THEBES, Ill. (AP) — Two Illinois congressmen on Monday inspected urgent efforts to clear Mississippi River bedrock that has crimped shipping on a crucial stretch of the waterway and said they're closely monitoring the situation.

Sen. Dick Durbin and newly elected Rep. Bill Enyart, both Democrats, were briefed by the Army Corps of Engineers and Coast Guard about the work before touring by boat the site near Thebes in southern Illinois that has grown especially worrisome to the barge industry.

Durbin said "Mother Nature has dealt us a difficult hand" with the lingering, months-long drought that has dropped river levels. Enyart said he's "deeply concerned" about the economic implications of the lower depths of the Mississippi.

"As goes the Mississippi, so goes much of the industry in Illinois," Durbin said later in a statement, noting that President Barack Obama's administration is "monitoring this situation carefully."

The rock-clearing effort about 150 miles south of St. Louis is considered vital in ensuring that stretch of river remains open to barge traffic. Industry trade groups have expressed concern that the river could drop to such a point — 3 feet on the river gauge at Thebes — that barge weight restrictions could be further tightened, effectively halting shipping.

Drafts, or the portion of each barge that is submerged, already are limited to 9 feet in the middle Mississippi. If the river gauge gets to 3 feet at Thebes, the Coast Guard may be forced to limit drafts even further.

Officials with the trade group say that if drafts are restricted to 8 feet or lower, many operators will stop shipping.

National Weather Service hydrologists forecast that the river at Thebes could drop to the 3-feet mark by Jan. 17 and continue falling to the 1.5-foot mark by early February.