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CAL JIFORNIA��
Water Boards
Central Valley Regional Water Quality Control Board
8 February 2013
Mr. Drew Squyres .
Pacific Gas and Electric Company
4325 S. Higuera Street
San Luis Obispo, CA 93401
PACIFIC GAS AND ELECTRIC COMPANY (PG&E) KERN POWER PLANT (FORMER),
2401 COFFEE ROAD, BAKERSFIELbg KERN COUNTY (SITE ID — 2050001)
Jacobson James & Associates, Inc. (JJ&A) prepared and submitted the following documents on
PG&E's behalf:
• Response to CVRWQCB Comments, Site Specific Soil Management Screening
Process for Demolition-Related Activities, Kern Power Plant, Bakersfield, California,
dated 15 June 2012 (,Response); and
• Technical Memorandum: Background Threshold Values for Metals in Soil, Kern Power
Plant, Bakersfield, California, dated 13 November 2012 (BTVMS Tech Memo).
Central Valley Water Board staff (Staff) has reviewed the above documents as applicable to
demolition of the PG&E Kern Power, Plant (Site) facilities and evaluation of potential impact(s)
from prior facility operations.
RESPONSE SUMMARY
The Response addresses each comment by Staff provided in the 21 May 2012 review letter.
Responses to Comment Nos. 6 and 7 indicated that new statistical calculations to determine the
background threshold values (BTVs) for metals in soil would be provided in a separate technical,
memorandum. The BTVMS Tech Memo was subsequently submitted addressing these two
comments.
BTVMS TECH MEMO SUMMARY
The BTVMS Tech Memo evaluates the BTVs for metals in soil utilizing two subsets of data. The
first subset being the site-specific background concentrations values of 21 metals in soil
previously reported in the Phase 11 Environmental Site Assessment (Phase 11 Report) by IT
Corporation (10 August 2000), designated the background data set (BDS). The BDS consists of
13 soil samples, including one duplicate sample, collected at depths of 0 and 4.5 feet below
ground surface (bgs), from six soil borings, at locations identified in the Phase 11 Report as "non-
impacted areas of the Site ".
The second subset -is the full data set (FDS) comprised of the complete Kern Power Plant soil
database from the Phase 11 Report (2000) through June 2012. The initial FDS consisted of
488 soil samples collected from 0 to 115 feet bgs. The BTVMS Tech Memo indicates that a
data reduction process was applied to the initial FDS that systematically removed samples in
KARL E. LONGLEY ScD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER
1685 E Street, Fresno, CA 93706 1 www,waterboards.0a.gov/centralvalley
RECYCLED PAPER
EDMUND G. BROWN JR.
GOVERNOR
MATTHEW RoomouEz
SECRETARY FOR
ENVIRONMENTAL PROTECTION
PACIFIC GAS AND ELECTRIC COMPANY (PG&E) KERN POWER PLANT (FORMER),
2401 COFFEE ROAD, BAKERSFIELbg KERN COUNTY (SITE ID — 2050001)
Jacobson James & Associates, Inc. (JJ&A) prepared and submitted the following documents on
PG&E's behalf:
• Response to CVRWQCB Comments, Site Specific Soil Management Screening
Process for Demolition-Related Activities, Kern Power Plant, Bakersfield, California,
dated 15 June 2012 (,Response); and
• Technical Memorandum: Background Threshold Values for Metals in Soil, Kern Power
Plant, Bakersfield, California, dated 13 November 2012 (BTVMS Tech Memo).
Central Valley Water Board staff (Staff) has reviewed the above documents as applicable to
demolition of the PG&E Kern Power, Plant (Site) facilities and evaluation of potential impact(s)
from prior facility operations.
RESPONSE SUMMARY
The Response addresses each comment by Staff provided in the 21 May 2012 review letter.
Responses to Comment Nos. 6 and 7 indicated that new statistical calculations to determine the
background threshold values (BTVs) for metals in soil would be provided in a separate technical,
memorandum. The BTVMS Tech Memo was subsequently submitted addressing these two
comments.
BTVMS TECH MEMO SUMMARY
The BTVMS Tech Memo evaluates the BTVs for metals in soil utilizing two subsets of data. The
first subset being the site-specific background concentrations values of 21 metals in soil
previously reported in the Phase 11 Environmental Site Assessment (Phase 11 Report) by IT
Corporation (10 August 2000), designated the background data set (BDS). The BDS consists of
13 soil samples, including one duplicate sample, collected at depths of 0 and 4.5 feet below
ground surface (bgs), from six soil borings, at locations identified in the Phase 11 Report as "non-
impacted areas of the Site ".
The second subset -is the full data set (FDS) comprised of the complete Kern Power Plant soil
database from the Phase 11 Report (2000) through June 2012. The initial FDS consisted of
488 soil samples collected from 0 to 115 feet bgs. The BTVMS Tech Memo indicates that a
data reduction process was applied to the initial FDS that systematically removed samples in
KARL E. LONGLEY ScD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER
1685 E Street, Fresno, CA 93706 1 www,waterboards.0a.gov/centralvalley
RECYCLED PAPER
Mr. Drew Squyres -2- 8 February 2013
areas of known or potential impacts from historical Site activities using a combination of
statistical analysis mndSitehnovvmdge. These included, but are not limited to, removal ofall
samples collected fromD-3feetboo(duetopotentia|irnpanU,renlova|ofoUG8nnp|os from all
depths at locations where impacts to soil were known or suspected, rem oval ofBDGsarnpkyo'
etc. This reduced the original F[}��by280amrnp|ea from 488aannp|eato 222 samples.
TheE][)S and the reduced FDS were then analyzed by various statistical methods to calculate
BT\/a including murnrn8ry statistics, substitution of non-detect values, outlier testing and
n*mov8\, population comparison and removal of multiple populations, goodness-of-fit testing,
and calculation of upper tolerance limits (UTL). The BTVMS Tech Memo contains more
detailed information regarding the statistical methods applied.
The proposed BTV for each metal in soil was selected by comparing the calculated UTL for the
BDS and FC>S. |f the UTLG were "sirn|\ar', the B[)8L]TL was "v@|idated" and selected (14of
22 metals eva|uated). |f the UTLa were not similar, the F[>8UTL was proposed (one meta|).
Due to its larger sample size and spatial dispersion of samples, the data from the F[>S\amore
likely to be representative of true Site background concentrations, and will have "more robust
UTLa" Data gaps in the B[]8 due to insufficient detections were addressed bV selecting the
FOS i]TL (three mOsta\a).
In the final step, the proposed BTV for each metal constituent was compared to the reporting
limits (F<Lm\ set in Addendum 1 to the QAPP. If the proposed BTV was below the ��L in
Addendum ''1totheQAPP,theRLvvmsthenused as metals evaluated). Table 7,
Summary Of Upper Tolerance Limits and Proposed Background Threshold Values, from the
BTVMS Tech Memo |aattached.
COMMENTS
The and the ��S�� Memo �U��|ya�m�����|�����
Staff comments presented in the 21 May 2O12 review letter. It|s our understanding that the
proposed BTV for metals in aoUe will be incorporated into @ revised analysis and Table 4, On-
Site Soil Reuse Screening Criteria, contained \n the technical memorandum Site-Specific Soil
Management Screening Process for Demolition-Related Activities, Ken7Power Plant
Bakersfield, California, doted 9Apr|| 2012' proposing @ Selected Site Screening Level (SSSL)
for each metal \nSOU. Each constituent of concern (C(]C) specific SSSL was determined by
selecting the lowest screening value from the US EPA Regional Screening Levels (RSLs); the
California Human Health Screening Levels (CHHSL8); and the California Regional Water
Quality Control Board, Region Environmental Screening Levels (ESLs); but not lower than
background conditions, \fapplicable. If the lowest screening level was below background
conditions for that COC, then the background concentration would be the SSSL.
VVe generally agree with the approach ae used for the intended purpose. Central Valley Water
Board Staff has some concerns about some of the methodologies used in deriving the BTVs.
However, Staff also looked at the intended use and reviewed the various screening levels
described above and the proposed BTVu for 22 metals constituents. For all metals, with the
m of arsenic, the E�TVe are below the lowest screening level. Therefore, the lowest aonen|ng|eve|vv\||betheSSGLandtheBTVamneno\ongerofconoiderat\onforthatpurpoee.
In the case of arsenic, the lowest screening level in a commercial I industrial scenario is
0.24 rn|Uigr8rnm per kilogram (rno/ho) (CHHS|) and the proposed BT\/ is 8.59 mg/kg. Therefore.
the proposed BTV for arsenic of 6.59 mg/kg is also proposed as the SSSL.
Mr. Drew Squyres -3- 8 February 2013
The natural occurrence of arsenic in California soils has been the issue of many studies. As an
example, studies by the California Department of Toxic Substances Control (DT@[) for school
sites in Southern California suggested that 12 mg/kg may be a useful screening number for
evaluating arsenic as a chemical of potential conmarm Studies at school sites in the Loa
om
Angeles -nMied��choo|[)\ethOtd8tomninedthe 9596 Upper [|on�denoeL\nn�of the 9�
Percentile Concentration for arsenic tobe8rng/kg. An additional study \n Santa Cruz and
Monterey Counties, California determined the arsenic background threshold value to be
14.4rn0/kg. Using the above examples as general guidelines for arsenic concentrations in
California soils, the proposed BTV and SSSL for arsenic of 6.56 mg/kg does not appear
Since the screening levels for metals, that will now be used as the SSSLs, are established to be
protective of human health and the proposed BTVs for metals, except arsenic, are no longer of
consideration, concerns regarding the methodology used in establishing the BTVs for these
metals are reduced. If, however, the BTVo are tobm used for any other purpose, the
methodologies and resulting BTVo may need tobere-8va|usdmd.
The Response and the BTVMSTech Memo mdemnmtely address comments |n the 21 May 2O12
review letter. PG&E needs tosubmit an amended Table 4. On-Site Soil Reuse Screening
Criteria, contained in the technical memorandum Site-Specific Soil Management Screening.
Process for Demolition-Related Activities, Kern Power Plant, Bakersfield, California, dated
9 April 2012' vvh\Ch updates the BTVa (Site Specific Ambient Thresholds) for metals and the
SSSLG.aaappropriate. With the incorporation of information provided \nthe Response and the
BTVM8Teoh Memo, the Site-Specific Soil Management Screening Process For Demolition-
Related Activities, Kern Power Plant, Bakersfield, California, dated 9Apri\ 2012, is hereby
approved.
|f you have any questions or wish to discuss this review, please contact me at (559) 444-2484
or by e-mail at dcarlson(a-),waterboards.ca.gov.
DANIEL L.CARUSON
Senior Engineering Geologist
PG 5379'C|EG1895.CHCB488
Enclosure
cc: Mr. Joel Bauman, Jacobson James and Associates, Roseville
Mr. Howard Wines, Bakersfield Fire Department, Bakersfield
Kern County Public Health Services Department, Environmental Health Division, Bakersfield
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