PORTSMOUTH/TIVERTON — Federal law prohibits the implementation of tolls on the Sakonnet River Bridge, say two experts whose written testimony has been included in the Town of Portsmouth’s lawsuit to get the toll removed.

Portsmouth Town Solicitor Kevin Gavin, in a motion filed Wednesday in U.S. District Court in Providence, included the opinion signed by Marcus J. Lemon and Valerie J. Southern.

Mr. Lemon was lead counsel for the Federal Highway Administration (FHWA) from 2008 to 2009. Ms. Southern was the deputy director of policy to former Gov. Edward D. DiPrete, overseeing statewide policy in transportation, land use and economic development from 1987 to 1990.

“It is our opinion, to a reasonable degrees of certainty in our field of expertise in transportation and FHWA matters, that the Sakonnet River Bridge does not qualify for tolling under 23 U.S.C. § 129 and, therefore, tolls are not permissible on the Sakonnet River Bridge pursuant to the “freedom from tolls” prohibition of 23 U.S.C. § 301,” Mr. Lemon and Ms. Southern wrote in their opinion, citing the specific federal law pertinent to the case.

The crux of their argument is that federal law does not allow tolls on any transportation facility once it has been opened to traffic. The Sakonnet Bridge tolls were implemented in August of this year, but the bridge was opened to traffic nearly a year earlier — in September 2012.

Michael Lewis, director of the R.I. Department of Transportation (RIDOT), has argued that the deadline to implement a toll on the bridge is when the contract with the builder — in this case, Cardi Corp. — is substantially complete. RIDOT still has Cardi under contract.

RIDOT, the opinion states, felt the 10-cent “placeholder” toll was required because federal participation in tolling is prohibited after a project is substantially completed by virtue of federal law.

“However, RIDOT misinterprets when substantial completion occurs, claiming that (it) arrives upon final completion of the project by Cardi with certification by the agency. That is not accurate when looking at the plain language (of federal law),” the opinion states. “We conclude that the bridge was substantially completed upon the date when it was opened to vehicular traffic on Sept. 20, 2012.”

Federal law, the opinion continues, “never mentioned substantial completion at all, and never says that a toll may be imposed ‘at any time,’ much less after ‘substantial completion’ by opening it to vehicular traffic.”

In the Town of Portsmouth’s lawsuit in U.S. District Court, the defendants are listed as Mr. Lewis; Daniel J. Berman, division administrator of FHWA; Victor Mendez, administrator of the FHWA; Buddy Croft, executive director of the R.I. Turnpike and Bridge Authority (RITBA); as well as RITBA as a whole.