Project Background
This underground drinking water reservoir was put into service in the early 1900’s to store and supply water to a large metropolitan area’s population. This approximate 350,000 gallon concrete tank, assessed in 2013, was found to have cracked walls; verification and assessment of the tank’s conditions were sought. Bowser-Morner, Inc. performed a geotechnical study as part of the evaluation of the concrete structure by others.
Work Performed
- Field Work began with a visual assessment of the site prior to active studies.After boring locations were identified and agreed upon by all parties, four soil borings using a rig mounted on a track vehicle were advanced.Split-spoon samples were collected and soils encountered in each boring were visually classified.Observations of depth to groundwater, if encountered, were also made.
- Laboratory Work was performed on soil samples only.Tests included consolidation by ASTM D2435; soil classifications (ASTM D-422, D-4318, D-2216 and D-2487); Atterberg limits (ASTM D4318); moisture content (ASTM D2216); and chemical properties of pH, water-soluble chlorite and water-soluble sulfate content (ASTM D4972, ASTM D512 and ASTM D116, respectively).
The final report contained recommendations on net allowable bearing pressure at each boring location, settlement computations and an evaluation of groundwater pressure against the reservoir side walls. These recommendations were used by the design engineer in their evaluation of the underground concrete reservoir.