A new estimated cost for the Advanced Water Purification project, a system of recapturing sewage and transforming it to drinkable water for about 500,000 East County residents, escalated to about $850 million, an increase of more than $300 million above the estimate three years ago.

Allen Carlisle, general manager of the Padre Dam Municipal Water District, revealed the number at a public forum held April 24 in Santee, saying the project should begin construction this summer.