The Coconut Road earmark was an unexpected gift of $10 million that the federal government had been prepared to throw in the direction of an interchange project in Lee County. Since it turned up in a piece of 2005 highway legislation, the earmark has continued to prompt calls for an investigation.

Those calls started in Southwest Florida as local officials expressed surprise that Congress and specifically Rep. Don Young, R-Alaska, would direct such a sum toward studying a new interchange along Interstate 75 at Coconut Road.

Now, the earmark has a growing number of members of Congress calling for an investigation.

Sen. Tom Coburn, R-Okla., an opponent of earmarks in general, has been asking for an investigation since December, and several media outlets reported Tuesday that Sen. Barbara Boxer, D-Calif., the chair of the Senate Ethics Committee, has now joined him in signaling some approval for an investigation. Senate Majority Leader Harry Reid, D-Nev., went as far as to suggest the earmark should be subject to a Justice Department investigation, according to The Hill, a congressional newspaper.

The Senate is considering a technical corrections bill this week, though, that would revisit the 2005 highway legislation containing the earmark.

According to a statement on Coburn’s Senate Web site, the senator planned to introduce an amendment to that technical corrections bill that would call for an eight-member committee to look into how and why language specifying that the $10 million should be used to study an interchange at Coconut Road came to be.

Coburn’s amendment is getting the endorsement from some heavy hitters.

Presidential front-runners Sens. Barack Obama, D-Ill., and John McCain, R-Ariz., signed on as co-sponsors Tuesday.

Both Florida senators, Republican Mel Martinez and Democrat Bill Nelson, are going to co-sponsor Coburn’s amendment, according to several media sources.

Martinez told The Hill that a probe by the non-partisan Government Accountability Office (GAO) might be the best solution.

“The people in Southwest Florida want to know exactly what happened here and I agree with them,” Martinez told The Hill. “I think it’s a good thing to have an investigation; how that is accomplished is a different question.”

The committee suggested in Coburn’s amendment would include members of both the House and Senate and would come back with initial findings by August.

Whether or not that investigation ever happens — or whether it takes that form — is not clear yet.

Coconut Road is a smaller road in south Lee County that comes to a dead end just west of I-75 within unincorporated Estero, a little to the north of the Bonita Springs city limits. East of the interstate lies the undeveloped land that landowner Daniel Aronoff has an interest in. There has been speculation that Aronoff’s ties with Young may have led to the earmark.

The Coconut Road earmark appeared in the 2005 bill after Young attended a fundraiser in Estero. The event was hosted by Aronoff, who owns about 4,000 acres east of the proposed interchange, and Aronoff also contributed money to Young’s campaign efforts.

The interchange hadn’t been something local officials had been interested in studying — and that raised eyebrows from the start.

Even now, talk to elected officials in Bonita Springs, and they’ll mention the existing Bonita Beach Road interchange as the top transportation need in the area. In fact, Bonita Springs mayor-elect Ben Nelson has expressed hopes that the earmark money could be redirected for that purpose. And talk to the citizens’ group in unincorporated Estero, and their concern is with traffic at the existing Corkscrew Road interchange and with keeping development east of the interstate to a minimum.

In Lee County, discussion of a push for an interchange at Coconut Road may divide those who see it as something that would open up new land to unwanted, new development and those who see the potential for new links in the transportation system in a region where traffic has been a long-standing gripe. The big questions remain if the $10 million — welcome enough without the Coconut Road restriction — would ever come back to Lee County, and if so, how.

Outside Southwest Florida, though, the earmark has raised larger concerns. It has become something of a stark example of all that’s distasteful about the practice members of Congress have of directing money toward very specific projects.

The earmark has drawn criticism from national watchdog groups such as Taxpayers for Common Sense, and this particular earmark — one of many that members of Congress designate each year — has made its way into the pages of the Washington Post and the New York Times.

It has also drawn attention because the specifics of the earmark changed between the time Congress passed the legislation and the time the president signed it into law — something Coburn’s statement said were “improper revisions” that were “inserted mysteriously.”

Initially, the earmark had been for widening and improvements to I-75 in Lee and Collier counties. The language ended up specifying the money was to be used at Coconut Road.

Modern interstate interchanges cost well more than $10 million to build, but the money would have paid for a study of whether the interchange was needed.