The price tag for driving Lawrence’s growth south of the Wakarusa River could reach $50 million.

That’s the unofficial estimate for building a new sewage-treatment plant on the banks of the river, a project that could be needed in the next 10 or 20 years to keep up with Lawrence’s burgeoning population, city engineering consultants said Thursday.

	Growing treatmentAn ongoing $45 million expansion of the city’s existing Wastewater Treatment Plant, 1400 E. Eighth St., is scheduled to be finished next year.The three-year project is designed to boost the plant’s reliability, add capacity and address regulatory issues. The plant treats sewage in the city of Lawrence and discharges its effluent into the Kansas River.The plant, built in 1950, previously had been upgraded in 1965 and 1975.

Steve Phillips, vice president for the Kansas City-based engineering firm Black & Veatch, said actual cost estimates and designs would be settled later. But, Phillips said, one fact exists: If Lawrence’s population is to exceed 100,000, the city either must expand its current treatment plant in eastern Lawrence or build a new one along the Wakarusa.

How fast the city grows will depend on the decision about expanding sewage treatment.

“In this area, there’s some truth to the ‘Field of Dreams’ statement that if you build it, they will come,” Phillips said, paraphrasing the haunting voice from the popular baseball-field-in-a-cornfield movie. “You have a significant opportunity to reduce those numbers if you do not support infrastructure development.”

During a joint study session Thursday morning, officials from Lawrence and Douglas County governments questioned Phillips about the prospects for building a plant south of town. They wanted to know where it would go, how long it would last, what regulations it would have to meet, and how much it would cost.

Those questions would need to be studied in the coming months to come up with detailed answers, Phillips said, although plants similar to the Wakarusa option cost $40 million to $50 million in other communities.

In previous years, such price estimates killed prospects for a Wakarusa plan. Expanding the city’s existing plant at 1400 E. Eighth St. which empties into the Kansas River was considered to be more cost-effective, because it would not be held to the same environmental standards as a plant on the smaller river.

But in recent weeks, Phillips learned that state regulators would hold both sites to the same environmental standards. The cost issue no longer overwhelms other considerations, such as timing and growth, Phillips said.

“Suddenly, the playing field has changed dramatically,” Phillips told commissioners.

City and county commissioners said they would meet Aug. 21 to discuss the future of public facilities, and possibly again Sept. 18 this time with the Lawrence school board to mull floodplain, growth and other topics.

If Lawrence officials want to require city development standards south of the Wakarusa, they’ll need to convince county commissioners that residents between the river and North 1000 Road could expect city services within a reasonable time frame.

A commitment to build a Wakarusa sewage-treatment operation would help make that case, County Commissioner Bob Johnson said.

“When I look at a map, it makes sense to me for the city to grow in that direction,” Johnson said after the meeting. “The plant solidifies the deal.”