delivered the opinion of the Court.
In this case, we determine whether an appraisal expert’s opinion regarding, the value of land taken by eminent domain satisfies the requirements for admitting expert testimony under the Texas Rules of Evidence. Exxon Pipeline Company condemned a 50-foot-wide pipeline easement on Daniel and Sandra Zwahrs’ 49-acre tract of land. The parties disputed Exxon’s right to condemn the land, and fоllowing the grant of summary judgments confirming that right, tried the case on the value of the land taken. At trial, Exxon objected to the testimony of the Zwahrs’ expert, arguing that he impermissibly relied on project enhancement to calculate the land’s value and that he improperly determined the property’s highest and best use. The trial court admitted the testimony over Exxon’s objections, and after receiving the jury’s verdict, rendered judgment for the Zwahrs. Exxon argued a number of points on appeal, including that the trial court erred by admitting the testimony of the Zwahrs’ expert. The court of appeals concluded that the trial court properly admitted the testimony, but reduced the amount awarded in the judgment on other grounds.
In 1989, the Zwahrs purchased a 49-acre tract of land in Fort Bend County for $44,408.43, about $900 per acre, and used the land for cotton farming. At that time, the property’s northeast corner was encumbered by a 50-fooF-wide pipeline easement that contained an underground natu *626 ral-gas pipeline owned by United Gas Pipeline Company. United transferred the easement to Koch Gateway Pipeline Company in 1993. The Koch easement does not affect cotton farming on the property’s surface.
In 1995, Exxon petitioned the Fort Bend County Court at Law to condemn a 50-foot-wide strip on the Zwahrs’ property for an ethane pipeline. See Tex. Nat. Res. Code § 111.019; Tex. PROp.Code § 21.012. The land Exxon sought to condemn has a total surface acreage of 1.01 acre and lies parallel to the existing Koch easement for much of its route, overlapping the Koch easement by approximately 82%. As the parties could not agree on the condemned land’s value, court-appointed special commissioners conducted a hearing to determine its fair-market value. See Tex. PROP. Code §§ 21.014-015. The commissioners awarded the Zwahrs $2,264.80. The Zwahrs objected to the award and requested a jury trial before the county court. See id. § 21.018. Exxon deposited the full amount in the court registry, and took possession of the easement on October 6, 1995. See id. § 21.021. Exxon then buried an 8%-inch diаmeter pipeline underneath the 49-acre tract, parallel to and approximately twenty-five feet from the Koch pipeline. Like the Koch easement, the Exxon easement does not affect the Zwahrs’ continued use of the surface for farming cotton.
Following the grant of summary judgments confirming Exxon’s right to condemn the Zwahrs’ land, the case proceeded to trial de novo on the amount due the Zwahrs for the easement taking. The primary controversy concerned the highest and best use of the condemned property. The Zwahrs’ expert, Brad Kangieser, maintained that the 1.01-acre easement was a self-contained, separate economic unit, which had a value independent from that of the surface acreage, with a highest and best use as a pipeline easement. Exxon presented two experts who testified that the land’s highest and best use was as farmland or rural-residential land and that the 1.01-acre easement was not a separate economic unit.
After valuing the 49-acre tract as a whole, Exxon’s experts estimated the market value of the 1.01-acre easement as either $1,727 or $707. Exxon’s experts did not provide a sеparate value for the right to assign the easement because they determined that this right was already included in the easement’s fair-market value. The Zwahrs’ expert estimated the value of the land taken as $36,077, which included $26,398 for the easement itself and $9,679 for the right to assign the easement. Each expert reduced his estimate by a percentage allocable to the Zwahrs’ retained usе of the land’s surface for farming cotton.
The jury awarded the Zwahrs $30,000 as the fair-market value of the easement and $10,000 as the fair-market value of Exxon’s right to assign the easement. Kangieser’s testimony is the only testimony that tends to support this verdict. After deducting the $2264.80 Exxon had previously deposited into the court registry, the trial court rendered judgment awarding the Zwahrs $37,735.20.
Exxon appealed, arguing that the trial court erred by: (1) admitting Kangieser’s testimony on the value of the land; (2) charging the jury with a question requiring two separate damages findings instead of one broad-form question; (3) improperly instructing the jury on the correct measure of damages; and (4) denying Exxon’s post-verdict challenges to the legal and factual sufficiency of the evidence. The court of appeals, with one justice dissenting, concluded that the trial court improperly submitted a separate damages ques
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tion on the right to assign the easement.
In all other respects, however, the court of appeals affirmed the trial court’s judgment, conсluding that the trial court did not abuse its discretion in admitting Kan-gieser’s testimony or in refusing to include Exxon’s requested instruction on damages, and that there was legally and factually sufficient evidence to uphold the jury’s verdict. Id. In determining that the trial court did not abuse its discretion in admitting Kangieser’s testimony, the court of appeals reasoned that the evidence supported his testimony that the property’s highest аnd best use was as a pipeline easement. Id. at 710-11. The court also concluded that his highest-and-best-use opinion was based on the existing Koch easement and was, therefore, neither speculative nor predicated on impermissible project enhancement. Id. at 711-12.
On petition for review, Exxon argues that the trial court improperly admitted Kangieser’s testimony concerning the valuе to the Zwahrs of the land taken by Exxon and that the trial court erred by refusing Exxon’s proposed jury instruction on damages. 1 Because we conclude that the trial court improperly admitted Kan-gieser’s testimony, we need not reach the jury-instruction issue.
We begin by reviewing the standard for valuing a pipeline easement in a condemnation proceeding. Compensation for land taken by eminent dоmain is measured by the fair-market value of the land at the time of the taking.
City of Harlingen v. Estate of Sharboneau,
In determining market value, the project-enhаncement rule provides that the factfinder may not consider any enhancement to the value of the landowner’s property that results from the taking itself.
City of Fort Worth v. Corbin,
504
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S.W.2d 828, 830 (Tex.1974);
Fuller,
On the other hand, the factfinder may cоnsider the highest and best use to which the land taken can be adapted.
Bauer v. Lavaca-Navidad River Auth.,
Finаlly, Texas law permits landowners to introduce testimony that the condemned land is a self-sufficient separate economic unit, independent from the remainder of the parent tract with a different highest and best use and different value from the remaining land.
See State v. Windham,
Exxon contends that under this well-established law, the trial court erred in admitting Kangieser’s opinion for two reasons. First, Exxon contends that Kan-gieser impermissibly included рroject enhancement in his valuation by relying on Exxon’s condemnation itself to compute the easement’s fair-market value. Specifically, Exxon argues that Kangieser used Exxon’s pipeline easement in concluding that a separate economic unit for pipeline easements exists on the Zwahrs’ farm and in assigning a value to that economic unit. Second, Exxon contends that Kаngieser’s conclusion that the property’s highest and best use was for a pipeline easement is flawed because it ignored controlling case law. The Zwahrs respond that Kangieser did not rely on the Exxon project in valuing the easement as a separate economic unit, but rather, reached his conclusion using the existing Koch easement. The Zwahrs also argue that applying thе factors for determining highest and best use shows that the 1.01 acre taken by Exxon had a highest and best use as a pipeline easement. We agree with Exxon that the trial court erred in admitting Kangieser’s testimony because he impermissibly relied on project enhancement in valuing the land taken.
For an expert’s testimony to be admissible under Texas Rule of Evidence 702, the expert must be qualified, and the expert’s opinion must be relevant to the issues in the case and based upon a reliable foundation. Tex.R. Evid. 702; Gam
*629
mill v. Jack Williams Chevrolet, Inc.,
The relevance requirement, which inсorporates traditional relevancy analysis under Texas Rules of Evidence 401 and 402, is met if the expert testimony is “ ‘sufficiently tied to the facts of the case that it will aid the jury in resolving a factual dispute.’ ”
Robinson,
In contrast, Rule 702’s reliability requirement focuses on the principles, reseаrch, and methodology underlying an expert’s conclusions.
Id.
at 557. Under this requirement, expert testimony is unreliable if it is not grounded “ ‘in the methods and procedures of science’ ” and is no more than “‘subjective belief or unsupported speculation.’ ”
Id.
(quoting
Daubert v. Merrell Dow Pharm., Inc.,
Although the trial court serves as an evidentiary gatekeeper by screening out irrelevant and unreliable expert evidence, it has broad discrеtion to determine the admissibility of evidence.
General Motors Corp. v. Sanchez,
Kangieser’s testimony as a whole reveals that he premised his valuation on the fact of Exxon’s condemnation, thus improperly including project enhancement in that valuation.
See Corbin,
The Zwahrs argue that Kangieser based his highest-and-best-use opinion on the fact of the existing Koch easement, not the Exxon project. It is true that in reaching his highest-and-best-use conclusion, Kan-gieser took into account that the existing pipeline increased the likelihood of another pipeline being installed in that area. But hiso reliance on the existing pipeline does not negate the fact that Exxon’s condemnation itself created the economic unit he used for determining highest and best use.
See 8.41 Acres,
Not only did Kangieser rely on the Exxon project to establish a separate economic unit, he rеlied on Exxon’s condemnation to assign a value to the condemned land.
See Fuller,
Because Kangieser relied on Exxon’s condemnation in establishing a separate economic unit and in assigning a value to that unit, his final opinion reflected enhancement in the land’s value that occurred only because of the Exxon project itself. As explained earlier, value that exists becаuse of the condemnation project is not, under the project-enhancement rule, value for which a landowner may recover.
See Corbin,
Notes
. We received amicus briefs supporting the petitioner from: Entergy Gulf States, Inc., The Lower Colorado River Authority, Marathon Ashland Pipe Line, LLC, and Marathon Ashland Petroleum, LLC, Reliant Energy, Inc., TE Products Pipeline Co., LP, and WesT-Tex 66 Pipeline Co. We received amicus briefs supporting the respondents from: International Paper Co. and Temple-Inland Forest Products Corp. The Independent Cattlemen’s Association of Texas and the Texas Forestry Association joined the amicus brief filed by International Paper Co. and Temple-Inland Forest Products Corp.
