Frontier Fertilizer

Description and History

The 8-acre Frontier Fertilizer Superfund site is located near the eastern boundary of Davis, California. The Barber and Rowland Company operated a pesticide and fertilizer distribution facility on the site from 1972 to 1982. The Frontier Fertilizer Company used the site from 1982 to 1987. Both companies handled chemicals on the western four acres of the site. Operations consisted of storing, mixing and delivering pesticides, herbicides, and non-bulk chemicals in cans, drums, and other containers. Both companies used a 4,000-cubic-foot former disposal basin in the northwest corner of the site to dispose of unused pesticides and fertilizers. Returned tanks and containers were washed and the rinsate was dumped into the disposal basin or onto the ground. In 1985, Frontier Fertilizer excavated approximately 1,100 cubic yards of contaminated soil from the former disposal basin and land farmed the soil on a field east of the site. In 2000, all structures, above-ground tanks, and underground tanks were removed with the exception of a warehouse which contains the groundwater treatment system. The Mace Ranch residential subdivision is approximately 800 feet north of the site. The field immediately north of the Frontier site is planned for development as the Mace Ranch Light Industrial/Business Park. Development in this area began in the Summer 2003 with completion of two sections of Faraday Road and below-ground utilities.

There are four water-bearing zones beneath the Frontier site, separated by layers of clay. The shallow zone, called the S-1, extends from approximately 30 to 50 feet below ground surface (bgs). Below the S-1 is the S-2 which extends from approximately 60 to 90 feet below ground surface. The S-1 and S-2 are not present or potential sources of drinking water. The A-1 aquifer, extends from approximately 110 to 130 feet bgs. The drinking water supply for the City of Davis comes from the deep A-2 aquifer that begins at approximately 180 feet bgs. No contaminants above drinking water standards have been detected in the A-2. Groundwater flows north- northeast in the S-1 and S-2 zones. Groundwater flow direction in the A-1 aquifer is quite flat, but generally flows southeasterly. Northerly flow directions have occasionally been observed. Contaminated groundwater has migrated north of the site and is beneath the Mace Ranch subdivision. Although contamination from the Frontier site has not been documented in any drinking water wells, the potential for contamination from the Frontier Fertilizer site exists since all four water-bearing zones are connected.

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Contaminants and Risks

The principal chemicals in groundwater and soil are three pesticides which were used as soil fumigants: ethylene dibromide (EDB), 1,2-dichloropropane (DCP), and 1,2-dibromo-3-chloropropane (DBCP) as well as the solvent carbon tetrachloride. Nitrate has also been detected in groundwater above drinking water standards.

Subsurface soil in the area of the former disposal basins is contaminated as well as groundwater in the S-1, S-2 and A-1 zones. The A-2 aquifer, which is the drinking water supply for the City of Davis, is not contaminated.

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Who is Involved

The site is being addressed through Federal and State actions.

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Investigation and Cleanup Activities

EPA's goals are to halt the migration of contaminated groundwater, to restore the water-bearing zones to drinking water quality standards, and to remediate the former waste pits area so that contaminants in soil are no longer a threat to groundwater.

The California Department of Toxic Substances Control installed a small groundwater extraction and treatment system in early 1993. EPA installed a larger system in 1995. The system was upgraded in Fall 2000 and again in 2002. The groundwater extraction wells for the existing system are in the field immediately north of the site. EPA has also installed groundwater monitoring wells on-site, in the field immediately north of the site and in the Mace Ranch residential subdivision. EPA collects samples of water chemistry and measures water levels in these wells on a quarterly, semi-annual, or annual basis, depending on the location of the well.

EPA collected samples of groundwater and surface and subsurface soil to determine the nature and extent of contamination and reported the results in an April 1997 Remedial Investigation (RI) Report. The studies showed that soil contamination was confined to the waste disposal basins area, and that contaminated groundwater existed in the upper three water-bearing zones and had migrated off-site. A June 1999 Supplemental Remedial Investigation Report describes sampling results from newly installed groundwater monitoring wells in the Mace Ranch Park subdivision as well as soil gas sampling results. Soil gas samples were collected on top of the former waste disposal basins and every 50 feet from the pits to the Mace Ranch Park subdivision. Groundwater sampling data showed much higher levels of contamination on-site and immediately north of the site than existed in Mace Ranch Park. Soil gas concentrations were high on-site and decreased rapidly north of the site.

A Baseline Risk Assessment was produced in April 1999. An indoor air risk assessment for the residents of Mace Ranch was included in the Baseline Risk Assessment. The indoor air risk assessment determined that there is no risk to residents of Mace Ranch from volatile chemicals in groundwater moving up through soil and into homes.

In Fall/Winter 2001 and Spring 2002, EPA collected additional groundwater samples in the Mace Ranch subdivision and collected soil, soil gas and groundwater samples on-site and in the field immediately north of the site to better define the geology and extent of groundwater contamination. A groundwater extraction well cluster was installed at the intersection of Caricia Drive and Arroyo Avenue and in the field immediately north of the former waste pits. A new groundwater monitoring well cluster was installed on Fifth Street near Entrada.

The groundwater sampling results show elevated concentrations in the S-1 and S-2 zones on-site and immediately north of the site. These concentrations generally decrease sharply within a few hundred feet of the former disposal basins, although there is a localized area of elevated pesticide concentrations in the S-2 zone near the intersection of Caricia and Arroyo in Mace Ranch Park. Soil gas concentrations were lower than those collected in 1997, indicating that the risk calculations performed for the 1999 Baseline Risk Assessment remain protective. Soil sampling identified a zone of soil contamination extending from near the ground surface down to about 30 feet below ground surface in the area next to the former disposal basins. Soil samples collected about 60 feet north of the disposal basins show contamination about 30 to 80 feet deep, although at much lower concentrations than the shallow soil contamination near the former disposal basins. The results of this field work are described in Supplement No. 2 to the Remedial Investigation Report, dated January 2003.

In June 2006, EPA finalized a Feasibility Study (FS) that includes a detailed analysis of alternatives for final clean-up of on-site contaminated soils and groundwater. EPA issued a Proposed Plan on June 12, 2006 that recommended clean-up alternatives for soil and groundwater. As part of a formal 30-day review process of the Proposed Plan, EPA held a public meeting on June 22, 2006, to discuss the proposed clean-up alternatives and record verbal comments.

The Record of Decision (ROD) for the site was signed on September 28, 2006. The major components of the ROD are to use electrical energy to heat the most contaminated area of site to reduce the contaminants to a less toxic state, continue the groundwater extraction and treatment system, to investigate possible secondary anaerobic bioremediation for nitrates present at the site, restrict access to the site and cap soil areas where there is contamination until the property is developed.

EPA expects to finish the heating treatment system design by September 2009, and begin system installation and start-up (heating) a few months later.

See above

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Cleanup Results to Date

As described above, EPA has been operating a groundwater extraction and treatment system since 1995. While the system has been effective in removing contaminants from groundwater in the field north of the site, quarterly groundwater monitoring data shows that the system is not capturing all of the plume (the area of contaminated groundwater) in the Mace Ranch subdivision. EPA expanded the groundwater extraction and treatment system starting in August 2003 to further enhance the plant effectiveness. Expansion included installation of five new wells capable of extracting and monitoring contaminated groundwater, completion of four extraction wells and replacement of pressurized treatment system discharge plumbing with a gravity flow line to facilitate increased pumping capacity and reduced energy demand. Groundwater extraction and plant optimization is on-going.

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Potentially Responsible Parties

Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.

EPA has found that the owners of the Frontier Fertilizer site are not financially viable PRPs. Therefore, contamination at the site is being addressed using funding from the Superfund budget.

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Documents and Reports

Administrative Records
		Groundwater and Soils Operable Unit
		Remedial Updates 2-4
Fact Sheets
	09/01/97	Update on Frontier Fertilizer Superfund Site
	05/01/98	Additional Groundwater Monitoring Wells to be Installed in Mace Ranch Park
	10/01/99	Extraction Wells And Additional Groundwater Monitoring Wells To Be Installed In Mace Ranch Park
	04/01/00	Extraction Well to be Installed at Mace Ranch Park
	07/01/00	New Location Proposed for Extraction Well in Mace Ranch Park
	06/01/01	Next Phase of Field Activities to Expand the Groundwater Extraction and Treatment System at the Frontier Fertilizer Superfund Site
	12/01/02	EPA Completes Planned Characterization of Site Contamination
	05/01/03	Community Update: Construction Planned for Summer of 2003
	08/01/03	Update: Treatment System Expansion Work to begin August 25, 2003
	06/01/05	Update on Groundwater Extraction, Treatment and Monitoring Activities
	06/01/06	Correction to June 2006 Proposed Plan Table of Preliminary Cleanup Levels for Soil and Groundwater
	06/01/06	EPA Proposes Groundwater and Soil Remedies and Requests Public Commnet
	07/01/06	U.S. EPA EXTENDS COMMENT PERIOD FOR FRONTIER FERTILIZER PROPOSED PLAN
	12/01/06	EPA Selects Cleanup for Frontier Fertilizer Superfund Site
	02/01/08	EPA Requests Public Comments on Target Argeement
	02/15/08	EPA Requests Public Comments on Target Agreement
	05/01/08	Community Involvement Plan
	04/10/09	Update: EPA Will Sample Groundwater and Test Soil Gas
	09/15/09	Cleanup Action Update Bulletin, Number 2
	10/23/09	Open House and Community Meeting on Electrical Resistive Heating Treatment System Design, Start-Up and Operation
Legal Documents
	01/14/08	Administrative Agreement And Orders On Consent For Certain Remedial Activities
		Proposed Notice Of Administrative Order On Concent For Certain Remedial Activities In Connection With The Frontier Fertilizer Superfund Site
Records of Decision
		Record of Decision - Soil And Groundwater Frontier Fertilizer Superfund Site - September 28, 2006
Technical Documents
	04/01/97	Final Interim Remedial Investigaiton Report Volume 1. Appendices Volume 2.
	06/01/99	Supplemental Remedial Investigation Report Volume 1. Volume 2- Appendices
	01/01/03	Final Supplemental Remedial Investigation Report No.2
	06/01/06	Final Feasibility Study
	09/29/09	Final In-Situ Thermal Treatment Frontier Fertilizer NPL Site

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Community Involvement

Public Meetings: Proposed Plan Public Meeting was held on June 22, 2006. Public meetings are planned for late 2009 / early 2010 to present final design for in-place heating remedy.

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Public Information Repositories

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Additional Links

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Contacts

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