Special Circumstances Many projects include special site characteristics that may not be apparent to the potential contractors unless they are specifically addressed in the specifications. These characteristics or conditions can dramatically affect the safe and productive execution of the ground improvement work. Special considerations that must be addressed include: 1. Obstructions: Many ground improvement tools are ill-suited to penetrate or bypass significant buried masses. Likewise, anticipated natural obstructions should also receive comment. A concrete block and a granite boulder each represent similar challenges to ground improvement equipment. The document should comment on the existence or potential for man-made, underground obstructions to be present. 2. Flowing and artesian water conditions: Often overlooked is the potential for artesian pressure or significant subsurface gradients/groundwater velocity to negatively impact ground improvement methods, specifically grouting and ground freezing techniques. The specification and data report should identify the potential for these conditions. 3. Hazardous materials: The presence or potential presence of hazardous materials or gases (e.g., methane, hydrogen sulfide, etc.) must be disclosed in the contract documents. Under many circumstances, ground improvement techniques are the appropriate solution to mitigate risks associated with such conditions, but the potential bidders must fully understand the project environment to prepare a responsive proposal. 4. Locale-specific considerations: The specification should identify any special, local conditions that could influence the work. These could include: a. Road or bridge weight restrictions. b. Frost laws which could adversely affect delivery of equipment and materials during the late winter and spring. c. Readily available local materials (e.g., gravel pits, quarries, etc.). d. Project Labor Agreements or local labor/wage/work rule requirements. Conclusions The specialized nature of ground improvement does not always lend itself to standardized specifications. In fact, the best value for Owners can often be achieved by allowing specialist Ground Improvement Contractors to select among several available techniques to offer the best combination of performance and economy. Accordingly, establishing a framework for the preparation of ground improvement performance specifications that allows for maximum flexibility in potential technologies, while explicitly defining the performance requirements has great value to project sponsors. The preceding discussion presents important considerations to be addressed, and the minimum content that should be included, in a ground improvement specification, such that Owners should receive proposals that reflect the delivery of equivalent project performance and competitive pricing. Deep dynamic compaction Authors: Raymond Franz, P.E., D.GE, Hayward Baker, Inc.; Dominic Parmantier, P.E., Condon- Johnson and Associates, Inc.; Martin Taube, P.E., P.G., Menard USA; Sonia Swift, P.E., GEI Consultants, Inc.; Christian Woods, P.E., G.E., D.GE, Densification, Inc.; Lyle Simonton, P.E., Subsurface Constructors, Inc.; Kimball Olsen, P.E., Kiewit Engineering Co.; J. Tanner Blackburn, Ph.D., P.E., Hayward Baker, Inc. 90 • DEEP FOUNDATIONS • MAR/APR 2016
