Families that for decades have used Olinda Park in Northwest Miami-Dade County for picnics and play will get their grassy venue back in about four months, county officials say.

By then, bulldozers will have scraped away the top two feet of lead-contaminated soil — 7,000 cubic yards in all — and replaced it with clean fill and new grass. The park’s storm sewers will be improved to prevent buildup of rainwater that might bring up more contamination from an old incinerator ash dump below. Cost: $1 million to $2 million.

“We’re in the early stages of cleanup. We’re moving as fast as we can,” said Luis Espinoza, communications director of the Miami-Dade Department of Environmental Resources Management.

The cleanup of the Miami-Dade County Park at Northwest 51st Street and 21st Avenue was prompted by the discovery last year of lead in the soil at concentrations more than 10 times the safe level, according to the U.S. Environmental Protection Agency and Miami-Dade’s DERM. The park was closed for cleanup on April 18.

The 6.1-acre park has a grassy play area, two lighted basketball courts and a parking lot. The contamination involves the grassy area that makes up 2.6 acres of the park. Paved areas are not involved, Espinoza said.

An EPA report dated June 2011 says the agency has found contamination at the park at least three times since 1985 but didn’t require cleanup until this year. Lead levels weren’t high enough to trigger action until the 2010 testing, an EPA official said.

Since the EPA testing last year, DERM has followed up with 70 more soil samples and eight monitoring wells in Olinda Park and announced its remediation plan.

So far, the lead seems to have done little harm, health officials say. They offered free screenings for lead exposure, first to children who had played there recently, later to people of all ages who might have played there as children.

“We’ve screened 230 people and found only one positive, and that one is still suspect,” said Dr. Asit K. Sarkar, manager of the county health department’s Lead Poisoning Prevention Program.

The one person — identified only as a male between 30 and 50 who played in the park as a child — tested marginally positive for lead, Sarkar said. He was asked to come back for further testing but didn’t return.

“We’re still trying to find him,” said Dr. Vincent Conte, the department’s chief epidemiologist. “He’s at very low risk, but we want to follow up.”

In children, lead poisoning can be particularly dangerous. Children under the age of 6 are especially vulnerable to lead poisoning, which can severely affect mental and physical development, experts say.

Testing by the EPA and DERM also found contamination of two other sites near Olinda Park. The pesticide DDT, long banned, was found in the soil near Ward Tower Senior Social Center at Northwest 53rd Street and 23rd Avenue. And gasoline byproducts were found in the soil at the Annie M. Coleman Gardens Complex at Northwest 52nd Street and 21st Avenue.

At Ward Tower, the contamination was from pesticides sprayed for weed control decades ago when the area was a junkyard. In the new testing, pesticide levels were below health-threatening levels, but DERM removed and replaced the contaminated soil to be safe, Espinoza said.