Sound Transit will start collecting soil samples next week in Bellevue as engineers assess the soil and groundwater conditions in locations along the proposed East Link light rail route.

Drilling will start as early as Monday, with soil samples collected from as deep as 200 feet. The drilling is limited to the alignment recommended by the Sound Transit board in May, which includes two options for downtown -- a surface route and the more expensive tunnel route.

Geotechnical contractors will drill about 100 soil borings near areas where structures like transit stations, elevated platforms, retained earth fills and tunnels are proposed, Sound Transit said.

Drilling will take place along Bellevue Way Southeast, the Mercer Slough area, 112th Avenue Southeast, downtown, Northeast 12th Street and the Bel-Red area, and will continue through mid-2010.

Drilling will limit some street parking, and crews will direct traffic and pedestrians. Drilling equipment noise is similar to a running truck engine with some hammering, Sound Transit said.