Environmental advocacy groups and alumni of Walter L. Cohen High School are threatening to sue the state Department of Education and the Recovery School District if they continue moving forward with construction of a new Cohen School on a contaminated site without first conducting more tests to determine whether it is hazardous.

The notice of the potential lawsuit, sent on Monday to school officials and contractors working at the former Booker T. Washington School site on Earhart Boulevard, is the latest step in efforts to block the construction, which opponents say would place the health of children attending the school at risk.

The group Advocates for Environmental Human Rights and the Sierra Club are calling on the RSD to do testing — in conjunction with experts from those organizations — to determine whether contaminants left over from the days when the school site was part of the Clio Street/Silver City dump represent an environmental hazard under the law.

The Cohen School alumni, who are being represented by the Tulane Environmental Law Clinic, are involved in the case because the school’s 500 students would be transferred to the new facility on the site. The school is now known as Cohen College Prep.

“There hasn’t been any determination of whether hazardous waste is on the site,” said Monique Harden, an attorney with Advocates for Environmental Human Rights. “If you’re digging it up, you need to know for certain that it’s not hazardous.”

The call for more tests, which Harden said are required by law but were never performed by the RSD, comes almost a month after work began on the Washington site following earlier battles between the environmental groups and the RSD.

Contaminants, including lead and carcinogens, have been found on the site and acknowledged by those on both sides. School officials have said their remediation plans, which involve removing about 3 feet of soil and placing a barrier between the rest of the contaminated ground and the new dirt to be laid on top of the barrier, would prevent any health problems.

Asked for comment, the state Department of Education responded with an emailed statement from RSD Superintendent Patrick Dobard that did not directly address the call for new testing.

“The RSD takes the health and safety of our students and school communities seriously, and we are confident that all precautions are being taken to build a school that is a safe learning environment for students,” Dobard said. “The RSD is following a remediation plan on the Booker T. Washington site that was approved by both the Louisiana Department of Environmental Quality and FEMA.”

But opponents say they have found contaminants at least 15 feet deep and that the RSD has not followed proper procedures for ensuring the site is safe.

State Rep. Joseph Bouie, D-New Orleans, this year proposed a bill that would have barred the construction of a school on a contaminated site, but it died in a Senate committee.

The demand by opponents would set in motion a series of tests to determine whether the contaminants constitute an environmental hazard; such a finding would trigger additional regulations from state and federal agencies.

As it is, Harden said, there have been no efforts by the school district to determine whether the soil is safe for a school or whether the construction itself could create health problems.

“What’s really horrible is you’ve got folks living around the site and people with nothing more than jeans and T-shirts on digging this stuff up and doing all this with no understanding of whether it’s a hazard,” she said.

Follow Jeff Adelson on Twitter, @jadelson.