Soil Quality Monitoring along the Purgatoire River

The Colorado Department of Public Health and Environment (CDPHE) requires annual soil quality monitoring in accordance with Part 1, Section A.3 (i.e., Reporting Codes 21599 and 50008) of the Colorado Discharge Permit System (CDPS) to monitor the effects of coalbed methane (CBM) produced water discharges into the Purgatoire River on irrigated lands in southeastern Colorado.

The objective of soil monitoring is to preserve agronomic soil properties and irrigated crops downstream of discharge points from the application of CBM produced water containing naturally elevated salinity and sodicity levels. Elevated salinity and sodicity in irrigation waters may impair agronomic soil properties and reduce crop growth and productivity.

Annual soil monitoring is conducted on two fields receiving irrigation waters from the Purgatoire River downstream of the closest discharge point. Soil samples are collected using a truck-mounted, hydraulically powered Giddings soil probe two times a year, prior to irrigation activities and following irrigation activities, to establish current soil physicochemical properties and to proactively determine any deleterious effects on soil quality from the application of irrigation waters receiving CBM produced water discharges. A technical report is developed bi-annually, following each monitoring activity, to discuss monitoring results and any changes/trends in soil chemistry (i.e., soil salinity, soil sodicity). Soil technical reports are also prepared to address any remediation efforts that may be required upon the recognition that irrigation is impacting soil quality.

Soil quality monitoring is an ongoing effort to establish trends in soil chemistry from the application of CBM influenced irrigation water and to fulfill CDPHE-CDPS permitting requirements. Soil analytical results to date indicate minimal changes in soil chemistry from the application of CBM discharge receiving irrigation waters of the Purgatoire River.