Attachment B - Specifications.pdf

NRCS-IOWA 2020 1

IOWA GEOLOGIC INVESTIGATION—SPECIFICATIONS

No. Investigation Specification Page

1. Mobilization and Demobilization 1

2. Soil Boring—Helical Flight Augers 1

3. Standard Penetration Test and Drive Sampling (Split-Barrel) 2

4. Backfilling of Test Holes 3

5. Installation of Piezometers 4

1. MOBILIZATION AND DEMOBILIZATION

Mobilization will consist of delivery to the work site of all personnel, equipment, tools, and supplies needed to carry out the work required under the contract. It will include the complete assembly (in satisfactory working order) of all equipment used on the site, and the temporary storage at the site of all materials, equipment, supplies, and samples in a clean, neat, and orderly condition satisfactory to the C.O.R.

Demobilization will consist of the removal from the work site of all personnel, equipment, and unused supplies and materials. This includes the disassembling and loading of equipment and the cleanup and restoration of areas disturbed by the Contractor.

Bid Items and Investigation Details. Items of work to be performed in conformance with this specification therefore are:

BID ITEM 1, Mobilization and Demobilization.

This item will consist of mobilization and demobilization work as described in this specification.

2. SOIL BORING—HELICAL FLIGHT AUGERS

The purpose of this specification is to obtain bulk disturbed samples of a wide range of unconsolidated materials in such a manner that the depth of the sample is known to within 1-2 feet of accuracy.

The Contractor will furnish a total of 100 linear feet of flight augers. Diameter of the flight augers will be a minimum of 6 inches. The flight augers will be advanced at maximum intervals of 10 feet. Cuttings will not be rotated out of the hole. The flight auger string will be pulled from the test hole after each 10-ft interval is bored to facilitate a reasonably accurate measurement of sample depth. The Contractor will keep track of how many augers have been pulled after each 10-ft interval so that the correct interval can be sampled. The Contractor will take representative grab samples off the augers at

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1-ft intervals and place the samples in correct order on a board or other suitable surface for examination by the C.O.R.

Bid Items and Investigation Details. Items of work to be performed in conformance with this specification therefore are:

BID ITEM 2, Soil Boring—Helical Flight Augers.

(a) This item will consist of obtaining disturbed samples with helical flight augers to a maximum depth of 100 feet.

(b) The minimum auger diameter will be 6 inches.

(c) Backfilling of test holes is subsidiary to this item.

3. STANDARD PENETRATION TEST AND DRIVE SAMPLING (SPLIT BARREL)

This test provides a measure of the resistance of soil to penetration of the sampler. The test is used to indicate relative in-place density of cohesionless materials and relative in-place consistency of cohesive materials for logging and other test purposes.

Standard penetration tests will be required at the discretion of the onsite geologist when soils are encountered that cannot be sampled properly for laboratory density and strength testing.

The standard penetration test equipment and procedure will comply with ASTM D-1586/D1586M-18. The sampler will have an outside diameter of 2 inches. It will consist of a hardened steel driving shoe at least 3 inches in length with an inside diameter at the cutting head of 1-3/8 inches. It will be sharpened by tapering the last 3/4 inch to a cutting edge not greater than 1/6 inch thick. Dented, distorted, or broken shoes will not be used. The split tube will have a minimum length of 16 inches and an inside diameter of 1-3/8 or 1-1/2 inches. The coupling head will have a minimum length of 6 inches. It will have four vents each with a minimum diameter of 1/2 inch, or it will contain a ball check valve and no side vents.

The drive hammer assembly will consist of a 140-pound weight, guide pipe sufficiently long to allow a 30-inch free fall, and a jar coupling (connection between the guide pipe and sampler rod string for the hammer to strike).

N-series drill rod will be used. Holes for penetration testing will be a minimum diameter of 3-1/2 inches. The hole is to be cleaned to the sampling depth by use of equipment that will not disturb the material to be sampled. Bottom discharge fishtail bits, jetting through an open tube, or sand water bailers will not be used to advance holes in preparation for split-tube sampling.

Other configurations of the test equipment and procedure may be allowed if approved in advance by the C.O.R., but only if those changes still comply with ASTM

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D-1586/D1586M-18. The C.O.R. will determine the location and depths for penetration resistance testing or sampling. The testing and sampling activities will be as specified herein.

The sampler will be clean and lightly coated with oil at the beginning of each test. The outer walls, inner wall or liner, and cutting bit will be smooth and free from scars made by tools and rocks. In preparation for the test, the split-tube sampler is lowered to the bottom of the cleaned hole. The sampler will then be driven 6 inches with light blows so it will not be overdriven. The sampler is then driven 12 inches or to refusal by dropping the 140-pound hammer 30 inches. The number of blows required for each 6 inches of the penetration test drive is to be recorded separately.

Handling and preservation of split-tube samples by the Contractor will be in accordance with industry standards and will ensure maximum protection of the samples.

Bid Items and Investigation Details. Items of work to be performed in conformance with this specification and the investigation details therefore are:

BID ITEM 3, Standard Penetration Test and Drive Sampling (Split-Barrel).

This item will consist of the penetration test and split-tube drive sampling to a maximum estimated depth of 60 feet.

4. BACKFILLING OF TEST HOLES

All drill holes that contain groundwater at the time of drilling will be left open for a minimum of 7-days in order to monitor changes in the groundwater level over that period. For safety concerns open holes will need to be covered for this 7-day period.

Drill holes will not be backfilled without the approval of the C.O.R. Following approval from the C.O.R drill holes will be backfilled with medium bentonite chips from the bottom of the boring up to an elevation equal to the seasonal high groundwater level.

The borehole starting at the seasonal high groundwater level shall be sealed with cement grout to an elevation four (4) feet below ground surface. The remaining four (4) feet to ground surface may be backfilled with compacted uncontaminated soil. Materials will be placed to avoid bridging in the hole as much as possible. This requires emplacing the bentonite chips at a rate of approximately 4 minutes per bag. The upper 4 feet of backfill in each hole will be tamped as much as is practicable.

Bid Items and Investigation Details. Items of work to be performed in conformance with this specification are:

BID ITEM 4, Backfilling of Test Holes.

(a) This item will consist of backfilling test holes with bentonite chips, cement grout and earth materials and tamping of the upper 4 feet of backfill in each hole.

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5. INSTALLATION OF PIEZOMETERS

Two boreholes, one along each downstream abutment, will be finished by installing piezometers for the purpose of long-term groundwater monitoring at the site. All material and installation specs will follow industry standards including materials used to fill the annular space around the piezometer. Two-inch PVC pipe will be used for the piezometers with a minimum of a 10-foot screen. Steel-casing with a cap will be used to cover the piezometer above the ground surface.

BID ITEM 4, Installation of Piezometers.

(a) This item will consist of installing piezometers into 2 boreholes downstream of the dam.