Seepage Improvements – Deep Cut Off Wall

Wood River Levee District, Madison County, Illinois

The project consisted of improvements to the Wood River Levee system. The improvements were along the Lower Wood River Levee system, between the intersection of IL-143 / Enviroway and IL-143 / Wood River Creek, in East Alton, Illinois.

GFA International performed quality control (QC) testing of the Deep Cut Off Wall’s Self Hardening Slurry (SHS). The Deep Cut Off Wall with permeability of not less than 1 x 10-6 extending to depths of upwards of 140’ and 2,000 lf in length into the existing embankment with total thickness of 24”.

The services GFA provided were as follows:

  • Mix design testing of proposed SHS for constant head permeability and unconfined compressive strength of controlled low strength material
  • Pre-placement sampling and testing of the SHS for constant head permeability (permeability range of (1×10-6 to 9×10-9) and compressive strength. GFA cast over 6,000 pre placement.
  • To achieve the number of test samples GFA constructed an on site testing laboratory with 20 constant head permeability test chambers and two (2) 40’ long containers outfitted as curing room for samples.
  • Verification HQ core borings with 95% recovery rate, GFA performed over 600 lineal feet of verification core borings on cut off wall material.

Challenges encountered during verification borings included compressive strengths as low as 28 psi. To overcome these challenges GFA’s highly experienced drillers utilized a triple barrel HQ wire line core barrel with low to water pressure. Additional challenges included extremely high hydraulic permeability test results from pre-placement sample in the range of 8×10-9 resulting in delays in the reporting. GFA coordinated with our client and the ACOE to reduce duplicative testing requirements and adding additional equipment to get the reporting of samples on time in order to meet the project schedule.