11231 Richmond Avenue

Suite D104 Houston, TX 77082 Tel (832) 916-3690

July 27, 2017 Project No. 4020

Mr. Rodney Bryant VCP-CA Section, MC-221 Remediation Division Texas Commission on Environmental Quality P. O. Box 13087 Austin, Texas 78711-3087 SUBJECT: VOLUNTARY CLEANUP PROGRAM (VCP)

CES GRIGGS ROAD VCP SITE 4900 GRIGGS ROAD, 4904 GRIGGS ROAD, AND 5910 WAYLAND STREET (VCP No. 2751; CN604824904; RN108370644) RESPONSE TO JUNE 16, 2017 COMMENTS ON REVISED APAR – COMMENT 4 ADDITIONAL GROUNDWATER ASSESSMENT

Dear Mr. Bryant: Pastor, Behling & Wheeler, LLC (PBW), on behalf of the CES Griggs Road PRP Group (the “Group”), has prepared this response to Comment 4 on the revised Affected Property Assessment Report (APAR). The APAR summarized the environmental assessment of the CES Griggs Road VCP Site (the “Site”) pursuant to the requirements of VCP Agreement No. 2751. The VCP Agreement was executed between the Group and the Texas Commission on Environmental Quality (TCEQ) on June 10, 2015. The revised APAR was submitted to TCEQ on April 17, 2017. Comments and requests for additional groundwater investigation were provided to the Group by the TCEQ on June 16, 2017. As quoted below, TCEQ requested an additional assessment of the second sand (approximately 40-60 feet below ground surface (bgs) in Comment 4.

“In addition, the TCEQ understands that cone penetrometer tests (CPT) were conducted to identify the presence of a laterally continuous clay layer that could possibly separate the upper groundwater bearing unit (GWBU) from a second sand unit. The TCEQ notes that the data located in the boring logs for the CPT test do no indicate a continuous clay layer. The 20’ [foot] thick clay layer identified contains numerous intermittent sands and clayey sands which may allow for vertical migration of contamination and connection of the first and second sands. Additional assessment of this second sand (approximately 40-60’ bgs) should be conducted to determine whether the contamination identified in the shallow sand is also present in the second sand.”

The Group respectfully disagrees with the TCEQ’s opinion that additional assessment of the second sand unit is warranted based on facts provided in the revised APAR (previously submitted) and the following five lines of additional evidence: 1) Texas Risk Reduction Program (TRRP) rule requirements and guidance, 2) Potential presence of dense non-aqueous phase liquids (DNAPL), 3) Soil chemical of concern (COC) concentrations, 4) Hydrogeology of the affected property, and 5) Potential migration from off-site properties. Each of these lines of evidence are detailed below.

Mr. Rodney Bryant July 27, 2017 Page 2 of 5

1. TRRP Rule Requirements and Guidance The TRRP rule states that assessment of the deeper GWBU is only required based on the likelihood that COCs have migrated deeper, including properties of COCs and affected property (30 TAC 350.51(d)(3)). As presented in the APAR, the Site does not have the attributes that would warrant an investigation into the second GWBU.

“The vertical extent of the soil assessment shall continue beyond the uppermost groundwater-bearing unit as appropriate based on the likelihood that COCs have migrated deeper considering the chemical and physical properties of the COCs (e.g., dense non-aqueous phase liquids) and the hydrogeology of the affected property. [emphasis added]”

These requirements are more fully described in the guidance document RG-366/TRRP-12 (Affected Property Assessment, May 2010), particularly with regard to transport of CVOCs to a deeper GWBU (see Groundwater Assessment section).

“Note that some COCs, tetrachloroethylene, for example, have a high specific gravity greater than that of water and relatively high mobility characteristics in the subsurface environment. Because of this, such COCs have a natural tendency to migrate downward when present at aqueous concentrations near saturation or as a NAPL. In such situations, … and possibly sampling of the deeper groundwater-bearing units may be necessary, depending on the hydrogeologic factors and COC chemical/physical properties….If migration to another, deeper groundwater-bearing unit is not possible (i.e., reasonably probable) based on the nature of the hydrogeology and the chemical and physical properties of the COCs, it is not necessary to sample the deeper groundwater bearing unit. For example, if a person demonstrates that a sufficient thickness and lateral extent of a confining layer underlies the first groundwater-bearing unit, it may not be necessary to sample the deeper unit to determine if it is affected. [emphasis added]”

As discussed in the following sections, DNAPL is not present on Site and CVOC concentrations in groundwater have been detected far below saturation conditions. In addition, numerous CPT and drilling logs from locations across the Site clearly demonstrate a continuous thick low-permeability clay layer between the upper and lower sandy units on site.

2. Potential Presence of DNAPL DNAPL was not encountered in any boring during drilling or in any well after completion and well purging. CVOC concentrations are several orders of magnitude lower than the chemical solubility (as shown in the table below) thus there is no evidence that DNAPL is present at the Site which might contribute to migration of COCs into the second GWBU.

Chemical of Concern Solubility (mg/L) Maximum Concentration (mg/L) cis-1,2-Dichloroethene 4.93E+03 1.4E-01

Tetrachloroethene 2.00E+02 6.7E-03 trans-1,2-dichloroethene 6.30E+03 3.4E-03

Trichloroethene 1.10E+03 2.0E-02 Vinyl chloride 2.76E+03 1.2E-02

Mr. Rodney Bryant July 27, 2017 Page 3 of 5

3. Soil COC Concentrations As shown in the table below, soil concentrations were approximately an order of magnitude below the protective concentration levels (PCLs) for protection of groundwater from soil leachate (GWSoilIng). These soil concentrations demonstrate limited leachability. Consequently, these results do not indicate the presence of a continuing source of CVOCs that would impact the second GWBU or the potential for DNAPL within the soil column.

Chemical of Concern GWSoilIng PCL (mg/kg) Maximum Concentration (mg/kg) cis-1,2-Dichloroethene 1.2E-01 3.1E-02 (21-22 feet bgs)

Tetrachloroethene 2.5E-02 1.2E-03 (4-5 feet bgs) trans-1,2-dichloroethene 2.5E-01 < 6.6E-04 (not detected)

Trichloroethene 1.7E-02 4.3E-03 (21-22 feet bgs) Vinyl chloride 1.1E-01 2.1E-03 (4-5 feet bgs)

4. Hydrogeology of Affected Property

As discussed in the APAR, a confining clay layer approximately 17 to 24 feet thick was identified under the first GWBU. Based on the six CPT borings located across the Site, this confining clay layer is laterally continuous. As shown on Figure 4C.3 in the APAR (Geologic Cross-Section B-B’), the 20 to 22 feet bgs interval in boring 4904-SB29 is identified as two intermittent silt and sand seams on the CPT-04 log. These silty lenses are approximately six inches thick, are laterally discontinuous, and are embedded in a thick, high-plasticity clay (CH) as identified by the field geologist. As discussed in the APAR, the coefficient of permeability of this interval was 8.80E-09. This demonstrates that the presence of such intermittent and discontinuous sands and clayey sands within the confining unit does not materially affect the competency of the clay to hinder the vertical migration of COCs to the second GWBU. This type of sedimentology is common in fluvial environments such as that found at the Site (note the variability in the adjacent VCP site sedimentology discussed below). Therefore, in accordance with TRRP guidance, it is not reasonably probable to hypothesize migration to the deeper GWBU.

Field Identification Visual Classification USC

Moisture Content

(%)

Dry Unit Weight

(pcf)

Wet Unit Weight

(pcf)

Coefficient of Permeability

(cm/sec)

4904-SB29 20-22 feet

bgs

Red-brown clay, very stiff, very plastic with trace organic black staining and

calcareous nodules; at 20’ slickensided and abundant calcareous nodules

CH 27.5 97.8 124.7 8.80E-09

5. Potential Migration from Off-Site Properties

A release of CVOCs has been documented at the adjacent, upgradient Former Joy Tabernacle VCP site. Although migration of CVOCs from this site toward the CES Site has been demonstrated in VCP 2729 documents, it is unclear if constituents have reached the CES Site. Based on a review of well completion logs and groundwater analytical data, CVOCs were identified in groundwater to a depth of 45 feet at the Former Joy Tabernacle site. The logs also demonstrate the difference in sedimentology between the CES and Former Joy Tabernacle sites. This variability in sedimentology is common in fluvial environments found in

Mr. Rodney Bryant July 27, 2017 Page 4 of 5 sediments deposited in this area. Ramifications of these results as they relate to the CES Site are discussed below. The extent to which the CVOCs identified in the shallow GWBU at the adjacent VCP 2729 (Former Joy Tabernacle) site (maximum tetrachloroethene concentration of 4.4 mg/L) has potentially impacted the CES Site is unclear. The attached Appendix 11B figure from the CES Site APAR shows the locations of monitoring wells for both the CES and VCP 2729 sites. The table below compares the CVOC solubilities to the maximum concentrations at the CES and VCP 2729 sites.

Chemical of Concern Solubility (mg/L)

CES Maximum Concentration (mg/L)

VCP 2729 Maximum Concentration (mg/L)

cis-1,2-Dichloroethene 4.93E+03 1.4E-01 (MW-01) 9.7E-01 (MW-03) Tetrachloroethene 2.00E+02 6.7E-03 (MW-01) 4.4E+00 (MW-03)

trans-1,2-dichloroethene 6.30E+03 3.4E-03 (MW-05) 1.5E-03 (MW-03) Trichloroethene 1.10E+03 2.0E-02 (MW-01) 2.7E-01 (MW-03) Vinyl chloride 2.76E+03 1.2E-02 (MW-05) < 5.0E-04 (MW-03)

A review of the cross-sections and boring logs provided in the March 2017 VCP 2729 APAR indicates that a significant thickness of sand is represented at VCP 2729 MW-03, which is screened from 15 to 40 feet bgs with the bottom of the screen in a clayey sand that extends to at least 45 feet bgs. The sand at VCP 2729 MW-03 appears as a single unit and is not divided into an upper and lower unit at this location. However, the sand unit represented at VCP 2729 MW-10 (located farther to the west nearer the CES Site) is only approximately 10-12 feet thick which correlates with the upper sand unit at CES MW-06 located on the eastern boundary of the CES property (installed approximately 140 feet east of CES MW-06). Both the VCP 2729 MW-10 and CES MW-06 logs show a clay to approximately 15 feet bgs with sand from approximately 15 to 25 feet bgs underlain by a sandy clay at approximately 25 to 26 feet bgs. The VCP 2729 MW-10 log indicates a hard, dark gray high plasticity clay from to 30 to 35 feet bgs. As shown on the VCP 2729 cross-section B-B’, the sand at MW-03, which is at least 35 feet thick, thins westerly into the sand at VCP 2729 MW-06 that appears to represent an intercalated or inter-fingered sand unit. Based on the log of VCP 2729 MW-04, there is no indication of this shallower sand further southwest. The first sand encountered in this well is approximately 38 feet bgs at a depth that corresponds to the second sand encountered in CPT-05 (which is located approximately 250 feet north of VCP 2729 MW-04). These data indicate that both of the southern VCP 2729 wells, MW-04 and MW-07, were installed in the second sand zone. As shown on Table 5B of the VCP 2729 APAR, CVOCs were not detected in the second sand zone wells, MW-04 and MW-07. In summary, based on geological observations the approximate 35-foot thick sand encountered in VCP-2729 MW-03 intercalates and thins to the west (identified in VCP 2729 MW-10 and CES MW-06) with an intervening clay layer between this upper sand and the second sand below. Further south, at VCP 2729 MW-04, VCP 2729 MW-07, and CES CPT-05, the boring and CES CPT logs show a clear, thick clay overlying the second sand zone with minimal transmissive sand in the shallow zone. In this portion of the area, groundwater would preferentially move through this deeper sand. Note that it is unknown if CVOCs (from the adjacent Former Tabernacle site) identified in the thick sand unit in VCP 2729 MW-03 have migrated laterally in both the shallow and deeper sands.

Mr. Rodney Bryant July 27, 2017 Page 5 of 5 The Group requests agency concurrence that the multiple lines of evidence presented in this response letter, in conjunction with data presented in the revised APAR, are sufficient to demonstrate that additional assessment of the second sand zone at the CES Site is not warranted. If you have any questions or comments, please call (832) 916-3691 or email brenda.basile@pbwllc.com. Sincerely, PASTOR, BEHLING & WHEELER, LLC

Brenda P. Basile, Ph.D. Senior Consulting Scientist cc: CES Griggs Road PRP Group Attachment: APAR Appendix 11B Location Map

Mr. Rodney Bryant July 25, 2017

FIGURE

01

11

12

14

13

10

17

18

16

09

19

20

21

23

08

07

01

22

15

02

03

4900 Griggs Rd.

4904 Griggs Rd.

5910 Wayland St.

01

03

04

02

06

05

06

03

02

24

25

27

28

29

30

29A

14

18

13

12

10

17

11

03A

16

15

07

04A

09

08

MW-02

MW-04

MW-03

04

05

26

MW-01

MW-05

31

32

MW-08

MW-06

MW-07

CPT-05

CPT-06

CPT-04

CPT-01

CPT-03

CPT-02

HA-02

HA-01

HA-03

HA-04

HA-05

MW-4

MW-7

SB-3/TMW-3

MW-6

6030 Grace Ln.

SB-2/TMW-2

MW-2

MW-5

Schroeder Rd.

SB-1/TMW-1

5906 Grace Ln.

MW-10

Former

Advance

Cleaners

MW-1

Auto

Repair

Shop

MW-8

Former

Auto Repair

Location of Former

Palms Cleaners

(4912 Griggs Rd.)

Former

Auto Repair

4906 Griggs Rd.

MW-9

MW-3

DATE:

PROJECT:

PASTOR, BEHLING & WHEELER, LLC

CONSULTING ENGINEERS AND SCIENTISTS

REVISIONS

CHECKED:

BY:

Appendix 11B

AJD

BBAPR., 2017

4020

150750

Scale in Feet

CES ENVIRONMENTAL SERVICES

4904 GRIGGS ROAD

HOUSTON, TEXAS

Source:

Imagery taken from Google Earth, photography dated July 31, 2015.

Approx. Site Property Boundary

PBW Sample Location

PBW Sample Location (Jan. 2017)

PBW Monitoring Well Location

PBW Monitoring Well Location (Jan. 2017)

Monitoring Well Location (By Others)

CPT Location

Hand Auger Location

Approx. VCP 2729 Boundary

Note:

VCP 2729 sample locations from SKA Consulting,

Affected Property Assessment Report, Former Joy

Tabernacle, VCP 2729, March 2017.