A project paved with good intentions has put the city between a rock—er, concrete—and a hard place.

For the unauthorized loading of hundreds of concrete slabs into a Waianae stream bed, the city faces federal fines, according to documents obtained from the U.S. Army Corps of Engineers.

But the slabs provided a roadway for heavy equipment to clear out alien vegetation and debris from Mailiili Stream, which then attracted a population of rare Hawaiian stilts.

Now the city has been ordered to remove the slabs while attempting to avoid disturbing the endangered birds.

City officials have submitted a removal and restoration plan for Mailiili Stream that is being reviewed by the U.S. Environmental Protection Agency.

According to documents obtained by the Star-Bulletin through the Freedom of Information Act, the city Department of Facility Maintenance, in violation of the federal Clean Water Act, unloaded 255 truckloads of concrete slabs in the stream area on 22 days in 2008, from Feb. 2 through May 9.

The volume of the concrete was estimated at 1,600 cubic yards, according to a July 9 letter to the Corps of Engineers from department Director Jeoffrey Cudiamat. The city declined to release the document.

Cudiamat said that the unloading of the slabs was not dumping, but an attempt to stabilize the earthen banks and enable equipment to remove vegetation and debris from the channel.

“;The removal of brush and debris had an unintended effect of creating a habitat for the Hawaiian stilt, an endangered species that had not previously been known to inhabit or nest in this area,”; Cudiamat said in the letter.

Cudiamat said after learning about the alleged unauthorized fill, city maintenance personnel were directed to cease deliveries.

He said some 109 tons of concrete rubble was removed and disposed of at a landfill on June 13.

The 109 tons was a fraction of the estimated 3,200 tons in the stream, which, according to a preliminary report from the city, came from torn-up sidewalks.

The state Division of Forestry and Wildlife said that on June 15, 13 Hawaiian stilts, including two chicks, were observed in the channel stream bed.

The wildlife branch said there was no evidence of dead stilts and that the removal of alien trees and grasses helped to create more habitat for the Hawaiian stilts by clearing brush and eliminating ambush points for predators.

The Corps of Engineers said it cannot accept a permit application to remove the concrete slabs from the stream until the city receives EPA approval for its removal and restoration plan.

Agency official Wendy Wiltse, who is reviewing the proposed plan, said restoration will probably begin in the fall.

City spokesman Bill Brennan said Cudiamat's department is investigating the illegal fill.