Past, present and future of town’s geothermal system discussed by town council

By Chris Mannara
Staff Writer

A report on the town’s geothermal heating utility was provided to the Pagosa Springs Town Council at a regular meeting on July 7.

The geothermal heating system has been operated and owned by the town since December of 1982, according to Public Works Director Martin Schmidt.

The town put out a bid and Alan Plummer Associates Inc. was awarded with an assessment of the utility, Schmidt explained.

Currently, the geothermal system has 32 customers that range from a school to small residences, Schmidt explained

The geothermal system is fully operational and the town has not experienced any failures that would inhibit the utility to heat those that the town committed to heating, Schmidt added.

A report from Alan Plummer Associates Inc. Project Engineer Steve Omer done for the town touches on the system’s current conditions, capacity and expansion opportunities.

Existing conditions

For existing conditions, Schmidt explained that Omer analyzed the way in which the town runs the utility, looking at daily logs and current water rights that the town is using, among other things.

“We saw that we’re operating our heat exchanger at a potentially less than optimal rate. We could have 20 percent more salable heat per day,” Schmidt said.

The town is using about 3.4 miles of distribution and return lines for the geothermal system. These lines include plastic, steel, copper and asbestos-reinforced concrete, according to Schmidt. 

Half of the system has insulated piping, but the return half does not, he added, noting, “We don’t have a good understanding as to why it was designed that way. We’d like to see more insulation.”

A private well showed “significant damage” according to Omer’s report, which the town could look into repairing or making the private well owner aware of the damage, Schmidt noted.

System capacity

According to Schmidt, about 75 percent of the transferred heat is lost and not sold to customers just due to “Mother Earth.”

“We don’t really have massive leaks of water or any of those things. At this point, 3.4 miles of lines we lose about a gallon a minute due to leaks,” he said. “When you consider that there’s a rubber gasket every 4 or 5 feet in the system, that’s pretty good to only lose a gallon over that distance. It’s not through leaking water, it’s just Mother Earth stealing heat out of our pipe.”

Most of the town’s pipes, valves and meters are in good shape, but the town’s heat exchanger has not seen a “real service.”

According to Omer’s report, the town’s heat exchanger was in its “final tolerances” of the gaskets that keep it in operation, and Omer advises that the heat exchanger should be serviced.

Specifically, Omer explained during the meeting that the issue for the gaskets is compression.

“We could heat more houses if we used more water, and currently, we’re not using about 100 gallons per minute water right out of the Rumbaugh well,” Schmidt said. “The issue is, we don’t have piping right now from the Rumbaugh well to our geothermal building.”

Schimdt noted that the town is not in danger of losing that water right, but the town must show use.

Expansion opportunities 

One idea for an expansion opportunity was to cool homes in the summer with the geothermal piping using river water, Schmidt noted.

“When you actually look at the river data, the average temperature of the river through the summer months is 63 and a half degrees, and 63 and a half degrees doesn’t give us enough of a difference,” he said. 

Another expansion opportunity looked into by Omer was the limits of the geothermal system and how many more customers the town could add to the system.

“We found that we could not add a customer like the high school. Just the high school would overwhelm the system …” Schmidt said.

Agenda documentation further explains, “The school district had asked the Town to look into connecting the high school to geothermal heat, but it was quickly determined that the geothermal utility does not have enough available heat to support the high school. Plummer recommends that the Town focus on new building heat connections on a smaller scale.”

Up to 13 more residential customers could be added or nine more mixed-use customers, according to Omer’s report.

“One of the things pointed out is that sidewalk and parking lot, intersection heating is a really variable heating use,” Schmidt said. “It’s a really big drain on the system. In order to guarantee we’re not going to have negative impacts on our customers, it was advised to steer away from sidewalks, intersections, parking lots, those kinds of things.”

The geothermal heat could also be used to produce power, according to Omer’s report.

“There’s the potential for an annual revenue of around $70,000,” he said. “It really depends on the reimbursement rate that LPEA [La Plata Electric Association] would give us.”

This would strip about 10 degrees from the outflow from the geothermal system and produce electricity that would be stored in batteries and put back into the grid, Schmidt described.

“The idea is that you could put it back on when LPEA would need it during peak use,” he said. 

This could produce up to 1,634 megawatt hours per year, according to Schmidt.

However, the unit cost for a test unit for a thermal energy storage system unit is about $800,000, which would take about 12 years to pay off at the approximate rate of $70,000 per year, Schmidt explained, noting that there could be grants the town could pursue.

“Our current system is generally working well and it’s been sustained for this 40 years, but we’re looking at the end of the lifespan, both for our Transite pipe, for the heat exchanger if we don’t do any service to it and generally we need to keep an eye out for the aging issues in the heat supply system,” he said. “It’s pretty clear and staff is aware that a lot of these amounts of money are more than the geothermal system can sustain so we would need to look for other funding opportunities.”

Doing a 3.4-mile pipe replacement with polyethylene raised temperature insulated pipe would cost about $4 million, Schmidt noted.

Heat exchanger maintenance would cost about $35,180, Schmidt noted, adding that a lot of the other actions have unknown costs at this time.

“We’re going to have some more in-depth discussions and talk about what this means for our capital budget, because obviously, we can’t do a full replacement of the system as is recommended,” Town Manager Andrea Phillips said during the meeting. “We’re anticipating that a lot of this will be discussed during our capital budgeting process during 2021 and beyond.”

This story was posted on July 22, 2020.