(dissenting).
I respectfully dissent. This case arises as a result of a petition for improvement of Murray County Ditch No. 34 filed by owners of property that would be affected by the proposed drainage system improvements. No petition seeking repair of the drainage system has been filed, therefore, there are ho issues relating to the repair of the system before' us. The project at issue is a project for the improvement of the entire main tile line of Murray County Ditch No. 34. In resolving the issues presented, the court improperly concludes that the project involves a separable portion of the drainage system. The court then compounds that errof by subtracting, absent statutory authority to do so and in defiance of common sense, avoided repair costs from the improvement costs in the cost-benefit analysis and by including re-determination benefits as part of the improvement benefit even though redetermi-nation benefits reflect the value of the entire drainage system and not simply the value of the repairs to the system. The net effect of these last two errors is that *50for all future drainage system improvement projects costs will always be understated and benefits will always be overstated. In addition, these errors will lead to absurd results.
The record before us does not support the conclusion that this improvement project is separable from the remainder of the drainage system. To overcome this problem, the court simply notes that the engineer’s report, the county board, and the trial court found the improvement to be a separable portion of the drainage system. The evidence, however, on this point was sparse and consists only of the engineer’s report and testimony. We have always required an adequate factual basis for any expert testimony. See Dunshee v. Douglas, 255 N.W.2d 42, 48 (Minn.1977); Bohach v. Thompson, 307 Minn. 332, 336, 239 N.W.2d 764, 767 (1976). There is no adequate factual basis here. The engineer’s report simply states, “[T]he Petition for Improvement is for a separable part of the existing drainage system, consisting of the main branch.” The engineer’s testimony is no more helpful. At the hearings, the engineer was asked a single question regarding separability. The question arose in the context of discussing the engineer’s estimate of repair costs. Counsel for the ditch petitioners asked the leading question, “And that is a separable part of the system; that is, the part that will be improved?” Answer, “Yes, that is the separable part.” The question was asked without establishing a foundation for the engineer’s opinion, or even explaining what the engineer understood separable to mean. An opinion that the project was separable, in the complete absence of foundation, is not helpful to the trier of fact. See Minn. R. Evid. 702.
In contrast, when the engineer described the nature of the project outside of the context of discussing repair costs, a much different impression is left. The engineer’s report describes the project as one “to replace the drain tile in its entirety.” The engineer confirmed that if the proposed improvement was approved, the main line would be changed from buried tile to an open ditch constructed continuously from one end to the point 600 feet from the terminus where an open ditch now exists. The engineer testified that opening the ditch would provide everybody along the ditch with an adequate outlet and admitted that the system would not function without the main line, as it provides the outlet for the entire drainage system.
Thus, the engineer’s opinion and trial court’s finding that the improvement project was separable are not reasonably supported by the evidence as a whole. Cf. Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975). Given the obvious importance of the main line to the entire drainage system, and given the extensive nature of the improvements to the main line contemplated, it is clearly erroneous to consider this project as separable from the rest of the drainage system. I am “left with a definite and firm conviction that a mistake has been committed.” Id.
That mistake leads the court to its next misstep, the conclusion that avoided costs of repair should be deducted from the costs of an improvement. The legislature provided that a ditch improvement should not go forward unless the drainage authority finds that the benefits are greater than the “total estimated cost, including damages.” Minn.Stat. § 103E.341, subd. 2(a)(4). The term “cost” is not defined in statute, so we adopt the common usage of the term. See Minn.Stat. § 645.08 (1998). Cost means “the amount or equivalent paid or charged for something: price.” Webster’s Seventh New Collegiate Dictionary 189 (1971). Landowners assessed for this project will not be able to deduct from the amount paid for the improvement the amount they would have paid for a repair. Accordingly, it contravenes the simple, common sense definition of cost to deduct avoided repair costs when determining the total cost of the improvement.
*51Deducting avoided repair costs also perverts the cost-benefit analysis and leads to absurd results. Imagine a repair cost of $100,000 that closely approximates the improvement cost of $110,000. Under the court’s analysis, the resulting improvement cost is only $10,000. Imagine further that viewers determined that the benefits of the project will add $25,000 in value to the drainage system. Under the court’s analysis, $25,000 in benefits offset an outlay of $110,000.
Moreover, even if we assume that this project is separable, the statute the court relies on provides no authority for considering avoided repair costs in the cost-benefit analysis. Minn.Stat. § 103E.215, subd. 6(a) states that the engineer “may include in the detailed survey report a statement showing the proportionate estimated cost of the proposed improvement required to repair the separable part of the existing system and the estimated proportionate cost of the added work required for the improvement.’’ Minn.Stat. §' 103E.215, subd. 6(a) (emphasis added). The statute says nothing about the estimated cost of repairs being factored into the cost-benefit analysis used to determine whether the improvement of the separable portion is to be approved. See Minn.Stat. § 103E.341. Surely if the legislature intended to have avoided repair costs deducted from the estimated improvement costs, it would have required the engineer to determine repair costs and not made their inclusion in the report permissive. The legislature also would have explicitly required the drainage authority to use that figure in the cost-benefit assessment on the petition. The court reads into section 103E.215, subd. 6(a) a purpose that is nowhere evident from its plain text. The question left open then is what is the purpose served by permitting the'engineer to show estimated costs of repair in the engineer’s report. The answer to that question is found in Minn.Stat. § 103E.215, subd. 6(b)(1) and (2), which set out how costs are to be assessed against benefited property.17
Respondents filed a petition for improvement, not repair. They nonetheless argue that because a repair is mandatory its costs are “saved” in an improvement. They are not in fact saved however, they are simply replaced by different costs, the costs of the improvement. Further, repair is not automatic. See Minn.Stat. § 103E.715, subd. 4 (1998) (requiring repair on petition to be made when drainage authority determines repairs are necessary and in best interests or that cost of repair will not exceed the total benefits). Just as one cannot deduct the cost of fixing a flat tire from the price of an entirely new tire, one cannot consider avoided repair costs as savings on an entirely separate and distinct improvement project.18 Doing so significantly underestimates the cost of the improvement.
Common sense does not allow, and the legislature has not authorized, exclusion of avoided repair costs from the assessment of costs of a ditch improvement. Therefore, the proper total cost of this project for cost-benefit comparison is the engineer’s estimate of $593,565.43.
The court states that not considering avoided repair costs disregards the repair costs and the redetermination benefits in *52the cost-benefit analysis, “ignoring that almost half of the ‘improvement cost’ is a repair cost yielding a $458,584 redetermi-nation benefit over and above the ‘improvement benefits.’ ” This statement demonstrates the second fundamental flaw in the court’s cost-benefit analysis, the purported comparison of redetermination benefits with the costs of repair. Of course, as noted above, there is no petition to repair the ditch before the court. Therefore, there is no reason to compare costs and benefits of a repair. But even if this case were before us on a petition for repair instead of a petition for an improvement, the court’s use of repair costs and redetermination benefits is incorrect.
The court misconstrues what redetermi-nation benefits represent. Redetermination benefits reflect the value of the entire drainage system, not simply the value of a repair. The drainage system’s benefits must be redetermined from time to time to reflect current land values and physical changes in the affected land, so that landowners may be properly assessed. See Minn.Stat. § 103E.351; Minnesota Public Drainage Manual 2.58-.59 (Minnesota Department of Natural Resources, 1991) (noting four reasons why redetermination might be necessary or beneficial, one of which is a repair project).19 On redetermi-nation, “[vjiewers need to determine benefits as if no drainage system existed.” Public Drainage Manual 4.8 (emphasis added). Therefore, the redetermination amount is not, as the court suggests, the difference between the current value of the ditch and its value as repaired; the rede-termination amount reflects the entire value of the ditch in a reasonable state of repair.20 Accordingly, it is inappropriate to compare the costs of a repair to redeter-mination benefits, as the court has done.21
Finally, it is not appropriate to add the entire redetermination benefit ($458,584.03) to the improvement benefit ($508,766.72) when considering the benefit of this project. While in need of repair, the ditch had value in the state it was in *53when this petition was filed. That pre-repair value is encompassed within the $458,584.03 of redetermination benefits, and therefore a repair will not produce $458,584.03 in added value. Further, including redetermination benefits as a benefit of the improvement dramatically overstates the added value to be derived from the project.
By erroneously comparing: a) the benefits from improvement plus the benefits of the entire drainage system to b) the cost of improvement alone, the court materially alters the proper cost-benefit analysis.
Including the entire redetermination benefit in the benefits of an improvement project has significant implications for agricultural land in Minnesota. The overestimate of benefits, especially when coupled with an underestimate of costs that results from deducting avoided repair costs, means that in the future no ditch improvement project will likely be denied. The court thereby thwarts the careful review and deliberativé process envisioned by the legislature for the establishment and improvement of drainage systems.
In sum, because the improvement project was not separable, the board and the lower courts were not authorized to even consider Minn.Stat. § 103E.215, subd. 6. Even if the project were separable, subdivision 6 does not allow a drainage authority to deduct avoided repair costs in performing the cost-benefit analysis required for approval of a drainage system improvement project. Deducting avoided repair costs leads to absurd results that the legislature could not have intended. Nor did the legislature intend for the drainage system’s redetermination benefits plus the project’s improvement benefits to be compared with the improvement cost. Because the damages and benefits were not properly determined, the drainage authority was not authorized to approve the improvement project. See MinmStat. § 103E.341, subd. 2(3).
I would reverse.
. The only use of the avoided repair cost described in section 103E.215, subd. 6 is in the assessment. Improvement costs for a separable improvement are assessed against only those landowners who benefit from the improvement; and repair costs are assessed against all landowners affected by the ditch. See Minn.Stat. §103E.215, subd. 6(b). Where the existing drainage system needs repair and the petition is for improvement of a separable part of the system, establishing what the cost of repair would be is necessary to properly assess the landowners affected if the improvement project is completed. See id. Repair costs may be included in the detailed survey report only for this purpose.
. The court’s zipper analogy fails. What the court's holding suggests is that the savings on the pants with the broken zipper can be used in the purchase of an entirely different pair of pants. With apologies to Wallace and Grom-it, the majority has "The Wrong Trousers.”
. Although the court asserts that "linking redetermination benefits with repair costs is logical since redetermination benefits, by definition, flow from the repair of the ditch, whether the repair is fictional or real," there is no statutory definition of redetermination benefits and no authority linking redetermination to a repair.
. The court quotes prefatory language in the viewer’s redetermination report indicating the report is "based upon a comparison of the conditions which will exist with the drainage system repairs to the depth, grades and tile sizes as shown on the original plans with the conditions which would have existed before the construction began.” The court apparently infers that "the construction” referenced is the hypothetical repair construction, but other references in the viewer's report make clear that the term refers to the construction of the entire drainage system. The report assigned benefit values for different types of land based upon an increase in the potential for agricultural production "as a result of constructing the drainage system." (Emphasis added.) The beginning land use, property value and economic productivity were considered "before the drainage system construction.” (Emphasis added.)
.Indeed, the court states the issue before the court as, "Does Minn.Stat. § 103E.215, subd. 6 allow a drainage authority to subtract repair costs from redetermination benefits and improvement costs from improvement benefits in a cost-benefit analysis under Minn. Slat. § 103E.341?” This statement is perplexing, as even respondents do not attempt to use the $458,584.03 of redetermined benefits to support either the cost of the (avoided) repair or the cost of the improvement. The district court made no finding regarding rede-termination benefits, simply noting that the drainage authority “determined that the estimated benefits are greater than the total estimated costs, including damages, both as to the redetermination of benefits and as to the improvement project.” The reason for the drainage authority to evaluate the redetermi-nation benefits is provided by statute. Minn. Stat. § 103E.351, subd. 2 requires the drainage authority to confirm the benefits and damages arrived at through redetermination. The approval of redetermination benefits and damages exists wholly independently of the ditch improvement approval process, however. See id. The drainage authority finding therefore relates only to establishing redeter-mination benefits of $458,584.03, which no one here challenges.