location restrictions summary – coal combustion residuals …€¦ · impoundments 1, 2, 3a, and...

Report

Location Restrictions Summary –

Coal Combustion Residuals Surface

Impoundments 1, 2, 3A, and 3B

Neal North Energy Center

Project I.D.: 18M014.00

MidAmerican Energy Company

Sergeant Bluff, Iowa

April 2020

Location Restrictions Summary – Coal Combustion Residuals

Surface Impoundments 1, 2, 3A, and 3B

Distribution

No. of Copies Sent To

1 (electronic) Elisa Zappacosta – MidAmerican Energy Company

1 (electronic) Jenny Coughlin – MidAmerican Energy Company

Location Restrictions Summary – Coal Combustion

Residuals Surface Impoundments 1, 2, 3A, and 3B

Project ID: 18M014.00

Prepared for

MidAmerican Energy Company

Neal North Energy Centert

Sergeant Bluff, Iowa

Prepared by

Foth Infrastructure & Environment, LLC

April 17, 2020

Copyright©, Foth Infrastructure & Environment, LLC 2020 390 South Woods Mill Road, Suite 325 • Chesterfield, MO 63017 • (636) 728-1034 • Fax: (636) 728-1035 www.foth.com

REUSE OF DOCUMENTS This document has been developed for a specific application and not for general use; therefore, it may not be used without

the written approval of Foth. Unapproved use is at the sole responsibility of the unauthorized user.

pw\clients\MidAmerican Energy\Secured\0018M014.00\10000 Reports\Location Restrictions Demonstration\R-MEC NNEC Location

Restrictions Summary.docx ii

Location Restrictions Summary – Coal Combustion Residuals

Surface Impoundments 1, 2, 3A, and 3B

Table of Contents

Page

Certification ................................................................................................................................... iii

1 Introduction .............................................................................................................................1

2 Location Restrictions ...............................................................................................................2

2.1 Placement above the Uppermost Aquifer ......................................................................2

2.2 Wetlands ........................................................................................................................2

2.3 Fault Areas .....................................................................................................................3

2.4 Seismic Impact Zones ....................................................................................................3

2.5 Unstable Areas ...............................................................................................................3

3 References ...............................................................................................................................5

Appendices

Appendix A USGS Quaternary Faults

Appendix B USGS Seismic Hazard Tool


Restrictions Summary.docx 1

1 Introduction

This Location Restrictions Summary was developed for MidAmerican Energy Company (MEC)

Neal North Energy Center (NNEC) Coal Combustion Residuals (CCR) Surface Impoundments

1, 2, 3A, and 3B in accordance with the CCR Rule (40 Code of Federal Regulations [CFR] Part

257).

Impoundment 1 (north) was previously closed by removal of CCR (Iowa Department of Natural

Resources [IDNR] - Doc #86660). Lined non-CCR wastewater ponds were constructed in the

closure by removal area. Impoundments 1 (south), 2, and 3A were previously closed with a final

cover system over in-place CCR in accordance with the CCR rule (40 CFR 257.102(d)).

Construction of the final cover system for Impoundments 1 (south), 2, and 3A was completed in

December of 2017. Impoundment 3B is in the process of closure in accordance with the CCR

Rule.

Pursuant to IDNR permit (Permit #97-SDP-22-16C) revision issued February 18, 2020 (Doc

#97026), the previously permitted closure for Impoundments 1 (south), 2, and 3A, leaving CCR

in place (40 CFR 257.102(d)), was modified to closure by removal of CCR (40 CFR 257.102(c)).

The closure modification for Impoundments 1 (south), 2, and 3A are incorporated in the closure

of Impoundment 3B.

As described in the Closure Plan for Impoundments 1, 2, 3A and 3B (Revision 1), the closure

design includes removal of CCR from Impoundments 1 (south), 2, 3A, and 3B and consolidation

of CCR in the footprint of Impoundment 3B at an elevation above the high groundwater level

observed in 2019. Clean fill soil will be placed at the base of Impoundment 3B to the high water

elevation prior to consolidation of CCR. The consolidated CCR footprint in Impoundment 3B

will capped with a composite cover system.

The intent of the closure design is to ensure that there will not be an intermittent, recurring, or

sustained hydraulic connection between any portion of the base of the CCR unit (i.e. the

consolidated CCR foot print in Impoundment 3B) and the uppermost aquifer due to normal

fluctuations in groundwater elevations (including the seasonal high water table) following

closure of the impoundments in accordance with the revised Closure Plan.

The CCR Rule includes five location restrictions which are specified in 40 CFR 257.60 through

40 CFR 257.64. A qualified professional engineer is required to certify that the location of

Impoundments 1, 2, 3A, and 3B has been evaluated regarding these location restrictions.

Additionally, the summary is to be placed in the Impoundments 1, 2, 3A, and 3B operating

record.

This summary contains a description of the information available to support the location

restrictions demonstration and the assessment of each location restriction. Based on this

assessment, Impoundments 1, 2, 3A, and 3B meet the wetlands, fault areas, seismic impact

zones, and unstable areas location restrictions, but do not meet the placement above the

uppermost aquifer location restriction.



2 Location Restrictions

2.1 Placement above the Uppermost Aquifer

40 CRF 257.60 Placement above the uppermost aquifer

“existing CCR surface impoundments…must be constructed with a base that is located no less

than 1.52 meters (five feet) above the upper limit of the uppermost aquifer, or must demonstrate

that there will not be intermittent, recurring, or sustained hydraulic connection between any

portion of the base of the CCR unit and the uppermost aquifer due to normal fluctuations in

groundwater elevations (including the seasonal high water table)…”

The rule defines the uppermost aquifer as, “…the geologic formation nearest the natural ground

surface that is an aquifer, as well as lower aquifers that are hydraulically interconnected with

this aquifer within the facility’s property boundary. Upper limit is measured at a point nearest to

the natural ground surface to which the aquifer rises during the wet season.”

The Annual Groundwater Monitoring and Corrective Action Report for Neal North CCR

Impoundment 3B and the Annual Groundwater Monitoring and Corrective Action Report for

Neal North CCR Impoundments 1, 2, and 3A were reviewed to assess groundwater elevation

data.

The uppermost groundwater elevations were above 1,059 feet above mean sea level (ft amsl) and

are within five feet of the minimum elevation (1,064 ft amsl) where CCR was encountered

within the surface impoundments during previous investigations. Therefore, the impoundments

do not meet the separation requirements of CFR 40 257.60.

2.2 Wetlands

40 CFR 257.61 Wetlands

“…existing CCR surface impoundments…must not be located in wetlands, as defined in § 232.2

of this chapter…”

40 CFR 232.2 defines wetlands as “Wetlands means those areas that are inundated or saturated

by surface or ground water at a frequency and duration sufficient to support, and that under

normal circumstances do support, a prevalence of vegetation typically adapted for life in

saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar

areas.”

40 CFR 232.2 states that “waste treatment systems, including treatment ponds or lagoons

designed to meet the requirements of the Clean Water Act are not Waters of the United States.”

Impoundments 1, 2, 3A, and 3B area part of a wastewater treatment system with a National

Pollution Discharge Elimination System (NPDES) permit. As such, and per 40 CFR 232.2, there

are no jurisdiction wetlands within Impoundments 1, 2, 3A, and 3B.

Therefore, Impoundments 1, 2, 3A, and 3B meet the requirements of 40 CFR 257.62.



2.3 Fault Areas

40 CFR 257.62 Fault areas

“…existing CCR surface impoundments…must not be located within 60 meters (200 feet) of the

outermost damage zone of a fault that has had displacement in Holocene time…”

Fault areas are defined as “…a fracture or a zone of fractures in any material along which strata

on one side have been displaced with respect to that on the other side.” Halocene time means

“…the most recent epoch of the Quaternary period, extending from the end of the Pleistocene

Epoch, at 11,700 years before present, to present.”

The USGS U.S. Quaternary Faults and Folds Database mapping application provides location

information for Quaternary age faults. The USGS database does not show any Quaternary age

faults within 60 meters (200 feet) of Impoundments 1, 2, 3A, and 3B (Appendix A).

Therefore, Impoundments 1, 2, 3A, and 3B meet the requirements of 40 CFR 257.62.

2.4 Seismic Impact Zones

40 CFR 257.63 Seismic impact zones

“…existing CCR surface impoundments must not be located in seismic impact zones…”

A seismic impact zone is “…an area having a 2% or greater probability that the maximum

expected horizontal acceleration, expressed as a percentage of the earth’s gravitational pull (g),

will exceed 0.10 g in 50 years.”

Utilizing the USGS Unified Hazard Tool, the peak ground acceleration for an earthquake with a

probability of occurrence of 2 percent in 50 years was determined to be 0.039g at the site

(Appendix B). This acceleration is associated with Site Class B/C which corresponds to a weak

rock, based on investigations performed at the site, the site is characterized as a Site Class D.

Since Site Class D material is weaker than Site Class B/C, it will cause amplification of the

seismic acceleration. Per approaches put forward in American Society of Civil Engineers ASCE

7-16, the amplification factor for a Site Class D is 1.6 (Appendix B). Utilizing this factor, peak

ground acceleration for this site, for the design earthquake, is 0.062g.

Based on available information provide by USGS and ASCE methodology, the peak ground

acceleration is below the threshold of 0.10g. Therefore, Impoundments 1, 2, 3A, and 3B meet

the requirements of 40 CFR 257.63.

2.5 Unstable Areas

40 CFR 257.64 Unstable areas

“…existing CCR surface impoundments…must not be located in an unstable area…”



An unstable area is “…a location that is susceptible to natural or human induced events or forces

capable of impairing the integrity, including structural components of some or all of the CCR

unit that are responsible for preventing releases from such unit. Unstable areas can include poor

foundation conditions, areas susceptible to mass movements, and karst terrains.”

In order to determine if an unstable condition exists, consideration of specific factors is required

(40 CFR 257.64(b)). These factors include:

(1) On-site or local soil conditions that may result in significant differential settling;

(2) On-site or local geologic or geomorphologic features; and

(3) On-site or local human-made features or events (both surface and subsurface).

The following documents provide the structural integrity criteria for existing CCR surface

impoundments and were prepared in accordance the CCR Rule (40 CFR 257.73).

♦ Initial Structural Stability Assessment of Neal North Surface Impoundments 1, 2, and 3A

♦ Initial Safety Factor Assessment for Neal North Surface Impoundments 1,2 and 3A

♦ Initial Structural Stability Assessment of Neal North Surface Impoundment 3B

♦ Initial Safety Factor Assessment for Neal North Surface Impoundments 1,2 and 3A

Based on review of the above documents Impoundments 1, 2, 3A, and 3B are not located in an

unstable area. Therefore, Impoundments 1, 2, 3A, and 3B meet the requirements of 40 CFR

257.64.



3 References

Burns & McDonnell, 2016 Initial Safety Factor Assessment for Neal North Surface

Impoundment 3B. 10 October 2016

Burns & McDonnell, 2016 Initial Structural Stability Assessment of Neal North Surface

Impoundment 3B. 10 October 2016

Burns & McDonnell, 2018. Initial Safety Factor Assessment for Neal North Surface

Impoundments 1, 2, and 3A. 11 April 2018

Burns & McDonnell, 2018. Initial Structural Stability Assessment of Neal North Surface

Impoundments 1, 2, and 3A. 11 April 2018

GHD, 2019. Annual Groundwater Monitoring and Corrective Action Report for Neal North CCR

Impoundment 1, 2, and 3A. 1 August 2019

GHD, 2020. Annual Groundwater Monitoring and Corrective Action Report for Neal North CCR

Impoundment 3B. 31 January 2020.

United States Environmental Protection Agency, 2015. Hazardous and Solid Waste

Management System: Disposal of Coal Combustion Residuals from Electric Utilities; Final Rule

(40 CFR Parts 257 and 261; Federal Register Vol. 80 No. 74). 17 April 2015.

Foth Infrastructure & Environment, LLC, 2020. Closure Plan – Coal Combustion Residuals

Surface Impoundments 1, 2, 3A and 3B. 17 April 2020.


Appendix A

USGS Quaternary Faults

U.S. Geological Survey Quaternary Faults

USGS, National Geographic, Esri, Garmin, HERE, UNEP-WCMC,USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, increment PCorp.

Fault Areas

Historic (< 150 years)

Latest Quaternary (< 15,000 years)

Late Quaternary (< 130,000 years)

Middle and Late Quaternary (< 750,000 years)

Undifferentiated Quaternary (< 1.6 million years)

Quaternary Faults Database

Historic (< 150 years), well constrained location

Historic (< 150 years), moderately constrained location

Historic (< 150 years), inferred location

Latest Quaternary (<15,000 years), well constrained location

Latest Quaternary (<15,000 years), moderately constrained location

Latest Quaternary (<15,000 years), inferred location

Late Quaternary (< 130,000 years), well constrained location

Late Quaternary (< 130,000 years), moderately contrained location

Late Quaternary (< 130,000 years), inferred location

Middle and late Quaternary (< 750,000 years), well constrained location

Middle and late Quaternary (< 750,000 years), moderately constrained location

Middle and late Quaternary (< 750,000 years), inferred location

3/27/2020, 12:58:21 PM0 90 18045 mi

0 150 30075 km

1:5,020,504

USGSNational Geographic, Esri, Garmin, HERE, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, increment P Corp. | USGS |

GRL

Callout

Approximate site location

GRL

Ellipse


Appendix B

USGS Seismic Hazard Tool

Two-percent probability of exceedance in 50 years map of peak ground acceleration

0 500 1,000 KILOMETERS

0 500 1,000 MILES

70°80°90°100°110°120°

45°

40°

35°

30°

25°

Areas where suspected nontectonic

earthquakes have been deleted

0.8

0.4

0.3

0.2

0.14

0.1

0.06

0.04

0.02

0

EXPLANATION

Peak acceleration, expressed as

a fraction of standard gravity (g)

Approximate site location

3/27/2020 Unified Hazard Tool

https://earthquake.usgs.gov/hazards/interactive/ 1/2

Uni�ed Hazard Tool

Input

U.S. Geological Survey - Earthquake Hazards Program

Please do not use this tool to obtain ground motion parameter values for the design codereference documents covered by the U.S. Seismic Design Maps web tools (e.g., theInternational Building Code and the ASCE 7 or 41 Standard). The values returned by the twoapplications are not identical.

Edition

Conterminous U.S. 2014 (v4.0.x)

LatitudeDecimal degrees

42.322

LongitudeDecimal degrees, negative values for western longitudes

-96.371

Site Class

760 m/s (B/C boundary)

Spectral Period

Peak Ground Acceleration

Time HorizonReturn period in years

2475

https://earthquake.usgs.gov/hazards/designmaps/

3/27/2020 Unified Hazard Tool

https://earthquake.usgs.gov/hazards/interactive/ 2/2

Hazard Curve

View Raw Data

Hazard Curves

Time Horizon 2475 yearsPeak Ground Acceleration0.20 Second Spectral Acceleration1.00 Second Spectral Acceleration

1e-2 1e-1

Ground Motion (g)

1e-5

1e-4

1e-3

1e-2

Annu

al F

requ

ency

of E

xcee

denc

e

Uniform Hazard Response Spectrum

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Spectral Period (s)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

Grou

nd M

otio

n (g

)

Spectral Period (s): PGAGround Motion (g): 0.0397

International Building Code (IBC) 2012

https://earthquake.usgs.gov/hazws/staticcurve/1/E2014R1/COUS0P05/-96.371/42.322/any/760

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