On Appeal from Superior Court, Environmental Division, Thomas S. Durkin, J.
Mark G. Hall of Paul Frank Collins P.C., Burlington, and Charles J. Ferrera, Honolulu, Hawaii, for Appellants.
Benjamin W. Putnam of Neuse, Duprey & Putnam, P.C., Middlebury, for Appellee.
PRESENT: Reiber, C.J., Dooley, Skoglund, Burgess and Robinson, JJ.
¶ 1. Applicant Charles Ferrera and property owners Ronald and Susan Fenn (hereafter “applicants) appeal from a decision of the Superior Court, Environmental Division affirming the Town of Middlebury’s denial of their application to operate a gravel pit. Applicants contend: (1) several key findings and conclusions were unsupported by the evidence; and (2) provisions of the Town’s zoning regulations are unconstitutionally vague. We affirm.
¶ 2. We first summarize the salient facts and procedural history. Additional material facts will be set forth in the discussion that follows. Applicants submitted a proposal to construct a gravel pit on a 71.5-acre property adjacent to Route 116 in the Town of Middlebury. Just north of the proposed project site is the Lindale residential community; to the west across Route 116 is another residential area known as the Butternut Ridge neighborhood. Several existing gravel-extraction companies also operate within several miles of the project.
¶ 3. Applicants’ property lies within both a Medium Density Residential (MDR) and Forest Conservation District. The proposed sixteen-acre gravel pit lies entirely within the Forest District, while the proposed 2300-foot access road from Route 116 crosses through both districts. Although gravel extraction is not allowed in the MDR district, it is a conditional use in the Forest District, and the Design Review Board (DRB) consequently subjected the proposal to conditional-use review under a provision of the Town’s zoning regulations requiring application of the rules pertaining to the “less restricted district” in mixed-zoning districts. Town of Middlebury Zoning & Subdivision Regulations, § 430(10) (hereafter “Regulations”).
¶ 4. The DRB conducted a site visit in October 2008, and held public hearings over the course of ten days concluding in August 2010. A thirteen-page written decision issued the following month. The DRB concluded that the proposed project failed to comply with eight provisions of the zoning regulations, including the requirement that the project “shall not have an undue adverse effect on the character of the neighborhood, or area affected, ” Regulations, § 540.III.B.1, and the noise-performance standard limiting “[n]oise volume... to levels that will not be a nuisance to adjacent uses.” Id. § 750.I. More specifically, the DRB found that, despite the existence of several other gravel pits within a few miles of the project site, the proposed new gravel pit—located in closer proximity to the adjacent residential neighborhoods—would substantially increase the noise in the area, stating: “The Lindale/Butternut neighborhood would, with the added proposed gravel pit and truck traffic, ... experience substantial added noise from a closer source.” Along with the noise, the added “dust, industrial level traffic and impacts on the land” resulting from “the increased proximity and intensity of the proposed project would, ” in the DRB’s view, “be adverse.” The DRB thus concluded that “the addition of another operation, as proposed, will disrupt the balanced diversity of uses currently in place and will disturb the essential character of the existing neighborhoods.” The application, accordingly, was denied. 
¶ 5. Applicants appealed the ruling to the environmental division, which conducted an on-the-record review based on the transcribed hearings before the DRB and the parties’ supplemental briefing. See 24 V.S.A. § 4471(b) (providing that environmental division may review municipal decisions “on the record” where local legislative body has so authorized). The court issued a written decision in November 2012, affirming the DRB’s denial of the application.  This appeal followed.
¶ 6. Applicants challenge several of the DRB’s findings and conclusions as unsupported. Our review is limited. Where, as here, review by the environmental division is on the record, our standard of review on appeal is the same as that used by the trial court. See Devers-Scott v. Office of Prof’l Regulation, 2007 VT 4, ¶ 4, 181 Vt. 248, 918 A.2d 230 (“Where there is an intermediate level of appeal from an administrative body, we review the case under the same standard as applied in the intermediate appeal.” (quotation omitted)); accord In re Stowe Highlands Resort PUD to PRD Application, 2009 VT 76, ¶ 7, 186 Vt. 568, 980 A.2d 233 (mem.). Thus, we will affirm the findings of the DRB if reasonably supported by the evidence. Devers-Scott, 2007 VT 4, ¶ 6. Our role is not to reweigh the evidence, and we will “defer to the finder of fact when there is conflicting evidence in the record.” Id. Conclusions of law, however, are analyzed independently “where such conclusions are outside the DRB’s area of expertise.” In re Stowe Highlands Resort, 2009 VT 76, ¶ 7.
¶ 7. Applicants first focus on the DRB’s finding, based on the testimony of their traffic engineer, that the proposed gravel pit would generate one truck trip every six minutes—or ten per hour—during operation. Applicants acknowledge that the DRB was “correct that the maximum frequency would be ten truck trips per hour” but “question... whether it is fair or legal to... judge the impact of the project on the basis of this maximum.” They cite evidence that the “average hourly” number of trips would correspond to one trip every twelve minutes and that loaded trips would average about once every twenty-four minutes.
¶ 8. Applicants must do more, however, than simply “question” the DRB’s reliance on the maximum number of trips per hour; they must show that this was reversible error. See In re S.B.L., 150 Vt. 294, 297, 553 A.2d 1078, 1081 (1988) (“It is the burden of the appellant to demonstrate how the lower court erred warranting reversal.”); V.R.A.P. 28(a)(4)(A) (appellant’s brief must set forth the issues presented, how they were preserved, and “appellant’s contentions and the reasons for them—with citations to the authorities, statutes, and parts of the record on which appellant relies”). Applicants have not cited any law or authority or advanced any argument to support their claim, nor have we discovered any basis to conclude that the DRB may not rely on the maximum number of trips in assessing the project’s impact on the character of the area. As the trial court here observed, “[w]e know of no barrier to a land use panel relying upon the maximum or most onerous impacts a project may have when attempting to determine if that project will bring undue adverse impacts to a neighborhood.” Absent such a showing, we discern no basis for a finding of error.
¶ 9. Applicants also contend the evidence failed to support the DRB’s finding that noise generated by the project would violate the noise-performance standard and detrimentally affect the character of the area. They assert that the evidence showed, on the contrary, that the project “would add only trivially to the already-existing noise level.” Applicants rely on the report and testimony of their acoustical expert that the project would not significantly increase the average daily decibel level ...