Cherokee Nation Businesses
Construction
Guidelines and Requirements for Geotechnical
Investigation, Soil Boring and Testing
1. General
A. The proposal shall include, but not be limited to, the tests listed in these requirements. When, in the opinion of the geotechnical engineer, site conditions warrant variation in these specifications, it shall be so stated when the Geotechnical engineer realizes site conditions warrant variation.
B. When the geotechnical engineer requires the use of equipment or personnel of another firm for purposes of remote investigation, the Construction Director shall be so advised in the proposal. In such cases, where the drilling is subcontracted out to another firm, the Construction Director shall be provided with the name of the other firm and the name and employer of the person observing the testing operations. Curriculae Vitae, resumes, project lists, references and proof of insurance may also be required from drilling subcontractors before the proposal may be considered.
C. All borings shall comply with all applicable codes and regulations.
D. The CNB designated construction representative shall be informed, by telephone and in writing, (e-mail), of the job progress and any unexpected or special conditions.
E. Soil samples shall be retained by the soil testing firm for a minimum of six months on projects where shallow foundations are recommended and a minimum of twelve months on projects where deep foundations are recommended. Differing periods may be acceptable. When deviations from the specified periods are proposed, state proposed periods, and state any additional cost to comply with the specified periods.
F. Indicate the time required to complete the soil boring, testing, and investigation report following authorization to proceed. Total time of ten calendar days or less is preferred.
G. At the end of the agreed upon time period, submit three copies of the report including black line prints of all logs, charts, diagrams, drawings, etc. on 81/2 inch x 11 inch sheets.
H. All reports are to be sealed by an engineer licensed in the state in which the work is performed.
I. Evidence of suitable levels of Professional Liability, General Liability and Workmen’s Compensation insurance coverage is required before commencing work. See Exhibit “X”
2. Boring
A. Provide a 100 foot grid in all building areas (i.e. Office - Administration, Service – Maintenance), from front to rear, Provide a minimum of one boring per 15,000 square feet well distributed throughout the parking areas.
B. Borings within the building areas shall be a minimum of 50feet in depth unless refusal is encountered at a shallower depth. When suitable bearing material is not encountered at 50 feet, borings should be extended to suitable material after contacting the Construction Director for authorization. Borings in the parking areas shall be a minimum of ten feet in depth unless refusal is encountered at a shallower depth. When sufficient data to recommend a pavement design has not been accumulated at ten feet, boring shall be extended as necessary to prepare paving recommendations after the Construction Director has been contacted for authorization. When local experience dictates boring depths other than those specified, state the proposed depth and additions to or deductions from the cost to perform the specified boring depths.
C. In granular soils, borings shall be standard penetration tests employing a 140 pound hammer having a free fall of 30 inches and using a 2 inch outside diameter (1-3/8 inch inside diameter) split spoon per ASTM method D-1586. In cohesive soils, standard penetration test per ASTM D-1586 or thin wall tube sampling of soils per ASTM D-1587 may be employed.
D. Soil samples shall be taken at two foot six inch intervals up to ten feet in depth and at five feet or at each change of strata thereafter.
E. Indicate as accurately as possible the water line in all holes, at the time of boring and twenty-four hours later.
F. Where fill is encountered, it shall be described in great detail, including such information as approximate amount of organic material. Topsoil, wood, or other decaying material, loose or well compacted, amount of moisture, amount and type of debris, where compatible or to be removed, etc.
G. When rock is encountered, rock core samples of a minimum one inch diameter and minimum five feet in length shall be obtained, recovery ratios shall be given as well as a clear description of the type of rock, in particular, the means required to excavate same.
H. The location of borings on the boring location plan is approximate and may be offset to clear obstructions, old foundations, etc. All obstructions should be identified and located on the boring location plan.
I. The soil boring contractor shall leave clearly identified, visible, and permanent stakes in the ground at the location of each boring.
J. Areas disturbed as a result of exploration shall be restored to a condition equivalent to that which existed prior to being disturbed (i.e. back fill bore holes, minimize damage to vegetation, patching of pavement areas, etc.).
3. Tests
A. Unconfined compression tests, as determined at the laboratory from Shelby Tube samples, when cohesive soils are encountered, shall be performed on at least one sample obtained from within the building pad areas unless specified otherwise in the authorization letter. Weaker samples are preferred for the above test.
B. Dry unit weights and water content determination shall be made for each change of soil strata or as deemed necessary by the soils
Engineer.
C. Maximum Density-Optimum Moisture determination per ASTM test method D-1557 shall be made.
D. Provide an additional separate cost to establish the California Bearing Ratio number per ASTM method D-1883 or the plate bearing value per ASTM method D-1195 by conducting tests on samples in place or in the laboratory or both, when needed to arrive at a recommended paving design. The field test shall be made on a surface at least twelve inches below finish grade where indicated on the boring plan. Test in the laboratory shall be made on a sample at maximum density-optimum moisture, indicate whether this test will be required in order for you to provide an acceptable pavement design.
4. Report
A. The report shall include a statement describing the field investigation technique and laboratory procedures. Include a commentary on the site in general and on the subsurface conditions.
B. Recommendations regarding type and depth of foundation, bearing capacities, both on natural deposits and on engineered fill, amount of fill surcharge, lateral bearing values, concentrated equipment loads, excavating and back filling, surface and sub-soil drainage, settlement, base for slabs and pavement, any limitations, etc., shall be part of the report.
C. The exact location, final depth, and ground elevation of each hole shall be shown on a boring location plan. Ground elevation at boring locations shall be established with reference to the same bench mark used on the survey, or as called for in the authorization letter.
D. Test data shall be illustrated on tables, charts, graphs, etc., as required to summarize the results.
E. Final boring logs shall give a detailed description of the various soil strata and they shall include the group symbol based on the uniform Soil Classification system.
F. Recommended specification for materials and placement of any required off site fill including granular and cohesive materials. Provide estimated cost per cubic yard installed for these materials.
G. Estimated total and differential settlements.
H. Recommend both a heavy and light duty paving system, including thickness and material specification for topping, asphaltic base primer (when required) and granular sub-base. Light duty paving should be based on an estimated (50 to 500) automobiles per day. Heavy duty paving should be based on (500 to 2500) automobiles per day, twelve shuttle buses per hour with 2000 pound wheel loads (axle load), plus three transport trailers per (day/week) with 10,000 pound wheel loads. Provide an estimated cost per square yard for both the paving and base in-place.
I. Provide recommendations regarding the criteria to be used in the design of site retaining walls.
J. When applicable, indicate if the site under investigation is suspected or known to be located over or adjacent to a mined area. If so, note any possible adverse conditions that could result from such a location.
K. Provide information regarding the corrosive characteristics of the encountered soils as they relate to the type of construction proposed for the site.
L. When poor subgrade material is encountered, recommend an alternate paving design using a reinforcing fabric (such as Mirafi 500x or Tensar 13X) and a thickened paving base, including thickness and material specifications for topping, asphaltic base, primer (when required) and reinforcing fabric and an estimated in-place cost per square yard for both the paving and fabric system.
M. Provide an indication of how susceptible the on-site materials are to moisture damage during the construction season at the proposed subgrade elevations and what recommended procedures should be taken to alleviate possible problems.
N. At the request of the Construction Director provide supplemental reports and evaluations for any area not sufficiently clarified in the original report. These may include, for example, comparison of the various construction options and their relative cost/benefits for the preporation of the subgrade, the building foundation or the design and construction sequence of the asphalt pavement.