A lightly traveled collector road east of Odessa could face less traffic than it has ever seen, in large part due to environmental issues that have made regular, safe passage of it difficult to sustain.

WDEL's Road Scholar: Old Corbitt Road, April 11, 2017

A recent public workshop, organized by the Delaware Department of Transportation (DelDOT), on March 27, 2017, sought to inform residents and users of Old Corbitt Road of its underlying concerns, and the agency's preferred solution for its remediation.

Specifically, on the western end of the roadway--which connects DE-9/Silver Run Road with DE-299/Old State Road--an existing bridge, built in 1965, spans the tidal marshes of a branch of the Appoquinimink River. 

Old Corbitt Road Bridge

The bridge on Old Corbitt Road, which spans a branch of the Appoquinimink River, near Odessa.

According to DelDOT, soil borings have revealed that the bridge and the approach roadway are located on poor soils, which have continued to fortify as water has pushed out of the voids in the tidal marsh. That has caused the bridge to settle six feet, over time, making it susceptible to water over the roadway during twice-daily instances of high tide, as well as significant washouts following flooding rains.

The settlement issues of the bridge had also created difficulty for regular inspections of the bridge, as well as put a 12-inch New Castle County sewer force main within three feet of the existing grade.

"We have looked at this project for a really long time," revealed Jason Hastings, DelDOT Bridge Design Engineer. "It's become evident that the flooding has continued to get worse, as the water levels through that area are rising, at the same time that the soil underneath is settling. So you have a combination of things there that [are] making the condition worse. The soils underneath the roadway are worse than almost every other location that we've run into throughout the state."

Considering the existing bridge already lies within a Federal Emergency Management Agency (FEMA) designation zone for moderate wave action, DelDOT had previously designed a replacement bridge to help enable the area to withstand regular flooding rains. Furthermore, designers wanted the proposed span (264 feet in length, 6 feet in elevation), that would bypass the poor soils, to endure the possible impacts from 10-, 25-, 50-, and 100-year floods.

Old Corbitt Road Flooding

Old Corbitt Road washed out at the bridge over tidal marshland along a branch of the Appoquinimink River, east of Odessa

However, since Old Corbitt Road is a local roadway, it would be ineligible for federal funding, meaning the steep price tag--$3 million for the construction of the replacement bridge, and another $500,000 for the required relocation of the sewer main--would have to be absorbed by taxpayers.

"All 100 percent state funds, with no participation from the feds, that's a big chunk of money in our program," Hastings admitted. "That's certainly the challenge here."

The construction-funding dilemma furnished a far different solution, which DelDOT presented at the workshop. Instead of going forward with the replacement bridge, the agency instead suggested a permanent, partial closure of Old Corbitt Road at the creek, providing "hammerhead" turn-around areas on each side.

Old Corbitt Road Partial Closure Plans

That proposal would improve public safety by eliminating high water vehicle rescues, enhance the public's recreational usage of the area by restoring wetlands, as well as allow for the state to leverage its financial resources with nearby flooding projects on federally-eligible roadways, such as DE-299.

Even Average Annual Daily Traffic, or AADT, statistics--- the number of cars which travel the roadway in a given year, divided by the days---have borne out the agency's conclusion.

"That daily traffic number [for Old Corbitt Road] has been cut in half over the years, as people have been discouraged by the flooding," shared Hastings. "They're finding alternate routes already, and that includes our emergency responders. They didn't have a problem with taking a detour route now, so a [permanent] closure wouldn't be that detrimental to their service."

Old Corbitt Road Washout

High water across Old Corbitt Road, east of Odessa. The long-standing settlement of the bridge that crosses the tidal marshland along a branch of the Appoquinimink River has made the roadway susceptible to regular flooding.

Still, the proposal wasn't considered a fait d'accompli by some attendees at the workshop, leaving the eventual resolution with plenty of uncertainty.

"People are very much concerned about their own livelihood and personal situation," acknowledged Hastings. "They're not as concerned about the price tag for a project like this to keep that roadway open, something that they've been driving, in some cases, for 60 or 70 years. It's a tough balance from our standpoint."