Advanced Earth Sciences, Inc. (AES) is currently providing geotechnical services during the design and construction phases of the Phase 1 improvements at the LA County Sanitation Districts’ new biosolids composting facility located in Kings County, California.

Proposed facilities include composting pads, Biofilter, mixing building, pump stations, mixing basins, stormwater reservoirs, wastewater treatment system, non-potable water system, buildings, roads and pipelines.

The site is underlain by several hundred feet of lakebed deposits consisting of soft to medium stiff high plasticity clays. Site constraints include the presence of highly compressible clays, shallow groundwater, very high expansion potential (EI in excess of 160) and very high sulfate content (in excess of 20,000 ppm).

Investigations included borings, CPTs, piezometers, geotechnical and chemical testing, falling weight deflectometer testing and settlement monitoring under surcharge loads. Conducted laboratory test trials for alternative stabilization methods including the use of lime treated soil (LTS), lime-flyash and soil cement (SC). Evaluated potential for ettringite formation under the high sulfate environment.

Performed flexible pavement design using Mechanical Empirical design methods. Used MEPDG and KenPAVE programs for pavement performance analyses and design utilizing the results of the falling weight deflectometer data.

Geotechnical design recommendations included shallow and pile foundations; wick drains and surcharging for settlement control; rammed aggregate piers for structure support; soil stabilization to mitigate against expansive soils; protection measures to mitigate against very high sulfate and chloride content and potential for ettringite formation; and design of LTS, lime-flyash and SC mixes.

AES prepared two Technical Memoranda and a Geotechnical Report with recommendations for ground improvement, soil stabilization corrosion protection and foundation design.