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. 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.

From 2015 to 2020, Central Coast Water Board staff conducted drinking water testing at 69 well locations as part of the investigation, including repeated sampling at some locations to monitor the TCE plume. Under a Central Coast Water Board Cleanup and Abatement order, responsible parties took over testing of wells in June 2020. Initially, up to 14 supply wells were found to be impacted by TCE above the drinking water standard of 5 micrograms per liter. As of March 2021, 10 supply wells (seven private domestic wells and three industrial wells), out of 70 locations tested since 2015 exceed the drinking water standard for TCE of 5 micrograms per liter (μg/L). The current maximum detected concentrations of TCE in a private domestic well and industrial well are 93 and 52 μg/L, respectively, and occur in the Thread Lane area. This compares with a maximum historical TCE concentration of 320 μg/L detected in a Thread Lane industrial supply well in 2003.

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 implementation of the investigation from August through December 2018. Results from the soil and soil gas investigation at 4665 Thread Lane did not reveal evidence for a surface discharge of TCE. However, the distribution of groundwater sample results in the Thread Lane area indicated 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 10 times 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 results of the investigations indicated 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 required documents including a Replacement Water Plan (RWP) dated November 1, 2019, and a workplan to conduct a remedial investigation/feasibility study (RI/FS)- dated November 22, 2019 to the Central Coast Water Board. According to the approved RWP, all accessible properties with an impacted well (e.g., concentrations above the drinking water standard) must be provided replacement water (including via wellhead treatment systems). As of April 2021, the RPs have installed wellhead treatment systems at all accessible properties and conducted four rounds of groundwater monitoring in the Buckley Road area. The RPs have not met reporting deadlines as they await grant funding for conducting the RI/FS work. Grant approval is anticipated in the first half of 2021.

At the request of the Central Coast Water Board, San Luis Obispo County completed an additional investigation for TCE at a former World War II aircraft hangar located adjacent to the airport windsock along Buckley Road. Sampling was also conducted directly south of the former hangar at 795 Buckley Road. Soil gas results indicate that 795 Buckley Road may be a source of TCE discharge. On February 1, 2021, the Central Coast Water Board issued an order requiring parties associated with the property to submit a workplan for additional investigation at 795 Buckley Road. The workplan has been approved with field work scheduled to occur during summer 2021.

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

2021 Thread Lane Area Investigation

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:

Monica Barricarte al (805) 549-3881


Central Coast Water Board