By Cassie McClure and Suzanne Michaels
Published in Las Cruces Sun-News 7/7/19
On June 20th, more than 30 residents came out to Desert Hills Elementary to hear Las Cruces Utilities (LCU) present the Assessment of Corrective Measures Report (ACM) on what is known today as the “Old Foothills Landfill” (OFL) at 555 S. Sonoma Ranch Blvd. The OFL today is closed to landfilling trash, but was an active, unlined landfill for city trash from 1966 to 1996. In the early 1990’s the Environmental Protection Agency (EPA) enacted new, more stringent regulations that required the nation’s landfills to be lined with multiple liners and with leachate collection systems installed. This was to protect adjacent property or groundwater from contaminants that could be carried by rain and stormwater passing through the waste zone. Joshua Rosenblatt, LCU regulatory and environmental analyst, explained to attendees at the June meeting, “As part of the OFL closing, seven on-site groundwater monitoring wells and two off-site groundwater monitoring wells were installed, and the 30-year annual and currently semi-annual groundwater sampling program began.” Water testing detected small amounts of elevated concentrations of volatile organic compounds common in a variety of solvents that had reached groundwater below the site from years of rain and stormwater flow before the landfill was closed.” Extensive soil vapor analysis was also conducted in 2017-2018 to determine how much of these solvents remained in the soils and how much was venting to the air. The detection of soil vapor was very low and well below the New Mexico and EPA air quality standards.
As part of the closure plan, two corrective measures were taken to mitigate further movement of the contaminants: redirection of stormwater around the entire site so that rains can no longer drive any more contaminants down through the trash, and capping of the entire trash mound with a membrane. The OFL was then topped with 18-22 inches of soil and planted with native vegetation effectively encapsulating the waste zone. “The OFL groundwater monitoring will continue through July 2041 by LCU and the New Mexico Environment Department Solid Waste Bureau,” explained Rosenblatt. After the public comment period ends for the ACM, the LCU will submit to the New Mexico Solid Waste Bureau that no additional corrective actions need to be undertaken at this time. “Because of the correction actions already taken, and the isolated nature of the plume, there is no threat to public safety, our drinking water, or to the air we breathe.” Over time, he added, the remaining pollutants will naturally attenuate and the monitoring program will continue to keep the State, the Utilities Department, and our customers informed. Today, the 160-acre OFL has been repurposed and is still a very active site. LCU accepts “clean fill” (inert materials such as clay, soil, rock, broken pieces of concrete) at the OFL and manages and composts the City’s green waste at this site. The closed landfill also provides a spectacular home for the City’s Model Airplane Park and Archery Range. The report presented at the meeting, “ACM of groundwater contamination at the Foothills Landfill site” is available online at: https://bit.ly/2NappJm or by request at (575) 528-3700.
The City welcomes public comments on the ACM report up to 30 days after the June 20th meeting. Comments may be mailed to:
City of Las Cruces - Solid Waste
P.O. Box 20000
Las Cruces, NM 88004
You can reach Las Cruces Utilities at 528-3500 from 8 a.m. - 5 p.m. Monday through Friday. Las Cruces Utilities provides GAS – WATER – WASTEWATER – SOLID WASTE services to approximately 100,000 Las Cruces residents and businesses.
PHOTO 1: Residents who attended the ACM presentation study maps and the data collected from groundwater testing below the closed landfill.