To limit access to the contaminated soil, contractors covered the entire lot with a 6-inch stone layer meant to provide an “engineered barrier” that would be routinely inspected and maintained by city workers. But homeowners on 38th Street are not convinced the land isn’t toxic. “We’re concerned, I mean, we’re concerned about our water; they shut off our water for a few hours to dig back there,” neighbor Javier Lopez said. “I’m sure the pipes are surrounded by these contaminants."