ONEOK FMGP - Abilene Site

Site Background

The Former Manufactured Gas Plant (FMGP) (Site) in Abilene, Kansas, is approximately one-quarter acre at the southeast corner of South Mulberry and Southwest Second Streets. The property is currently a vacant lot. The Site is secured by a chain link fence with locking gates and is surrounded by mixed-use properties which include residences, evidence of a former railroad spur; and a Burlington Northern Santa Fe railroad right-of-way.

Investigation Findings

Results from several investigations identified environmental contamination in soil and/or groundwater above the Risk-based Standards for Kansas (RSK) values. These contaminants include:

  • Polycyclic aromatic hydrocarbons (PAHs), benzene, ethylbenzene, and toluene inside and outside the below-ground gas holder and tar well
  • Benzene, ethylbenzene, and toluene in and around the former aboveground oil tanks
  • Arsenic in one surface soil sample collected in the northeast portion of the Site
  • The probable presence of hydrocarbon-rich non-aqueous-phase liquid (NAPL) in the subsurface

In early 2005 ONE-Gas completed an Interim Removal Action (IRA) in which FMGP residuals and visibly impacted soil were removed from the below-ground gas holder and tar well structures. The IRA activities resulted in the removal of:

  • Approximately 280 tons of soil and debris inside the gas holder tank
  • Approximately 30 tons of oil and debris inside the tar structure
  • Approximately 205 tons of soil and debris outside of and between the tar structure and gas holder tank

While 515 tons of contaminated soil and waste have been removed from the site and disposed in an approved hazardous-waste land fill, residual soil contamination remains.

Several phases of groundwater investigation took place from August 2005 to 2009, with further groundwater sampling in 2015, 2016, and 2017. The primary constituents of concern (COCs) in groundwater are benzene, ethylbenzene, naphthalene, and arsenic. These primary COCs were detected at least once at concentrations above the RSK Residential and Non-Residential Tier II Groundwater values. Benzo(a)anthracene has also been periodically detected in two wells, but to a lesser extent than the other COCs.

In 2016 ONE-Gas conducted a Supplemental Site Investigation (SSI) using direct-push boring/groundwater sampling and hollow-stem auger drilling techniques. The investigation identified residual soil contamination near the location of former FMGP structures and delineated the extent of groundwater contamination.

In December 2017 a door-to-door receptor survey was conducted for the properties surrounding the Site (Figure 2). Respondents were asked a series of questions including if their home or business had a basement and if a water well was located on the parcel. Several homes directly east and downgradient of the Site do have basements, and one has a water well. The owner of this water well stated that the well had been dry for the duration of their ownership.

Based on current Site use and surrounding off-Site parcels, the potential exposure pathways only include human risk receptors. There are unlikely to be completed exposure pathways for ecological receptors due to urban nature of the Site and the remedial actions already taken. Potential human receptors include future construction workers, and future residents or indoor workers.

Off-Site groundwater impacts indicate that exposure via vapor intrusion is unlikely. There is a potential for exposure to impacted groundwater though ingestion, dermal contact, and/or inhalation of vapors if private water well(s) are installed in the future.

Proposed Remedy

KDHE identified remedial action objectives which include: 1) preventing human exposure through direct contact with contaminated soil, 2) preventing human exposure through direct contact and/or ingestion of contaminated groundwater, and 3) restoring groundwater conditions to the extent practicable. The corrective action goals are meant to reduce contamination levels below Residential and Non-Residential RSKs in soil and groundwater. Groundwater monitoring will continue until the Site is eligible for closure in accordance with KDHE Bureau of Environmental Remediation (BER) Policy, BER-RS-024, Site Closure in the State Cooperative Program.

The recommended remedial action identified by the Corrective Action Study, is Alternative 4 - In-Situ Stabilization with Groundwater Treatment. This remedy also includes establishing an Environmental Use Control to restrict future property use in order to prevent exposure to contamination. The cost of this remedy (in 2018 dollars) is $5,763,682 USD with an additional estimated contingency cost of $1,149,636 USD. Therefore, the total estimated cost for this remedy is $6,913,318 USD.

A Public Information Plan was developed by KDHE and includes implementation criteria satisfying public participation requirements. All pertinent documents related to the Former Manufactured Gas Plant site are available for review at the KDHE offices in Topeka, Kansas, or at the links below.

Site Documents