Court Opinion

ID: 9403590
Source: CourtListenerOpinion
Date Created: 2023-06-21 15:03:08.808401+00
Date Added: 2024-06-11T17:20:08.250097
License: Public Domain

Case: 22-1581   Document: 59     Page: 1   Filed: 05/31/2023

   United States Court of Appeals
       for the Federal Circuit
                 ______________________

        CITY OF WILMINGTON, DELAWARE,
                 Plaintiff-Appellant

                            v.

                   UNITED STATES,
                   Defendant-Appellee
                 ______________________

                       2022-1581
                 ______________________

     Appeal from the United States Court of Federal Claims
 in No. 1:16-cv-01691-MHS, Judge Matthew H. Solomson.
                  ______________________

                 Decided: May 31, 2023
                 ______________________

     PAUL THOMAS NYFFELER, Hunton Andrews Kurth,
 Richmond, VA, argued for plaintiff-appellant.

     P. DAVIS OLIVER, Commercial Litigation Branch, Civil
 Division, United States Department of Justice, Washing-
 ton, DC, argued for defendant-appellee. Also represented
 by BRIAN M. BOYNTON, PATRICIA M. MCCARTHY, FRANKLIN
 E. WHITE, JR.

     AMANDA WATERS, McGuireWoods LLP, McLean, VA,
 for amicus curiae National Association of Clean Water
 Agencies.
                 ______________________
Case: 22-1581    Document: 59      Page: 2    Filed: 05/31/2023

 2                       CITY OF WILMINGTON, DELAWARE    v. US

     Before PROST, WALLACH, and CHEN, Circuit Judges.
 PROST, Circuit Judge.
     This case arises under the Clean Water Act (“CWA”)
 and concerns the requirement that federal entities comply
 with local efforts to abate water pollution. The city of Wil-
 mington, Delaware (“Wilmington”), appeals a decision by
 the U.S. Court of Federal Claims holding that certain fees
 Wilmington assessed against the United States for storm-
 water management are not reasonable service charges un-
 der 33 U.S.C. § 1323. Wilmington appeals. We affirm.
                         BACKGROUND
     As part of its efforts to manage local water pollution,
 Wilmington charges its residential and non-residential
 property owners a stormwater management fee. The U.S.
 Army Corps of Engineers (“USACE”), which owns five
 properties in Wilmington, disputes whether the CWA, 33
 U.S.C. § 1323, waives the USACE’s sovereign immunity
 with respect to this fee.
                               I
     The Court of Federal Claims provides a thorough reci-
 tation of the statutory history of the CWA. City of Wilming-
 ton v. United States, 157 Fed. Cl. 705, 710–11 (2022)
 (“Decision”). Briefly, in 1948, Congress passed the prede-
 cessor to the CWA, the Federal Water Pollution Control Act
 (“FWPCA”), to reduce water pollution. Pub. L. No. 80-845,
 62 Stat. 1155 (1948). After a series of other amendments,
 Congress in 1972 revised the FWCPA (the “1972 amend-
 ments”) and enacted the modern version of the CWA. Fed-
 eral Water Pollution Control Act Amendments of 1972,
 Pub. L. No. 92-500, 86 Stat. 816. The 1972 amendments
 attempted to limit pollutants in state waters and required
 states to establish “total maximum daily loads” (“TMDLs”)
 setting forth the maximum amount of a pollutant
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 CITY OF WILMINGTON, DELAWARE    v. US                         3

 permitted to enter waterbodies the state had identified as
 impaired. 86 Stat. at 848.
     As part of the 1972 amendments, Congress first en-
 acted the provision of the CWA at issue: 33 U.S.C. § 1323
 (the “Federal Facilities Section”). The Federal Facilities
 Section requires federal facilities to comply with federal,
 state, interstate, and local requirements related to the
 abatement of water pollution. 1
     Section 1323 currently provides in relevant part:
     (a) Compliance with pollution control requirements
     by Federal entities
     Each department, agency, or instrumentality of the
     executive, legislative, and judicial branches of the
     Federal Government (1) having jurisdiction over
     any property or facility, or (2) engaged in any activ-
     ity resulting, or which may result, in the discharge
     or runoff of pollutants, . . . shall be subject to, and
     comply with, all Federal, State, interstate, and lo-
     cal requirements, administrative authority, and
     process and sanctions respecting the control and
     abatement of water pollution in the same manner,
     and to the same extent as any nongovernmental
     entity including the payment of reasonable service
     charges. The preceding sentence shall apply (A) to
     any requirement whether substantive or proce-
     dural . . ., (B) to the exercise of any Federal, State,
     or local administrative authority, and (C) to any
     process and sanction. . . . This subsection shall

     1   Congress expanded the Federal Facilities Section
 in 1977 to clarify that federal facilities must also comply
 with local permitting requirements. Clean Water Act of
 1977, Pub. L. No. 95-217, 91 Stat. 1566. The 1977 amend-
 ment in large part solidified the current language of § 1323.
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 4                       CITY OF WILMINGTON, DELAWARE   v. US

     apply notwithstanding any immunity of such agen-
     cies . . . under any law or rule of law.
 33 U.S.C. § 1323(a) (emphasis added).
    In 2011, Congress amended the CWA (the “2011
 amendments”) to define the term “reasonable service
 charges” as used in subsection 1323(a), as follows:
     For the purposes of this chapter, reasonable service
     charges described in subsection (a) include any rea-
     sonable nondiscriminatory fee, charge, or assess-
     ment that is—
     (A) based on some fair approximation of the propor-
     tionate contribution of the property or facility to
     stormwater pollution (in terms of quantities of pol-
     lutants, or volume or rate of stormwater discharge
     or runoff from the property or facility); and
     (B) used to pay or reimburse the costs associated
     with any stormwater management program . . . .
 Id. § 1323(c) (emphasis added); see also Federal Responsi-
 bility to Pay for Stormwater Programs Act of 2011, Pub. L.
 No. 111-378, 124 Stat. 4128.
                              II
     Wilmington must comply with federal water pollution
 requirements and the TMDLs established for the Christina
 River Basin and other local waters. J.A. 993–94. As a
 source of pollution, stormwater discharge is subject to
 TMDLs. In January 2007, Wilmington implemented a
 stormwater management program “to enhance surface wa-
 ter quality by reducing the quantity and rate of stormwater
 runoff and the amount of pollutants discharged into the
 rivers.” J.A. 220. In support of this program, Wilmington
 charges all owners of property within its corporate bound-
 aries—both residential and non-residential—a monthly
 stormwater management fee based on an estimation of
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 CITY OF WILMINGTON, DELAWARE    v. US                       5

 each property’s contribution to stormwater runoff. 2
 WILMINGTON, DE CODE § 45-53 (“Wilmington Code”).
      Because no city can precisely measure the actual
 amount of stormwater pollution from each property, the
 city devised a methodology for approximating the runoff at-
 tributable to each property based on recommendations
 from the engineering firm Black & Veatch. For non-resi-
 dential properties, the city assesses each parcel’s monthly
 stormwater fee based on a formula comprised of four vari-
 ables. 3
     The first variable in the city’s formula is the total area
 of the property (“gross parcel area”), as measured by the
 New Castle County (“County”) Department of Land Use
 tax assessment records. Wilmington Code § 45-53(a). The
 second variable is a “runoff coefficient,” which is a multi-
 plier based on estimates of a property’s imperviousness.
 Wilmington determined that imperviousness is a useful
 method for approximating a property’s contribution to run-
 off because more rain runs off highly impervious proper-
 ties, such as buildings or paved surfaces, than less
 impervious areas like a marsh or open field. See J.A. 134
 at 129:1–8; J.A. 175 at 293:6–8. Accordingly, the runoff

     2    Wilmington previously charged property owners on
 a quarterly basis before adopting a monthly billing cycle.
 See Decision, 157 Fed. Cl. at 715 n.8.
      3   Due to the greater availability and precision of data
 for residential properties, the city uses the actual square
 footage of the main, attached, and detached structures
 from County records and calculates “the impervious area
 as the sum of the square footage” of those structures. J.A.
 228; see also J.A. 132 at 122:2–23. The city’s methodology
 for calculating stormwater fees for residential properties is
 not at issue.
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 6                        CITY OF WILMINGTON, DELAWARE      v. US

 coefficient ranges from 0 to 1, with a higher coefficient in-
 dicating greater imperviousness. See J.A. 227.
     To determine a property’s runoff coefficient, Wilming-
 ton starts with County tax records. The tax records assign
 each parcel a land use code based on the occupancy permit
 issued to the parcel (referred to as either a “land use code”
 or “occupancy code”). J.A. 464. The County “has defined
 over 200 land use [codes] to designate the specific type of
 land use for a parcel,” to include, for example, “hotels,” “sin-
 gle-family,” or “vacant” properties. J.A. 226. Wilmington
 uses these land use codes to assign each property to one of
 11 “stormwater classes.” J.A. 227; see J.A. 238–43 (tabu-
 lating each code and its associated stormwater class).
     Once the various properties were categorized into a
 particular stormwater class, each stormwater class needed
 a runoff coefficient such that every property in each class
 would be assigned the same coefficient. The engineering
 firm Black & Veatch developed Wilmington’s runoff coeffi-
 cients using a 1962 study authored by Dr. Ven Te Chow
 (the “1962 Study”), which specified a range of potential
 runoff coefficients for various “types of land use” described
 by a few words, e.g., “Parks, Cemeteries,” “Playgrounds,”
 “Railroad Yard Areas,” and “Unimproved Areas.” J.A. 228
 (Table 2). These types of land use were then roughly
 matched with Wilmington’s stormwater classes, and the
 higher end of the runoff coefficient range for each type of
 land use from the 1962 Study was assigned to each storm-
 water class. J.A. 82 at 322:3–7. For instance, it appears
 that the stormwater class “Parks & Cemeteries” was
 matched with the type of land use “Parks, Cemeteries” hav-
 ing a runoff coefficient range of 0.10–0.25. Thus, the storm-
 water class “Parks & Cemeteries” was assigned a runoff
 coefficient of 0.25. J.A. 229 (Table 3). Similarly, the storm-
 water class “Recreational Playgrounds / Arenas” was ap-
 parently matched with “Playgrounds” and assigned a
 coefficient of 0.35. Id. Relevant here, the stormwater class
 “Vacant Land” was apparently matched with “Unimproved
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 CITY OF WILMINGTON, DELAWARE    v. US                       7

 Areas” from the 1962 Study and assigned a runoff coeffi-
 cient of 0.30. Id.
     The third variable—impervious area—is calculated by
 multiplying the property’s total area by the property’s as-
 signed runoff coefficient. Wilmington Code § 45-53(a). The
 impervious area variable attempts to measure “the total
 square feet of hard surface areas” on the property. Id.; see
 also J.A. 227 (impervious area measures how impervious a
 property is to the permeability of rainfall). Fourth, Wil-
 mington standardizes properties (i.e., provides a “common
 denominator”) by using an “equivalency stormwater unit”
 (“ESU”) of 789 square feet, derived from the size of the me-
 dian single-family home in Wilmington. Wilmington Code
 § 45-53(a). Wilmington normalizes the impervious area of
 properties by dividing the impervious area by the ESU. Id.
 § 45-53(d)(8); J.A. 229. This calculation results in the num-
 ber of ESUs, or the “ESU factor,” for the property. Wil-
 mington Code § 45-53(a).
     Wilmington then calculates the monthly charge to a
 property owner by multiplying the ESU factor by the city’s
 charge rate to yield the total monthly charge for the prop-
 erty. Id.; see also id. § 45-53(d), (d)(9).
      For Wilmington property owners who dispute the city’s
 stormwater charges, the city provides an administrative
 appeal process that permits property owners to appeal:
 “(1) the calculation of the storm water charge; (2) the as-
 signed storm water class; (3) the assigned tier, if applica-
 ble; and (4) the eligibility for a credit.” Id. § 45-53(d)(7).
 Property owners must pay all outstanding fees in order to
 appeal, and a successful appeal resolves only future
 charges; it is not retroactive. Wilmington assesses interest
 on unpaid charges. Id. § 45-176.
                              III
     The USACE owns five properties in Wilmington (the
 “Properties”) spanning 270 acres and nearly 11,888,000
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 8                       CITY OF WILMINGTON, DELAWARE    v. US

 square feet. The Properties serve as a dredge material dis-
 posal site in support of the USACE’s work dredging water-
 ways near Wilmington. While stormwater runs off the
 Properties into the nearby river, none of the Properties dis-
 charges water directly into the city’s stormwater system.
 Decision, 157 Fed. Cl. at 714; J.A. 163 at 247:3–8. Only one
 parcel contains paved surface area. See J.A. 2029–30.
      The city assigned the Properties to the “Vacant” storm-
 water class. J.A. 2048 ¶ 123. The Vacant class has an as-
 signed runoff coefficient of 0.30, meaning that
 approximately 30 percent of all stormwater will run off a
 given parcel. J.A. 133 at 126:15–127:8. Based on the 0.30
 runoff coefficient and Wilmington’s methodology for calcu-
 lating fees, the city assessed the USACE $2,577,686.82 in
 fees for the Properties between January 4, 2011, and April
 16, 2021. The USACE has never paid Wilmington the as-
 sessed service charges, nor has the USACE pursued the
 city’s appeal process.
     In December 2016, Wilmington sued the United States
 in the Court of Federal Claims under the CWA, 33 U.S.C.
 § 1323, seeking to recover the unpaid stormwater manage-
 ment fees. Wilmington seeks $2,577,686.82 in fees and
 $3,360,441.32 in accrued interest. The parties cross-moved
 for partial judgment on the pleadings under Rule 12(c) of
 the Rules of the Court of Federal Claims (“RCFC”); the
 court denied both motions in 2018. City of Wilmington v.
 United States, 136 Fed. Cl. 628 (2018) (“Wilmington I”).
 The case proceeded to trial in April 2021. Wilmington pre-
 sented evidence from two witnesses: the city’s Commis-
 sioner of Public Works and an expert witness. Following
 the close of Wilmington’s case-in-chief, the court suspended
 trial, and the government moved for judgment on partial
 findings under RCFC 52(c).
     The trial court granted the government’s motion, hold-
 ing that the Federal Facilities Section waives the United
 States’ sovereign immunity only for “reasonable service
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 CITY OF WILMINGTON, DELAWARE      v. US                     9

 charges” and that Wilmington failed to meet that standard
 by failing to prove its charges are a fair approximation of
 the Properties’ proportionate contribution to stormwater
 pollution. Decision, 157 Fed. Cl. at 720.
    Wilmington appeals. We have jurisdiction under 28
 U.S.C. § 1295(a)(3). 4
                         DISCUSSION
      We review the legal conclusions of the Court of Federal
 Claims de novo and its factual findings for clear error.
 Martin v. United States, 54 F.4th 1325, 1327 (Fed. Cir.
 2022). To disturb the trial court’s factfindings, we must be
 “left with the definite and firm conviction that a mistake
 has been committed.” Gadsden Indus. Park, LLC v. United
 States, 956 F.3d 1362, 1368 (Fed. Cir. 2020).
     Wilmington challenges the trial court’s determination
 that Congress did not waive the United States’ sovereign
 immunity with respect to the stormwater fees Wilmington
 assessed against the Properties because those fees did not
 satisfy the definition of “reasonable service charges” under
 the Federal Facilities Section. We interpret the Federal
 Facilities Section before turning to Wilmington’s argu-
 ments.
                               I
     The Federal Facilities Section requires federal entities
 such as the USACE to comply with local water pollution
 requirements, including payment of “reasonable service
 charges,” and waives the United States’ sovereign immun-
 ity with respect to those requirements. 33 U.S.C. § 1323.
 The text of the section is broad, subjecting agencies to “all”

     4   The Court of Federal Claims had jurisdiction under
 28 U.S.C. § 1491(a)(1) and 33 U.S.C. § 1323. There is no
 dispute that § 1323 is a money-mandating statute.
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 10                      CITY OF WILMINGTON, DELAWARE   v. US

 requirements “notwithstanding any immunity . . . under
 any law or rule of law.” Id. § 1323(a).
     Congress emphasized its intent for federal entities to
 contribute their proportionate share of costs by providing
 an equally broad definition of “reasonable service charges”
 in the 2011 amendments. A charge is a “reasonable service
 charge” when it is “based on some fair approximation of the
 proportionate contribution of the property or facility to
 stormwater pollution (in terms of quantities of pollutants,
 or volume or rate of stormwater discharge or runoff from
 the property or facility).” Id. § 1323(c) (emphasis added).
 The 2011 definition thus establishes a low standard: for a
 service charge to be “reasonable,” it need only represent
 “some fair approximation” of a property’s proportionate
 contribution to stormwater pollution.
     Where possible, we interpret statutes to give meaning
 to every word in a provision. Doyon v. United States, 58
 F.4th 1235, 1247 (Fed. Cir. 2023) (“[A] statute ought, upon
 the whole, to be so construed that, if it can be prevented,
 no clause, sentence, or word shall be superfluous, void, or
 insignificant.” (citation and internal quotation marks omit-
 ted)). Here, the word “some” does meaningful work. The
 Merriam-Webster Dictionary defines “some” as “being of an
 unspecified amount or number.” Merriam-Webster Online
 Dictionary,      https://www.merriam-webster.com/diction-
 ary/some (last visited April 25, 2023). Accordingly, as used
 in the Federal Facilities Section, “some fair approximation”
 refers to any one of an unspecified number of possible fair
 approximations, and the approximation used by a state or
 local entity need not be the most accurate 5 or most fair

      5  We note that the trial court expressed concern in
 several instances that Wilmington’s chosen coefficient
 might not be “accurate” as to the amount of stormwater
 pollution attributable to the Properties. The text of § 1323
 makes no mention of the accuracy of a local jurisdiction’s
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 CITY OF WILMINGTON, DELAWARE    v. US                      11

 approximation. The standard is thus an objective standard
 based on what a reasonable person would consider a fair
 approximation.
      In light of the leniency of this standard, we agree with
 the trial court’s observation in this case that there is noth-
 ing inherently wrong with Wilmington’s general methodol-
 ogy for determining a property owner’s stormwater
 management fee. See Decision, 157 Fed. Cl. at 720 (“[T]he
 [c]ourt takes no issue with Wilmington’s general ap-
 proach—i.e., the use of property categories and runoff coef-
 ficients.”). Indeed, trial testimony demonstrates that
 Wilmington, through its consultant Black & Veatch, took
 some care in designing its system. Wilmington’s expert
 testified that at least three-quarters of municipalities base
 their stormwater utility rate methodologies on impervious
 area. J.A. 177 at 303:10–16. The city’s expert further tes-
 tified that Wilmington’s “process is solid,” reflecting qual-
 ity work from Black & Veatch. J.A. 179 at 312:18–22. The
 expert averred that county land use records are generally
 “good sources” for determining property characteristics.
 J.A. 180 at 314:1–2.
     Despite the general reasonableness of Wilmington’s ap-
 proach, however, trial testimony supports the court’s find-
 ing here that Wilmington’s approach, as applied to the
 Properties, does not meet the statutory definition of

 fee structure and requires only a “fair approximation.”
 While the degree of accuracy might be a factor in determin-
 ing the fairness of an approximation, it is not the only fac-
 tor to be considered. We therefore disagree with the trial
 court’s references to accuracy. Nevertheless, we do not
 find, as Wilmington suggests, that the trial court improp-
 erly imposed a standard of accuracy on Wilmington’s data
 beyond what § 1323 requires. The trial court’s comments
 amount to dicta, and the court ultimately reached the cor-
 rect conclusion. Decision, 157 Fed. Cl. at 723–24.
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 12                       CITY OF WILMINGTON, DELAWARE     v. US

 “reasonable service charges.” We find no clear error in the
 court’s factfindings.
      First, the city failed to show that the County tax as-
 sessment records “properly categorize the Properties for
 stormwater purposes.” Decision, 157 Fed. Cl. at 720. On
 appeal, Wilmington argues that “[n]o trial evidence demon-
 strated the County’s property records’ ‘vacant’ classifica-
 tion of the Properties misrepresented their actual
 conditions.” Appellant’s Br. 37. That may be the case.
 Nevertheless, while the Vacant classification may accu-
 rately describe the Properties in a general sense and spe-
 cifically for the purpose of the County’s tax assessments, it
 is not a label designed to classify the Properties for the pur-
 pose of stormwater management. As the trial court found,
 “Wilmington’s system merely assumes that the County’s
 tax records reflect land categories whose definitions mirror
 those described in Dr. Chow’s 1962 Study,” and Wilming-
 ton’s expert “made no independent attempt to substanti-
 ate” that assumption or to “provide[] evidence to fill that
 gap in the record.” Decision, 157 Fed. Cl. at 720–21.
      The city’s expert explained that Black & Veatch
 “looked at those land use records in the County records and
 made an engineering judgment” to match those records to
 the ranges Dr. Chow identifies. J.A. 182–83 at 324:22–
 325:3. What’s missing from the record is how. The lack of
 explanation is troublesome given that the County uses 220
 different land use codes, and the record does not meaning-
 fully describe how those codes are divided into 11 non-res-
 idential stormwater classes. J.A. 175 at 296:10–12. While
 the County records could be a fair and representative data
 source for classification of the Properties, Wilmington does
 not explain here how those records correlate to Dr. Chow’s
 1962 Study. As trial testimony reflects, when asked how
 Wilmington knows that when the 1962 Study “uses the
 range of .10 to .30, that that’s what the tax records are talk-
 ing about in terms of the character of the land,” Wilming-
 ton’s expert testified: “I don’t know that. . . . I would
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 CITY OF WILMINGTON, DELAWARE     v. US                       13

 assume that Black & Veatch, in allocating those classes –
 land classes, those occupancy codes, had some basis for do-
 ing so. But I don’t personally know that.” J.A. 194 at
 373:13–22.
     In light of the evidence before it, the trial court reason-
 ably found that Wilmington has not met its burden to show
 by a preponderance of the evidence that the County rec-
 ords’ description of the properties, which is crucial to the
 assignment of a stormwater class and runoff coefficient,
 fairly classifies the Properties for stormwater purposes.
      Second, the trial court did not clearly err in finding that
 the city failed to show the runoff coefficient of 0.30 (i.e.,
 30% impervious) applicable to the Vacant stormwater class
 provides a fair approximation of the Properties’ rate of run-
 off. See J.A. 227. A runoff coefficient may, in general
 terms, fairly describe the runoff conditions of most proper-
 ties in a particular stormwater class. Indeed, the Wilming-
 ton Code intends for properties grouped in the same
 stormwater class to have similar characteristics. See Wil-
 mington Code § 45-53(a) (“Storm water class means classes
 of uses defined such that customers within a class have
 similar land use characteristics.” (emphasis added)). But
 in this case, the trial court correctly recognized the poten-
 tial risk of unfair charges to the federal government be-
 cause “if there is wide variation in the actual
 characteristics of properties within a particular occupancy
 code, that could well mean the government is being over-
 charged vis-à-vis other properties assigned the same code.”
 Decision, 157 Fed. Cl. at 721.
     As the USACE argues, “Wilmington is assuming that
 the Properties contribute volumes of runoff similar to all
 other properties within [the Vacant] class and that 30 per-
 cent of all stormwater runs off the Properties,” without
 proving “that the [variation of the] actual characteristics of
 properties within a particular tax-record category is rela-
 tively small.” Appellee’s Br. 23 (citing Decision, 157 Fed.
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 14                        CITY OF WILMINGTON, DELAWARE      v. US

 Cl. at 721). We agree. Wilmington has not shown “the de-
 gree of similarity within an occupancy code” or shown that
 the code matches the reality of the Properties’ physical
 characteristics. Id. at 24. Further, Wilmington admits
 that it established its appeals process specifically to ad-
 dress instances in which its stormwater fee methodology
 subjects property owners to unfair fees, where due to “site
 specific variances,” “in some situations, the resulting meas-
 ure of imperviousness may differ from the actual impervi-
 ousness that exists in a specific property.” J.A. 229.
      The witness testimony is particularly damaging in this
 respect. There are 1,724 parcels in the Vacant stormwater
 class, all of which Wilmington assigned the same runoff co-
 efficient. J.A. 135 at 135:9–12. The Commissioner agreed
 in her testimony that “the volume of runoff from a property
 is impacted by various property characteristics,” like “their
 level of imperviousness, the soil, [and] the land covers,” and
 that “a property should be put into a class with other prop-
 erties that are similar to it, in terms of the characteristics.”
 J.A. 133 at 127:13–17; J.A. 142 at 161:18–21. Yet, when
 asked whether Wilmington knows “if the dredge disposal
 sites have similar characteristics to other properties in the
 vacant stormwater class,” the Commissioner testified only
 that “it’s vacant. . . . it’s similar in that there’s no structure
 on it.” J.A. 142 at 162:14–19. The mere fact of vacancy
 says nothing about the other physical characteristics of the
 land that would impact stormwater runoff. In fact, the
 Commissioner testified that properties with land covers
 “like marshes or wetlands” could be included in the vacant
 stormwater class to the same extent as properties with
 “wooded areas,” “regular grass,” “loose gravel,” “concrete
 and asphalt,” or “different kinds of soils.” J.A. 142–43 at
 164:16–165:22. In short, the Commissioner agreed that
 “properties with completely different land covers could be
 included in the vacant stormwater class.” J.A. 143 at
 165:16–19.
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 CITY OF WILMINGTON, DELAWARE    v. US                       15

      Wilmington argues that the court “neglected to con-
 sider how size differences allow charges on a class contain-
 ing ‘totally different properties’ to remain proportional to
 runoff while retaining ‘similar land use characteristics.’”
 Appellant’s Br. 20. Wilmington also contends that because
 it “normalizes each Property’s estimated impervious area
 by converting to Runoff Units and assessing charges per
 Runoff Unit, the stormwater charge assessed on a Property
 is proportionate to that Property’s runoff.” Id. at 38.
     We are not convinced. Even if Wilmington were correct
 on both points, the trial testimony reflects both the im-
 portance of impervious area to Wilmington’s methodology
 for non-residential properties and the fact that the Vacant
 stormwater class contains properties with wide disparities
 in imperviousness. See Decision, 157 Fed. Cl. at 724. Nei-
 ther the trial testimony nor Wilmington’s briefing makes
 clear how parcel size or ESU alone can negate the impact
 of the city’s flawed assignment of runoff coefficients. We
 see no clear error in the trial court’s factfinding on this is-
 sue.
      The runoff coefficient is an independent variable in
 Wilmington’s formula that is mathematically essential to
 that formula in order to calculate stormwater fees for the
 Properties. It is also the main representation within the
 formula for the actual stormwater characteristics of the
 Properties. Without any substantiation that the runoff co-
 efficient corresponds, even in a loosely approximate way, to
 the actual stormwater characteristics of the Properties,
 Wilmington has not proven the chosen runoff coefficient as
 applied to the Properties is a “fair approximation.” As a
 result, the trial court did not err in concluding the fees at
 issue were not reasonable service charges under § 1323(a).
     In determining that Wilmington’s fees are not reason-
 able service charges under 33 U.S.C. § 1323, we emphasize
 that our holding is limited to the facts and circumstances
 in this case. There is nothing necessarily problematic
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 16                       CITY OF WILMINGTON, DELAWARE     v. US

 about a stormwater fee methodology that uses a multifac-
 tor formula, or a formula that includes impervious area or
 runoff coefficients as variables. We do not seek to disturb
 other municipalities’ systems that meet the statutory defi-
 nition of “reasonable service charges.” See Nat’l Ass’n of
 Clean Water Agencies’ Amicus Br. 8–10. A city need not
 visit properties in its jurisdiction nor perform a “tape meas-
 ure” analysis to satisfy the “some fair approximation”
 standard in estimating the amount of stormwater runoff
 emitted by a specific federal property.
     Here, however, Wilmington did not explain how the
 Vacant land use code corresponded to the runoff coeffi-
 cients in the 1962 Study nor whether its stormwater class
 fairly captured variability in Vacant parcels, where in this
 instance the Properties are used as dredge material dis-
 posal sites and only one parcel contains any paved surface.
 For these reasons, Wilmington’s methodology, as applied,
 led to charges that are not a fair approximation of the Prop-
 erties’ proportionate contribution to stormwater pollution.
 As a result, the fees Wilmington charged the USACE are
 not “reasonable service charges” as defined by 33 U.S.C.
 § 1323(c), and the CWA does not waive the USACE’s sov-
 ereign immunity with respect to those charges.
                               II
      Wilmington argues that the United States was re-
 quired to exhaust the city’s appeal process. Appellant’s Br.
 62; Wilmington Code § 45-53(d)(7). Specifically, the city
 contends that while the United States “could challenge
 Wilmington’s ‘general methodology’ without appealing,” it
 “could not rely on the Properties’ ‘site-specific’ characteris-
 tics that could have been raised in an appeal.” Appellant’s
 Br. 62.
     The trial court held that the USACE was not required
 to exhaust the city’s appeal process. In denying the parties’
 RCFC 12(c) motions, the court found that the “appeal right
 is permissive,” not mandatory, and declined to “apply the
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 CITY OF WILMINGTON, DELAWARE    v. US                       17

 exhaustion doctrine.” Wilmington I, 136 Fed. Cl. at 632.
 In ruling on partial findings, the court further noted that
 (a) appealing a charge is not a process “respecting the con-
 trol or abatement of water pollution” under § 1323, (b) Wil-
 mington’s appeal process is not a “local requirement,” and
 (c) legislative history also supports rejecting exhaustion.
 Decision, 157 Fed. Cl. at 735. The court rejected Wilming-
 ton’s argument that Delaware state law requires exhaus-
 tion and concluded that Wilmington’s forward-looking
 process cannot provide the USACE’s requested relief. Id.
 at 736.
      We agree, principally because Wilmington’s appeal
 process is permissive rather than mandatory and solely for-
 ward looking. 6 Wilmington does not require that property
 owners pursue its appeal process, and an appeal accord-
 ingly cannot be a local “requirement.” Wilmington I, 136
 Fed. Cl. at 632. Further, because the appeal does not allow
 for the adjustment of fees Wilmington has assessed to date
 apart from the correction of clerical errors, it cannot pro-
 vide the relief the USACE seeks. J.A. 160 at 233:10–12.
 The USACE was not required to exhaust the appeal pro-
 cess. As a result, the trial court did not abuse its discretion
 by refusing to mandate exhaustion.
                               III
    We find the remainder of Wilmington’s arguments un-
 availing.

     6   Notably, Wilmington does not even permit prop-
 erty owners to appeal their stormwater fees unless they
 have paid all outstanding fees, including those not related
 to stormwater management. J.A. 127 at 103:9–15 (explain-
 ing that if a property owner has “anything outstanding,”
 such as “taxes, water fees, sewer fees, [or] parking tickets,”
 the city “won’t consider an application”).
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 18                      CITY OF WILMINGTON, DELAWARE     v. US

     First, we reject the city’s argument that the trial court
 erroneously “assessed issues under the de novo standard of
 review.” Appellant’s Br. 43. The court appropriately con-
 ducted a trial and made factual findings on a clean slate.
 See RCFC 52(a) (“In an action tried on the facts, the court
 must find the facts specially and state its conclusions of law
 separately.”); cf. Int’l Paper Co. v. United States, 36 Fed.
 Cl. 313, 322 (1996) (explaining in tax refund context that
 suit requires “a trial de novo”). In doing so, the court did
 not fail to consider Wilmington’s evidence. Further, the
 court held the city to the correct standard of proof—prepon-
 derance of the evidence—in determining whether the city’s
 charges satisfied 33 U.S.C. § 1323.
     Second, the trial court duly considered Wilmington’s
 evidence. The city argues that the trial court was required
 to consider a 2008 EPA publication that described approv-
 ingly Wilmington’s stormwater management system as
 “fair and equitable” as a “binding factual admission.” Ap-
 pellant’s Br. 46; see J.A 1078. The trial court correctly
 found that the 2008 publication predates the 2011 amend-
 ments’ definition of “reasonable service charges” and, in
 any event, does not satisfy the city’s burden.
     Third, we do not reach Wilmington’s argument that the
 United States is required to pay interest on its unpaid
 stormwater management fees. Although the trial court de-
 termined that Wilmington’s assessed fees are not “reason-
 able service charges,” it proceeded to conclude that the
 CWA does not waive the USACE’s sovereign immunity
 with respect to interest because the Federal Facilities Sec-
 tion does not provide an express waiver of sovereign im-
 munity.     Decision, 157 Fed. Cl. at 738.            Because
 Wilmington’s fees are not reasonable service charges, how-
 ever, any discussion of interest for fees that are not owed is
 advisory. We decline to reach this issue.
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 CITY OF WILMINGTON, DELAWARE   v. US                   19

                       CONCLUSION
     Because Wilmington’s stormwater management fees
 are not “reasonable service charges” under 33 U.S.C.
 § 1323, the CWA does not waive the USACE’s sovereign
 immunity. Accordingly, we affirm the decision of the Court
 of Federal Claims.
                       AFFIRMED