Rock Island aldermen tonight will consider spending nearly half a million dollars on more engineering for the city wastewater treatment plant project, as well as $73,000 to acquire west-end properties for future redevelopment.

The engineering and consulting firm Symbiont -- which designed the $47 million expansion of the Mill Street wastewater treatment facility -- is proposing an updated electronic operations and maintenance manual for the construction project. The additional services, costing $473,800, are primarily for a new wet-weather treatment system at the expanded plant, which has been under construction for more than a year.

Part of Rock Island is served by combined sewers that carry both sanitary sewage and storm water in the same pipes.The treatment plant expansion will increase the plant's maximum treatment capacity from 16 million gallons a day to 106 million gallons a day. Up to now,any storm water received after the first 16 million gallons is diverted directly into the Mississippi River, so the expansion will mean less pollution.

The city council also will discuss two separate proposals to buy properties along 10th and 12th streets. The first is a plan to purchase an existing house and three vacant lots on the west side of 10th Street, between 6th and 7th avenues, for $65,000.

The plan supports the city's removal of blighted properties that started in 2006, according to a city council memo. The planned cleanup of vacant lots and demolition of the house also will help showcase nearby homes for sale by Rock Island Economic Growth and support the development of the new Martin Luther King Park on the adjacent property to the west, the memo says.

Funding for the purchase will come from the North 11th Street tax-increment-financing district.

In the second proposal, the city has been asked to purchase and donate the lot at 600 12th St. and donate the existing city-owned lot at 610 12th St. to support a planned $100,000 investment by Forest Siding at 619 11th St. The city plans to buy the lot for $8,000.

Forest Siding plans to pave the area and use it for outdoor storage. The project will help retain the existing business and its 10 employees, according to the city. The roofing company also will landscape the area.

The city council meeting will start at 6:45 p.m. on the third floor of city hall, 1528 3rd Ave., Rock Island. For a complete agenda, visit rigov.org.