Differing Site Conditions (DSC) Process to determine, analyze, present, and adjudicate a differing site condition. By Dr. Peter J. Tarkoy WWW.GeoConSol.COM

What makes you suspect a DSC? By experiencing: Delays, slower progress High usage of supplies, tools, support High rate of equipment wear Costlier construction in general

Cause of delays & excess costs? Excess Time For repair & maintenance To excavate, support, etc. Excess Supplies Tools Equipment wear Increase manpower to maintain schedule

Standards for Preparing DSC Claim What are the components? How are the necessary requirements fulfilled?

Components of a DSC Claim A DSC consists of two parts namely: Entitlement Quantum ($)

Elements for Entitlement in DSCs Industry Standards For geotechnical differing site conditions, entitlement must be analyzed, established, and presented according to the following principles: There must be a difference between reasonable anticipated and documented encountered conditions, There has to be a difference between reasonable anticipated and documented encountered construction performance, A cause-and-effect relationship must be demonstrable between the differences in conditions and difference in construction performance, There must be a demonstrable impact on time or costs, Contract conditions must be fulfilled (reliance, notice, mitigation) and No other factors (self-inflicted) can have caused the difference between anticipated and encountered performance.

Step 1 – to establish entitlement? Establish: Current geological condition that may be causing the delay Geological condition that was indicated in the contract documents or anticipated based on factual pre-bid information Determine if there is a difference

Step 2 – to establish entitlement? Is there a difference between: Reasonable anticipated construction performance and Documented encountered construction performance?

Case 1.1 – Clay zone in rock tunnel

Case 1.2 – Clay zone in rock tunnel Tunnel boring machine encountered a clay zone in a rock tunnel, The machine sank into the invert, The ground had to be stabilized and the machine re-aligned, and Normal excavation had to be resumed

Case 1.3 – Clay zone in rock tunnel Was the unanticipated condition compensable under the differing site condition clause? Let us take a look at the borings to see what should have been anticipated. In the tunnel zone of concern, we found the following core ------

Case 1.4 – Clay zone in rock tunnel

Case 1.5 - Clay zone in rock tunnel Observation The boring showed RQD=10% The core was deeply altered It was an indication of a shear zone The encountered condition was consistent with indications in the rock core Conclusion A DSC cannot be demonstrated

Step 3 – to establish entitlement? Is there a cause & effect relationship? Between: Differences in conditions and Differences in performance?

Step ? – to establish entitlement? Is an impact demonstrable? In time, In space, and Related to the unanticipated condition.

Step ? – to establish entitlement? Have the contra\ct conditions been fulfilled, namely: Reliance Notice Mitigation

Step ? – to establish entitlement? Were there any other causes that may have resulted in: Increased project time & costs? Were there any self-inflicted problems?