United States Court of Appeals, District of Columbia Circuit
February 20, 2018
Petitions for Review of Final Agency Action of the United
States Environmental Protection Agency
Catherine E. Stetson argued the cause for petitioner. With
her on the briefs were Douglas E. Cloud, C. Max Zygmont,
Jennifer A. Simon, and Scott H. Reisch.
Cirino, Trial Attorney, U.S. Department of Justice, argued
the cause for respondent. With him on the brief was Jeffrey
H. Wood, Acting Assistant Attorney General.
Before: Henderson, Circuit Judge, and Edwards and Ginsburg,
Senior Circuit Judges.
Edwards, Senior Circuit Judge
to the Comprehensive Environmental Response, Compensation,
and Liability Act of 1980 ("CERCLA"), 42 U.S.C.
§ 9601 et seq., Environmental Protection Agency
("EPA") maintains a National Priorities List
("NPL") of hazardous waste sites that are high
priorities for remedial action due to their "relative
risk or danger to public health or welfare or the
environment." Id. § 9605(a)(8)(A). The
primary method EPA uses to determine which sites to add to
the NPL is the Hazard Ranking System ("HRS"),
see 40 C.F.R. Pt. 300, App. A, § 1.0, a
comprehensive scientific methodology that quantifies
site-specific risk-based criteria. In 2015, EPA conducted an
HRS analysis of the West Vermont Drinking Water Contamination
Site ("Site"), a site of ground water contamination
beneath Indianapolis, Indiana. Because the final HRS score
exceeded the threshold required for listing a site, EPA added
the Site to the NPL by regulation in 2016. National
Priorities List, 81 Fed. Reg. 62, 397 (Sept. 9, 2016). This
case presents petitions for review of that final rule.
Site includes a contaminated ground water plume located
beneath a commercial and residential area. EPA believes that
the Site's contamination emanates from polluted soil
sources at two facilities: the Genuine Parts Company
("Genuine Parts") facility, an area associated with
auto parts degreasing operations and waste burial activities,
and Aimco Michigan Meadows Holdings, LLC
("Aimco")'s Michigan Plaza facility, a former
shopping center where discharges of solvents from a dry
cleaning business entered a leaky sewer line. In scoring the
Site, EPA assessed the Site's aquifers - bodies of
permeable rock, sediment, or soil that can contain or
transmit ground water. EPA determined that a porous upper
aquifer, consisting of sand and gravel, rested directly on
top of a limestone bedrock aquifer within two miles of the
Site. Because the two aquifers were considered to be
interconnected such that contamination could migrate from one
aquifer to the other, EPA treated both aquifers as a single
hydrologic unit. Had EPA treated the aquifers separately, the
final HRS score would not have qualified the Site for
studies that EPA relied on to support its conclusion that the
aquifers interconnect included three different diagrams, as
explained below. The problem is that the diagrams appear to
contradict the agency's position. The cross sections on
the diagrams show independent layers of sediment dividing the
upper and lower aquifers throughout the relevant area.
Petitioners pointed this out to EPA in their comments on the
proposed rule. EPA, however, never addressed the cross
sections in the rule making record. Because EPA
"entirely failed to consider an important aspect of the
problem" by failing to address evidence that runs
counter to the agency's decision, we hold that the
listing of the Site is arbitrary and capricious. Motor
Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins.
Co., 463 U.S. 29, 43 (1983).
be able to offer convincing scientific evidence to support a
conclusion that the aquifers are hydraulically
interconnected. That evidence has yet to be shown, however.
Regarding the action before us, we are constrained to grant
the petitions for review because EPA has failed to offer
substantial evidence to support its finding of an
interconnection, it has ignored evidence undercutting its
conclusion, and it has failed to state a reasoned basis for
overcoming the regulatory presumption of non-interconnection.
See 40 C.F.R. Pt. 300, App. A, § 188.8.131.52.1.
also claim that the rule should be vacated because EPA failed
to take into account the direction of ground water flow
beneath the Site when calculating the target population
potentially subject to contamination. We reject this claim.
EPA relied on established HRS instructions and reasonably
took into account the distance between the sources of
contamination and drinking water wells in computing the
Site's "targets" score. We have no grounds to
second guess EPA's decision on this point.
Statutory and Regulatory Background
CERCLA, EPA is authorized to establish and revise annually a
National Priorities List of known hazardous waste sites
considered high priorities for environmental remediation.
See 42 U.S.C. § 9605(a)(8)(A). Sites listed on
the NPL are eligible for CERCLA-funded remedial action
through EPA's "Superfund program." CTS
Corp. v. EPA, 759 F.3d 52, 56 (D.C. Cir. 2014). While
placement on the NPL does not automatically render any party
liable for cleanup costs, it "can have significant
adverse consequences for the owner of a listed property"
by, for example, damaging the business's reputation or
property values. Carus Chem. Co. v. EPA, 395 F.3d
434, 437 (D.C. Cir. 2005); see also U.S. Magnesium, LLC
v. EPA, 630 F.3d 188, 190 (D.C. Cir. 2011).
the statute, listing criteria are based "upon relative
risk or danger to public health or welfare or the
environment" of actual or threatened releases of
hazardous substances. 42 U.S.C. § 9605(a)(8)(A).
Pursuant to this mandate, EPA promulgated the Hazard Ranking
System, 40 C.F.R. Pt. 300, App. A, "a comprehensive
methodology and mathematical model the agency uses to . . .
quantify the environmental risks a site poses."
Carus Chem., 395 F.3d at 437. EPA is required by the
statute to "assure, to the maximum extent feasible, that
the hazard ranking system accurately assesses the relative
degree of risk to human health and the environment posed by
sites and facilities subject to review." 42 U.S.C.
measures the risk posed by migration of hazardous substances
through four possible pathways: air, soil, surface water,
and, relevant here, ground water. See 40 C.F.R. Pt.
300, App. A, § 2.1. Each potentially affected pathway
receives a numerical score based on the "[l]ikelihood of
release, waste characteristics, and targets" of the
contamination associated with that pathway. Id.
§ 2.1.2. EPA must then "plug the resulting
individual pathway scores into a formula to obtain the site
score, " US Magnesium, 630 F.3d at 189-90,
which ranges from 0 to 100, 40 C.F.R. Pt. 300, App. A, §
2.1.1. Sites with scores at or above 28.50 are eligible for
inclusion on the NPL. National Priorities List, 77 Fed. Reg.
15, 276, 15, 278 (Mar. 15, 2012).
analyzing ground water migration pathways, EPA computes an
individual pathway score for each aquifer located within a
four-mile radius of a site's sources. See 40
C.F.R. Pt. 300, App. A, §§ 3.0, 184.108.40.206. EPA must
"[a]ssign the highest . . . score that results for any
aquifer as the ground water migration pathway score for the
site." Id. § 3.0. However, if two or more
aquifers are interconnected "within 2 miles of the
sources at the site, " EPA must "combine the
aquifers having interconnections in scoring the site."
Id. § 220.127.116.11.1. EPA may not assume
interconnection within the two-mile radius. "If data are
not adequate to establish aquifer interconnections, "
the HRS instructs EPA to "evaluate the aquifers as
separate aquifers." Id.
considers aquifers to be interconnected if their boundaries
do not "impede the flow of ground water and hazardous
substances between the aquifers." Hazard Ranking System
Guidance Manual, EPA, at 116 (Nov. 1992), available
at Joint Appendix ("J.A.") 434, 444,
"HRS Guidance"). Aquifers are not
interconnected if they are separated by a "confining
layer" of materials that serves as an aquifer boundary
that water cannot easily move through. Id. A
"confining layer" serves as such a boundary if it
has lower "hydraulic conductivity" - a measure of
the permeability of a geologic material - than adjacent
geologic materials by "at least two orders of