The state Department of Environmental Protection might have used incomplete and inaccurate test information to decide whether chemicals leaking from a Marcellus Shale wastewater impoundment and a drill cuttings pit contaminated a water well and springs in Washington County.

The disclosures came last week during sworn testimony by Vincent Yantko, a DEP water quality specialist and supervisor of the department’s investigation at Range Resources’ Yeager farm drill site in rural Amwell Township, as part of a case before the state Environmental Hearing Board in Pittsburgh.

Mr. Yantko was the first defense witness the DEP called in the case brought by Loren Kiskadden, who is appealing the department’s determination that his private drinking-water well wasn’t contaminated by pollutants leaking from Range Resources’ 13.5 million-gallon wastewater impoundment and mud and cuttings pit in 2010 and 2011.

The case before Thomas Renwand, chief judge of the hearing board, is the first in the state to challenge a DEP water supply determination denying contamination. It started last week and will resume Tuesday.

The DEP sent a determination letter to Mr. Kiskadden on Sept. 9, 2011, saying Range’s gas operations on a ridge above rolling farm fields did not contaminate his well water.

Range has repeatedly denied its shale gas development operations on the Yeager farm site produced any impacts on Mr. Kiskadden’s well or the well water of other residents of the narrow valley below the drill pad, impoundment pit and cuttings pit. The company blames Mr. Kiskadden’s problems on natural contaminants, bacteria from livestock and septic systems.

Mr. Kiskadden, who lives about a mile from the Yeager drill pad at the lower end of the valley, wants Range to provide a replacement water supply.

He and two other families also have filed a lawsuit against Range alleging that they experienced serious health problems due to exposure to water and air pollutants from the Yeager site.

Last week, during cross-examination by Kendra Smith, who is representing Mr. Kiskadden with her husband, John, Mr. Yantko admitted the DEP did not follow its regulations to determine whether leaks had occurred and did not report all of its findings to Mr. Kiskadden.

Although Mr. Yantko said the DEP had “concerns about leaks and migration of fluids” through the soil and groundwater in March 2010, it did not order Range to drain the double-lined impoundment and check for leaks, conduct dye tests to track leak migration or perform its own water sampling until August 2011.

DEP samplings at a leak-detection manhole next to the wastewater impoundment in August 2011 found total dissolved solids at more than 29,000 milligrams per liter — four to five times greater than what is expected in normal groundwater and more than 50 times what is acceptable for drinking water.

Mr. Yantko testified that even though those tests showed “a strong possibility of a leak,” the department had no reason to believe the contamination was moving through the groundwater off-site and did not tell Mr. Kiskadden or any other area residents about the results.

Mr. Yantko testified that the DEP did not tell Mr. Kiskadden that seven months after it sent the September 2011 determination letter, tests showed acetone in soil around the drill cuttings pit and in Mr. Kiskadden’s drinking water. Acetone is a component of some fracking fluids, and the U.S. Environmental Protection Agency has detected it in investigations of shale gas contamination in Wyoming.

Although Range has admitted contaminating the Yeager farm springs, Matt Pitzarella, a Range Resources spokesman, said state and federal regulators have confirmed the company’s operations have caused “no impacts on any other water supplies in the area,” including Mr. Kiskadden’s.

Mr. Yantko also testified that Range did not seek or receive permission from the DEP to flush the drill cuttings pit with 30,000 gallons of clean water on July 14, 2011, in an attempt to dilute contaminants in the soil.

In his field notes, Mr. Yantko wrote, “This action was both intentional and reckless, and may have resulted in additional contaminants entering the Yeager spring water supply.”

Range had trouble digging out all the contaminated soil around the drill cuttings pit. According its own records, between June 17 and July 7, 2011, it removed 722 tons of drilling mud and cuttings, the waste rock that comes to the surface during the gas well drilling process, plus 131 tons of contaminated soil beneath the pit.

Soil tests done after that excavation still found carbon disulfate, benzene, toluene, oil and grease and total petroleum hydrocarbons in the soil that remained, Mr. Yantko confirmed in his testimony.

Some of those contaminants also were present in the laboratory test results on Mr. Kiskadden’s tap water, according to court documents filed with the Environmental Hearing Board in October 2011.

Range conducted five excavations of the pit from June through September 2011, digging up a total of 2,135 tons of dirt and cuttings.

The DEP eventually approved Range’s pit closure plan because it was able to show that the chemical residue in the pit matched that in a background or baseline soil sample taken outside of the drilling area. That’s a regulatory requirement before a closure plan can be approved.

But there are indications, according to testimony, that test results on the background soil sample might have been altered to include chemical components that were not actually present in the sample. That allowed DEP to conclude that the samples matched and approve Range Resources’ request to close the pit.

Ms. Smith raised questions about the baseline report, and Mr. Yantko testified that benzene and toluene did not show up in DEP’s laboratory findings and were actually listed as not detected by the lab.

Ms. Smith: “The report says toluene was detected in the background sample, but the lab report indicates it was not detected?”

Mr. Yantko: “Yes.”

Ms. Smith: “Was that inaccurate?”

Mr. Yantko: “The numbers don’t match.”

Ms. Smith: “Not only don’t they match, one says it’s not there.”

Mr. Yantko: “That’s correct.”

The Yeager impoundment was one of five Range Resources impoundments in Washington County that the DEP ordered closed earlier this month. The consent order also required Range to pay a $4.15 million penalty, upgrade two existing impoundments and begin soil and groundwater investigations.