jim bridger fgd pond 1 history of construction...fgd pond 1 is located in the deadman wash watershed...

Status: Rev. 0 i 28 March 2018 Document No: JB-TR-001 Jim Bridger FGD Pond 1 History of Construction

JIM BRIDGER FGD POND 1 HISTORY OF CONSTRUCTION

Prepared for: PacifiCorp, Jim Bridger Power Plant Project Manager: Chad Tomlinson Date: 28 March 2018

Document No.: JB-TR-001

Quality Assurance Statement

Office Address Stantec Consulting Services 2890 Cottonwood Parkway, Suite 300 Salt Lake City, UT 84121

Prepared by Peter Bernhard Reviewed by Alex Edstrom Approved for Issue by Chad Tomlinson

Revision Schedule

Rev No. Date Description Prepared By Reviewed By Approved By

0 03/28/18 Issued For Use P. Bernhard A. Edstrom C. Tomlinson Comments:

This document has been prepared for the benefit of PacifiCorp in accordance with the generally accepted practices and standards in use at the time it was prepared. No liability is accepted by this company or any employee or sub-consultant of this company with respect to its use by any other person.

This disclaimer shall apply notwithstanding that this document may be made available to other persons for an application for permission or approval to fulfill a legal requirement.

Status: Rev. 0 1 28 March 2018 Document No: JB-TR-001 Jim Bridger FGD Pond 1 Pond History of Construction

REPORT OF §257.73 (C)(1) – SURFACE IMPOUNDMENT HISTORY OF CONSTRUCTION

The Environmental Protection Agency’s (EPA’s) Coal Combustion Residuals (CCR) Rule - 40 CFR Parts 257 and 261, “Hazardous and Solid Waste Management System; Disposal of Coal Combustion Residuals From Electric Utilities; Final Rule (the CCR Rule) was published in the Code of Federal Regulations (CFR) on April 17, 2015 with an effective of October 19, 2015. The CCR Rule applies to all CCR generated by electrical utilities and independent power producers that fall within the North American Industry Classification The purpose of the CCR Rule is to set minimum standards for existing and new CCR landfills and existing and new CCR surface impoundments and all lateral expansions consisting of location restrictions, design and operating criteria, groundwater monitoring and corrective action, closure requirements and post closure care, and recordkeeping, notification, and internet posting requirements. On June 14, 2016, the United States Court of Appeals vacated 40 CFR 257.100 which allowed inactive surface impoundments to take advantage of “early closure” provisions. On August 5, 2016, the EPA published new regulations requiring the inactive surface impoundments which had taken advantage of the “early closure” provisions to comply with the substantive requirements of the rule with new compliance deadlines. This report addresses the History of Construction (§257.73(c)(1)) requirements of the CCR Rule as it pertains to the inactive Flue Gas Desulfurization (FGD) Pond 1 at the PacifiCorp’s Jim Bridger Power Plant near Kemmerer, WY.

Date: March 14, 2018

Purpose: §257.73(c)(1) – Coal Combustion Residuals Storage Facility History of Construction, pertaining to FGD Pond 1 at the PacifiCorp Jim Bridger Power Plant

CCR Unit Name(s): FGD Pond 1

CCR Unit Owner/Operator: PacifiCorp, Jim Bridger Power Plant

Owner/Operator Address: 9 miles E, Point of Rocks, WY 82942

Location of CCR Unit: See Figure 1

§257.73(c)(1).i. CCR Unit Name: CCR Unit Owner/Operator: PacifiCorp, Jim Bridger Power Plant

Owner/Operator Address: 9 miles E, Point of Rocks, WY 82942

CCR Unit Name: FGD Pond 1

CCR Unit WY State ID No.: WY State Engineer’s Office Permit #WY01643


§257.73(c)(1).ii. Location of CCR unit identified on most recent U.S. Geological Survey (USGS) 7-1⁄2 minute or 15 minute topographic quadrangle map:

FGD 1 Pond 1 is identified in USGS Black Rocks 15-Minute Quadrangle. This map was updated in 2017. See Figure 1 for facility layout relative to quadrangle extent.

Figure 1 – USGS Quadrangle Extents and Jim Bridger Facility Extents

§257.73(c)(1).iii. Purpose for CCR Unit Use: The FGD Pond 1 was used to store spent flue-gas desulfurization fluid from Jim Bridger’s Unit 1, 2, and 3 scrubber. It ceased operation in 2005 and is currently being closed.

The operational data, including pertinent elevations and associated storage capacities, discharge structures, etc. for FGD Pond 1 is summarized in Table 1.

Black Rocks, WY Quadrangle

Point of Rocks, WY Quadrangle

FGD Pond 1


Table 1 – Operational Data for FGD Pond 1

Operational Data Design Value

Pond Data

Normal Pool Elevation 6745 feet above mean sea level (ft amsl)

Operating Pond Capacity (at Normal Pool Elevation)

4520 acre-feet

Surface Area (at Normal Pool Elevation)

175 acres

Drainage Area 820

Design Freeboard 7 ft

Embankment Data

Embankment Type Homogeneous embankment with blanket drain

Maximum Embankment Height 58 ft

Design Crest Elevation Upstream 6750 ft amsl

Downstream 6752 ft amsl

Design Crest Width 25 ft

Design Crest Length 2440 ft

Upstream Design Slope 3 Horrizontal:1 Vertical (3H:1V)

Downstream Design Slope 3H:1V

§257.73(c)(1).iv. Name and size of watershed CCR unit located within: FGD Pond 1 is located in the Deadman Wash watershed is the principal drainage and flows to the southeast across the site. It joins with Bitter Creek, a tributary of the Green River, south of the facility. The upper reaches of Deadman Wash are ephemeral in nature, but the wash becomes swampy southeast of the Plant.

§257.73(c)(1).v. Description of physical and engineering properties of the foundation and abutment materials:

The following reports cover all physical and engineering properties of the construction materials used for the construction of FGD #1 Pond.


• Bechtel Power Corporation, 1981, FGD Waste Disposal Pond 1 Design Report, Jim Bridger Power Plant, Prepared March 1981

A figure showing the configuration of the FGD Pond 1 is provided in Figure 2.

Figure 2 – FGD Pond 1 Pond Layout

Status: Rev. 0 5 28 March 2018 Document No: JB-TR-001 Jim Bridger FGD Pond 1 History of Construction

§257.73(c)(1).vi. CCR unit zones of construction description: Table 2 – FGD Pond 1 Zones of Construction Descriptions Table

CCR Unit Construction Description Embankment Zone: Material

Type Physical/Eng.

Properties Method of Site Preparation Method of Construction Dates of

Construction

Core (Zone 1): Watered shale and silty clay Shell (Zone 2): Silty sand Chimney Drain (Zone 3): sand Horizontal Drain (Zone 3A and 3): Sandy Gravel and sand Transition Zone: Zone 2 material Upstream Embankment Protection (Zone 4, 4A and 5): Rip rap with rip rap bedding and a sand transition layer. Downstream Embankment Protection (Zone 6): Rip Rap

See Design Report for specific information on optimal moisture content, particle distribution, Atterburg limits, UCS strength, and permeability.

Embankment foundation was cleared and grubber of vegetation and the top 3 feet of soil was stripped.

Zone earthen embankment consisting of 6 zones. A cut-off trench was excavated to a minimum depth of 5 feet and backfilled with Zone 1 material to preclude seepage.

1981


§257.73(c)(1).vii. Detailed design drawings, cross-sections, identified features which may impact performance:

Relevant detailed design drawings, cross-sections, and identified features for the configuration of FGD Pond 1 were obtained from the following report and are provided in Appendix A.

• Bechtel Power Corporation, 1981, FGD Waste Disposal Pond 1 Design Report, Jim Bridger Power Plant, Prepared March 1981

§257.73(c)(1).viii. Type, purpose, and location of existing instrumentation: There is no instrumentation associated with FGD Pond 1.

§257.73(c)(1).ix. Area-Capacity Curves for the CCR Unit:

The design stage-storage curve for FGD Pond 1 is provided in Appendix B.

§257.73(c)(1).x. Existing Spillways & Diversions: There are no spillways or non-process outlet structures associated with this pond. Water level was controlled through varying the effluent inflow and through evaporation of the water contained in this effluent. Based on a review of the design report for FGD Pond 1 (Bechtel, 1981), the five feet of freeboard that was provided was capable of containing the total average annual runoff, plus the 100-year flood plus the probable maximum flood.

§257.73(c)(1).xi. Construction specifications and provisions for surveillance, maintenance, and repair of the CCR unit:

Construction Specifications: Construction specifications for FGD Pond 1 are presented in Appendix C.

Provisions for Surveillance, Maintenance and Repair: Given that this pond has been inactive since 2005 and no longer receiving inflows, there are no routine inspection or maintenance being conducted.


Record or knowledge of structural instability of the CCR Unit: No signs of instability have been identified for the FGD Pond 1.


REFERENCES

Bechtel Power Corporation, 1981, FGD Waste Disposal Pond 1 Design Report, Jim Bridger Power Plant, Prepared March 1981

Appendix A

Construction Drawings

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Appendix B

Stage-Storage Curve

Appendix C

Construction Specifications

39 · -. (__)

9.3 .FOUNDATION PREPARATICN It is recognized that the foundation preparation for the embankment will require a::insiderable care because of the weathering and the fractured nature of the shale. After excavation of the cut-off trench is completed, it should be inspected by a geologist to ensure that sound shale has been reached. 'Ihe rock surface will have to l:e ade quately watered and prewetted prior to the placement of earth fill. Slush grouting will l:e required as a part of the foundation prepara tion. Within the foundation area of the embankment, all overhangs,

Clay fran the cut-off trench excavation may be used as Zone l material. If silty sand material is encountered it may be used as Zone 2 material. Similarly, weathered shale may be used as Zone l material.

.:

9.2 CUI'-OFF TRENCH EXCAVATIOi.~

The cut-off trench for the embankrrent should be excavated to sound shale. Cut slopes should be l horizontal to l vertical. If the slopes of the excavation are not stable at this angle, flatter slopes should be used. All lc:ose, soft, or broken materials at the foundation level should be rerroved.

9.1 STRIPPING The embankment foundation should be stripped to rerrove all organic topsoil, roots, grass, frozen, soft, lc:ose, and other deleterious materials within the foundation limits. 'Ille minimum depth of stripping is estimated to be 3 feet.

SECTION 9 CCNSTRUCTION PROCEDURES

40

The depth of excavation in the borrow area for Zone 1 material will be limited to silty clay or weathered shale material with liquid

When a borrow pit is opened for core material, the opened area should be scarified after stripping. Disking should be performed to break down any shale lumps. A sprinkler system may be used for moisture conditioning the borrow pits prior to excavation. Prewetted material can then be excavated with scrapers. kly layer of dry shale Iumps , either existing as the top layer in the natural state or having been dried after the opening of the borrow pi ts, will be wasted. 'lhe open area of the borrcw pits should be limited at all times so as to mini mize such drying and wastage of material.

Borrcw Areas Impervious core material may be obtained fran Borrow Areas 1 arrl 2 (Drawing C-670R) and silty sand for shell material may be obtained fran Borrow Areas C and 3 (Drawing C-670R). M:>re exploration will be required at the designated borrow areas 1, 2 and 3 to define the extent of suitable materials.

BORRCW AREA PREPARATION General 'l'bpsoil arid other unsuitable material in the borrow areas should be stripped prior to use. 'l'bpsoil can be replaced in the borrow area located outside the .FGD I;;Qrrl UI;;Qn canpletion of work.

cavities, or steep rock should be trirnrred back to a slope not steeper than 1 horizontal to 1 vertical.

9.4.2

9.4 9.4.l

r

41

The gradation ranges of Zone 1 (core) and Zone 2 (shell) materials must satisfy the gradation range shewn on Figs. 8 and 9 respectively.

The core (Zone 1) material must be silty clay or weathered shale with liquid limits in the range of ( 40 to 70) and the plasticity index of not less than 15. The material passing 200 mesh sieve must exceed 95 percent. The shell zone material must l:e silty sand (non-plastic) fran borrow area C or other sources of similar silty sand near the project site that cculd l:e identified by further exploration and testing.

FILL PLACEMEN!'

General The materials used in the various zones of the embankment must be controlled to ensure that their engineering properties are ccmpar able to those used in design.

Available borrow quantities fran various borrow areas are estimated assuming the depth of useable material to l:e about 10 feet. The results are shown in Table 6.

At greater depths, the shaie l:ecomes less weathered and chunky, and

must not be used as Zone 1 material. The depth of excavation in

borrow areas C and 3 will l:e limited to the upper silty sand material.

limit in excess of 40, and plasticity index in excess of 20. Non plastic silt, if any, must be discarded.

9.5 · 9 .5.1

42 .

and rolling are as follows: Reccmrnen:Jed canpaction effort an:J noisture control for fill placement

foot canpaction energy. dance with AS'IM D 1557 but m:x:lified to 20,000 foot-p:Junds per cubic at least 95 percent of the maximum d:ry density, determined in accor-

Ccmpaction Embankment materials placed in Zone 1 should l:.e canpacted to attain

of optimum for Zone 2 material. optimum moisture content for materials of Zone 1 and -1 to +2 percent

is too wet, or sprinkling and disking if it is too dry. 'Ibe allowable range of placernerit moisture content is limited to Oto 3 percent above

during canpaction must be distributed unifonnly throughout each layer of the material. 'Ibis can l:.e achieved by disking and air drying if it

on the fill. 'Ihe moisture content of the fill material prior to and moisture and may l:.e moisture-con:Jitioned either at the borrow pits or optimum moisture content. The shell material will readily accept

. . content of the shell material can l:.e considerably lower than the ccmpaction. repending on weather conditions, the natural.moisture borrow area or on the fill by sprinkling and disking prior to

borrow area. Zone 2 material may be moisture conditioned in the Moisture conditioning of Zone 1 materials can !:est be done in the Moisture Con:Jitioning

.l)

9.5.3

9.5.2

43

. c·

shown in detail on Drawing C-676R • The clay liner must be connected to the core of the embankment as

that the canpactive energy shall be limited to 20,000 ft lbs/cubic ft. the maximum dry density as deter:rn.ined by AS'"! 1557, Methc:d D, except to drying. The clay should be compacted to a minimum of 95 percent of be placed at or near optimum rroisture content to minimize· cracking due weathered shale fran the northern slopes of the pond. The clay must A 3-ft thick canpacted clay liner may be constructed by processing the Conpacted Clay Liner PREPARATICN FOR LINER PLACEMENT 9.7

9.7.l

gallons of water per cubic yard for other embankment materials. gallons of water per cubic yard of Zone l material and about 100 It is estimated that rroisture conditioning will require about 135

9.6 WATER SUPPLY

A camber of l foot shall be provided of the deepest section of the embankment.

Sprinkled with water

4 12

-1 to +2% of optimum

4 12

Oto +3% of optimum

12 8

Moisture Content

Minimum Passes

Uncompacted Lift Thickness (inches)

~) Compaction Zone Equipnent l Sheepsfoot roller

2 Rubber-tired roller (Tire pressure 90 psi minimum)

3,4, Rubber tired roller 5, or crawler tractor

44

9. 8 EMBANKMENT QUP.NI'ITIES

The estimated ernbanklrent and clay liner quantities are shown on Table 7.

'Ihe liner must extend into the ern.bankm:nt and the edges of the membrane rust be anchored. Typical details are shown on Drawing C-676R. 'Ihe placement and preparation of joints must be ve"ry carefully rronitored.

Membrane Liner Placement of a membrane liner would require stripping of the reservoir bed to a depth of 1 foot. The stripped surface must be moisture conditioned and disked so as to eliminate any hard spots, rocks and sharp objects. 'Ihe material should l:e compacted by a vibratory roller to provide a: snooth surface and the membrane liner placed over the moist soil surface. If local cracks are encountered in the soil, the soil must be disked and recompacted. 'Ihe membrane liner should l:e

covered by a 12-inch thick blanket of sand or silty sand, rol.l.ed by a light roller to provide a snooth surface.

Source of Material for Canpacted Clay Liner Material for clay liner construction may l:e obtained by excavation in the reservoir bottom. Approximately two thirds of the area consists of weathered shale or silty clay. 'Ihe weathered shale and silty,clay may be used as a liner by rroisture conditioning and compacting, to act as a liner. 'Ihe minimum thickness of clay liner should l:e 3 feet.

9.7.3

9.7.2

jim bridger fgd pond 1 history of construction...fgd pond 1 is located in the deadman wash watershed...

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