SALT LAKE CITY — PacifiCorp, the parent company of Rocky Mountain Power, is suing the state of Utah in a dispute over the price of public lands.

The Oregon-based utility company is challenging a land appraisal conducted by a state agency and the utility is claiming eminent domain for a 1.3 mile portion of its 100-mile Mona-Oquirrh transmission line, which passes through Tooele County, according to documents filed Thursday in 3rd District Court.

That line is part of a PacifiCorp project that includes the construction of a substation in the southwestern portion of the Tooele Valley to address the growing demand for power along the Wasatch Front.

The lands are held in trust by the state of Utah and managed by the Utah School and Institutional Trust Lands Administration. Money generated from school trust lands is deposited into a fund that annually distributes revenue to public schools in Utah.

PacifiCorp and SITLA entered into an agreement in 2011, the suit states, which allowed PacifiCorp to begin construction while negotiations over the purchase of an easement to the lands took place.

PacifiCorp states in the lawsuit that SITLA conducted an appraisal of the public lands, finding the market value to be more than $4 million. PacifiCorp conducted its own appraisals, which found the value of the land to be much lower, between $55,000 and $70,000.

"Pacificorp has made good faith efforts to negotiate with SITLA to purchase the easement from the state of Utah, but SITLA has refused all reasonable offers," the lawsuit state.

Pacificorp alleges that an easement on the property would not interfere with public use and is necessary to continue providing power to its customers. The company has asked the courts for a decree of condemnation on the public lands and for a determination on the amount to be paid to the state for compensation.

Rocky Mountain Power spokeswoman Margaret Oler could not comment on the lawsuit but said construction on the line will continue and is expected to be in service by the summer of 2013. She said the line is "critical" to providing reliable and safe power to Wasatch Front customers.

Requests for comment at SITLA were not returned.