Opponents of an Edmonton solar farm project planned for 23 hectares of river valley land want to take at least one more public stand against the proposal when it comes before city councillors next week.

The Sierra Club of Canada is among eight speakers slated to address EPCOR's bid to develop a 12-megawatt solar farm on land adjacent to the E.L. Smith water treatment plant. The site is on the banks of the North Saskatchewan River, near the Cameron Heights neighbourhood.

While the city-owned utility says the solar farm will be an innovative source of green energy, the conservation group says the benefits don't make up for the location.

"The problem is that every time you take a piece out of the river valley, it's gone essentially forever. Rarely, once developed, does a piece of land get returned to a natural state," Charles Richmond, urban issues co-ordinator for the Sierra Club of Canada, said Thursday.

The EPCOR project has already made it past most regulatory hurdles. It has secured support from city administration and approval from provincial bodies such as the Alberta Utilities Commission and Alberta Culture and Tourism.

Still, Richmond says he wants to speak out against industrial development in the river valley. He said it would set a negative land use precedent and go against city bylaws designed to protect the valley from all non-essential projects.

"The law is, in fact, one of the major tools the Sierra Club operates with. We take bylaw seriously and city policy seriously."

EPCOR has been pitching the project, to be located near 169th Street and 35th Avenue, since 2016.

The solar farm is unique because of its connection to the water treatment plant, and because the company has secured grant funding to also construct a battery energy storage system at the site, said Craig Bonneville, director of the E.L. Smith Solar Farm Project.

"That battery presents a pretty unique opportunity to understand how that integrated system works together," he said.

"Part of the research and learning we'll get out of it is how to best utilize batteries at this scale. So it's a 12-megawatt solar farm attached to a large battery array. And one of the benefits certainly is to provide a resiliency to the water treatment plant but it also allows to better understand how future power systems work."

While EPCOR owns the land adjacent to the water treatment plant, the land is currently zoned as a metropolitan recreation and environmental protection zone. The company is requesting the zoning be changed to a "direct development control provision" to permit the development of a utility service.

Under that provision, the city would retain some control of what the final development would look like, including provisions for landscaping and fencing.

City councillors are expected to vote on the rezoning application on Monday. EPCOR says the project aligns with city goals to secure more energy from renewable sources.

Richmond said EPCOR could have purchased green power from elsewhere or put the solar farm in another location.