Buckley Road Area Trichloroethylene (TCE) Cleanup and Abatement

Project Description and Background

Buckley Road AreaThe Central Coast Regional Water Quality Control Board (Central Coast Water Board) is the lead agency overseeing the investigation of trichloroethylene (TCE) in groundwater in the Buckley Road area, adjacent to the San Luis Obispo County Regional Airport (as shown on the adjacent map). The initial investigation area included properties along Buckley Road, Thread Lane (also known as Noll Road), Davenport Creek Road, Evans Road, Angie Lou Lane, Mello Lane, Three Sisters Road, Hidden Springs Road, Edna Road, Windmill Road, Rancho Oaks Drive, Sherpa Ranch Road, and Airport Drive. Central Coast Water Board staff has conducted drinking water testing at 69 locations. Currently, nine private domestic wells and three industrial wells out of 69 locations tested since 2015 exceed the drinking water standard for TCE of 5 micrograms per liter. The current maximum detected concentrations of TCE in a private domestic well and industrial well are 97 and 48 micrograms per liter (μg/L), respectively, and occur in the Thread Lane area. Based on the distribution of TCE detected in supply wells, Central Coast Water Board staff focused the primary area for further investigation to the Thread Lane, Davenport Creek Road, Evans Road, Angie Lou Lane, Mello Lane, and Three Sisters Road area, where TCE concentrations are near or above the drinking water standard.

In 2016, the Central Coast Water Board required San Luis Obispo County to conduct soil gas and groundwater investigations on its regional airport property to investigate potential sources of TCE associated with industrial operations and old dump sites at the airport. The County completed their fieldwork investigation in September 2016. The results of the County’s soil gas and groundwater investigation indicated there is no evidence of a TCE source present on the airport property contributing to the Buckley Road Area TCE plume. Given the results from the County’s soil gas and groundwater investigations, the next step was to conduct additional investigations and delineation of TCE in the industrial area overlying the highest concentrations of TCE along Thread Lane. Investigations at 825 Buckley Road and 795 Buckley Road were completed and investigation reports were submitted by mid-2017. Based on the results reviewed for the two investigations, a TCE source remained undiscovered and an investigation at 4665 Thread Lane was still required. The property owner for 4665 Thread Lane applied for a grant from the State Water Resources Control Board (State Water Board) to assist with funding of the investigation costs. Central Coast Water Board staff worked with the property owner and State Water Board grant personnel to secure funding, which resulted in investigation work being implemented from August through December 2018. Results from the soil and soil gas investigation at 4665 Thread Lane did not reveal evidence of a surface discharge of TCE. However, the distribution of groundwater sample results in the Thread Lane area indicates that elevated TCE concentrations occur in deep groundwater beneath the 4665 Thread Lane property at a concentration of up to 783 micrograms per liter. This TCE concentration is approximately 157 times greater than the drinking water standard and over a magnitude greater than recent sampling results from adjacent properties.

TCE detections in the Buckley Road Area form a 1/2-mile-long by 1/3-mile wide plume extending from approximately Thread Lane to Davenport Creek Road. The 4665 Thread Lane property is located above the highest concentrations of TCE detected in the Buckley Road area. The Central Coast Water Board interprets the results of the investigation to indicate that a source of TCE in the Buckley Road area originates from 4665 Thread Lane. Maps showing the distribution of TCE in the vicinity of Buckley Road and Thread Lane were prepared by the Central Coast Water Board and are included in a January 23, 2019, technical memorandum available for review along with the current investigation report for 4665 Thread Lane on this website in the section titled "Buckley Road Area TCE Investigation Reports and Correspondence".

The Central Coast Water Board issued Cleanup and Abatement Order (CAO) No. R3-2019-0090 to responsible parties (RPs) on July 31, 2019. As required in the CAO, the RPs submitted a Replacement Water Plan (RWP) dated November 1, 2019, a Workplan to Delineate Extent of Waste and Conduct Remedial Investigation and a Preliminary Conceptual Site Model (both dated November 22, 2019) for review; the Central Coast Water Board subsequently issued conditional concurrence letters on the documents on January 21, 2020, and February 24,2020, respectively. According to the approved RWP, all accessible properties with an impacted well (e.g., concentrations above the drinking water standard) are required to be provided replacement water (wellhead treatment) by June 30, 2020. A report on the first phase of the remedial investigation is due May 22, 2020, to the Central Coast Water Board.

Central Coast Water Board staff has created this website to help provide residents with current information. An email subscription ("Lyris") for the Buckley Road Area TCE Investigation has also been developed to keep interested parties notified of current events (you can subscribe to the email list by clicking the link at under "Subscribe to our Email Lists" section.

Additional information on the Buckley Road Area TCE Investigation, including documents, reports, and correspondence for all related investigations can be found on the State Water Resources Control Board’s public GeoTracker website: https://geotracker.waterboards.ca.gov/profile_report.asp?global_id= T10000010079

Check for updated information in the "Announcements & Public Notices" and "Buckley Road Area TCE Investigation Reports and Correspondence" section below. The most recent announcements will be at the top of the list. A summary of Central Coast Water Board actions is also available under the "Executive Officer’s Report" on this webpage.

Announcements and Public Notices

Buckley Road Area TCE Investigation Reports and Correspondence

2020 Thread Lane Area Investigation

2019 Thread Lane Area Investigation





Contacto en español

El Consejo Regional de la Costa Central para el Control de Calidad de Agua (Central Coast Regional Water Quality Control Board) está proporcionando esta notificación a propietarios, inquilinos e interesados acerca de nuestra investigación del químico "trichloroethylene", encontrado en aguas subterráneas en el área de “Buckley Road" en San Luis Obispo. Si desea obtener información en español, póngase en contacto con:

Hector Hernandez al (805) 542-4641


Central Coast Water Board