Differing site conditions in construction projects can cause schedule delays, cost increases, and dangerous working conditions, or invalidate design assumptions. Construction projects necessarily involve the assessment of site surface (and subsurface) conditions to select the best means and methods to develop a construction schedule and bid and to complete the project. For traditional design-bid-build projects, the assessment of site conditions is typically based on information provided by the owner/agency in the bid package, familiarity gleaned from a site walk, as well as insight regarding conditions that could be reasonably expected. In some cases, contractors are encouraged to perform additional investigations, as needed, to become better acquainted with the field conditions. For design-build projects, the contractor typically accepts additional responsibility for evaluating site and subsurface conditions. Bidding contractors may be provided with a stipend to conduct additional subsurface investigations.
Contractual provisions to deal with differing site condition (DSC) claims in design-bid-build projects have evolved primarily in the transportation sector. The Federal Highway Administration (FHWA) developed a dual-test system that defines a method of classifying claims—commonly referred to as Type I and Type II claims—according to the basis for the contractor’s pre-construction knowledge and understanding of site conditions. A Type I DSC claim involves situations in which the site surface or subsurface conditions deviate substantially from those represented in the bid package. A Type II DSC claim refers to situations in which the site surface or subsurface conditions are substantially different from those that might be reasonably expected. Some form of these FHWA provisions are contained in most construction contracts for public works projects. The language of the differing site conditions clause becomes a critical component of the construction contract.
Exponent has been engaged by design-build engineering firms, general contractors, and specialty subcontractors to prepare and substantiate differing site conditions claims and has been engaged by project owners and public agencies to evaluate claims submitted by contractors. Exponent has in-house multidisciplinary expertise of engineers, geologists, construction management professionals, and schedulers to analyze all aspects of DSC claims. The results of our development and evaluation of DSC claims have been presented in discussions with our clients, written reports, and testimony at review board hearings, arbitrations, mediations, and trials.
In general, Exponent has expertise to evaluate issues related to:
- Entitlement (technical merits of claim)
- Cost analysis
- Delay impacts
- Acceleration
In Exponent’s evaluations of entitlement, our engineering and construction professionals have used their education, training, and expertise to address issues related to the following types of site conditions:
- Excavation and trench failure
- Embankment failure
- Pile-driving refusal
- Rock suitability for drilled shafts
- Import fill suitability
- Borrow source characterization
- Unsuitable material
- Subgrade suitability
- Embankment/subgrade R-value
- Construction equipment mobility
- “Pumping” and “rutting” of subgrade
- Expansive soil
- Collapsible soil
- Liquefiable soil
- Cobbles and boulders (particle size)
- “Running ground”
- Sinkholes
- Excessive ground moisture
- Groundwater and seepage
- Groundwater pumping rates and volumes
- Rock rippability
- Back-cut slope stability
- Unmapped landslides
- Faults
- Ground fissures
- Hazardous materials (naturally occurring and manmade)