Weld County said Monday that it's ready to begin offering water-testing services for residents concerned about potential contamination of their wells from oil and gas activity near their property.

The county's Department of Public Health and Environment has a new gas chromatograph and mass spectrometer instrument that can measure chemicals in the parts per billion.

"That is like saying we can measure something that is as small as one eyedropper drop of water in an Olympic-sized swimming pool," county chemist Mark Thomas said.

Thomas expects that people who have water wells will take advantage of the test before drilling occurs so that they can compare it to future tests.

The instrument, purchased with a grant from the Federal Mineral Lease Board, cost $145,000.

"This instrument provides valuable information and will not only help protect public health, but also provide assurance," Commission Chairman Sean Conway said.

The county will offer free testing for volatile organic compounds. For additional fees, the county can test water samples for metals, ions, pH and bacteria.

County residents interested in having their well-water tested can call the Weld County Department of Public Health and Environment at (970) 304-6415 and provide a name, address and phone number. A member of the Weld County staff will contact the resident to set up an appointment to collect a sample.