The Town of Kittery (Town) appeals from a judgment of the Superior Court (York County, Fritzsche, J.) reversing the decision of the Town Zoning Board of Appeals (Board) denying the application of Walter and Rosemary Perrin for a wetland setback variance for the purpose of constructing a residence on their Lot 7B. The Perrins cross-appeal contending that the court erred in determining that the Perrins’ application to the Code Enforcement Officer (CEO) for a building permit on Lot 7B was not a part of a pending proceeding within the purview of 1 M.R.S.A. § 302 (1989) and contending that the Town was collaterally estopped to argue that a wetland existed on Lot 7B. Because we agree with the Town’s contention that the court erred in reversing the Board’s determination that the Perrins failed to meet their burden of proof for the granting of a variance and find no merit in the Perrins’ cross-appeal, we vacate the judgment as to Count II and affirm the judgment as to Counts I and III of the Perrins’ complaint.
I.
In 1980 the Perrins purchased Lot 7, a two-acre lot located in Bartlett Farms, an approved subdivision in the Town’s Rural Residence Zone, and thereafter constructed a residence on a portion of the lot. In September 1987 the Planning Board approved the Perrins’ application to divide Lot 7 into two one-acre lots.1 The portion of the lot designated as 7A was the site on which the Perrins had constructed their residence, and the portion designated as 7B was unimproved. At that time the Town’s zoning ordinance required that a building in a Rural Residence Zone be set back a minimum of 100 feet from any “streams, water bodies and wetlands.” In October 1987 the Town amended its ordinance concerning wetlands and classified wetlands into “coastal,” “inland,” and “transitional,” see Ordinance Ch. I, § III,2 and required that there be a minimum setback of 100 feet for coastal and inland wetlands and a 50-foot setback from transitional wetlands. Ordinance Ch. I, § VI(D)(2).
In April 1989 the Perrins applied to the CEO for a building permit to construct a single family dwelling on that portion of Lot 7 designated as 7B. In May 1989 the CEO denied the application on the ground that the site of the proposed structure was within 25 feet of a wetland. After a hearing on the Perrins’ appeal, the Board concluded there were wetlands on the property and the proposed house would have to be 100 feet from these wetlands, and affirmed the denial of the building permit. The Per-rins did not seek a judicial review of this decision. In August 1989 the Perrins filed an application for a variance from the wetland setback requirement. As a part of this proceeding the evidence presented to the Board on the appeal from the denial of the building permit was incorporated into the record requesting a variance. Following a public hearing at which no additional witnesses were presented on behalf of the *863Perrins, the Board denied the variance on the ground that the Perrins “could not meet all four criteria for hardship for a variance.”
By a complaint against the Town, filed in the Superior Court pursuant to M.R.Civ.P. 80B, the Perrins sought review of the decision of the Board and the CEO.3 By Count I of their complaint the Perrins alleged that the application for a building permit was part of a pending proceeding at the time of the enactment in October 1987 of the provision of the Ordinance relating to wetlands and therefore the provision did not apply to Lot 7B. Count II alleged that the Board had improperly denied a variance to the Perrins. Count III alleged that the wetlands issue was determined by the Planning Board at the time of its consideration of the Perrins’ application to divide Lot 7 and could not be reexamined by the CEO or the Board. After a hearing, the court granted a judgment to the Town on Counts I and III and to the Perrins on Count II, and the parties appeal.
II.
On appeal from the judgment as to Count II the Town contends that the court erred in reversing the Board’s decision to deny the Perrins’ application for a variance. We agree. A zoning board of appeals may grant a variance from the strict application of a zoning ordinance only when that application would cause undue hardship as defined by 30-A M.R.S.A. § 4353(4) (Pamph. 1990), which provides in pertinent part:
A. The land in question cannot yield a reasonable return unless a variance is granted;
B. The need for a variance is due to the unique circumstances of the property and not to the general conditions in the neighborhood;
C. The granting of a variance will not alter the essential character of the locality; and
D.The hardship is not the result of action taken by the applicant or a prior owner.
The law is well established that the burden is on the variance applicant before the Board to prove by competent evidence that all of the statutory requirements for the granting of a variance have been met. See Curtis v. Main, 482 A.2d 1253, 1257 (Me.1984); Sibley v. Inhabitants of the Town of Wells, 462 A.2d 27, 30 (Me.1983); Driscoll v. Gheewalla, 441 A.2d 1023, 1029 (Me.1982). In reviewing the Board’s action, the Superior Court was bound, as are we, to affirm the Board’s decision unless the evidence before the Board would compel a positive finding that the applicant had established undue hardship by all four of the criteria set forth in section 4353(4)(A)-(D). See Tompkins v. City of Presque Isle, 571 A.2d 235, 236 (Me.1990). When acting in direct judicial review, a court may not make findings independent of those explicitly or implicitly found by the Board or substitute its judgment for that of the Board. Id., Driscoll v. Gheewalla, 441 A.2d at 1029. “The reasonable return prong of the undue hardship test is met ‘where strict application of the zoning ordinance would result in the practical loss of all beneficial use of the land.’ ” Curtis v. Main, 482 A.2d at 1257 (quoting Thornton v. Lothridge, 447 A.2d 473, 475 (Me.1982)). We have repeatedly recognized that a reasonable return is not the maximum return. See, e.g., Marchi v. Town of Scarborough, 511 A.2d 1071, 1073 (Me.1986); Leadbetter v. Ferris, 485 A.2d 225, 227 (Me.1984).
In the instant case, to satisfy the first prong of undue hardship the only evidence before the Board was that the application of the wetland setback would prevent the Perrins from building another residential structure on that portion of Lot 7 designated as 7B. The record does not address the value of Lot 7B if used for the construction of a residence nor its value if *864used for other purposes, including its use as an unimproved lot contiguous to Lot 7A on which the Perrins had constructed their residence. See Sibley v. Inhabitants of the Town of Wells, 462 A.2d at 31; Barnard v. Zoning Bd. of Appeals, 313 A.2d 741, 747, 749 (Me.1974); cf. Marchi v. Town of Scarborough, 511 A.2d at 1073 (no reasonable return from unbuildable lot where applicant is not the abutting owner). The Perrins failed to prove that beneficial uses did not exist for Lot 7B other than its use for the construction of a residence. On the evidence presented to it the Board was not compelled to conclude that the Perrins had satisfied the first prong of the undue hardship test. Accordingly, we need not determine whether the Perrins met their burden of proof as to the remaining three prongs of that test. See 30-A M.R.S.A. § 4353(4)(A)-(D).
III.
By their cross-appeal from the judgment as to Count I the Perrins contend that the building permit application is a part of the subdivision approval process and, accordingly, under the provisions of 1 M.R. S.A. § 302 (1989)4 the wetlands provisions of the zoning ordinance enacted in October 1987 cannot be applicable to the proposed construction on Lot 7B. We find no error in the trial court’s determination that the Perrins’ application for a building permit was a separate proceeding from the Per-rins’ previous application for the division of Lot 7 into two lots, and that since the application for the building permit was made after the effective date of the new wetlands requirements, the Board properly affirmed the CEO's denial of a building permit to the Perrins. See Larrivee v. Timmons, 549 A.2d 744, 746 (Me.1988).
Nor do we find any error in the trial court’s determination as to Count III that neither the CEO nor the Board was collaterally estopped from determining whether wetlands existed on Lot 7B. The Perrins rely on a statement, made at the May 14, 1987 hearing on their initial application to the Planning Board for a division of Lot 7 by the Town Planner, to the effect that Lot 7 was not at that time designated as a wetland. It is clear from this record that the Planning Board did not at any time, either in response to the Perrins’ first5 or second application to it, make any factual finding on this issue or address’the issue in its decision. See Spickler v. York, 505 A.2d 87, 88 (Me.1986) (no collateral estoppel where issue not litigated on its merits and resolved by a valid final judgment in a prior action between the parties or their privies).
The entry is:
Judgment as to Counts I and III affirmed. Judgment as to Count II vacated. Remanded to the Superior Court for entry of a judgment affirming the decision of the Kittery Zoning Board of Appeals.
ROBERTS, WATHEN, CLIFFORD and COLLINS, JJ., concur.. On May 14, 1987, the Planning Board approved an application of the Perrins to divide Lot 7. Pursuant to M.R.Civ.P. 80B, an abutter sought judicial review of this approval. By stipulation of the parties that the approval would be of no force and effect, the action was dismissed with prejudice, and the Perrins submitted to the Planning Board a revised plan for division of Lot 7, which was approved September 24, 1987. No review was sought of this approval.
. Ordinance Ch. I, § III provides this definition of wetlands:
An area of land on which the ground surface is seasonally or commonly saturated with water and which consists of hydric soils. In the absence of conclusive evidence, wetlands will be identified by vegetational types usually associated with these conditions, and by the following physical conditions:
Coastal — Those lands contiguous to tidal waters and generally within the reach of normal high tide (elevation 6), but more specifically identified by the landward reach of salt-tolerant vegetation including, but not limited to, seaside goldenrod, salt hay grass, cordgrass and sea lavender.
Inland — Those lands of one acre or more which support a stable and functional wetland environment, whether natural or man-made, as indicated by vegetation including, but not limited to, cattails, rushes, horsetail, sensitive fern, alder or sumac.
Transitional — Areas of wetland vegetation less than one acre, which shall not include drainage ditches.
. The Perrins complaint was in five counts. Counts IV and V sought a declaration that portions of the Ordinance were unconstitutional. By order of the court, these counts were separated from Counts I, II, and III. Pursuant to M.R.Civ.P. 54(b) the court directed entry of a final judgment on these three counts.
. Section 302 provides in pertinent part that "... proceedings pending at the time of the passage, amendment or repeal of an ... ordinance are not affected thereby."
. The Planning Board's approval of the Perrins’ first application was stipulated by the parties to be of no effect. See I, supra n. 1.