American Compensation Insurance Company, Respondent (C1-00-1209, C5-00-1214), vs. Blue Cross Blue Shield of Minnesota, Defendant (C1-00-1209), Appellant (C5-001214), Crum & Forster Insurance Company, Appellant (C1-00-1209), Defendant (C5-00-1214), AND Bradley L. Schulz, by his mother and natural guardian, Katherine Schulz, and Katherine Schulz individually, Respondents (C4-00-1401), vs. American Compensation Insurance Company, intervenor, Appellant (C4-00-1401), vs. Park 'N Go of Minnesota, a Limited Partnership, and David H. Bailly, as Special Administrator of the Estate of Randall L. Carlson, Respondents (C4-00-1401).

may not be cited except as provided by

Minn. Stat. § 480 A. 08, subd. 3 (1998).

 STATE OF MINNESOTA

 IN COURT OF APPEALS

 C3-98-1209

Julie Rohling, et al.,

Respondents,

vs.

City of Champlin,

Appellant.

 Filed February 16, 1999

 Affirmed as modified

 Crippen, Judge

Hennepin County District Court

File No. 978578

Lawrence P. Marofsky, Lawrence P. Marofsky Law Office, 7022 Brooklyn Boulevard, Brooklyn Center, MN 55429 (for respondents)

Scott M. Lepak, Barna, Guzy & Steffen, Ltd., 400 Northtown Financial Plaza, 200 Coon Rapids Boulevard, Coon Rapids, MN 55433-5876 (for appellant)

Considered and decided by Toussaint, Chief Judge, Crippen, Judge, and Mulally, Judge.[*]

 U N P U B L I S H E D O P I N I O N

 CRIPPEN, Judge

The trial court voided appellant City of Champlin's assessments against 22 property owners for the costs of a street and sewer improvement, finding that "the best evidence presented fails to show any increase in value to the properties in question because of the work performed by the City," and further finding that the assessments were made "without any attempt to determine actual increase in value to the property." The trial court found that the study on which the assessments were based was "totally without a factual basis or scientific study and is based solely on speculation."

Appellant contends (1) that the trial court should have deferred to the Champlin City Council's findings on property value, (2) that the evidence was sufficient to show an increase in value to the affected properties, and (3) the trial court erred in prohibiting the city from re-assessing the property owners. As modified to allow re-assessment, we affirm.

 FACTS

In February 1997 the Champlin City Council ordered a road improvement project for Pleasant Avenue, which was in poor condition. The city rebuilt the street and installed a curb, gutter, and storm sewer. The council based the final assessment on a formula used by its appraiser, Fred Gergen, who had been hired to prepare a report showing how the project would affect the value of local properties. Twenty-two of the 25 assessed property owners challenged the assessments, presenting to the trial court the question of whether the assessments exceeded the special benefits to the properties, measured by the difference in market value before and after the improvements.

At trial, both sides presented evidence and provided estimates of the effect of the improvements on property values. Gergen explained his appraisal technique and concluded that the improvements increased property values. The city also presented testimony by another appraiser who reviewed and approved Gergen's initial appraisal. In contrast, all property owners who testified stated that the improvements had not increased the market value of their property, and the owners' expert testified that the only increase in market values was due to inflation. In its April 1998 order, the trial court found that the evidence "fails to show any increase in value to the properties," ordered the assessments voided, and prohibited the city from re-assessing the property owners. This appeal followed.

 D E C I S I O N

 1. Standard of Review

This court reviews the trial court's determination of a special assessment by carefully examining the record to ascertain whether the evidence supports the court's findings and whether the findings support its conclusions. Schumacher v. City of Excelsior, 427 N.W.2d 235, 237 (Minn. 1988).

 2. Trial Court Standard of Review

Although this court's standard of review is undisputed, appellant contends that the trial court erred in conducting an independent review of the evidence. If the trial court determines only the question of whether an unconstitutional taking has occurred, involving a finding of whether the amount of each special assessment exceeded the benefit to the assessed property, then an independent review of the evidence by the trial court is appropriate. Buettner v. City of St. Cloud, 277 N.W.2d 199, 203 (Minn. 1979). If the questions before the trial court involve the city council's exercise of legislative discretion or the regularity of its procedure, the city's conclusions cannot be upset unless clearly erroneous. Id.

Initially, the parties stipulated that the sole issue before the court was whether individual assessments exceeded the value increase to individual homes. Appellant argues that the trial court did not limit its inquiry to that issue but instead reviewed the regularity of the proceedings. This is a misconstruction of the record. The trial court addressed procedural matters only in the context of its review of the benefits evidence, in the course of which it criticized the city's assessment technique. The trial court's mention of procedural matters in its findings was only collateral to its conclusions on the issue of benefits.

Appellant also argues that the issue before the court involved a challenge based on the proportionate distribution among individual property owners of the total costs of the improvement. But the court did not look at individual assessments to see whether any property owner's assessment was disproportionate. Instead, the court determined whether the cost of the improvements, as assessed against an individual property owner, exceeded the benefit received by the property owner. The trial court correctly made an independent review of the evidence.

 3. Sufficiency of Evidence

The trial court found that the evidence presented failed to show any increase in property values due to the improvements. Because the parties presented conflicting evidence, this is a credibility determination to which we must defer. See Alstores Realty, Inc. v. State, 286 Minn. 343, 353, 176 N.W.2d 112, 118 (1970) (stating it is for trier of fact to decide weight and credibility of expert witnesses testimony); Minn. R. Civ. P. 52.01. The trial court explained why it found appellant's expert testimony flawed and lacking adequate foundational basis, and it appropriately refused to speculate as to the effect of the improvements on property values.[1]

Appellant also argues that that trial court erred in not applying a presumption of validity to the special assessment. A municipal special assessment is entitled to a presumption of validity. Buettner, 277 N.W.2d at 202. But the presumption "disappears when adverse evidence on the question of value is introduced." Id. at 204. Here, the testimony of the property owners and their expert was sufficient to overcome the presumption. See Dosedel v. City of Ham Lake, 414 N.W.2d 751, 756 (Minn. App. 1987) (noting that testimony by property owner and expert has overcome presumption in a series of cases).

Appellant also faults the trial court for its critical characterization of the assessment procedure and the role played by the city council and city engineer. There is merit in appellant's contention that the trial court erred in saying that the city followed an improper procedure. A dummy assessment, as was used here, is a normal part of assessment procedure, and the city council and city engineer were properly involved in the assessment process. Also, contrary to the trial court's assertion, Mr. Gergen's report was not an after-the-fact attempt to support arbitrary assessments by the city. But these errors by the trial court take nothing away from the court's finding that the city had an insufficient factual basis for the assessed increases in property values. Cf. Minn. R. Civ. P. 61 (harmless error to be ignored).

 4. Reassessment

Appellant contends that it is entitled to reassess the property owners. When a trial court sets aside an assessment, the court must order a reassessment. Minn. Stat. § 429.081 (1998); Buettner, 277 N.W.2d at 204-05. The exception to this rule is that a trial court need not order a reassessment if the court finds that there were no benefits conferred, impliedly setting the permissible ceiling at zero. In re Village of Burnsville Assessments, 287 N.W.2d 375, 377 (Minn. 1979) (stating that reconsideration by city would be pointless where trial court made finding that no benefits were conferred, so that "zero" was permissible ceiling for assessments); see Buettner, 277 N.W.2d at 204-05 (trial court findings on special benefits may establish ceiling for reassessment). Here, the trial court made a finding with substantially less impact, merely determining that the city had failed to produce evidence to show any increase in value to the properties. Absent a finding of no benefit conferred, it is inappropriate to deny the city an opportunity to seek appropriate evidence.[2] The trial court erred in failing to order a reassessment by the city, and the trial court's judgment is modified to include this order.

  Affirmed as modified.

[*] Retired judge of the district court, serving as judge of the Minnesota Court of Appeals by appointment pursuant to Minn. Const. Art. VI, § 10.

[1] Appellant argues that it is not realistic to require cities to present evidence of property values based on sales made before and after an improvement in order to validate an assessment. This fear is overstated. The trial court did not premise its opinion on the need for such evidence but on the remoteness of the evidence that the city did present.

[2] The only evidence of no value increase due to the improvements was the self-serving testimony of the property owners.