CHARLTON – Sewer officials put the owners of Tree House Brewing Co. on notice this week, after a town consultant reported test results that indicate high levels of metals and other contaminates discharging into the town's system from the new business.

Charlton Water & Sewer Commission administrator Steve Wandland sent a letter Wednesday to the engineer for the 55,000-square-foot brewing company, which opened on Route 20 in July. Bohler Engineering of Southboro works for Tree House Brewing.

The letter said Charlton has “many troubling questions” about discharge flow and sampling results it received from McClure Engineering of Charlton, a town consultant.

The letter went on to say that effluent flow and values for metals — specifically lead, copper, aluminum and zinc — as well as biochemical oxygen demand, total suspended solids, ammoniacal nitrogen, phosphorus, nitrate and nitrite exceed the values submitted by Tree House Brewing’s engineers during the planning phase for the business’s opening.

Mr. Wandland told commissioners this week that Charlton had been sending discharge to the Upper Blackstone Water Pollution Abatement District in Millbury at a rate of three to five truckloads per month.

It is now sending eight to nine trucks per month attributable to the brewing company.

According to data supplied to the town by McClure Engineering, the biochemical oxygen demand exceeded the maximum allowable level of 250 micrograms per liter each of the nine times McClure took samples, including 5,580 micrograms per liter recorded on Sept. 7.

The consultant also reported that four of nine samples taken exceeded total suspended solids, which also have a maximum allowable level of 250 micrograms per liter.

Commissioners instructed Mr. Wandland to send notice to Tree House Brewing advising that it was in violation, and the company would be fined, according to video of the meeting posted on YouTube.

Town wastewater operator Veolia North America is presently reporting that the town is compliant concerning metals discharge. As such, commission member Robert Lemansky suggested that the town could apply a surcharge to Tree House Brewing. Many other customers have a zero effect on the system, thus diluting the waste for which Charlton tested high, and one could say the net result is “negligible,” Mr. Lemansky suggested.

But Mr. Wandland said he had a problem with assessing a surcharge because in his view it sent a message that the discharge is acceptable, when it is not. Also, Mr. Wandland said he didn't think Mr. Lemansky's suggestion would go over well with the state Department of Environmental Protection.

The town letter also expressed concern about the commission’s uncertainty about the setup and calibration of two waste stream volume meters, and the town agency recommended that Bohler Engineering confirm the installation and setup of meters by a third party, to ensure accuracy.

The letter asks for Tree House to respond in 15 days.

A spokesperson for Tree House Brewing said the company had not received the letter.