Discharges of water from geothermal energy systems at two Traverse City properties have raised questions about whether this green technology could have an environmental downside.

Staff at Watershed Center Grand Traverse Bay take their mission to monitor the area’s waters seriously, so when someone spots unexplained fluid flowing from a pipe into a creek or river, they try to get answers. As Patrick Sullivan writes in this week's Northern Express - sister publication of The Ticker - this happened twice recently when water pumped through open loop geothermal climate systems was found flowing into the Boardman River and a tributary to Kid’s Creek from developments including 101 N. Park and Cordia at the Grand Traverse Commons.

According to Christine Crissman, Watershed’s executive director, while geothermal systems transfer the heat of the earth into renewable green energy, there is reason to be concerned about possible negative side effects. Water that has been heated could threaten cold water ecosystems, while water from a contaminated groundwater source could threaten water quality. But it's also possible the water outflows are harmless: If the water is clean and the temperature is close to the temperature of the water it’s flowing into, it wouldn’t adversely affect the environment.

Unanswered questions about their potential impact on the local watershed means the city may need to develop clearer regulations regarding geothermal systems, according to City Engineer Tim Lodge, particularly regarding whether they are closed loop or open loop systems. Closed loop geothermal systems - meaning the fluid is contained in the pipes and constantly recirculated - are preferable environmentally to open loop systems, in which water is pumped from a well and discharged after.

“We’ve been made aware by our water quality partners of their concerns, so we’re looking at our regulations,” Lodge says. “We’re not there yet, but that’s the discussion we’ve been having.” He adds, “Moving forward, we’re saying, ‘Okay, open loop systems are not allowed; closed loop systems are allowed.’” (A proposed new development from Darga in the Warehouse District calls for a closed loop system.)

Read more about the energy systems, their potential enviromental impact and the questions being raised about their use in this week's Northern Express, available online and at more than 600 distribution spots across 14 counties in northern Michigan.