SAN DIEGO (CBS 8) - The Sweetwater Authority is expanding its groundwater desalination plant in Chula Vista. 

Ground broke on the $42 million project on Tuesday. The expansion will include more wells and reverse osmosis equipment to convert brackish groundwater into drinkable water. It is expected to double the plants daily output from 5 million gallons to 10 million. 

Federal and state grants are covering about three-quarters of the construction costs. The expansion is expected to be finished by 2017.