Average contaminants per soil sample across the four neighborhoods are 172.9 ppm Pb and 8.9 ppm As The average Pb level across 3 out of 4 neighborhoods is more than double the state-recommended maximum Potrero Hill has the largest mean sample Pb levels at 287.4 ppm, with Presidio Heights having the second largest at 211.1 ppm. They also have the highest concentrations of As, at 10.9 ppm and 9.4 ppm, respectively.