frontier Fertilizer installed 24 groundwater monitoring wells on and off the Property in 1985 and 1986. The site was placed on the California State Priorities List of hazardous waste sites in 1987. In September 1987, the DTSC issued a Remedial Action Order to Frontier Fertilizer to define the extent of soil and groundwater contamination at the site (1). In November 1987, Frontier Fertilizer's consultant Luhdorff and Scalmanini Consulting Engineers completed a Preliminary Assessment Report and Work plan for a Remedial Investigation/Feasibility Study (RI/FS) (2). The report presented the results of soil and groundwater sampling which had been conducted at the site. In December 1987, Frontier's consultant Dr. Lee R. Shull completed a Preliminary Environmental Risk Assessment Report for the site (3). However, in February 1988, DTSC issued a Notice of Final Determination of Non-Compliance to the responsible parties named in the Remedial Action Order (1). Subsequently, DTSC authorized it's contractor, Medcalf & Eddy, Incorporated (M&E), to conduct an RI/FS for the site. M&E conducted three rounds of sampling of monitoring wells in September and October of 1988. In January 1989, M&E completed an RI/FS Work plan for the site (4).

Ramco Enterprises, Inc., one of the Mace Ranch Park development investors, contracted Groundwater Technology, Incorporated (GTI) to summarize existing work at the site and complete additional work to determine the potential impact of the site on the Mace Ranch Park development. GTI completed an RI/FS report on February 15, 1990 (1). The GTI work included additional soil sampling at 53 locations, installation of 12 additional monitoring wells (bringing the total to 36 wells), and sampling all wells which contained water (a total of 34) (1). GTI's soil sampling at the disposal pit area indicated that contamination remained in the soil below 20 feet and that contaminated soil nearby and inside the pole barn had not been removed in 1985, probably to avoid undermining the structure.

Ramco Enterprises, Inc. contracted with Envirologic Data to complete a risk evaluation for its Mace Ranch Park development. In May 1990, Envirologic Data submitted a report entitled "Evaluation of Potential Health Risks Associated with Exposure to Pesticides at Frontier Fertilizer" (5). An addendum to this report was prepared in 1991 (6). DTSC completed a Mace Ranch Park Border Zone Property Determination on March 11, 1992 (7). The final border zone property determination for Mace Ranch Park was issued on October 13, 1993.

M&E completed a draft Focused RI/FS for DTSC in June 1992 (8). This work included installing four additional monitoring wells and sampling wells at two locations. The final Focused RI/FS was completed in October 1992. This work included installation of three additional monitoring wells and sampling of the following monitoring wells: MW-7B, MW-7C, MW-7D, MW-13A, MW-13B, and MW-13C.

On December 6, 1991, DTSC decommissioned the ANDCO private water supply well on the Property; and on July 14, 1992, the Labor Camp private water supply well was decommissioned. The Labor camp well was the only well ever used on the Property; the ANDCO well did not contain a pump and was apparently never used. The Labor Camp and ANDCO wells were suspected of acting as conduits to downward migration of contaminants.

The City of Davis contracted Harding Lawson Associates to conduct a soil gas investigation on the Mace Ranch Park property in 1992. The purpose of the investigation was to locate source areas for carbon tetrachloride found in groundwater monitoring wells north of the Property. A plume was partially defined, but no sources were confirmed.

U.S. EPA prepared an HRS Documentation Record for the Frontier Fertilizer site and proposed the site for the National Priorities List (NPL) in 1993 (9). The site is using the Superfund Accelerated Cleanup Model (SACM) to address the clean-up issues. The groundwater is currently being addressed through early action (viz., installation of extraction wells and a 30 to 50 gallon per minute groundwater pump-and-treat system). An Engineering Evaluation and Cost Analysis (EE/CA) is also currently being developed to evaluate an early action (non-time critical removal) for contaminated soils in the former pesticide pond. As part of the U.S. EPA's SACM work at the site, U.S. EPA's contractor Ecology and Environment, Incorporated, (E&E) conducted soil, soil gas, and groundwater sampling in 1993 and completed a sampling report in January 1994 (10).

DTSC began operating an interim groundwater extraction and treatment system at the site in January 1994. The system involves three extraction wells and carbon absorption treatment (11). Bechtel carried out groundwater sampling at the site for U.S. EPA in March 1994. The site was placed on the NPL on May 27, 1994.

Bechtel completed a Phase I RI/FS work plan for U.S. EPA on March 30, 1994. This document contained quarterly groundwater sampling data, and outlined community relations tasks and risk assessment tasks for the site (12). The last groundwater sampling data available for review was conducted for U.S. EPA by Bechtel in August 1994. Bechtel recently drafted a Phase II RI/FS work-plan which was completed in September 1994. The Phase II work-plan outlined well installation, environmental sampling activities, Preliminary Remediation Goals, and the EECA and associated risk analysis. The Phase II work-plan was implemented in January 1995.

A comprehensive Remedial Investigation, which is conducted by U.S. EPA at the site, begun May 1995. This investigation will include both soil and groundwater sampling. The purpose of this investigation was to identify and fully characterize, the areas of contamination on the entire 18 acre site and to determine the extent of off-site groundwater contamination. The report will not be available for review until 1996. The City of Davis and U.S. EPA have already completed the soil sampling in the area proposed for the widening of Second Street (which will extend several feet onto the Property along its southern border). Results of this investigation have indicated that no contaminants were present above regulatory levels. The City of Davis is planning to widen the road. The road widening will include the demolition of several buildings directly adjacent to Second Street (37).

U.S. EPA is currently the lead agency for overseeing remediation of contamination at the site and have assumed responsibility for the operation of the groundwater pump-and-treat system constructed by DTSC.


On July 25, 1994, Sherry Chan and David Borgeson of the CDHS/ATSDR cooperative agreement project visited the site, accompanied by the DTSC remedial project manager for the site. Before entering the site, we drove along Second Street, which was currently not open to through traffic due to road construction activities. The site was completely enclosed by a chain-link fence. No trespassing signs in both English and Spanish were posted along the fence.

Most of the structures on the property were still standing. These structures, as described below, are shown in Figure 2. On the northwest corner of the site, there were five fertilizer storage silos which were no longer in use. Directly south of the silos, we observed an anhydrous ammonia tank. We noted that the pressure gauge read empty, however, the gauge may be inaccurate. The former pesticide disposal basin was located approximately 150 feet east of the fertilizer storage tank.

Near the western border of the Property, we observed the former pesticide storage warehouse, which is currently used to store the groundwater treatment system. East of the former pesticide storage warehouse is the pole barn, which was used in the past as a farm equipment repair shop. Currently, the pole barn is used to store hay. South of the pole barn, we observed a tomato grading station.

To the east of the pole barn, we observed the three former labor camp buildings. Two rusted railroad cars were located adjacent to the camp. Currently, one of the labor camp buildings houses a wood shop and machine shop. On the east side on the site, we observed a large building which was used to repair farm equipment. Northwest of this building, there was a Baker tank which was filled with drilling mud excavated from remedial activities conducted by DTSC.

Physical hazards were noted on the site, including broken and rusted equipment abandoned south of the pole barn and north of the labor camps, and a large pile of concrete rubble located south of the anhydrous ammonia tanks.



According to the 1990 Census, the population of the City of Davis was approximately 46,209. The racial/ethnic distribution is: 80% White, 13% Asian/Pacific Islander, 3% black, 1% American Indian/Eskimo/Aleut, and 3% other. According to the 1990 Census, about 9,358 people live within a one-mile radius of the site. When complete, the Mace Ranch Park development will add an additional 1,540 housing units to the area approximately 600 feet north of the Property (north of the drainage channel). Based on the observations from the site visit, the community in the vicinity of the site appears to be predominantly middle income.


Land uses in the vicinity of the Frontier Fertilizer Property are depicted in Figure 3. The Frontier Fertilizer property is located in a residential, commercial, and agricultural section of Yolo County. The site is bounded to the west and north by land which up until recently was used for growing tomatoes, sugar beets, and winter wheat. Currently, the lands to the north and west, approximately within a quarter mile of the Frontier Fertilizer Property , are used for growing winter wheat. The Mace Ranch Park service/commercial and light industrial development is proposed to be constructed adjacent to this land. The Mace Ranch Park residential development is being constructed approximately 450 feet north of the Property. The land between the residential development and the Frontier Fertilizer Property is zoned for light industrial development.

Currently, the nearest residents to the Property are located about 1,000 feet to the south of the Property, across Interstate I-80. The area just south of Interstate I-80 in the vicinity of the Property is zoned for Auto Mall and Planned Development Residential Transition. This area includes office buildings, auto dealerships, insurance offices, and fast food restaurants.


Surface water

There are no persistent surface water bodies on or in the immediate vicinity of the Property. After rain, some ponding occurs on the property. Three drainage culverts lead off the Property to the south, under Second Street, and into the east-flowing ditch south of Second Street. Surface water run-off from the Frontier Fertilizer Property is channeled to the drainage ditch south of Second Street. There is also a drainage channel north of the Property which receives runoff from Mace Ranch Park but not from Frontier Fertilizer.


Groundwater in the vicinity of the Frontier Fertilizer Property is used for municipal and agricultural purposes. There are four water-bearing zones. Both the horizontal and vertical movement of groundwater varies seasonally. The general groundwater flow direction is north and northeast. The shallow groundwater zone, S1, lies 25 to 50 feet below ground surface. The intermediate groundwater zone, S2, lies 60 to 90 feet below ground surface. The first aquifer, the A1 zone, lies 110 to 130 feet below ground surface. The second aquifer, the A2 zone, lies below 150 feet below ground surface. The groundwater zones are separated by semi-confining layers of clay and silty clays. It is important to note that the groundwater is moving contaminants north from the pesticide basin and the unknown source of carbon tetrachloride and down from the S-1 zone to the S-2 zone and to the A-1 aquifer (31).

There are two private wells in the vicinity of the Property, including the Mizaguchi well located about 50 feet west of the Property and the Anderson well located about one quarter mile to the east of the Property. The Anderson well is reported to be 260 feet deep; information concerning the depth of the Mizaguchi well was not available. The Mizaguchi well pump has been removed and the well is no longer in use. The Anderson well is currently in use. No contamination has been detected in the Anderson well or the Mizaguchi well (34, 35, 36).

Two private water supply wells, the Labor Camp well and the ANDCO well, are located on the Frontier Fertilizer Property. The ANDCO well was screened in the A-2 aquifer. Both the ANDCO well and the Labor camp well had extensive gravel packs which would have served as potential conduits for contaminants to move from the shallow water bearing zones to deeper aquifers. The ANDCO well was decommissioned (i.e., sealed and abandoned) in December 1991 and the Labor Camp well was decommissioned in (i.e., sealed and abandoned) July 1992.

The City of Davis operates 21 municipal wells that are screened below the A1 zone to depths of 500 feet; 18 of the wells are located within a 4-mile radius of the Property. The nearest wells (#EM-3 and #21) are located approximately 3,400 feet and 3,800 feet, respectively, from the Property. The municipal wells are screened at depths ranging from 180 feet below ground surface to 470 feet below ground surface.

There is a deed restriction on the Mace Ranch Park property. The deed restriction was a requirement of the stipulated agreement for the border zone determination. The deed restricts the placement of groundwater wells. Currently, the City of Davis is proposing an ordinance that will strongly discourage private citizens from installing private groundwater wells (32).


Sources of existing health related data in California that may be useful in evaluating hazards from environmental exposures include the California Birth Defects Monitoring Program, the California Cancer Surveillance Program, and vital statistics review. In addition, medical records which may exist in employment records, physician offices, and local hospitals and clinics may be useful. The California Birth Defect Monitoring Program collected data on birth defects in Yolo County from 1986 until 1989, when monitoring was stopped due to budget constraints. Mandatory reporting of cancer cases in Yolo County began in 1987 and was still required at the time this public health assessment was prepared. The most recent year that data are available is currently 1991.

The pertinence of these data bases to the Frontier Fertilizer site will be discussed in the Public Health Implications section of this public health assessment.


According to the public participation plan prepared for DTSC in 1992 (14), community health concerns about Frontier Fertilizer were first registered in 1983 with the death of a dog owned by one of the Frontier employees. In 1987, the public was polled about their concerns related to the site and the predominant concern was about site clean-up: how long it would take, who was responsible, and how much it would cost. At that time, there was general frustration about how long it was taking to clean-up the site. The public was also interested in knowing the health hazards connected with the site.

Since that time, DTSC has written a series of fact sheets (dated May 1991; November 1991; May 1992; January 1993; and October 1993) updating the community on the plans for Frontier including development of a Public Participation Plan, well sampling plan by the Regional Water Quality Control Board, closure of Labor Camp well and the ANDCO well, installation of monitoring wells, plans for treating and disposal of contaminated groundwater, and final construction schedule for the interim groundwater treatment system. The Public Participation Plan was completed in July, 1992 and noted several community health concerns. The most frequent concern was about site contamination impacting groundwater quality since residents were uniformly aware that drinking water in Davis comes from local groundwater wells. One resident and one local educator were concerned the site would be an "attractive nuisance" for teenagers who rode their bikes by the site every day on the way to school. Several people were concerned about whether residents would be exposed to toxins during site clean-up.

CDHS staff contacted DTSC public participation staff, the Davis City Manager, the Chair of the Natural Resources Commission for the City of Davis, residents from the Mace Ranch Park Development, and several community activists and none of them was aware of any health-related complaints from residents living closest to the site. The Chair of the newly-formed Frontier Fertilizer Superfund Oversight Group had heard that residents were concerned about their children playing in soil that could be contaminated. She supplied CDHS staff with articles from the mid 1980's documenting workers' complaints when the site was still in operation. On September 27, 1994 she had a meeting at her house to allow U.S. EPA community relations staff to meet with residents and explain their plans for upcoming community relations activities. Residents at that meeting were also asked if they had any health concerns and one person wanted to know if the site currently posed any danger to those living in the Mace Ranch Park Development. Attenders were told if they had any health concerns to contact CDHS staff.

U.S. EPA has developed a mailing list and is in the process of updating DTSC's 1992 Community Relations Plan. A community meeting was held December 15, 1994. CDHS attended the community meeting.

Historical and current community concerns are as follows:

  • Has contaminated water gone down far enough to reach the municipal water supply?
  • Could there be a problem if children played in the fields adjacent to Frontier?
  • Could any of the chemicals at Frontier Fertilizer cause air pollution in the surrounding areas?
  • Will site cleanup activities allow exposure to toxic chemicals to occur?
  • Does the site currently pose any danger to the health of residents living closest to the site?

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