SECTION_02_41_20_-_Piezometer_Abandonment_R2_0004.pdf

BUREAU OF INDIAN AFFAIRS OGLALA DAM SPILLWAY AND OUTLET WORKS

OGLALA DAM SPILLWAY AND OUTLET WORKS SECTION 02 41 20

JUNE 2023 PIEZOMETER ABANDONMENT

FOR BID REV 2 PAGE 1 OF 4

SECTION 02 41 20

PIEZOMETER ABANDONMENT

GENERAL

1.01 SCOPE OF WORK

A. This Section specifies the requirements for permanent abandonment of the existing wells and piezometers including furnishing all permits, labor, equipment, materials, and supplies required to permanently abandon wells and piezometers.

1.02 REFERENCES

A. ASTM International (ASTM)

ASTM C150 Standard Specification for Portland Cement

ASTM C595 Standard Specification for Blended Hydraulic Cements

1.03 SUBMITTALS

A. Shop Drawings

At least 30 days prior to first piezometer abandonment, submit a Piezometer Abandonment Work Plan, including a detailed listing of equipment and materials to be used; methods of abandonment for each piezometer and well; a layout and plan for accesses to piezometer and well locations; estimated bedrock elevation; estimated volumes of grout to be used based on field dimensions; and any other information necessary to review the CONTRACTOR’s plans for effective and safe piezometer abandonment prior to performing the work.

The Work Plan shall be prepared and submitted in accordance with applicable state laws, including preparation and sealing by a licensed Geologist or Professional Engineer experienced with the type of Work.

The materials and methods in the Work Plan shall meet the requirements specified herein and the South Dakota Codified Law 46-6-18 and 46-6-27.

At least 30 days prior to first piezometer abandonment, submit vendor information for cement, bentonite, aggregate, and any additives approved for the Work.

B. Quality Control

At the end of each well or piezometer abandonment, CONTRACTOR shall submit complete records of the well or piezometer abandoned or removed. Well and piezometer abandonment records shall meet the requirements of Paragraph 3.02

RECORDS.

Upon completion of Work, CONTRACTOR shall provide a written report to the COR.

The report shall include a narrative describing the well or piezometer abandonment

BUREAU OF INDIAN AFFAIRS SECTION 02 41 20

FOR BID REV 2 PAGE 2 OF 4

activities and copies of all required records collected in accordance with Paragraph

3.02 RECORDS.

1.04 SCHEDULE, COORDINATION, AND INSPECTION

A. CONTRACTOR shall retain the piezometers as long as possible to allow water level monitoring during the early stages of the work. Piezometers shall only be abandoned or removed as required for the construction activities to progress.

B. Different wells and piezometers will be abandoned or removed on different dates. The abandonment schedule for each well or piezometer will be proposed by CONTRACTOR based on the progress of the work and requires approval by the BIA Representative.

C. CONTRACTOR shall not abandon or remove any well or piezometer without the prior written approval from the BIA Representative allowing abandonment or removal of that well or piezometer.

D. CONTRACTOR shall notify the BIA Representative at least 72 hours in advance of each in place piezometer abandonment activities activity so that the BIA Representative may be present to observe the activities.

1.05 GENERAL

A. Provide an adequate water supply and handle the disposal of well and piezometer abandonment materials in a manner that avoids surface erosion and contamination.

B. All trash, debris, and waste shall be contained and removed from the site. CONTRACTOR is responsible for making appropriate arrangements to legally dispose of all such material.

PRODUCTS

2.01 CEMENT BENTONITE GROUT

A. Grout mix: The wells or piezometers to be abandoned shall be filled with a sanded cement-bentonite grout. The grout shall be a sanded slurry mix with approximate proportions by weight of 2 parts sand to 1 part cement, 6 to 7 gallons of clean water per 94 lb. sack of cement, and no more than 30 lbs. of bentonite for each 94 lb. sack of cement.

B. Sand: 100% passing the No. 4 sieve with rounded particles. The proportions of the various materials may be varied by the BIA Representative in the field.

C. Portland Cement: ASTM C150, Type I or III, or ASTM C595, Type IL, cement.

D. Bentonite: natural Wyoming sodium bentonite containing no additives, ground to pass a No. 200 sieve, and meeting the criteria defined by the American Petroleum Institute (API) Specification 13A.

FOR BID REV 2 PAGE 3 OF 4

EXECUTION

3.01 GENERAL

A. Document and maintain information about the well or piezometer conditions, depth and type of casing, depth of well or piezometer, and bore diameter.

B. Wells and piezometers that terminate above the bottom of excavation elevation will be removed during excavation. Wells and piezometers that extend below the bottom of excavation shall be fully grouted in accordance with the procedure in this Specification Section. The following table identifies two piezometers that will be backfilled with grout.

The table provides approximate elevations for the bottom of excavation and bottom of well/piezometer. The CONTRACTOR shall confirm the bottom of excavation elevations and the bottom of the wells/piezometers by sounding the well/piezometer in the field prior to excavation.

Piezometer Estimated Bottom of Excavation Elevation

(feet)

Estimated Bottom of Well Elevation

(feet) Status

DH-18-A 2947 2957 EXCAVATE

DH-18-B 2956 2952 GROUT

DH-20-03 2948 2956 EXCAVATE

DH-20-06 2950 2950 EXCAVATE

DH-21-01(P) 2978 2967 GROUT

DH-21-02(P) 2948 2960 EXCAVATE

C. Clean and sound piezometer to determine its condition and whether there are obstructions that could interfere with the abandonment process. Compare the sounded depth to the available installation records.

D. Mix grout either by circulating through a pump or using a high shear mixer approved by the COR.

E. Perform cement-bentonite grouting mixing and placement as follows:

Place the water in the mixing tub and start the mixing equipment.

Slowly add the cement to the water while mixing to avoid clumping of cement.

After cement and water are completely mixed, slowly add the sand and bentonite to avoid clumping. If clumps start to form, stop adding bentonite until the clumps dissolve. Add sand and continue mixing until the mix reaches the consistency of heavy paste or as directed by the BIA Representative.

F. Fill the piezometer from bottom to top using tremie methods and by gradually withdrawing tremie pipe as grout is added. Compare injected grout volume to theoretical grout volume.

Do not pressurize the piezometer during abandonment.

FOR BID REV 2 PAGE 4 OF 4

G. After initial filling, allow grout to set for a minimum of 24 hours prior to performing additional filling.

3.02 RECORDS

A. Keep daily records of all well and piezometer abandonment activities performed and products used. The records shall contain the following information:

Date(s), weather, and time.

CONTRACTOR representatives at site.

Location and identifying number of well or piezometer and reference to survey data.

Approximate ground elevation at well or piezometer.

Results of investigation of construction details and condition of each well or piezometer including the depth, vertical arrangement, thickness, and a description of the character of well or piezometer materials; well or piezometer condition; and the details and locations of any obstructions that may interfere with well or piezometer abandonment.

Depth below ground surface at which groundwater was encountered.

Complete well or piezometer abandonment details including documentation of obstruction removal; sealing and filling grout mix proportions; the volumes, types, vertical arrangement, and placement details of grout backfill material placed in each piezometer; a comparison of theoretical and actual grout backfill volumes.

END OF SECTION