MEA, a UES Company, was selected by a Pennsylvania earth moving contractor and his attorney to investigate his dispute with the owner over the hard excavation quantity. The project involved installing the third phase of a major sewer line mainly in an open cut in soil and rock. Phase III was about 2 miles long (see Figure 1). Figure 2 shows the excavator attempting to rip rock in the bottom of the trench excavation. The hard excavation quantity measured and reported by the owner and the contractor were drastically different. The owner considered the contractor paid in full at about 3,700 cubic yards. The contractor reported about 12,000 cubic yards.
Under the contract specification, hard excavation was basically stated as: “… “Hard” excavation shall include materials that cannot be effectively removed by a late model hydraulic excavator with greater than 160 flywheel horsepower, and equipped with a rock ripping bucket. Hard and compact material such as claystone or relatively soft or disintegrated rock will not be considered as such because of the intermittent use of hydraulic hammers to break up rock or concrete merely to increase production…” MEA’s forensic investigation of the above dispute included the review of project documents and depositions, data reduction, and evaluation of engineering design and field reports, as well as project discussions with construction personnel. Based on this investigation MEA found that the engineer neglected to count a significant quantity of material from the own records which amounted to approximately an additional 1,000 cubic yards. After this difference was brought to their attention the owner recognized the error; however, a significant difference in measured amount of hard excavation still existed between the contractor and owner.
MEA further determined that the main basis for the dispute in measuring hard excavation lay in the contract definition. MEA found:
- Based on their interpretation of hard excavation specification at the time of bid the contractor assumed that hard excavation was encountered whenever rock could not be excavated freely and required use of a hoe ram. A more stringent standard than expected was applied during construction by the Owner’s Representative.
- As pointed out by MEA, variant field assessment of hard excavation by all parties (individually and as a group) involved in this project is symptomatic of an ill-defined and defective specification of hard excavation. Consequently, there are many valid interpretations of what hard excavation is. For example, the ripping force of an excavator can vary significantly even if it has the same horsepower. Analogous to a fulcrum, the stick length of the hoe excavator plays a critical role. In other words, the shorter the stick, the greater the digging force (see Figure 3).
- Further, the actual method of excavation used to remove rock was incompatible with the way hard excavation was to be measured per the specifications. For example, the contractor used a 300 hp excavator compared to the 160 hp machine required by the contract to determine hard excavation. After depositions and trial, the court ruled in the favor of our findings and awarded the contractor his measured quantity with damages.