SR-37 Gravity Sewer Project

SR-37 Gravity Sewer Project
Geofoam Foundation Design

Madrid CPWG designed an alternative foundation for a 30-inch gravity sewer pipeline on the east side of SR37 in Mulberry/South Lakeland, Florida. Two sections of the pipeline totaling approximately 1,100 linear feet, were underlain by very soft waste phosphatic clay (WPC). This underlying soil (up to 25 ft thick) is generally almost pure clay with very high plasticity and is both weak and compressible. Early attempts to bed the pipe in WPC using conventional geotechnical methods have proven unsuccessful.

Madrid CPWG Approach
Madrid CPWG designed and performed Construction Materials Testing & Inspection for a cost-effective solution primarily consisting of a Geofoam® support platform that is made up of lightweight material (1% to 2% the weight of soil). The buoyancy of the Geofoam was eliminated by placing the Geofoam layer deep enough that the weight of overlying soil will prevent “floating”. Geofoam provided the following advantages:

• Geofoam replaced much heavier soil, such that the net “new” load on the WPC would be near zero.
• Additional long-term settlements would be minimized.
• Geofoam will not break down and will not pollute the surrounding soil.
• Limited labor is required for construction (installation by hand).

Madrid CPWG also designed a dewatering/drainage system adjacent to the Geofoam blocks to be left in place to help with dewatering efforts if needed in the future. All work was completed in-house.

Madrid CPWG Benefit
Although the installation of any material in WPC can be problematic, the benefits to the County of our Geofoam solution were many:

• Geofoam saved an estimated $800,000 versus the pile-supported pipeline alternative
• Geofoam reduced construction schedule
• Geofoam provided a permanent solution to minimize long-term settlement.

The County and Madrid CPWG were awarded Project of the Year for innovation and cost savings (ASCE Ridge Branch, FL Section).