Updated

Two sites where levees breached during Hurricane Katrina and led to catastrophic flooding in New Orleans will not be listed on the National Register of Historic Places alongside notable landmarks such as Civil War battlefields and presidential birthplaces, the National Park Service said.

The park service rejected a proposal from the advocacy group Levees.Org, which has been pushing for almost two years to have the sites listed on the register, arguing the breaches reflected the worst civil engineering disaster in the nation's history.

In a letter to the organization, released Friday, the park service said the organization's nomination was "technically and professionally inadequate" to meet requirements for listing on the register. The letter said the nomination can be revised and submitted again, and Levees.Org founder and director Sandy Rosenthal said the organization will do so.

When Katrina struck on Aug. 29, 2005, levee breaches at numerous sites flooded 80 percent of New Orleans. Flood water lifted some houses off foundations and reached the roof lines of others. Close to 2,000 deaths were blamed on the storm. Stories and pictures of the tens of thousands of stranded people dominated media for days.

Levees.Org nominated two breach sites for the register: one on the Industrial Canal at the edge of the Lower 9th Ward, and one on the 17th Street Canal at the Lakeview neighborhood. Both areas were among the worst-hit in the city.

Under normal circumstances, getting a site placed on the register is an arduous bureaucratic task requiring painstaking compilation of technical and historical information and approval from state authorities before it reaches the National Park Service for consideration. The site of an event that is less than 50 years old is especially difficult to get listed.

Complicating the Levees.Org effort was the involvement of the Army Corps of Engineers, which built the levees and floodwalls and owns the Lower 9th Ward site.

Corps approval isn't essential to getting the designation, but owners must be given a voice in the decision.

The breaches remain the subject of litigation and the corps, citing the legal complexities, was slow to weigh in on the Levees.Org nomination.

When it did, it came out against the nomination. In letters to the park service that were made public Friday, the corps said one reason was the nomination's reliance on opinions from experts cited by plaintiffs in various lawsuits over the breaches, without consideration of opposing views from other experts.

In a letter explaining the decision, interim keeper of the register Carol Shull cited several reasons for the rejection. One was the lack of an explanation for the nomination of only two sites from among more than 50 breach sites.

Rosenthal has said that her organization hopes to nominate more breach sites. She listed several reasons Friday why the two in the initial nomination are significant, including the diversity of the two neighborhoods affected.

"The two locations demonstrate that people of all ages, races and economic status were impacted," she said.

Shull said some of the sources for information used in the nomination are not clear.

"In addition, the nomination does not adequately describe the effects of the flood on New Orleans beyond a description of the flooding and the resultant deaths," Shull said. More is needed, she said, on the effects on people, the environment and the economy.

In a news release Friday, Rosenthal and H.J. Bosworth Jr. of Levees.Org said they found some of Shull's findings "somewhat odd" in that the organization had worked with guidance from her staff since October 2010. They also note public statements from corps officials themselves that the corps is responsible for the levee breaches. The statement said Levees.Org will likely seek further clarification from Shull's office.