06 Below Grade Condition Requirements.pdf

1. The anticipated below-grade conditions described herein are provided solely to establish a baseline for bidding and planning purposes. They are not intended to represent a guarantee of actual subsurface conditions, nor do they relieve the contractor of its obligation to examine the site and account for variability reasonably anticipated within these classifications. Subsurface conditions that are consistent with, equal to, or more favorable than the anticipated conditions described herein shall not constitute a diƯering site condition and shall not be grounds for additional compensation or time extensions. Variations in quantity, continuity, or distribution of anticipated materials, groundwater, or obstructions shall be considered inherent to the site and shall not constitute a diƯering site condition.

2. The contractor shall anticipate the presence of perched groundwater, seasonal groundwater fluctuations, and moisture variations within excavations. Dewatering, drying, or moisture conditioning necessary to achieve required compaction or construction tolerances shall be included in the contract price and schedule unless otherwise expressly stated.

3. Shoring, benching, sloping, and excavation safety measures shall be designed and constructed assuming OSHA Class C soils unless the contractor demonstrates, through testing and documentation acceptable to NIST, that more favorable conditions exist.

4. The NIST Boulder campus is located on a mixture of Slocum Alluvium and Terrace Alluvium. Based on previous on-site investigations, the contractor should anticipate that material on site falls into the following categories.

a. Undisturbed areas are classified as clayey gravels or silty gravels with at least 20% of the material not passing a 3-inch sieve. Cobbles and boulders ranging from 3 inches up to 24 inches in maximum dimension are anticipated and shall be considered incidental to excavation. Removal, handling, and disposal of such materials shall be included in the Contract Price.

b. Due to the age of the campus, developed areas of the site are made up of fine to coarse grained silty sand or clayey sand with gravel and at least 10% of the material not passing a 3-inch sieve. Existing material should be considered unsuitable for reuse as structural fill without being graded and conditioned. Processing, conditioning, blending, or replacement of existing materials to meet structural fill requirements shall be included in the Contract Price. No additional compensation will be provided for rejection or reworking of materials consistent with the anticipated conditions. In developed areas, excavations more than 24” below grade should use the undisturbed area classification.

i. Where asphalt is present, it ranges from 9 to 12 inches thick with 3 to 4 inches of aggregate base course below.

ii. Where exterior concrete slabs and pavements are present, anticipate that they are 5,000 psi concrete that range from 6 to 12 inches thick with a typical area of steel of 0.3 in2/ft.

iii. Where sidewalks are present, anticipate that they are 5,000 psi concrete that is 6 to 8 inches thick with 6”x6” (W2.9xW2.9) welded wire reinforcement.

iv. The contractor shall anticipate the presence of undocumented obstructions associated with previous site development, including foundations, slabs, utilities, and construction debris. Removal of such obstructions consistent with the anticipated site development history shall be included in the Contract Price.

c. The above assumptions are to be used as a basis for construction bidding purposes. For design-build projects, the contractor shall bear full responsibility for subsurface investigations, foundation design, and performance. NIST makes no representations regarding subsurface conditions beyond the anticipated conditions stated herein.

5. For construction projects not requiring a design, the following minimum fill compaction requirements shall be met per ASTM D698. All fills shall be adjusted to +/-3% of optimum moisture content. The contractor shall be responsible for all testing, rework, and corrective measures necessary to achieve the specified compaction requirements, at no additional cost to NIST. Over-excavation, replacement, or stabilization required to achieve specified compaction consistent with the anticipated conditions shall be included in the Contract Price.

a. Beneath slabs on grade – 95%

b. Utility trenches – 95%

c. General site grading and landscape areas – 95%

d. Beneath footings and foundations – Project specific