LEBANON — Initial plans to upgrade and expand Dartmouth College’s library storage facility on Etna Road have been challenged by city officials who worry the project could negatively impact surrounding wetlands.

The Lebanon Conservation Commission voted unanimously last month to recommend that the state reject a wetlands permit the college needs to build a 31,000-square-foot facility at 56 Etna Road.

Instead, it asked the Department of Environmental Services to request additional plans from Dartmouth, including a proposal for stormwater management that could stem flooding in the Route 120 corridor.

Dartmouth spokeswoman Diana Lawrence said Tuesday that the college has “submitted a revised plan to the state based on the commission’s comments, and the state will now review it. The permitting process is proceeding.”

Dartmouth said last month the standalone building proposed for the 11.5-acre site would be used to house “low-use print collections and college records” that it has no room for on campus.

The new facility would be capable of storing 1.2 million books and 35,000 “record units” to free-up space in Baker-Berry Library.

An existing storage facility at 56 Etna Road is full, college officials added.

The Conservation Commission’s recommendation wasn’t binding, but it did provide expectations to state regulators charged with reviewing the wetlands application, according to Lebanon Planner Mark Goodwin.

“It’s rare that if there was a strong recommendation, the DES would go in the opposite direction,” he said in a phone interview.

The contention surrounding Dartmouth’s proposed building mainly stemmed from plans to impact 3,855-square-feet of wetlands around its property, which the school purchased in 2005 for $3.7 million, according to city accessing records.

The site and its existing 86,492-square-foot structure previously housed New Hampshire Industries, a manufacturer of industrial pulley systems that moved to Claremont last year.

The college contended the wetlands appear to be manmade and argued that building there helps comply with fire safety standards.

The Lebanon Fire Department requires there be two ways to access the site, meaning the college must build 26-foot access roads that can accommodate large fire vehicles.

Conservation Commission members worry that infringing on the wetlands could contribute to flooding in the Route 120 corridor.

Lebanon’s natural resources inventory, which was completed in 2012, lists the wetlands around Etna Road as “medium-low value,” the second-lowest ranking in terms of ecological importance.

That’s largely because the west side of Route 120 has been “significantly altered,” with fill covering much of the low-lying areas over the last 200 years.

Still, “the marshes and shrub swamps currently bear the burden of concentrated floodwaters, road salt and stormwater runoff, sediments, organic debris and chemical pollutants,” the inventory said. “For this reason, these residual wetland areas play an extremely important role in water quality remediation.”

DES spokesman Jim Martin said Tuesday that regulators do take local comments into consideration when issuing permits. However, there are other factors that determine whether an application is approved or denied, he said.

“Many times, the conservation commissions have really valuable local perspectives or information that the department may be able to get clarification from an applicant on,” Martin said.

That might be the case with Dartmouth’s proposal, he added. While the DES has until Thursday to make a ruling, it could instead ask for more time and information on the project, which is listed as “under technical review” on the state’s wetlands database.

In the meantime, Goodwin said the city was recently informed of Dartmouth’s alternative plan, which isn’t expected to impact the wetlands as heavily.

If approved by the DES, that plan would be presented before the Lebanon Zoning Board, which will ultimately decide whether to issue a wetlands special exception for the project. That board hasn’t yet scheduled a meeting to discuss the matter.

Tim Camerato can be reached at tcamerato@vnews.com or 603-727-3223.