Government_Supplemental_Response_to_DSM_Question_0002.docx

Question: Regarding measurement and payment for Section 31 32 35 Deep Soil Mixing, how is the cubic yard of DSM measured? Would the Grouted Column Treatment Details figure shown on Sheet 21-D-60006 constitute full payment of the 1,800 cyd quantity published within the Section B Price Schedule?

Government Supplemental Response: The cubic yard quantity calculated for the test sections is based solely on the area of the test section and the depth of the soil treatment. Each test section is 20 feet by 20 feet in area (400 square feet). The depth of treatment is from excavated elevation 2242 feet to bottom of treatment elevation 2180 (62 feet total depth). Thus, each test section volume of soil treated is 400 square feet by 62 feet depth, 24,800 cubic feet and 900 cubic yards. The total volume of both test sections is then 1,800 cubic yards. Contractor’s should come reasonably close to constructing deep soil mixed columns to the full extent of each test section area. Overlapped columns outside and inside the test section are not included in the cubic yard measurement.

With respect to the grouted column treatment detail shown on Sheet 21-D-60006. This is primarily a detail of the minimum overlap for each deep soil mixed column within one possible column layout pattern. Contractors may use different column installation layouts as approved in the submittals for construction. Additionally, the detail on Sheet 21-D-60006 is not to scale. The number of columns installed to fill the 400 square feet test section will be dependent on the individual column diameter (additional columns of smaller diameter will be needed to reasonably fill the 400 square feet test section area and fewer columns of larger diameter may be needed to reasonably fill the 400 square feet test section area). Contractors are encouraged to use the largest possible column diameter (and the fewest number of columns) in each test section. In the event that the column diameter results in a column construction area significantly larger than the test section area (for instance, 12-foot diameter columns are installed which would result in 452 square feet when installing 4 columns), the number of columns will be adjusted to provide the square foot area closest to the test section area and the additional column area will be used (in conjunction with the treatment depth and subtracting the column overlap of 5 percent) to adjust the cubic yards quantity.