In May 2012 the US’ Northern Colorado Water Conservancy District flipped on the switches at its first power facility, the Robert V Trout hydropower plant in Northeastern Colorado.
Permitting, construction and initial operation of the plant provided a new and exciting experience for Northern Water, who is pursuing similar projects, and the facility’s success has been an encouraging first step in Northern Water’s efforts to build and produce small hydro.
Northern Water, headquartered in Berthoud, Colorado, was created in 1937 to contract with the US Bureau of Reclamation to build the Colorado-Big Thompson(C-BT) project. Completed in 1957, the project diverts snowmelt runoff from the Colorado River and transports it in a 21km tunnel underneath the Continental Divide to Northeastern Colorado cities, farms and businesses. Northern Water’s boundaries encompass portions of eight counties with a population of about 850,000 people and 2590km2 of irrigated land.
Northern Water operates and maintains C-BT’s reservoirs and other water features. Reclamation owns most of the project’s facilities and operates its six original hydropower plants.
First hydro venture
The seventh C-BT project (Robert V Trout hydro plant) is Northern Water’s first venture into power production. The facility harnesses pressure that was already being created by releases from an outlet at Carter Lake, a reservoir southwest of Loveland, Colorado. Water stored in Carter Lake is delivered to water users south through the St. Vrain supply and Boulder Feeder canals and east through the underground Southern Water Supply Project Pipeline.
The new hydro project serves as an example of how changes in the region’s water demands have driven the construction of not only new water infrastructure, but also new power facilities to go along with this infrastructure. The Southern Water Supply Project is a 177km underground pipeline that delivers water to 12 municipal water providers and a power authority. The pipeline’s construction, which took place in the 1990s, was the impetus that eventually led to the addition of small hydro.
The southern pipeline created challenges because Carter Lake’s original outlet, in the south dam, was built to deliver water from April through October to irrigate crops. But the new pipeline was built to meet municipal, not agricultural, water demand and needed to deliver water all year, cutting off crews’ ability to make repairs in the winter.
To address this issue, Northern Water started discussing the possibility of constructing a second outlet out of Carter Lake, and after receiving approval from Reclamation in 2006 engineers began designs. The US$12M outlet, completed two years later, has a three-level intake tower and connects to the St. Vrain Supply Canal using 366m of tunnel and pipeline.
Under state law, Northern Water can pursue hydro projects, a logical undertaking for an agency that already operates the C-BT Project. Engineers therefore designed the second Carter Lake outlet with the possibility of adding future power in mind and began planning hydro facilities soon after the outlet’s completion in 2008.
Permitting and other reviews for the power project were straightforward and went smoothly. One of the key permitting requirements was approval to pursue hydro on the outlet, because Carter Lake is owned by Reclamation. This was the first project in the region to receive this approval through Reclamation’s Lease of Power Privilege process.
Northern Water also spent two years working to determine who would market the power. In 2011, the Poudre Valley Rural Electric Association signed an agreement to purchase the project’s projected output of 7-10GWh/yr, or enough to power about 1000 homes.
Plant construction began in fall 2011 and power generation started in May 2012. The plant is named Robert V Trout after Bob Trout, Northern Water’s legal counsel for more than 35 years. Like many other initiatives, Trout was instrumental to the hydro project, from creation of its money management fund to negotiations with key agencies.
The facility connects to the existing tower outlet at the south end of Carter Lake with 76m of new pipeline. The other new connection hooks up to the existing St. Vrain Supply Canal. To tie into Poudre Valley REA’s distribution system, crews added 183m of power line.
The plant has 2x1300kW horizontal Francis units operating at 480V. The turbines and the generator equipment were purchased out of England from Gilkes. Although the turbines harness power from existing delivery flows out of Carter Lake, the addition of the power facility does not modify reservoir operations, including the outlet flows.
Local Berthoud company Aslan Construction’s work included constructing the new power house, a 279m2 building to house the turbines, built next to the existing building that houses the energy dissipation valves.
The total capital cost for the project was US$6.2M. The largest expenses were US$3.5M for Gilkes and its turbines and US$1.9M for Aslan’s construction work.
To fund construction, the Colorado Water Resources and Power Development Authority provided a US$2M loan through its low-interest hydro programme, and Northern Water’s general district fund provided a loan for the remainder of the cost to its hydropower enterprise fund, which was created in 2011.
Annual gross revenue is estimated at US$600,000, which will defray construction and maintenance costs.
The project is working very well and demonstrates the value of adding small hydro to existing infrastructure. It supports Colorado’s renewable energy ethic, which is easily demonstrated by state standards and elected officials’ directives.
Given this success, Northern Water is pursuing a similar project on Lake Granby, a C-BT reservoir on the west side of the Continental Divide. Northern Water has obtained a preliminary Lease of Power Privilege for this project from Reclamation, and the agency also remains open to other conduit projects in the future.
Carl Brouwer, Project Management Department Manager, Northern Water. Email: cbrouwer@northernwater.org
