On a rainy day on Fearing Street in Amherst, the first thing one might notice on the road might be the sound of a small brook – hidden at first by vegetation and a deep trench – roaring out of a culvert on its way to the University of Massachusetts’ Campus Pond.

Another thing one might notice might be the smell near the brook. Heavy and and oily, the water of the brook – called Tan Brook – smells suspiciously like a gas station. Occasionally, white foam appears at the mouth of the culvert – a fact that has not gone unnoticed by some of the residents on Fearing Street.

Joe Lyn, whose property abuts the brook, said “occasionally, it stinks of fuel oil. Not the tangy kind, but a thick heavy petroleum.”

Tan Brook is a small brook, about 2 to 3-feet wide, which starts at Strong Street, goes by Wildwood Cemetery and flows through the Campus Pond before continuing into the Mill River. The brook, which cannot even be found on Google Maps, is relatively unknown as large sections of it have been contained in culverts under the center of town and Haigis Mall at UMass.

While creating culverts for a stream to make way for the construction of roads and buildings is a common practice, the culverts have caused increased flooding in the watershed, increased the number of pollutants flowing into the stream, and degraded the overall water quality of the stream, according to Amherst Planning Director John Tuck.

“In other words, the usual,” he said.

The stream has a history with pollution that some residents believe might still be affecting it today.

“The brook was doubtless used for disposal of tanning waste by-products,” said Tucker, referring to the dumping of chemicals from local tanneries into the brook in the 1820s, which is how the brook received its name.

Residents are suspicious that oil may have been spilled into the brook in the 1970s. While oil degrades slowly enough that if that happened, the oil still could be in the brook causing the spill, there is currently no way to prove these claims.

Over the years residents have complained about the smell and flooding from the brook to officials, including the Amherst Conservation Commission, but no action has been taken.

According to Stephanie Ciccarello, Amherst’s wetlands administrator and sustainability coordinator who works with the town’s Conservation Commission, many residents have complained about the brook.

“Concerns about Tan Brook have been expressed for years and include concern over storm water runoff, little to no treatment for removal of pollutants, sediment, odor, potential contamination, etc.,” said Ciccarello. She went on to note that residents who live near the day lighted, or non-culverted, sections of the brook have complained of a distinctive odor.

However, Ciccarello said the brook is not her problem.

“The Conservation Commission is not necessarily responsible for improving the quality of Tan Brook,” said Ciccarello. She explained that while Tan Brook is a project the commission would like to work on one day, it is not legally required to do so, and currently Tan Brook is not in the budget.

“Tan Brook is one on the list of projects,” Ciccarello said. “At some point, we would really like to investigate what we can, but financial limitations are often a barrier.”

In May 2009, the Conservation Commission and UMass applied to the Massachusetts Water Quality Management Planning Grant Program for a $48,500 grant to do a watershed assessment, water quality analysis and develop a plan for how to improve the brook. The groups were denied the grant due to lack of state funds.

The commission has not applied for another grant to study Tan Brook. According to Ciccarello, grants are cyclical in nature and the commission has not seen a grant application that applies to Tan Brook. However, if an opportunity popped up, Ciccarello thinks it is likely the Conservation Commission would apply again.

“We are always looking for grants,” said Ciccarello.

If the commission were to receive a grant, the Conservation Commission would want to do the same things it wanted to do in 2009.

“First thing, we would to a study on where problem locations are and then we would want some kind of report that would outline a course of action,” said Ciccarello.

In the meantime, at least one resident does not think the efforts of the commission have been good enough.

“Officials just say ‘don’t worry about it,’ when we ask about the brook,” said Lyn.