As lawmakers demanded answers as to what caused a landslide that closed Route 65, new details emerged suggesting that engineering plans for the proposed shopping center site bypassed some township regulations, and that blasting earlier in the week might have loosened an already unstable hillside.

The construction site for the River Pointe Plaza shopping complex in Kilbuck, once occupied by Dixmont State Hospital, "sits on the most landslide-prone soil and bedrock in the Pittsburgh area," according to John Harper, a geologist with the state Department of Conservation and Natural Resources.

When approving the project, which is to be anchored by a Wal-Mart, Kilbuck supervisors permitted the township's engineer to waive an ordinance that required "benching" -- the construction of large, step-like intermediate areas on a steep hill to reduce the possibility of a slide. Instead, the developers, ASC Development and its subsidiary, Kilbuck Properties, were allowed to develop a steep slope that eventually gave way last week.

The site design was done by the Coraopolis firm of Lennon, Smith, Souleret Engineering Inc. An engineer there, Kevin Brett, referred all questions about the site's development to ASC.

John A. Atwood, ASC president, said the site's slopes, which he said are at a 2-1 ratio, are not unusually steep and their proportions have been used successfully at other ASC shopping center developments.

The waiver of the benching regulations was one of several issues raised by opponents of the development, who also complained in court last year that the township engineer, Marie Hartman, worked for the same Connellsville firm, Widmer Engineering, that had been hired to do the traffic engineering study for the developers.

The courts rejected arguments against the project and permitted it to proceed.

The township ordinance was not the only place where the subject of benching the hillside came up.

An Aug. 12, 2004, report by David R. Freudenrich, senior engineer of The Maguire Group Inc., a Downtown engineering firm hired by Communities First!, a group opposing the Wal-Mart development, criticized a study done by Widmer for having too low a traffic flow estimate, and then added this observation:

"Rock slope stability analysis -- no benches are provided. This is especially important given the close proximity of the rock slope to Route 65 and the main access driveway which could be closed off if a rock slide were to occur. The rock bench would help to prevent this occurrence."

At some point, the Maguire Group ordered Mr. Freudenrich to stop working with the citizens group. Bob Keir, of Communities First! said he believed the order was given because of Maguire Group's extensive work with the Pennsylvania Department of Transportation. Mr. Freudenrich this week would say only that "there was a conflict on that, and that contract was cancelled, so I can't comment."

Yesterday, state Rep. T. Mark Mustio, R-Moon, and state Sen. John Pippy, R-Moon, sent a letter to state Department of Environmental Protection Secretary Kathleen McGinty, asking for a range of details on the engineering and oversight of the project.

"We would like to know what geotechnical firm was used and if that firm was on site the day of the slide. Also, what engineer and geotechnical firm inspected the work as the earth-moving was completed?" the lawmakers wrote. They also asked if DEP would be hiring an outside geotechnical engineer to review data about the site's design.

In separate remarks yesterday, Mr. Mustio accused both DEP and PennDOT of "running away" from their responsibility in the landslide.

"The development wouldn't be there if they had not issued permits," he said. "We should be able to just get a quick answer as to who is responsible for overseeing this."

Betsy Mallison, a spokeswoman for DEP, said that, while the department issues some permits for developments, "we don't have a lot to do with landslides."

Rather, oversight of the whole site appears to be a locally controlled matter. Yesterday, officials in Kilbuck were saying nothing about their roles in the development.

"I don't want to be ignorant, but I am not going to comment on anything," said James T. Pool, the township secretary, who voted for the project when he served as a supervisor. "Until the facts are all on the table, it's just not prudent to comment on anything. Our solicitor told us not to comment."

Ms. Mallison yesterday said DEP was exploring whether it would act as the lead agency in investigating the cause of the slide, which has likely closed Route 65/Ohio River Boulevard until Oct. 7 and for several days tied up rail traffic between Indiana and New Jersey when it spread onto the adjacent Norfolk Southern Railroad mainline.

Precisely who was responsible for overseeing soil and hillside conditions during construction was unclear yesterday, even to Mr. Atwood. While his partner in the project, Tony Chammas, is an engineer -- his company, ACA Engineering, has shared officers with ASC Development -- Mr. Atwood was uncertain whether Mr. Chammas' firm played a role in the design.

Construction on the site was being carried out by Penn Development Services, based in Uniontown. One foreman with that firm, John Herby, declined to say much, but said it would be wrong to characterize the landslide as rapid.

"Nothing cascaded. It's a land mass migration," he said. "It took four days, five days."

Ralph Stroyne, the Kilbuck area developer who sold Mr. Atwood's company the land, said occupants of a building he owns on the site heard blasting Sept. 18 and thought at first a jetliner had crashed.

Mr. Atwood acknowledged that work crews set off a series of blasts that Monday while clearing the site.

"We don't know what effect that may or may not have had on the slope," he said.

Mr. Stroyne theorized that the dirt slope along Route 65 "may have been a little too steep."

"If you had put two or three or five benches and a retaining wall in there, that might have prevented the slide," he said.

"I think they gambled that they could put in a slope that the engineering study would allow, that would allow them to put as many parking spaces as possible on top, and they lost."

Yesterday, Mr. Atwood said crews were installing earthen benches to stabilize the hill as the soil from the slide was removed from the highway.

But ASC construction coordinator Bob Goldie suggested that the loose earthen fill was not the source of the problem. Rather, he suggested, underlying rock strata might have collapsed.

"The soil wasn't what failed. It was the rock," Mr. Goldie said.

Mr. Atwood insisted that the engineering study had been done carefully and that his company had taken no undue risks.

"We're going to put a $28 million development on the top of that hill. Believe me, the last thing we want is to have any kind of question on the slope's stability," he said. "How does that help us?"