A0002_Att_8_(Replacement)_31_03_33_-_Removal_and_Control_of_Water_0002.pdf

Hyrum Dam Spillway Replacement Hyrum Project, Utah

Removal and Control of Water

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SECTION 31 03 33

REMOVAL AND CONTROL OF WATER

PART 1 GENERAL

1.01 MEASUREMENT AND PAYMENT

A. Stilling Basin Unwatering:

1. Payment: Lump-sum price offered in Price Schedule A:

a. Includes the following:

1) Labor, power and standby power, materials, equipment, and other items needed to furnish, install, operate, and maintain an effective unwatering system.

2) Includes sediment basin or other method(s) for removing suspended particles.

3) Abandoning and removing the unwatering system.

B. Crest Structure Unwatering:

1. Payment: Lump-sum price offered in Price Schedule A:

a. Includes the following:

1) Labor, power and standby power, materials, equipment, and other items needed to furnish, install, operate, and maintain an effective unwatering system.

2) Includes sediment basin or other method(s) for removing suspended particles.

3) Abandoning and removing the unwatering system.

C. Upper Chute (Phase 3 Excavation) Unwatering:

1. Payment: Lump-sum price offered in Price Schedule A:

a. Includes the following:

1) Labor, power and standby power, materials, equipment, and other items needed to furnish, install, operate, and maintain effective unwatering systems at the upper chute and the downstream channel.

2) Includes sediment basin or other method(s) for removing suspended particles.

3) Abandoning and removing the unwatering systems.

D. Deep Wells:

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1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule A:

a. Includes the following:

1) Furnishing and installing the materials required for the installation of deep wells, which includes but is not limited to:

a) Filter pack (includes below bottom of casing).

b) Screen and casing (including stick-up length above ground surface).

c) Pump and motor.

d) Manifold piping.

2) Labor for drilling, development, and installation of a functional deep well.

3) Drilling.

4) Removal and abandonment of deep wells.

E. Deep Wells Operation and Power:

1. Payment: Lump sum price offered in Price Schedule A:

a. Includes the following:

1) Labor and other equipment required to operate and maintain the deep wells.

2) Standby pumps for deep wells.

3) Design, installation, and removal of deep wells discharge and collection system(s) and electrical supply system(s).

4) Power includes the following:

a) Primary power for operation of submersible pumps for deep well system.

b) Standby power for operation of submersible pumps for deep well system.

F. Well Points:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule A:

a. Includes the following:

1) Furnishing and installing the materials required for the installation of well points, which includes but is not limited to:

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a) Filter pack (includes below bottom of casing).

b) Screen and casing (including stick-up length above ground surface).

c) Manifold piping.

2) Labor for drilling, development, and installation of a functional well point.

3) Drilling.

4) Removal and abandonment of well points.

G. Well Points Operation and Power:

1. Payment: Lump sum price offered in Price Schedule A:

a. Includes the following:

1) Labor and other equipment required to operate and maintain the well points.

2) Vacuum pumps for well points.

3) Standby vacuum pumps for well points.

4) Design, installation, and removal of well points discharge and collection system(s) and electrical supply system(s).

5) Power includes the following:

a) Primary power for operation of vacuum pumps for well point system.

b) Standby power for operation of vacuum pumps for well point system.

H. Passive Wells:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule A:

a. Includes the following:

1) Furnishing and installing the materials required for passive wells, which includes but is not limited to:

a) Filter pack.

b) Screen and casing (including stick-up length above ground surface).

2) Labor for drilling, development, and installation of a functional passive well.

3) Drilling.

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4) Removal and abandonment of passive wells.

I. Temporary Observation Wells:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule A:

a. Includes the following:

1) Furnishing and installing the materials required for the temporary observation wells, which includes but is not limited to:

a) Filter pack.

b) Screen and casing (including stick-up length above ground surface).

2) Labor for drilling, development, and installation of a functional temporary observation well.

3) Drilling.

4) Removal and abandonment of temporary observation wells.

J. Supplementary Deep Wells Installation/Removal:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule C:

a. Includes the following:

1) Labor for drilling, development, and installation of a functional supplementary deep well.

2) Drilling.

3) Removal and abandonment of supplementary deep wells.

4) Drill rig(s) standby time.

K. Supplementary Deep Wells Materials:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule C:

a. Includes the following:

1) Furnishing the materials required for the supplementary deep wells, which includes but is not limited to:

a) Filter pack.

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b) Screen and casing (including stick-up length above ground surface).

c) Pump and motor.

d) Manifold piping, if required.

L. Supplementary Deep Wells Operation and Power:

1. Payment: Lump-sum price offered in Price Schedule D:

a. Includes the following:

1) Labor, electrical system, discharge system, and other equipment required to operate and maintain the supplementary deep wells.

2) Standby pumps for supplementary deep wells.

3) Power includes the following:

a) Primary power for operation of submersible pumps for supplementary deep well system.

b) Standby power for operation of submersible pumps for supplementary deep well system.

M. Supplementary Well Points Installation/Removal:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule E:

a. Includes the following:

1) Labor for drilling, development, and installation of a functional supplementary well point.

2) Drilling.

3) Removal and abandonment of supplementary well points.

4) Drill rig(s) standby time

N. Supplementary Well Points Materials:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule E:

a. Includes the following:

1) Furnishing the materials required for the supplementary well points, which includes but is not limited to:

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b) Screen and casing (including stick-up length above ground surface).

c) Manifold piping, if required.

O. Supplementary Well Points Operation and Power:

1. Payment: Lump-sum price offered in Price Schedule F:

a. Includes the following:

1) Labor, electrical system, discharge system, and other equipment required to operate and maintain the supplementary well points.

2) Vacuum pumps for supplementary well points.

3) Standby vacuum pumps for supplementary wells points.

4) Power includes the following:

a) Primary power for operation of vacuum pumps for well point system.

b) Standby power for operation of vacuum pumps for well point system.

P. Supplementary Passive Wells Installation/Removal:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule G:

a. Includes the following:

1) Labor for drilling, development, and installation of a functional supplementary passive well.

2) Drilling.

3) Removal and abandonment of supplementary passive wells.

4) Drill rig(s) standby time.

Q. Supplementary Passive Wells Materials:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule G:

a. Includes the following:

1) Furnishing the materials required for the supplementary passive wells, which includes but is not limited to:

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b) Screen and casing (including stick-up length above ground surface).

R. Supplementary Temporary Observation Wells Installation/Removal:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule H:

a. Includes the following:

1) Labor for drilling, development, and installation of functional supplementary temporary observation well.

2) Drilling.

3) Removal and abandonment of supplementary temporary observation wells.

4) Drill rig(s) standby time.

S. Supplementary Temporary Observation Wells Materials:

1. Measurement: Linear foot of well installed, measured from ground surface to the bottom of the casing.

2. Payment: Unit price offered in Price Schedule H:

a. Includes the following:

1) Furnish the materials required for the supplementary temporary observation wells, which includes but is not limited to:

a) Filter pack (includes below bottom of casing).

b) Screen and casing (including stick-up length above ground surface).

1.02 REFERENCE STANDARDS

A. ASTM International (ASTM):

1. ASTM C150/C150M-22 Standard Specification for Portland Cement

2. ASTM D1785-21a Poly(Vinyl Chloride) (PVC) Plastic Pipe, Schedules 40, 80, and 120

3. ASTM D2487-17 Classification of Soils for Engineering

Purposes (Unifed Soil Classification System)

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4. ASTM D4043-17 Selection of Aquifer Test Method in

Determining Hydraulic Properties by Well Techniques

5. ASTM D4050-20 Withdrawal and Injection Well Testing for

Determining Hydraulic Properties of Aquifer Systems

6. ASTM F480-14 Thermoplastic Well Casing Pipe and

Couplings Made in Standard Dimension Ratios (SDR), SCH 40 and SCH 80

7. ASTM D5521/D5521M-18 Standard Guide for Development of

Groundwater Monitoring Wells in Granular Aquifers

B. Bureau of Reclamation (USBR)

1. Bureau of Reclamation Engineering Geology Field Manual, Second Edition, Volume I, 1998, Reprinted 2001

1.03 DEFINITIONS

A. Dewatering: Removal and control of groundwater from pores or other open spaces in soil or rock formations to allow construction activities to proceed as intended. This includes relief of groundwater pressure and the control and discharge of effluent water.

B. Unwatering: Control and removal of ponded, seeping, or flowing surface water, emerging subsurface water from excavated surfaces, and water from precipitation within and adjacent to excavations and construction zones using channels, ditches, gravel drains, gravel blankets, pipes, sumps, pumps, and discharge lines. This includes the control and discharge of effluent waters.

C. Well: A combination of blank and screened casing installed below the ground surface.

Blank casing may stick above the ground surface, depending on the application. Filter pack (poorly-graded silica sand) is installed in the annular space around the screen.

D. Surging: The result of lowering the pumping water level in a well to the level of the pump intake such that the pump draws in air in a cyclic pattern causing the discharge to come out in surges.

E. Primary: When used to describe power, equipment, and materials indicates operating components of the dewatering and unwatering systems.

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F. Standby: Power, equipment, and materials kept on site, unused, but ready for use if primary or supplementary operating components of the dewatering or unwatering system fail.

G. Abandon: To grout well to prevent movement of surface water into aquifers penetrated by the well or sump and to prevent movement of water through the well between aquifers.

H. Dewatering System:

1. Deep wells and supplementary deep wells: A system of wells pumped by submersible pumps installed within each well.

2. Temporary observation wells and supplementary temporary observation wells:

Used to monitor groundwater levels and is not pumped or have water removed in any fashion beyond development or other diagnostics.

3. Well points: A system of wells pumped by vacuum pumps.

4. Passive wells: A system of wells that are not pumped.

I. Length of Well: The length of blank casing and screen required to provide a deep well, temporary observation well, well point, or passive well in accordance with the casing and screen lengths shown on the drawings. This is measured from the bottom of the casing shown on the drawings to the ground surface. Stick-up length above the ground surface is not included in this measurement.

J. Development: The act of vigorously moving water in and out of the slots of a well screen in order to accomplish the following:

1. Compact/settle the material immediately adjacent to the slots.

2. Remove finer particles immediately around the slots (whether naturally occurring or induced via drilling).

3. Create a “filter cake” that is more pervious than the surrounding aquifer but does not allow a significant number of particles pass through to the slots.

K. Run time: The time period shall begin with Government acceptance of the completed dewatering system (entire original designed system) and shall be complete once the Contractor has written approval to begin excavation.

1. If required, the run time will reset after the installation of supplementary dewatering systems or other method(s).

L. Dewatering Period: Time during which the dewatering system is operational.

M. Winterization: Preparing the dewatering and unwatering systems for use when ambient temperatures are near, at, and/or below freezing.

N. Soft Restart: Restarting the dewatering system in a staged fashion to reduce the required amperage at a given time.

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O. Drill rig standby time:

1. Standby time starts when the drill rig(s) has completed the well installation, the dewatering system, or supplementary system, is operational, and the Contractor maintains the drill rig(s) on site.

2. Standby time ends when the Government allows the Contractor to remove the rig(s) from the site.

3. Idle time due to failure of or required maintenance of drill rig equipment, negligence of the Contractor, or inclement weather conditions shall not be considered as standby time.

1.04 SUBMITTALS

A. Submit the following in accordance with Section 01 33 00 - Submittals.

B. RSN 31 03 33-1, Dewatering Plan:

1. Detailed plan for removal and control of groundwater in order to facilitate construction.

a. Include, at a minimum, the following:

1) Protection of the dewatering systems, discharge systems, electrical supply systems, and any other associated components of the dewatering system(s) during construction activities.

2) Design and selection of discharge systems.

3) Manifold line locations (by site maps or drawings) showing type/size of pipe, above ground vs. below ground, flowmeters, and wiring layout.

4) Locations and types of valves used.

5) Control and disposal of water used in drilling.

6) Plan for dry-running protection or use of cycling pumps to continue removing water while protecting pumps.

7) Plan to remove water within well points to within 12 inches of bottom of casing.

8) Sedimentation basin design and details.

9) Estimated location of power supply and standby power.

10) Plan and schedule for reducing microbiological growth.

a) Include how and where system will be monitored for microbiological growth and fouling.

11) Winterization of installed dewatering system and addressing freezing temperatures. Includes the following:

a) Primary power systems, standby power systems, and fuel.

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b) Header pipes and discharge lines.

2. Sequence and Schedule

a. Schedule of mobilization and delivery of personnel, equipment, and materials for drilling, installing, and testing the dewatering systems and temporary observation wells.

b. Sequence of the dewatering systems and temporary observation wells construction and operation including initial drawdown period, duration, and schedule(s) or period(s) of active dewatering operation for each system.

3. Products and Materials Certifications

a. Well screen manufacturer: Certifying slot width, open area, collapse strength, strength coupling specifications, and slot cleanliness of the screen.

b. Filter pack supplier: Certifying gradation data, source of filter pack material, and physical characteristics of the filter pack material.

4. Equipment Data:

a. Types, sizes, quantities, capacities, sources, and other identifying characteristics for pumps, drive units, power systems, standby equipment, monitoring equipment, flowmeters, valving, and other dewatering system components.

1) Include performance, efficiency and net positive suction head (NPSH) curves for each pump submitted.

a) If the NPSH curve is not available, supply minimum submergence or documentation of discussions with manufacturer about minimum submergence recommendations.

b. Joint method used to connect well casing sections.

1) Include manufacturer’s recommended installation procedure, if applicable.

5. Dewatering System Installation:

a. Method(s) and equipment for drilling deep wells, well points, passive wells, and temporary observation wells. Include description of use of water (drilling fluid) to counteract heaving materials.

b. Method(s) of joining well screen and casing.

c. Method(s) of installing well screen, well casing, and filter pack.

d. Method(s) and equipment for developing deep wells, well points, passive wells, and temporary observation wells.

e. Method(s) of constructing discharge manifolds, settling basins, and erosion control features.

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f. Method(s) of controlling water from drilling operations.

g. Method of cutting down wells and obtaining updated top of casing elevations, as required.

C. RSN 31 03 33-2, Unwatering Within Excavation Plan:

1. Include the following:

a. Installation sequence and method.

b. Design for pumping and discharge system.

c. General narrative describing unwatering plan and methods.

1) Include sketches, figures, site maps, etc.

2) Specific plans for controlling runoff and ponded water.

d. Plan and method(s) for removal and abandonment of unwatering system.

e. Estimated location of power supply and standby power supply.

2. Equipment Data:

a. Types, sizes, quantities, capacities, sources, and other identifying characteristics for pumps, drive units, power systems, standby equipment, monitoring equipment, flowmeters, valving, and other unwatering system components.

D. RSN 31 03 33-3, Key Personnel Resumes:

1. Qualifications submitted shall meet minimum requirements of Article 1.05 Qualifications.

a. Drilling Superintendent/Dewatering Specialist(s) responsible for directing dewatering and unwatering system installation and operation.

1) List background and past experience with at least 5 relevant projects similar in nature to that required by this contract with similar soils, dewatering depths, construction techniques, and project durations.

2) Include expertise as it relates to dewatering system(s) design, installation, and operation in the following areas:

a) Submersible pump selection for use in dewatering applications

b) Drilling techniques

c) Well installation

d) Well development

e) Pump installation

f) Discharge system design and installation

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g) Electrical system design and installation

b. Dewatering and Unwatering Specialist Assistant(s) responsible for directing unwatering system installation and operation:

1) List background and past experience.

2) List relevant projects with similar subsurface soils, dewatering depths, unwatering depths, construction techniques, and project durations.

3) Dewatering Specialist(s) may fulfill this role.

c. Drill Crew Foreman:

1) Resume verifying experience meeting qualifications with similar subsurface soils, dewatering depths, construction techniques, and project durations.

d. Geologist:

1) List background and past experience.

2) List relevant projects with similar subsurface soils, dewatering depths, construction techniques, and project durations.

3) Relevant experience with visual USCS logging.

E. RSN 31 03 33-4, Company Experience:

1. Project experience, include as a minimum for five (5) projects:

a. Name of Project.

b. Location of Project.

c. Description of dewatering system for each project.

d. Duration of dewatering system operation for each project.

F. RSN 31 03 33-5, Geologic Log Template:

1. Proposed template to be used for geologic logging.

2. Refer to Bureau of Reclamation Engineering Geology Field Manual, Second Edition, Volume I for example geologic logs. See Article 3.04.

G. RSN 31 03 33-6, Drill Records, Geologic Logs, Well Installations, and Reports:

1. Submit the following information for each deep well, supplementary deep well, well point, supplementary well point, passive well, supplementary passive well, temporary observation well, and supplementary temporary observation well:

a. Location by elevation and coordinates.

1) Measure ground elevation and top of casing.

b. Coordinate system (Northing and Easting for reference) and hole numbering system shown on drawings.

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c. Hole depths.

d. Water level at the end of development and recovery for each well.

e. Caving conditions and cased intervals.

f. Types of drilling equipment used, including sizes and types of bits and barrels.

g. Rate of borehole advancement, changes in drilling rate, and depth of material changes.

h. Amount of casing, well screen, filter pack, and backfill installed.

i. Location (depth) of centering guides.

j. Depth to top of filter pack.

k. Well development and installation of pump.

1) Include turbidity (NTU) and sanding rates (ppm).

l. Other major factors affecting borehole advancement.

m. Dates of drilling, driller comments, and material descriptions (USCS), drill cuttings, problems during drilling, drill methods and reason for hole abandonment or termination (if applicable).

n. Section view drawing of the hole, showing the depth of material changes, hole size, location of casing, well screen, filter pack, centering guides, water loss zones, and how the hole was completed and developed.

H. RSN 31 03 33-7, Dewatering/Unwatering Reports:

1. Daily reports of operational, maintenance, and performance data including test results and records for work performed during that day.

a. Include routine testing results such as, but not limited to the following:

standby power testing, step tests, shutdown test, pumping test, and systems tests.

b. Include regular inspection reports of the dewatering and unwatering systems.

c. Average, maximum, and minimum pumping rate and flow for each pump in each system.

d. Turbidity measurement.

1) Report in NTU’s or sanding rate, whichever method is used.

2) If a dewatering or unwatering system is not operational, mark “Not operational” and note the reason why.

e. Include depth to water and water level elevation in each deep well, temporary observation well, and in approved existing instrumentation.

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1) Begin recording levels every four hours once the first deep well or well point is installed and operational.

f. Testing, maintenance, and calibration of equipment.

g. Microbiological testing and mitigation.

h. Summation of duration and timing of operation of the dewatering/unwatering systems, amount of water pumped, records of water level measurements, problems or unscheduled down time and the resolution thereof, and in general a discussion of unusual conditions or events that impacted dewatering/unwatering activities.

1) Include minutes from any dewatering-related meetings. Meetings may occur more or less frequently, but minutes are to be submitted weekly.

2. Include weekly groundwater elevation contour map showing current ground water elevations.

I. RSN 31 03 33-8, Primary and Standby Power for Unwatering and Dewatering Systems:

1. Complete description of power systems.

2. Automatic transfer between primary and standby power system(s).

3. Pump starting sequence for soft restart.

4. Connection to utility meter.

5. Standby power: In accordance with Article 2.01 – Power Source.

J. RSN 31 03 33-9, Abandonment Plan for Wells:

1. Include sequencing, methods, and material required to abandon the deep wells and supplementary deep wells.

2. Include sequencing, methods, and materials required to abandon the well points and supplementary well points.

3. Include sequencing, methods, and materials required to abandon the passive wells and supplementary passive wells.

4. Include sequencing, methods, and materials required to abandon the temporary observation wells and supplementary temporary observation wells.

1.05 QUALIFICATIONS

A. Drilling Superintendent/Dewatering Specialist(s):

1. Minimum 10 years of experience in dewatering projects.

B. Dewatering and Unwatering Specialist Assistant(s):

1. Competent employees selected by the Dewatering Specialist(s).

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a. Qualified personnel shall have experience on a minimum of 5 similar dewatering jobs.

2. Shall communicate directly with dewatering specialist.

C. Drilling Company Experience:

1. Minimum of 10 years of experience in dewatering projects and at least 5 successful projects similar in nature to that required by this contract.

D. Dewatering Company Experience:

1. Minimum of 10 years of experience in dewatering projects and at least 5 successful projects similar in nature to that required by this contract.

1.06 GOVERNMENT RESPONSIBILITY

A. Government has designed the dewatering system, which is limited to well depth, intake depth, spacing, screen slots size, filter pack, screen length, blank casing length, and layout.

B. For offering purposes, assume excavation can begin after the defined “run time”. The Government will provide written notification to the Contractor once the run time has completed; the CO may provide written direction to the Contractor to begin excavation prior to the completion of the run time. The Government will evaluate the functionality of the completed and operating dewatering system(s) to determine if supplementary systems (or other methods) are needed. Use of supplementary systems, and other changes in the dewatering system to achieve adequate performance, shall be directed by the CO.

1. Direction of use of supplementary systems may occur prior to the run time.

C. The Government reserves the right to evaluate the effectiveness of the unwatering system at any time. If the COR determines that water in the excavation is impacting the construction, the CO will request changes to the unwatering system(s) in writing. The CO may halt construction if water in the excavation continues to impact construction.

1.07 CONTRACTOR RESPONSIBILITY

A. For all unwatering aspects of the project, refer to Section 53 10 00 – Geologic Investigations for more information. Specifically, the unwatering system shall control and remove water due to the following:

1. Seepage water entering the excavation not intercepted by the dewatering system(s).

2. Surface runoff caused by possible seepage down the excavated spillway chute.

3. Surface runoff caused by precipitation.

B. Design, furnish, install, operate, maintain, and remove facilities, systems, and components required for unwatering including trenches, channels, ditches, gravel drains, gravel blankets, pipes, sumps, pumps, and discharge lines.

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C. Furnish and install Government designed dewatering facilities according to Drawings and other specified requirements.

D. Material for the deep wells, well points, passive wells, temporary observation wells, and supplementary wells shall be onsite before drilling begins.

E. The Contractor shall not rotate, transfer, or otherwise replace dewatering specialist(s) and/or dewatering specialist assistant(s) without prior notification.

F. Contractor shall have a geologist on site while drilling.

1. Geologist shall be competent in USCS soil logging.

G. Provide primary power for operation of dewatering and unwatering systems on a 24 hour, 7 days a week timeframe.

H. Provide a standby power system sufficient to power the dewatering and unwatering facilities in the event of a loss of primary power.

I. Provide on-site standby equipment during times that dewatering and unwatering systems are operational.

J. Design, furnish, install, operate, maintain, and remove facilities, systems, and components required for dewatering collection and discharge including piping systems, electrical supply, sediment control, and discharge lines.

K. Contractor shall control seepage from the perimeter of the excavation.

L. Design and install facilities to collect discharge water from dewatering and unwatering systems. Convey water to identified discharge areas in accordance with approved dewatering system plan.

M. Winterization of dewatering and unwatering system(s) and repair any damage due to lack of winterization of the systems.

N. Continuously operate dewatering system during construction to maintain stable slopes and facilitate excavation and backfilling operations. Unwater as necessary to remove surficial water.

O. Monitor and evaluate effectiveness of dewatering and unwatering systems on a continuous basis while systems are in operation.

P. Inhibit and remove microbiological growth and detritus from other processes that may reduce the effectiveness of the dewatering system(s) over time.

Q. Design, construct, and maintain sedimentation basin or basins to meet requirements of Section 01 57 30 – Water Pollution Control.

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R. Provide required equipment and monitor water levels in deep wells and temporary observation wells, rates of discharge from dewatering and unwatering systems, and sediment content of the discharge.

S. The dewatering specialist’s and the dewatering specialist assistant(s)’ only responsibility shall be the installation, operation, maintenance, repair, and monitoring of the dewatering and unwatering systems.

T. Minimum Required Personnel:

1. Dewatering Specialist:

a. On site a minimum of 8 hours per day during dewatering system installation unless otherwise approved by the COR.

b. On call 24 hours a day, 7 days a week, and able to reach the site within 72 hours when dewatering systems are in operation.

2. Dewatering Specialist Assistant(s):

a. Specifically trained and under supervision of the dewatering specialist.

b. On site 24 hours a day, 7 days a week when dewatering systems are in operation.

c. Dewatering specialist can fulfill requirement.

3. Operation/maintenance personnel experienced in pump operation and maintenance.

a. On site 24 hours a day, 7 days a week when the dewatering system is in operation.

b. Dewatering specialist and/or dewatering specialist assistant(s) can fulfill requirement if qualified.

U. Supplementary Well Installation:

1. If written notification is provided by the Government to install supplementary deep wells, well points, passive wells, or temporary observations wells, the Contractor shall begin installation within 7 days after receipt of notification. Time between the notice to install supplementary wells and the time drilling begins shall not count as drill rig standby time.

V. The Contractor shall notify the COR within 4 hours if a pump failure occurs.

W. Remove pumps and equipment from deep and temporary observation wells. Abandon wells in accordance with approved submittal(s).

X. Remove equipment and materials associated with the dewatering and unwatering systems from the site at the end of the project including related power systems.

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Y. Damaged or destroyed dewatering and/or unwatering systems, or any component of those systems, resulting from construction activities and/or human error shall be repaired or replaced by the Contractor at the Contractor’s expense.

Z. The elevation of the top of casing must be re-established/surveyed any time the top of casing of a deep well, passive well, temporary observation well, or supplementary well is disturbed, in accordance with approved submittal.

1.08 DEWATERING SEQUENCING

A. Government will evaluate effectiveness of unwatering and dewatering systems and provide direction to Contractor before or during the run time.

B. Removal and control of water of the stilling basin shall follow the following sequence:

1. Install cutoff as specified in RSN 31 56 20 - Cutoff.

2. Install, develop, and operate temporary observation wells TOW-1 through TOW- 18 and deep wells DW-1 through DW-24.

a. Log and sample holes.

b. Begin removing water from deep wells in 5 well increments after each 5 well increment is installed.

3. Excavate Phase 1 to El. 4568.

a. Unwater as necessary.

4. Install, develop, and operate deep wells DW-25 through DW-45 and well points WP-1 through WP-62.

a. Log and sample holes.

b. Begin removing water from deep wells in 5 well increments after each 5 well increment is installed.

c. Cut down temporary observation wells TOW-1 through TOW-14, as needed.

5. Operate dewatering system for a minimum run time of 30 days prior to the beginning of excavation below El. 4568, unless directed otherwise in writing by

CO.

a. Operate DW-1 through DW-45 and WP-1 through WP-62.

6. Drill, install, and develop the supplementary deep wells, well points, and temporary observation wells, if necessary, as directed by CO.

7. Operate dewatering system including supplementary deep wells and supplementary well points, as installed, for a minimum run time of 30 days prior to the beginning of excavation below El. 4568, unless directed otherwise in writing by CO.

8. Operate dewatering system continuously.

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9. Abandon wells in accordance with approved submittal.

a. Abandon well points WP-1 through WP-62, deep wells DW-34 through DW-45, and temporary observation wells TOW-9 through TOW-14.

b. Abandon supplementary wells, if installed, as directed by CO.

10. Excavate below El. 4568, per approved plan.

11. Install approved unwatering system as needed during/after excavation.

C. Removal and control of water of the upper chute shall follow the following sequence:

1. Install temporary observation wells TOW-19 through TOW-27.

2. Excavate upper chute to surface shown on drawing 188-D-60204.

3. Install passive wells PW-1 through PW-38.

4. Install supplementary temporary observation wells and passive wells, if necessary, as directed by CO.

5. Install approved unwatering system as needed during/after excavation.

D. The dewatering and unwatering systems are to remain operating continuously while the excavation is open during construction until backfill is complete to El. 4568, unless directed otherwise by the CO.

E. Abandon and remove dewatering and unwatering systems in accordance with approved submittal.

F. Deviations in the sequence may be approved by COR.

1.09 DELIVERY, STORAGE, AND HANDLING

A. Deliver, store and handle materials in accordance with manufacturers’ recommendations.

1.10 PROJECT CONDITIONS

A. Refer to Section 53 10 00 – Geologic Investigations.

B. Adequate unwatering, dewatering, and control of groundwater is critical to the following:

1. The stability of the excavation and safety of the workers.

2. Loss of unwatering and/or dewatering capability could result in substantial delays in completing excavation, and earth material placement activities.

3. Total loss of unwatering and/or dewatering capacity could result in excavation slope failure.

C. Expected unwatering flows within excavation.

1. Expected Range: 0 to 200 GPM.

a. Additional inflow from precipitation may require additional capacity.

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D. Conditions which may influence the dewatering and unwatering systems as well as the initial drawdown period may include:

1. Seepage through the excavation surfaces.

2. Frequency and rate of precipitation at the site.

3. Subsurface conditions including natural layering, thickness, permeability, and storativity of materials.

4. Initial groundwater levels.

5. Efficiency of dewatering systems, unwatering trenches, sumps, collectors, and discharge systems.

6. Reservoir levels.

7. Spillway releases.

8. Releases through the East Field Canal.

E. Cold Weather Considerations:

1. If dewatering and unwatering systems are operated during cold weather, use winterization techniques and developing procedures.

2. Pipes, sumps, pumps, and discharge lines capacity shall not be reduced due to frost and/or ice accumulation.

3. If the dewatering and unwatering system are not to be operated during winter, pumps and other systems may be removed at the Contractor’s discretion. Any items removed as a part of winterization must be reinstalled prior to restarting the system(s).

F. Refer to drawings for estimated well yield.

G. Not all water may be removed from highly permeable layers by dewatering systems.

Unwatering in conjunction with dewatering will be required to remove perched groundwater from permeable layers and will necessitate the use of open pumping techniques such as open trenches and sumps.

H. Materials within the portions of the excavation furthest from the dewatering system (i.e.

the middle) are anticipated to be wetter and more difficult to excavate and/or process compared to the areas closer to the dewatering system (i.e. the perimeter).

I. Actual yields from any given dewatering system should be determined based on field testing of the dewatering systems as they are installed and tested.

1. Yields from any individual wells, and cumulative yields from the dewatering systems necessary to achieve the dewatering goals, may be estimated based on results of testing during installation of the dewatering system(s).

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J. It is anticipated that at initial start-up, maximum yields will exceed yields necessary to maintain dewatered conditions. After drawdown goals are achieved, exact yields should be determined by testing and operational observations.

K. For offering purposes, assume the following:

1. Supplementary Deep Wells Materials:

a. 12 total Supplementary Deep Wells.

b. Use 74-foot average length of Deep Wells.

2. Supplementary Deep Wells Installation/Removal:

a. 12 total Supplementary Deep Wells.

b. Use 74-foot average length of Deep Wells.

3. Supplementary Well Points Materials:

a. 31 total Supplementary Well Points.

b. Use 15-foot average length of Well Points.

4. Supplementary Well Points Installation/Removal:

a. 31 total Supplementary Well Points.

b. Use 15-foot average length of Well Points.

5. Supplementary Passive Wells Materials:

a. 19 total Supplementary Passive Wells.

b. Use 54-foot average length of Passive Wells.

6. Supplementary Passive Wells Installation/Removal:

a. 19 total Supplementary Passive Wells.

b. Use 54-foot average length of Passive Wells.

7. Supplementary Temporary Observation Wells Materials:

a. 14 total Supplementary Temporary Observation Wells.

b. Use 48-foot average length of Temporary Observation Wells.

8. Supplementary Temporary Observation Wells Installation/Removal:

a. 14 total Supplementary Temporary Observation Wells.

b. Use 48-foot average length of Temporary Observation Wells.

L. Drilling, Groundwater and Soil Conditions: Refer to Sections in Division 53 – Geological Investigations and Records.

M. Primary Power Source:

1. Power cost shall be paid by Contractor directly to utility.

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2. Contractor shall connect to meter for primary power for removal and control of water and may be used for other power needs.

a. Additional power required shall be supplied by generator.

PART 2 PRODUCTS

2.01 POWER SOURCE

A. Primary and standby power: In accordance with approved submittal.

B. Standby Power:

1. Operate equipment in same manner as primary power.

2. Connected to the dewatering and unwatering systems during primary operations.

3. Come on-line automatically with failure of the primary power system.

4. Non-operational time length: No more than 5 minutes.

a. Test standby power equipment monthly under standard operating conditions. Replace or repair equipment failing to perform.

1) Record dates, times, equipment tested, and results.

2) Perform testing in presence of COR.

5. Provide a standby power system to ensure safe, continuous operation of the unwatering and dewatering facilities in the event of malfunction of the primary power source, including a line power outage.

6. Outages of individual facilities, such as individual unwatering pumps, or system-wide outages are not acceptable.

7. Provide motors, generators, and/or drive engines, as applicable, as standby power to ensure continued operation of facilities.

8. Automatic transfer switch.

9. Pump starting sequence in accordance with approved plan

2.02 WELL PUMPS

A. Turbine or submersible pumps: Meet or exceed 110 percent of anticipated discharge requirements for the heads, depth settings and other requirements in each well.

B. Operational pump specifications shall be determined by the Contractor based on site conditions.

1. Net Positive Suction Head (NPSH) was assumed to be 5 feet for the deep wells under atmospheric pressure.

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C. Equip each well with discharge header, column pipe, drive unit, valves, flow meter, and water level measurement device. Installed and operated in accordance with manufacturers’ recommendations.

D. Standby equipment and pump handling equipment.

1. One standby pumping unit, (pump and drive unit), for each ten (10) installed units of a similar capacity and head range.

2. A minimum of two (2) standby pumps per pump size/type of similar capacity shall be on-site at all times. Standby pumps shall be replaced within 24 hours in the event of primary pump failure.

E. Centering devices mounted on the pump or column pipe to prevent damage to the well casing.

F. Use pump shrouds.

G. Capable of developing the necessary total dynamic head to deliver water to the approved discharge point.

H. Each pump shall be driven by an electric motor capable of continuous service with minimum downtime.

I. Pumps to have dry-running protection.

1. Includes, but is not limited to; float switches, voltage detection equipment, and variable-frequency controllers.

2. Cycling of pumps (pumping until hole is dry, then turning the pump off) is also acceptable as a part of the approved submittal.

J. Refer to the drawings for flow rates.

2.03 VACUUM PUMPS

A. Use float-controlled air/water separator to prevent liquid phase water from entering pump.

B. Use air-cooled models to avoid need for supply of coolant water.

2.04 PASSIVE WELL AND TEMPORARY OBSERVATION WELL CASING AND

WELL SCREEN

A. PVC Casing and Screen:

1. PVC: Schedule 40 or Schedule 80, ASTM D1785 and ASTM F480.

2. Casing and screen: Provided by same supplier with water- and airtight, compatible joints and features to permit any combined makeup of casing and screen.

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B. Slot Size:

1. At least 95 percent of slots in each section of the screen free of burrs, frayed edges, cuttings, or defects.

2. Refer to well tables on drawings.

C. Water- and airtight joints in solid casing.

1. Joints may be threaded or glued.

D. Use centering guides spaced approximately every 10 feet.

E. Applies to supplementary passive wells and supplementary temporary observation wells as required.

2.05 DEEP WELL AND WELL POINT CASING AND WELL SCREEN

A. PVC Casing and Steel Screen:

1. PVC Casing: Schedule 80, ASTM D1785 and ASTM F480.

2. Stainless Steel Screen: Type 304, continuous or wire-wrapped screen.

3. Casing and Screen: Provided by same supplier as screen with watertight, compatible joints and features to permit any combined makeup of casing and screen.

B. Slot Size:

1. Uses continuous or wire-wrapped slot design.

2. Refer to well tables on drawings.

C. Open Area:

1. Minimum Open Area:

a. Deep well: 25 square inches per linear foot.

b. Well point: 2.9 square inches per linear foot.

D. Watertight joints in solid casing.

1. Joints may be threaded or solvent-cemented.

E. Use centering guides spaced approximately every 10 feet.

F. Applies to supplementary deep wells and supplementary well points as required.

G. Use drawdown tubes (or similar) to draw down water within well points to within 12 inches of the bottom of the casing.

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2.06 FILTER PACK

A. Colorado Silica Sand or approved equal with the following essential characteristics:

1. Washed, screened, natural sand and gravel composed of not less than 85-percent hard, dense, non-angular, non-reactive, stable particles.

2. Do not use soluble materials such as limestone or gypsum, mineral salts, soft materials, crushed rock, or angular sand and gravel.

3. Protect bulk materials from contamination by ground and cover cloths and other means as necessary.

4. Prior to construction, stockpile on-site filter pack materials in sufficient quantities to construct required systems.

5. Filter Pack Gradation:

a. Refer to drawings.

2.07 GROUT SEALS

A. Cement Grout Mix:

1. Approximately 7.5 gallons of water and 4 pounds of bentonite per sack of cement.

2. Cement: ASTM C150, Type II low alkali.

2.08 DEVELOPING EQUIPMENT

A. Jetting or high-pressure water is not to be used in well development.

1. Use of surge blocks, pump surging, and airlift pumping is allowed.

2.09 WELL PUMP VALVES

A. Equip pumps and discharge manifolds with pinch, gate, or check valves to permit control of discharge, to isolate deep wells connected to discharge manifolds, to prevent reverse flow in such systems, and to facilitate tuning and repairs.

B. Equip system discharge with a butterfly, or similar-type valve, to permit adjusting the discharge and isolating the unit, if necessary.

C. Equip each deep well connected to a discharge header system which could be subject to flow reversal with a pinch or gate valve.

2.10 FLOWMETERS

A. Flow Ranges:

1. Deep Wells: 5 gpm.

a. Individual deep wells may exceed the listed capacity and additional capacity may be warranted based on field conditions.

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2. Vacuum Pumps: Up to 200 gpm.

a. May use calibrated weir with automated pressure transducer.

3. Total System: Up to 2,000 gpm.

a. May use calibrated weir with automated pressure transducer.

B. Do not use pitot tubes.

C. Flow meters shall be totalizing and have an instantaneous readout.

D. Installed, maintained, serviced, and calibrated according to the manufacturer’s recommended schedule and procedures.

E. Location:

1. At a minimum:

a. One flow meter per deep well.

b. One flow meter per well point system.

c. One flow meter for the total dewatering system.

d. One flow meter per unwatering system (3 total).

F. Use electromagnetic-type flow meters.

G. Calibrate meters by volumetric means (e.g., bucket and stopwatch) before operation and at other times if accuracy is questioned. Replace meters not calibrating with standby meter.

H. Have one standby for every 10 units.

2.11 COLLECTOR, DISCHARGE PIPE, OUTFALLS

A. Collector and discharge pipes extending from the deep wells to points of outfall or settling ponds.

B. Minimum discharge pipe size: Capable of handling 125 percent of anticipated peak discharge.

C. Water-tight joints.

D. Discharge in accordance with permit requirements in Section 01 57 30 – Water Pollution Control.

2.12 WATER LEVEL MEASURING DEVICE

A. Each deep well shall have a means of measuring water level whether pumping or idle.

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1. May be an electronic sensor or a direct-reading airline with a minimum 1-inch-diameter open-ended steel or PVC pipe extending from within 12 inches of the top bowl of the pump to the top of well head.

2. Install electronic sensors in open-ended, rigid standpipes to protect from the turbulence created by the pump intake.

B. Observation wells: Manual recording.

2.13 MICROBIOLOGICAL CONTROL

A. Use products that can be removed from the effluent water prior to discharge, or that can be discharged in accordance with State permits and approved submittals.

2.14 SEDIMENT CONTROL

A. In accordance with approved dewatering plan to meet permit requirements listed in Section 01 57 30 – Water Pollution Control.

PART 3 EXECUTION

3.01 REMOVAL OF WATER

A. Monitor performance of the dewatering system.

1. Measure and record water levels to within plus or minus 0.1-foot in the deep wells and temporary observation wells (as applicable).

2. Measure rates of discharge from individual deep wells and combined systems.

3. Record water levels at least every four hours.

3.02 DEEP WELL, WELL POINT, PASSIVE WELL, AND TEMPORARY

OBSERVATION WELL LOCATIONS

A. Locations shown on drawings may be adjusted in the field.

1. Final locations as approved by the COR.

2. Stake locations in the field in advance of drilling.

3.03 DRILLING EQUIPMENT AND MATERIALS

A. Allowable Drilling Method:

1. Sonic drilling or other cased method.

a. Use approved clear water to counter-act heaving materials.

b. Maintain minimum differential head of 1 ft per 10 ft total drilling depth above ground water table (5 ft minimum).

2. Using fluid circulation (air or water) to remove cuttings is not permitted.

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3. Do not use drilling procedures which reduce the porosity and/or the permeability of the native materials.

B. Collection and Storage of Material Collected from Borings:

1. Store material near borings for a minimum of 30 days.

2. Allow Government access to material retrieved from borings.

C. Protect drill holes with protective cover.

D. Drill each well plumb and straight to permit installation of the well, well materials, pumps, monitoring devices, and other components.

E. Abandoning Boreholes During Drilling:

1. Contractor to abandon caving, sloughing or unstable boreholes by backfilling with clean sand (SP or SW).

2. No payment shall be made for abandoned boreholes.

3. Remove ungrouted casing and screen when possible and seal the borehole or well in accordance with approved plan.

4. Drill new borehole/well(s) 5 to 10 feet from the abandoned borehole, or farther as approved by the COR.

F. Provide water for drilling and other purposes in accordance with Section 01 51 00 - Temporary Utilities. Control water from drilling operations per approved submittal.

G. Temporary casing shall be advanced simultaneously with the drilling penetration for the entire length of the borehole.

1. Drilling fluid as approved.

H. Drill cuttings shall be considered as waste and shall be disposed in accordance with Section 01 74 00 - Cleaning and Waste Management and 31 23 39 - Disposal of Excavated Materials.

I. Any deviations from the above requirements shall be submitted and approved by the

COR.

J.…