EAST CHICAGO | A family-owned Lake County, Ill., firm was chosen Thursday to build the city's new North Harbor water filtration plant.

The $29.8 million base bid from Joseph J. Henderson & Son, of Gurnee, was considered to be most responsible, said Eric Horvath, of Indianapolis-based American Structurepoint, the city's engineering consultant for the project.

Add-ons for other parts of the facility brought Henderson's total bid to $30.4 million, $102,500 more than the actual lowest bidder for the work, Walsh Construction, of LaPorte.

The city plans to borrow $14 million of the estimated $55 million total cost of the new treatment plant, pump station, water pipe and storage tank through a state program that provides low-interest loans for municipal infrastructure improvements.

That loan is scheduled to close Nov. 12, American Structurepoint coordinator Chris Murphy said, after which city Utilities Director Al Velez can issue a notice to proceed, and Henderson can begin work at the site.

The new plant will occupy 7 acres along Block Avenue just east of Guthrie Street and process 17 million gallons of water a day through a micro-filter system scheduled to go online in spring 2011.

Incorporated in 1928, Henderson has built water and wastewater treatment facilities across the Midwest, including filtration plants in Lake Forest, Elmhurst and Carol Stream in Illinois.

The contract calls for at least 6 percent of workers on the project to be local, minority or disadvantaged, Murphy said, and subcontractors will be held to the same guidelines, with compliance monitored by American Structurepoint.

In addition to the state loan, the project will be funded through $6 million collected through the lakefront tax increment financing allocation area, $3 million in federal stimulus money, $2 million in other federal grants and $3 million per year pledged by the City Council to be taken from casino revenue.