ITEM 17: PETITION OF MALCOLM COBRINK FOR REVIEW OF DENIAL OF PETROLEUM UNDERGROUND STORAGE TANK SITE CLOSURE AT 2402 SOUTH BRISTOL STREET, SANTA ANA, CALIFORNIA (METRO CAR WASH)

DISCUSSION: Health and Safety Code 25299.39.2, subdivision (b) provides that a petroleum underground storage tank (UST) owner or operator who believes that the corrective action plan for the owner's or operator's site has been satisfactorily implemented may petition the manager of the UST Cleanup Fund (Fund) for review of the owner's or operator's case. Malcolm Cobrink (petitioner) filed a petition for review pursuant to this provision.

Petitioner contends that his case should be closed because the concentrations of petroleum at his site do not pose a threat to human health and safety, or the environment.

The Fund manager has reviewed petitioner's case and has concluded that petitioner's contention has merit. Accordingly, the proposed order finds that the concentrations of petroleum at petitioner's site do not pose a threat to human health and safety, or the environment, and do not unreasonably affect current or probable future beneficial uses of water. In addition, the level of site cleanup is consistent with the maximum benefit to the people of the state. Therefore, the proposed order requires petitioner's case to be closed.

POLICY ISSUE: Should the State Water Resources Control Board (SWRCB) adopt the proposed order?

RWQCB IMPACT: Regional Water Quality Control Board, Santa Ana Region

FISCAL IMPACT: If the case is not closed and more corrective action is required, costs would be $250,000-$500,000. (Estimate based upon past remediation and monitoring.)

STAFF RECOMMENDATION: Adopt the proposed order.

I. The sentence which starts on the last two lines of page 2 and continues on page 3 should be amended to include a footnote as follows:

Health and Safety Code section 25299.39.2, subdivision (b) provides that a UST owner or operator who believes that the corrective action plan for the owner's or operator's site has been satisfactorily implemented, but where closure has not been granted, may petition the manager of the UST Cleanup Fund for review of the owner's or operator's case.1

_________________________

1 To the extent that the SWRCB may lack authority to review this petition pursuant to Health and Safety Code section 25299.39.2, subdivision (b) because the petitioner did not submit a corrective action plan for the site, the petition is being reviewed on the SWRCB's own motion pursuant to Water Code section 13320.

II. The first paragraph in page 4 should be amended as follows:

The results of the April 1995 investigation were submitted to the RWQCB in June of 1995. The RWQCB requested petitioners to conduct an additional soil and water investigation in September of 1995. The petitioner submitted a draft workplan for this investigation in May of 1996. Following addendums to workplan, the RWQCB conditionally concurred with the workplan in June of 1996. In response September of 1996, the petitioners requested the RWQCB to close their case on the basis that it posed a low risk to human health, safety, and the environment. When RWQCB staff denied petitioners' request, petitioners filed an appeal with the RWQCB. On April 4, 1997, the RWQCB upheld the staff determination, and reiterated the request for an additional soil and water investigation. In July 1997 petitioners requested review of their case by the UST Cleanup Fund manager pursuant to Health and Safety Code section 25299.39.2, subdivision (b).

DRAFT May 4, 1998

BY THE BOARD:

Malcolm Cobrink (petitioner) seeks review of the decision of the Regional Water Quality Control Board, Santa Ana Region (SARWQCB) not to close petitioner's case, involving an unauthorized release from a petroleum underground storage tank (UST) located at 2402 South Bristol Street, Santa Ana, California (Metro Car Wash). For the reasons set forth below, this order determines that petitioner's case should be closed and no further action related to the release should be required.

Several statutory and regulatory provisions provide the State Water Resources Control Board (SWRCB), RWQCBs, and local agencies with broad authority to require responsible parties to clean up a release from a petroleum UST. (E.g., Health & Saf. Code, § 25299.37; Wat. Code, § 13304, subd. (a).) The SWRCB has promulgated regulations specifying corrective action requirements for petroleum UST cases. (Cal. Code of Regs., tit. 23, §§ 2720-2728.) The regulations define corrective action as "any activity necessary to investigate and analyze the effects of an unauthorized release; propose a cost-effective plan to adequately protect human health, safety and the environment and to restore or protect current and potential beneficial uses of water, and implement and evaluate the effectiveness of the activity(ies)." (Cal. Code Regs., tit. 23, § 2720.)

SWRCB Resolution 92-49, Policies and Procedures for Investigation and Cleanup and Abatement of Discharges Under Water Code section 13304 also applies to petroleum UST cases. Resolution 92-49 directs the RWQCBs to ensure that water affected by an unauthorized release attains either background water quality or the best water quality which is reasonable if background water quality cannot be restored. (SWRCB Resolution 92-49, III.G.) Any alternative level of water quality less stringent than background must be consistent with the maximum benefit to the people of the state, not unreasonably affect current and probable future beneficial use of affected water, and not result in water quality less than that prescribed in the water quality control plan for the basin within which the site is located (hereafter basin plan). (Ibid.)

Resolution 92-49 does not require, however, that the requisite level of water quality be met at the time of site closure. Even if the requisite level of water quality has not yet been attained, a site may be closed if the level will be attained within a reasonable period. (SWRCB Resolution 92-49, III.A.)

The soil underlying petitioner's site consists predominantly of low permeability silty sand, silt, and clay to a depth of at least 20 to 25 feet. Groundwater at the site is encountered at shallow depths of about three to six feet in fine-grained, low permeability silty sand, silt, and clay deposits which act as an aquitard overlying deeper, high quality confined groundwater in the so-called Santa Ana Pressure Zone. The semiperched groundwater exhibits a generally low, southerly hydraulic gradient of about 0.004 beneath the site.

The basin plan for the Santa Ana River basin designates the Santa Ana Pressure Zone as having the beneficial use of municipal supply, or drinking water use. (SARWQCB & SWRCB, Water Quality Control Plan, Santa Ana River Basin (1995) at p. 4-41.) The basin plan also distinguishes between the groundwater contained in deeper aquifers within the pressure zone, which is a source of drinking water, and the shallow groundwater overlying the deeper aquifers, which is not. (Id. at p. 5-49.) The shallow groundwater is incapable of sustaining sufficient pumping rates to be considered a potential source of drinking water. (Ibid.) Footnote1

The basin plan recognizes, however, that the groundwater in the shallow water-bearing zone is in close proximity to the groundwater contained in the deeper aquifers. Accordingly, the basin plan provides for the regulation of petroleum releases in shallow groundwater to ensure protection of the groundwater in deeper aquifers as follows:

"In the pressure zone of Orange County, the uppermost sediments are fine-grained materials which are unable to sustain sufficient pumping rates. However, due to the large volume of water held within these sediments, the close vertical proximity of these areas to underlying pumping locations, and the existence of pathways for movement into the deeper aquifers, the shallow waters in this area are considered as contributing to the sources of drinking water in Orange County. Leaking underground storage tank cleanups must be conducted accordingly." (Ibid.)

In order to protect beneficial uses, the basin plan specifies the following taste and odor narrative water quality objective: "The groundwaters of the region shall not contain, as a result of controllable water quality factors, taste- or odor-producing substances at concentrations which cause a nuisance or adversely affect beneficial uses." (Id. at p. 4-14.) The basin plan also contains the following narrative water quality objective for toxic substances: "All waters of the region shall be maintained free of substances in concentrations which are toxic, or that produce detrimental physiological responses in human, plant, animal or aquatic life." (Ibid.)

With regard to the water quality objective for toxicity, the State Department of Health Services (DHS) has set a maximum contaminant level (MCL) for drinking water of 1 ppb for benzene. (Cal. Code of Regs., tit. 22, § 64444.) Although DHS has not yet set an MCL for methyl-tertiary-butyl-ether (MTBE), DHS has set an interim action level of 35 ppb. (DHS Memorandum from Joseph P. Brown, Ph.D., Acting Chief, Water Toxicology Unit to Alexis M. Milea, P.E., Acting Supervisor, Standards and Technology Unit, Office of Drinking Water (February 19, 1991) at p. 2.) DHS has more recently proposed a 5 ppb MTBE concentration as a secondary drinking water standard for taste and odor. The threshold odor concentration of commercial gasoline (measured as TPH-g) in water is commonly accepted to be 5 ppb, with 10 ppb giving a strong odor. (SWRCB, Water Quality Criteria (2d ed. 1963) p. 230.)

Health and Safety Code section 25299.39.2, subdivision (b) provides that a UST owner or operator who believes that the corrective action plan for the owner's or operator's site has been satisfactorily implemented, but where closure has not been granted, may petition the manager of the UST Cleanup Fund for review of the owner's or operator's case.

The following is a brief summary of the site history. The site is a car wash located at 2402 South Bristol Street in the City of Santa Ana. Prior to June 1992, it dispensed gasoline and diesel fuel from three 12,000 gallon USTs.

In June 1992, UST removal and soil excavation activities commenced at the site. After the first day, excavation was halted due to high ambient hydrocarbon vapor concentrations. Soil vapor extraction reduced the vapor emissions by removing an estimated 1,830 pounds (equivalent to 295 gallons) of volatile petroleum constituents. The three USTs, five fuel dispensers, and all associated piping were then removed and an estimated 2,400 cubic yards of gasoline affected soil to a depth of about eight feet was subsequently excavated and replaced with clean backfill.

Subsequent investigations were completed in 1994. By that time a total of 24 monitoring wells (21 currently exist) and 37 soil borings had been installed. On August 4, 1994, SARWQCB staff informed petitioner that no further soil or groundwater investigation was required at that time. At about the same time, active groundwater remediation began with extraction from three monitoring wells (MW5, MW10, and MW14), treatment by carbon filter, and onsite reuse of treated groundwater as landscape irrigation.

Pump and treat remediation continued until March 19, 1996, when SARWQCB staff approved petitioner's request to deactivate the pump and treat system. SARWQCB staff concluded that best available technology levels had been achieved, and concurred with petitioner's claim that site could be considered a low risk site. A short time before SARWQCB staff reached this conclusion, residual benzene concentrations in MW5, which had exceeded 100 ppb in the October 1995 sampling, had measured 10.2 ppb in January 1996 sampling. Residual benzene concentrations have subsequently diminished to nondetect in all wells sampled except one which reported 0.5 ppb in January 1998. Prior to considering site closure, however, SARWQCB staff required an additional year of post-remediation monitoring.

During this post-remediation monitoring program MTBE analyses became standard analytical protocol in all UST cases across the state. Beginning in June 1996 and in subsequent quarterly monitoring, MTBE was detected in several monitoring wells at petitioner's site. On October 25, 1996, SARWQCB staff concluded that the site could no longer be considered low risk and could not be closed because of "elevated levels of MTBE" compared to its informal guideline of 100 ppb.

In March 1997, petitioner requested review of his case by the UST Cleanup Fund manager pursuant to Health and Safety Code section 25299.39.2, subdivision (b). The case was presented as an information item to the Board members of the SARWQCB on January 23, 1998. The conclusion of the SARWQCB's staff that the site should not be closed has since been affirmed by the Executive Officer of the SARWQCB, Gerard J. Thibeault.

Contention: The petitioner contends his case should be closed because the limited, localized, and diminishing impacts of residual petroleum constituents pose a "low risk" to current or probable future beneficial uses of water.

Findings: Petitioner's contention has merit. The facts in the record support the finding that residual petroleum constituents at petitioner's site do not pose a threat to human health and safety, or the environment, and do not adversely affect current or probable future beneficial uses of water. In addition, the level of site cleanup is consistent with the maximum benefit to the people of the state.

The record indicates that source removal, the extensive remediation and abatement to date, the distance to existing water supply wells, standard well construction practices in the area which include sanitary seals to depths of at least 100 feet, and natural hydrogeologic barriers between shallow affected groundwater and deeper production zones, effectively minimize any potential risk to current or probable future beneficial uses of groundwater from localized, residual detectable petroleum constituents remaining at the site.

The primary source of the release as well as substantially affected soils which could contribute to further groundwater degradation have been removed. Soil vapor extraction and groundwater extraction have reduced residual concentrations of petroleum constituents to best available technology levels. Declining trends in dissolved concentrations of petroleum constituents (including both benzene and MTBE) indicate the effectiveness of source removal as a method to ensure the limited, localized, and diminishing extent of residual petroleum constituents presently detected in the low permeability, fine-grained, shallow water-bearing zone.

The SARWQCB declined to close petitioner's case because concentrations of MTBE remained above an informal guideline of 100 ppb or less, the basin plan designates groundwater in the area as municipal supply, and the extent of the dissolved MTBE plume had not been fully defined.

We are confident, however, that a reasonable estimate of the maximum extent of the plume for purposes of evaluating potential risks associated with it can be based on the six monitoring wells reporting MTBE detections (ranging from about 10 to 558 ppb) and the remaining 15 nondetect wells. Based on our interpretation of the spatial and time-series distributions of residual MTBE concentrations, we estimate that a total volume of less than one acre foot (assuming a porosity of 40 percent for the silty sand, silt, and clay beneath petitioner's site) of shallow groundwater remains affected by residual, detectable MTBE.

A highly-retarded groundwater flow regime has contributed substantially to the observed limited migration of detectable petroleum constituents beyond the immediate vicinity of the original release. The flow regime is illustrated by the pumping rates of the wells used to pump contaminated groundwater from the shallow water-bearing zone which immediately underlies petitioner's site. The wells were capable of sustaining a mere 100 gallons per day (gpd) for all three wells combined. By contrast, the nearest drinking water wells in the vicinity of the site, which extract groundwater from deeper, confined aquifers, pump at sustained rates of 3-6 million gpd per well.

The nearest drinking water wells are located between 2,300-5,000 feet away, have sanitary seals to depths of 100-440 feet below ground surface, are perforated at depths of 385-1,460 feet, and extract groundwater from the highly productive, confined aquifers in the pressure zone. It is highly unlikely that these wells will be impacted by residual petroleum originating from petitioner's site due to their distance from the site; their construction, including sanitary seals to depths of at least 100 feet; the highly retarded groundwater flow regime discussed above; and natural hydrogeologic barriers between shallow affected groundwater and deeper production zones.

Moreover, in the unlikely event that residual petroleum constituents reach the deeper aquifers, it will be in concentrations too low to have an adverse impact on the beneficial use of the water. Residual benzene concentrations have diminished to nondetect in all wells sampled except one which reported 0.5 ppb in January 1998. The distribution of concentrations across the site for the past seven sampling rounds also indicates a limited and diminishing extent of detectable MTBE. Time series data from June 1996 through January 1998 indicate that residual concentrations of MTBE are attenuating such that only one well (MW20) remains above 100 ppb. Concentrations of MTBE in MW20 have diminished from a high of nearly 1,500 ppb in December 1996 to 558 ppb in January 1998. In the five other monitoring wells with residual MTBE "hits," the most recent detectable concentrations range from 10-85 ppb. The localized, diminishing concentrations of MTBE can be attributed to minimal advective transport within the low permeability silty sands, silts, and clays of the shallow water-bearing zone and dilution by dispersion.

The declining trend suggests that with no further regulatory action residual concentrations of MTBE will continue to diminish at the current rate to below 35 ppb within the next five years and, within a decade or so, to below 5 ppb. Thus, the shallow groundwater, though not a source of drinking water, will meet the basin plan narrative objective for toxicity within a reasonable period. It follows that the concentrations of benzene and MTBE in the shallow groundwater will not adversely affect the groundwater in the deeper aquifers, or cause the groundwater in the deeper aquifers to exceed the objective for toxicity.

Though concentrations of TPH-g in the shallow groundwater are likely to remain above 5 pbb (the commonly accepted odor threshold for water) for a significant period of time, the concentrations of TPH-g, like the concentrations of benzene and MTBE, pose no threat to current or probable future beneficial uses. Concentrations of 1,900 ppb (MW5) were reported in March 1997, and concentrations of 484 ppb (MW17) and 125 ppb (WB1) were reported in January 1998. It is highly unlikely, however, that TPH-g detected in localized areas immediately surrounding MW5, MW17, and WB1 will migrate substantially beyond its current limited spatial extent. Though the longer chain hydrocarbons comprising TPH-g biodegrade more slowly than certain petroleum constituents, such as benzene, they are also more recalcitrant (i.e., less volatile, less soluble, and highly adsorbent) and much less mobile.

In sum, the residual petroleum constituents at petitioner's site do not pose a threat to current or probable future beneficial uses. Moreover, to improve the quality of affected shallow groundwater would essentially require either "strip mining" to several feet below the water table, re-establishment of the pump and treat system for an indefinite period of time, or both. Such an approach would cost in the neighborhood of $250,000-$500,000 and at best would provide very limited water quality improvement to affected water in the shallow, low permeability, fine-grained water-bearing zone.

In light of the expense and the fact that beneficial uses are not threatened, attaining background water quality at petitioner's site is not feasible. It is impossible to determine the precise level of water quality that will be attained, but in light of all the factors discussed above, a level of water quality will be attained that is consistent with the maximum benefit of the people of the state. Footnote2

1. Residual concentrations of benzene, MTBE, and TPH-g at petitioner's site do not pose a threat to human health and safety, or the environment, and do not adversely affect current or probable future beneficial uses of water.

2. The level of site cleanup is consistent with the maximum benefit to the people of the state.

3. Given the expense of further active corrective action and the minimal benefits, if any, that would be gained by further corrective action, it is not feasible to attain background water quality at petitioner's site

4. Therefore, no further corrective action is necessary.

IT IS THEREFORE ORDERED that petitioner's case be closed, and no further action related to the release be required. The case is remanded to the SARWQCB for action consistent with this order.

The undersigned, Administrative Assistant to the Board, does hereby certify that the foregoing is a full, true, and correct copy of an order duly and regularly adopted at a meeting of the State Water Resources Control Board held on May 27, 1998.

AYE:

NO:

ABSENT:

ABSTAIN:

_____________________________________

Maureen Marché

Administrative Assistant to the Board

Footnote1

SWRCB Resolution 88-63 provides that "all surface and ground waters of the State are considered to be suitable, or potentially suitable, for municipal or domestic water supply . . . with the exception of . . . [s]urface and ground waters where . . . [t]he water source does not provide sufficient water to supply a single well capable of producing an average, sustained yield of 200 gallons per day." Resolution 88-63 has been incorporated into the basin plan. (SARWQCB, Resolution 89-42, approved SWRCB, Resolution 89-75.)

Footnote2

In approving an alternative level of water quality less stringent than background, the SWRCB has also considered the factors contained in California Code of Regulations, title 23, section 2550.4, subdivision (d). As discussed earlier, the adverse effect on shallow groundwater will be minimal and localized, and there will be no adverse effect on the groundwater contained in deeper aquifers, given the physical and chemical characteristics of petroleum constituents; the hydrogeological characteristics of the site and surrounding land; and the quantity of the groundwater and direction of the groundwater flow. In addition, the potential for adverse effects on beneficial uses of groundwater is low, in light of the proximity and withdrawal rates of groundwater supply wells; the current and potential future uses of groundwater in the area; the existing quality of groundwater; the potential for health risks caused by human exposure; the potential damage to wildlife, crops, vegetation, and physical structures; and the persistence and permanence of potential effects.

Finally, a level of water quality less stringent than background is unlikely to have any impact on surface water quality, in light of the volume and physical and chemical characteristics of petroleum constituents; the hydrogeological characteristics of the site and surrounding land; the quantity and quality of groundwater and the direction of groundwater flow; the patterns of precipitation in the region; and the proximity of residual petroleum to surface waters.