PHASE II SEEP INVESTIGATION RATON BASIN, COLORADO

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1 COMPLIANCE / ENGINEERING / REMEDIATION Contact us: LT Environmental, Inc PROJECT DESCRIPTIONS COLORADO OIL AND GAS CONSERVATION COMMISSION (COGCC) PROJECTS PHASE II SEEP INVESTIGATION RATON BASIN, COLORADO LTE teamed with Apogee to complete a methane seep investigation for the COGCC. This project incorporated many of the same aspects as those defined Rule 608. Apogee conducted a mobile survey of the area using a truckmounted IRS to locate methane seeps and LTE analyzed the data and performed field verification of methane seeps. Approximately 3,200 miles of roads in the Raton Basin were surveyed and 59 methane seeps were identified. Of the 59 seeps identified, detailed mapping identified 55 sites for field investigation. LTE performed the detailed mapping of the methane seep sites where access was granted. The investigation identified 35 of the 55 sites mapped contained active methane seepage.

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3 COGCC EMERGENCY RESPONSE FUND WELL INVESTIGATION SOUTHEAST AND SOUTHWEST COLORADO LTE was retained by COGCC to conduct soil gas surveys under the Emergency Response Fund for 48 orphaned plugged and abandoned (P&A) wells in the southeast region of Colorado and 38 orphaned P&A wells in the southwest region of Colorado. LTE researched the COGCC online database to review files for orphan well sites and any relevant information to the location and boundaries of the well site and/or associated wellhead. LTE also used aerial photography, interviews with landowners, COGCC databases, and field observations to identify and locate well sites. This information was incorporated into the GIS and used to develop a sampling grid for each well site. Results were sent to landowners and the COGCC summarized the findings of the investigations. LTE sent the data to COGCC in an electronic deliverable format.

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5 METHANE SEEP INVESTIGATION RATON BASIN, COLORADO LTE and Apogee conducted independent methane seep investigations at the Primero High School in Weston, Colorado at the request of the COGCC. The purpose of the investigation was to determine if methane seeps were occurring in an area where several sensitive receptors (school and teacher residences) had been identified. Apogee conducted a mobile survey of the area using a truckmounted IRS to locate methane seeps and LTE inspected the interior structures at the school and residences for the presence of methane, define the extent of any methane seeps identified on the property, and assess potential risk to nearby receptors by collecting shallow soil gas samples using a slide-hammer and rod, hand-held field gas meter, and a GPS. Both the Apogee and LTE surveys detected methane gas in the vicinity of the bus barn at the site. A follow-up field mapping survey of the site was conducted by LTE. Results indicated that methane gas continues to seep in the area around the bus barn. This project demonstrates the ability of the LTE/Apogee team to work in tandem to efficiently and systematically identify, define, and assess methane gas seeps in the Raton Basin.

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7 METHANE SEEP MAPPING AND MITIGATION RATON BASIN, COLORADO LTE was contracted by the COGCC to conduct an initial reconnaissance methane seep survey at two residences located in the Purgatoire River Valley in the Raton Basin, Colorado. The survey included the collection of approximately 30 subsurface gas measurements around and inside the residential structures, including the basement/crawlspace areas. A second survey included investigations of the entire property with the collection of more than 200 measurements on a grid system, mapping of vegetative features indicative of methane seepage, mapping of visible seeps in surface water bodies and additional gas sampling from within seep area. The survey identified several methane seep areas across the 55-acre parcel of land. The surveys identified the presence of elevated methane concentrations in the soil surrounding the structures as well as in the ambient air within the basement/crawlspace areas. Analytical results indicated the presence of thermogenic methane at the seep area. LTE designed and installed methane detection systems within the two residences to warn the occupants if and when methane gas concentrations in the ambient air approached the lower explosive limit. LTE designed and installed two active methane mitigation systems to ventilate the basement/crawlspace of each structure with ducting fans that were actuated by the previously installed detection system to prevent the accumulation of explosive vapors. To date, the systems have been effective at preventing the buildup of explosive vapors. This project incorporated extensive detailed seep mapping in compliance with Rule 608.

8 PRIVATE RESIDENCE EMERGENCY RESPONSE INVESTIGATION LAS ANIMAS COUNTY, COLORADO LTE was contracted by COGCC to investigate the cause of a house explosion in Las Animas County, Colorado, suspected to be the result of methane gas. In order to identify potential sources of methane gas, nearby water wells, coal outcrops, nearby producing gas wells, a mine core hole, and plugged and abandoned production wells were reviewed. As part of the investigation, a soil gas survey was conducted at a private residence, nearby plugged and abandoned production wells, and a mine core hole. The soil gas was characterized and analyzed. The horizontal extent of the seepage was investigated using a grid pattern to place borings. A follow-up survey was performed near plugged and abandoned wells to confirm the extent of the methane seepage. GPS data was used to log points and a four-gas meter was

9 used to collect subsurface methane, oxygen, carbon dioxide, and hydrogen sulfur gas concentrations. A mine core hole was also investigated as a potential source of methane gas. Survey methods and field confirmation did not suggest the presence of a methane source. Water well investigations, inspection of residences in close proximity of the private residence, a surface geology reconnaissance were also conducted as possible sources of methane gas.

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