Hemet has filed a federal lawsuit against Dow Chemical and Shell Oil seeking reimbursement for the cost of removing a cancer-causing chemical from the city’s water wells. According to its Sept. 21 suit, the contaminated wells have been tainted by TCP, a “highly toxic substance” used until the 1980s to fumigate soil where crops were grown. The solvent’s chemical name is “1,2,3-trichloropropane.” Hemet Mayor Michael Perciful said low levels of the chemical were discovered in two wells during routine tests at least six months ago.