Wares Creek Sediment Sampling Project

Bradenton, Florida

Project Description/Services

Madrid Engineering Group, Inc. completed a geotechnical site investigation for our client, URS Corporation, to determine sediment, soil, and rock characteristics for a proposed dredging project of Wares Creek, Bradenton. The project area is located on the south side of the Manatee River and extends from near the mouth of Wares Creek south more than 2 miles.

The watershed serviced by Wares Creek is approximately 6.2 square miles of highly urbanized, mostly residential development. These areas experience severe flooding during storm events. MEG provided critical geotechnical data used by URS to design improvements to the drainage system that minimized the potential for future flooding.

The field investigation consisted of two separate tasks; standard penetration test (SPT) borings (from land and water) and wash borings (probes) completed within the creek. SPT borings depths ranged from 10.25 feet and 31 feet, as measured from the elevation of the top of the boring (or the water surface). Borings from the surface of the creek were completed using a barge mounted drill rig. In general, the SPT borings were sampled continuously until refusal conditions were encountered. At the depth of refusal, rock coring was completed using a 4-inch diameter (OD) core barrel. After the core run, split-spoon sampling was resumed on five-foot intervals until the target depth of the boring was achieved.

MEG provided an innovative approach to sampling at highly inaccessible areas (due to tidal fluctuations). In lieu of the SPT borings, MEG sampled utilizing a piston tube sampler, obtaining samples from the creek bottom at regular intervals to elevations at or below the proposed depth of excavation or dredging. Visual observations confirmed that the sediments were weight-of-rod strength and of similar composition to sediments near the mouth of the creek. The surface soils consisted of sand and silty sand, underlain by silty clays and interbedded limestone. Sediments in the creek range from sand and shell to highly organic silts.

Laboratory testing included percent moisture content Atterberg Limits, grain size, organic content, specific gravity and strength tests.