The city wants to know if the drinking water piped downstate from the Croton reservoir needs to be filtered. So who did they ask to study the question? A joint-venture company that already holds a $50 million city contract to design the filtration plant.

Late last year, the city gave the joint venture between two consulting firms, Hazen & Sawyer and Metcalf & Eddy, $3.7 million to study the need for filtering the water from the reservoir in Westchester County. The same firm already held the much larger design contract.

“They’re being given a lot of money to find out whether or not they should get the $50 million,” says Assemblyman Jeffrey Dinowitz, the Bronx Democrat who represents area where the plant might be built. “I think I know what their determination will be. This is an obvious conflict of interest.”

Dinowitz, other elected officials and several community groups recently asked City Comptroller Alan Hevesi to investigate the matter. Congressman Elliot Engel, who represents the northern Bronx, has asked the Environmental Protection Agency to make sure the study is unbiased.

A Hazen & Sawyer engineer refused comment on the contract. Calls to the city Department of Environmental Protection on Friday were not returned.

Community groups are opposed to a plan that would site the filtration plant in Jerome Park in the northern Bronx. They say the huge construction job would endanger thousands of local schoolchildren, and other environmental hazards would harm the surrounding neighborhood. They are calling on the city to scrap the plant altogether–or place it in Westchester.

“We’re going to keep pushing and knocking on doors,” says Tina Argenti, chairperson of the Croton Citizens Advisory Committee.