ITEM 5: PETITION OF ALTO BROTHERS TRUCKING, INCORPORATED, FOR REVIEW OF DENIAL OF PETROLEUM UNDERGROUND STORAGE TANK SITE CLOSURE AT 3610 OLD ARCATA ROAD, ARCATA, CALIFORNIA

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. Alto Brothers Trucking, Incorporated (petitioner) filed a petition pursuant to this provision for review of the denial of case closure by the Humboldt County Department of Environmental Health. Petitioner contends that its case should be closed because the concentrations of petroleum at its 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 detectable concentrations of residual petroleum at petitioner's site do not pose a threat to human health and safety, or the environment, and will not unreasonably affect current or probable future beneficial uses of water. Therefore, the proposed order requires petitioner's case to be closed.

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

RWQCB IMPACT: North Coast RWQCB

FISCAL IMPACT: None

STAFF RECOMMENDATION: Adopt the proposed order.

DRAFT 26 October 1998

BY THE BOARD:

Alto Brothers Trucking, Incorporated (petitioner) seeks review of the decision of the Humboldt County Department of Environmental Health (County) not to close petitioner's case involving an unauthorized release from a petroleum underground storage tank (UST) located at petitioner's site at 3610 Old Arcata Road, Arcata, California. 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.

Tank owners and operators who are eligible for reimbursement from the UST Cleanup Fund can petition the Fund Manager for a review of their case if they feel the corrective action plan for their site has been satisfactorily implemented, but closure has not been granted (Health and Saf. Code, § 25299.39.2, subd. (b)). Footnote1

Several statutory and regulatory provisions provide the State Water Resources Control Board (SWRCB), regional water quality control boards (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 County has been designated as an agency to participate in the local oversight program for the abatement of, and oversight of the abatement of, unauthorized releases of hazardous substances from USTs. (Health & Saf. Code, § 25297.1) 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). Corrective action consists of one or more of the following phases: (1) preliminary site investigation, (2) soil and water investigation, (3) corrective action plan implementation, and (4) verification monitoring. (Cal. Code Regs, tit. 23, § 2722, subd. (a).)

The preliminary site assessment phase includes initial site investigation, initial abatement actions, initial site characterization and any interim remedial action. (Cal. Code Regs., tit. 23, § 2723, subd. (a).) Corrective action is complete at the conclusion of the preliminary site assessment phase, unless conditions warrant a soil and water investigation. A soil and water investigation is required if any of the following conditions exists: (1) There is evidence that surface water or groundwater has been or may be affected by the unauthorized release; (2) Free product is found at the site where the unauthorized release occurred or in the surrounding area; (3) There is evidence that contaminated soils are or may be in contact with surface water or groundwater; or (4) The regulatory agency requests an investigation, based on the actual or potential effects of contaminated soil or groundwater on nearby surface water or groundwater resources or based on the increased risk of fire or explosion. (Cal. Code Regs., tit. 23, § 2724.)

The purpose of a soil and water investigation is "to assess the nature and vertical and lateral extent of the unauthorized release and to determine a cost-effective method of cleanup." (Cal. Code of Regs., tit. 23, § 2725, subd. (a).)

SWRCB Resolution No. 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 No. 92-49 directs 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 No. 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 No. 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 No. 92-49, III.A).

The North Coast RWQCB Basin plan identifies beneficial uses of groundwater in the Eureka Plain to include agricultural and industrial supply (NCRWQCB & SWRCB, Water Quality Control Plan, North Coast Region (1993) at p. 2-5) and municipal and domestic (MUN) supply "...in accordance with the provisions of State Water Resources Control Board Resolution No. 88-63..." (NCRWQCB & SWRCB, Water Quality Control Plan, North Coast Region (1993) at p. 2-1). The Basin Plan specifies a narrative taste and odor water quality objective for groundwater as follows: "Groundwaters shall not contain taste- or odor-producing substances in concentrations that cause nuisance or adversely affect beneficial uses." (Id. at p. 3-11.) The Basin Plan also contains the following narrative water quality objective for chemical constituents as follows: "Groundwaters used for domestic or municipal supply shall not contain concentrations of chemical constituents in excess of the limits specified in California Code of Regulations, Title 22, Chapter 15, Article 5, Section 64435 Tables 2, 3 and 4." (Id. at 3-11.)

With regard to the water quality objective for chemical constituents as specified in the above reference to Title 22, the State Department of Health Services (DHS) has set a maximum contaminant level (MCL) for drinking water of 1 ppb for benzene, 100 ppb for toluene, 680 ppb for ethylbenzene, and 1,750 ppb for xylene. (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 total petroleum hydrocarbon gasoline, or TPH-g) in water is commonly accepted to be 5 ppb, with 10 ppb giving a strong odor. The threshold odor concentration of commercial diesel (measured as TPH-d) in water is commonly accepted to be 100 ppb. (SWRCB, Water Quality Criteria (2d ed. 1963) p. 230.)

The following is a brief historical summary of petitioner's site at 3610 Old Arcata Road in the City of Arcata. The site is an active truck storage and maintenance facility located about one mile southeast of Arcata Bay in the Eureka Plain hydrologic basin. Shallow groundwater flow is generally from north to south.

The site includes a former barn converted into a truck maintenance building, a driveway and parking area north of the building, and a septic system leachfield located north and east of the building. The former USTs were located in two separate areas. Two former 1,000 gallon tanks with gasoline and diesel, respectively, were located immediately south (i.e., down-gradient) of the truck maintenance building and about 75 feet south (i.e., down-gradient) of the storm drain which collects runoff from the truck washdown area. A single 12,000 gallon diesel tank was located about 100 feet east of the truck maintenance building and about 75 feet south (i.e., down-gradient) of the septic system leachfield.

The three USTs were removed from these two separate areas in November 1991. The two 1,000 gallon tanks removed from the area immediately adjacent the maintenance shop reportedly had been inactive since 1979 or earlier. An additional 500 cubic yards of petroleum affected soil related to these older tanks were over-excavated to a depth of about 18 feet. The 12,000 gallon diesel tank east of the maintenance shop was also removed at this time along with an estimated 1,400 cubic yards (or the equivalent of 30 or more truckloads) of petroleum-affected soil to a depth of 20 feet. Shallow groundwater was not encountered in either of the excavations, indicating static water levels greater than 18-20 feet bgs at that time.

In January 1992, the depth to water in the onsite water supply well (located less than 200 feet south of the nearest UST excavation) was reported to be about 44 feet bgs. The well log for this private well indicates that it was installed in July 1979, when, according to the driller's observations, a "small water bearing gravel" was encountered between 80-85 feet bgs where the drilling terminated. The well log further indicates that the well was completed with blank casing (e.g., no perforations) from 0-75 feet bgs, a surface sanitary seal to 20 feet bgs, and a screened interval from 75-85 feet bgs. Water levels reportedly stabilized after well completion at about 12 feet bgs, indicating significant confining pressures in the deeper water-bearing gravel zone. Groundwater produced by this well is generally of poor aesthetic quality due to its typically milky, orange, opaque appearance. According to the December 24, 1997 monitoring report, water from this well is not used for drinking but rather supplies the bathroom facilities and garden hose at the truck maintenance building. According to petitioner's consultant, bottled water provides the drinking water supply at the facility.

Thirteen monitoring wells were installed in October 1996 which encountered groundwater at depths of about 13-15 feet bgs, indicating that shallow groundwater levels had risen at least several feet in the intervening four years since tank removal and over-excavation. The boring logs indicate shallow, fine-grained, low permeability clay and silt overlie deeper water-bearing sand typically encountered at about 10 feet bgs.

Groundwater sample analyses between October 1996 and December 1997 have indicated that benzene and MTBE were "not detected." Furthermore, two "hits" of toluene in MW-2 (25 ppb) and MW-8 (less than 1 ppb) were below its 100 ppb MCL, two "hits" of xylene in the same wells (17 and 1.1, respectively) were below its 1,750 ppb MCL, and one "hit" of ethylbenzene (2 ppb in MW-2) is below its 680 ppb MCL. Four groundwater samples detected TPH-g at concentrations ranging from 61-540 ppb, but laboratory analyses indicated the predominance of diesel range constituents in these analyses. The highest concentrations of TPH-d have been consistently reported in MW-8 (510-2,000 ppb), MW-9 (190-1,700 ppb), and MW-13 (7,200-8,400 ppb) which are in the immediate vicinity of the truck washdown area and storm drain that lie 50-80 feet up-gradient of the nearest UST excavation and 90-150 feet away (and up-gradient) of the furthest UST excavation. The monitoring well network has also indicated "non-detect" polynuclear aromatic hydrocarbons (which are sometimes associated with diesel or heavier petroleum fractions) and chlorinated hydrocarbons.

The onsite private well is located 170-180 feet south of the nearest UST excavation and 275 feet south of MW-13, which has reported the highest TPH-d concentrations. In December 1997, TPH-d concentrations declined from 8,400 ppb in MW-13 to 200 ppb down-gradient in MW-5 (in the immediate vicinity of the two former 1,000 gallon USTs) which indicates a 40-fold decrease in about 100 feet. MW-5 is located about 170 feet up-gradient of the onsite private well. The onsite private well reported "non-detect" for all gasoline and diesel constituents in December 1997. This onsite private well has also reported detectable chlorinated solvent "hits" of trichloroethylene at 0.56 ppb in December 1996 and 0.71 ppb in December 1997, and perchloroethylene at 1.3 ppb in December 1996 but "not-detected" in December 1997. The MCL for both of these non-petroleum related constituents is 5 ppb.

On January 21, 1997, petitioner asked the County to close the case. On April 8, 1997, the County replied that it would not close the case and stated that its "...primary concern is the delineation of the extent of the groundwater contamination plume...." Petitioner requested review of its case by the UST Cleanup Fund manager pursuant to Health and Safety Code § 25299.39.2, subdivision (b) in January 1998. In a July 7, 1998 letter to the UST Cleanup Fund manager, the County provided the record for review and stated that it "...cannot recommend closure of the site..." but provided no further discussion of the facts in the case to support its recommendation.

Contention: The petitioner contends its case should be closed because the limited, localized impacts of residual weathered petroleum constituents do not threaten human health, safety, and the environment, and pose a "low risk" to current or probable future beneficial uses of water.

Findings: Petitioner's contention has merit. As explained below, the facts in the record support the finding that additional soil and groundwater investigation is not necessary and that residual weathered 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 and will meet the applicable objectives in the North Coast RWQCB Basin Plan within a reasonable time frame.

The USTs have been removed along with a combined total of nearly 2,000 cubic yards of petroleum-affected backfill and soil which was over-excavated in the immediate vicinity of the former USTs to depths of about 18-20 feet. No MTBE or benzene have been detected in soil or groundwater at petitioner's site. A single monitoring well (i.e., MW-13 located up-gradient of the former USTs) has reported detectable toluene (less than 1 ppb to 25 ppb), ethylbenzene (2 ppb), and xylene (1.1 ppb to 17 ppb) all of which are below their respective MCLs (100 ppb, 680 ppb, and 1,750 ppb). The principal constituents of regulatory concern related to the former USTs are thus limited to the heavier molecular weight, low solubility, non-volatile, highly adsorbent TPH-d range of constituents. These residual TPH-d constituents are essentially immobile and will not migrate beyond their present limited, localized extent. There is also no evidence in the record to indicate any connection between the former leaking USTs and the detection of trace (less than MCL) concentrations of chlorinated solvents in the onsite private well.

The County contends that the extent of contamination has not been "adequately" delineated. We strongly disagree. The soil and groundwater sample data provide substantial evidence that (1) there is no groundwater "contamination" (e.g., "an impairment of the quality of the waters of the state . . . to a degree which creates a hazard to the public health . . . ." as defined in Wat. Code, § 13050, subd. (k)), (2) the localized, residual TPH-d "plume" originates up-gradient of the former USTs, (3) localized, residual, detectable concentrations of TPH-d in shallow groundwater attenuate from 8,400 ppb to 200 ppb (100 ppb is the commonly accepted threshold odor concentration for diesel fuel in water) in less than 100 feet down-gradient, and (4) given the proximity of this residual diesel to up-gradient septic system discharges, it is not likely that this shallow groundwater would be used in the foreseeable future for drinking water.

The absence of detectable MTBE and benzene from all groundwater and soil sample analyses is consistent with other substantial evidence of weathered, localized residual petroleum from several possible contributing sources at the trucking facility. Furthermore, the predominance of low-solubility, non-volatile, high molecular weight petroleum hydrocarbons detected provides additional substantial evidence that residual, detectable concentrations of petroleum will not migrate beyond their current limited extent in shallow groundwater.

Thus, the available facts indicate the absence of a "dissolved" plume of soluble, mobile constituents and do not support the County's request for additional groundwater investigation to determine plume extent. The facts in the record indicate that with no further regulatory action, residual detectable concentrations of weathered petroleum will remain localized within the immediate vicinity of the maintenance shop and will continue to attenuate naturally over time. The evidence in the record does not support the assumption that elevated TPH-d in shallow groundwater samples from the vicinity of the truck maintenance building were the result of former leaking USTs, but rather indicate a localized source up-gradient of the former USTs, possibly the storm drain or septic system discharges.

The lingering but slowly diminishing residual concentrations of petroleum constituents will not affect beneficial uses of groundwater. Concentrations of TPH-d in shallow groundwater in immediate contact with (albeit limited) residual TPH-d adsorbed to soils will likely remain above the commonly-accepted 100 ppb odor threshold for water in a localized volume of surrounding groundwater for a significant period of time. Considering the proximity of the ongoing septic system discharge up-gradient of the area of localized, residual, detectable TPH-d, and the fact that state well standards prohibit placement of a water supply well within a minimum 100 feet of a septic system and require a surface sanitary seal to exclude shallow groundwater, it is highly unlikely that this localized volume of shallow groundwater would unreasonably affect existing or probable future beneficial uses.

To remove all traces of residual petroleum constituents at petitioner's site would require additional excavation of soil unrelated to the former USTs, including areas north of, south of, and probably beneath the existing truck maintenance building. It would also require cessation of truck maintenance operations and perhaps even septic system use if a connection can be confirmed between these ongoing operations and the detectable TPH-d in shallow groundwater up-gradient of the former USTs. Such additional excavation and operational changes would interfere with the normal conduct of business at petitioner's site while providing little or no benefit to current or potential beneficial uses of the minimal area of groundwater not meeting water quality objectives for TPH-d. Furthermore, if complete removal of detectable traces of petroleum constituents (e.g., TPH-d) becomes the standard for UST corrective actions, the statewide technical and economic implications will be enormous. For example, disposal of soils from comparable areas of excavation throughout the state would greatly impact already limited landfill space. In light of the minimal, if any, benefit of attaining further reductions in concentrations of TPH-d at this site, the precedent that would be set by requiring additional excavation, the proximity of the residual detectable concentrations to up-gradient septic system discharges, and the fact that beneficial uses are not threatened (including the onsite private well), 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 given the limited residual TPH-d that remains at the site, but in light of all the factors discussed above, a level of water quality will be attained that is consistent with the maximum benefit to the people of the state. Footnote2

The final step in determining whether cleanup to a level of water quality less stringent then background is appropriate for this site requires a determination that the alternative level of water quality will not result in water quality less than that prescribed in the relevant Basin Plan. Pursuant to SWRCB Resolution No. 92-49, a site may be closed if the Basin Plan requirements will be met within a reasonable time frame.

In this particular case, as discussed above, TPH-d in the shallow groundwater will likely remain above 100 ppb (the commonly accepted odor threshold for water) and thus violate the basin plan's narrative odor objective in a localized volume of groundwater in the immediate vicinity of the truck maintenance building for a significant period of time.

Nonetheless, during this time these localized residual concentrations above 100 ppb TPH-d will not pose a threat to current or future beneficial uses. It is highly unlikely that localized TPH-d concentrations will migrate substantially beyond current limited spatial extent. Although the longer chain hydrocarbons comprising TPH-d biodegrade slowly, they are also less volatile, less soluble, highly absorbent, and much less mobile. It is also highly unlikely that this particular limited volume of shallow groundwater will be used directly as a source of drinking water. Thus, the significant period of time that it will take for water quality in this limited area to meet all Basin Plan objectives is a reasonable time frame. Closure of the site, given the facts in this particular case, is appropriate.

1. There is no evidence of MTBE or benzene at this site. The only detectable concentrations of toluene, ethylbenzene, and xylene reported were many times less than their respective MCLs.

2. The site has been adequately investigated to determine that residual concentrations of low solubility, immobile, non-volatile petroleum hydrocarbons (measured as TPH-d) which still exceed water quality objectives in shallow groundwater are not related to the three former USTs located south and east of the truck maintenance building, but rather appear to originate on the northside of the truck maintenance building in an area substantially up-gradient of the former tanks.

3. Shallow groundwater is recharged locally by a septic system leachfield, surface water infiltration from the truck maintenance area, and a storm drain.

4. Residual TPH-d in shallow groundwater consists of detectable but immobile concentrations which strongly adsorb to soil and which diminish from a maximum 8,400 ppb in the apparent localized source area north of the maintenance building to 200 ppb (i.e., two-times the commonly-accepted 100 ppb drinking water odor threshold) in MW-5 within about 100 feet down-gradient of the maximum reported concentrations (MW-13) and 170-180 feet up-gradient of the nearest water supply well.

5. The nearest well is an onsite private well for non-potable use (drinking water at the site is provided by bottled water) about 170-180 feet down-gradient of the nearest "hit" of TPH-d above detection limits in shallow groundwater. The active water supply well has a surface sanitary seal to 20 feet bgs and is screened only from 75-85 feet bgs in a confined groundwater zone, such that shallow groundwater is effectively precluded from the deeper groundwater production zone.

6. Residual, detectable concentrations of petroleum hydrocarbons measured as TPH-d 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.

7. Since conditions pose a low risk to human health, safety, and the environment, additional soil and water investigation at petitioner's site is not necessary.

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

9. Given the cost of achieving further reductions in levels of TPH-d at this site, the adverse technical and economic implications statewide if further corrective action was required, 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.

10. Detectable TPH-d in shallow groundwater in immediate contact with the limited, weathered residual TPH-d adsorbed to soil particles will likely remain above 100 ppb (the commonly accepted odor threshold for drinking water) and thus violate the basin plan's narrative odor objective in a very localized, small volume of surrounding groundwater for anywhere from decades to hundreds of years.

11. The determination as to what constitutes a reasonable period must be based on evaluation of all relevant factors, including but not limited to the extent and gravity of any threat to public health and the environment during the period require to meet Basin Plan objectives. Although the time required to attain objectives in this case is lengthy, it is a reasonable period considering the facts of this particular case, including that it is highly unlikely that TPH-d detected in localized areas up-gradient of the former USTdischarge will migrate substantially beyond the current limited spatial extent, and it is highly unlikely that this particular limited volume of shallow groundwater will be used directly as a source of drinking water.

12. Therefore, no further corrective action is necessary.

13. The above conclusions are based on the site-specific information relative to this particular case.

IT IS THEREFORE ORDERED that petitioner's case be closed, and no further action related to the release be required. The UST Cleanup Fund Manager is directed to issue petitioner a closure letter consistent with Health and Safety Code section 25299.37, subdivision (h).

The undersigned, Administrative Assistant to the Board, does hereby certify that the foregoing is a full, true, and correct copy of a resolution duly and regularly adopted at a meeting of the State Water Resources Control Board held on November 19, 1998.

AYE:

NO:

ABSENT:

ABSTAIN:

______________________________

Maureen Marché

Administrative Assistant to the Board

Footnote1

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 Health and Safety Code section 25297.1, subdivision (d) and SWRCB Resolution No. 88-23.

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 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.