ANR Western Coal Development Co. v. Basin Electric Power Cooperative , 276 F.3d 957 ( 2002 )


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  •                      United States Court of Appeals
    FOR THE EIGHTH CIRCUIT
    ___________
    No. 00-1625
    No. 00-1628
    ___________
    ANR Western Coal Development          *
    Company,                              *
    *
    Appellant/Cross-Appellee,       *
    * Appeal from the United States
    v.                              * District Court for the
    * District of North Dakota.
    Basin Electric Power Cooperative;     *
    The Coteau Properties Company;        *
    Dakota Coal Company,                  *
    *
    Appellees/Cross-Appellants.     *
    ___________
    Submitted: June 13, 2001
    Filed: January 10, 2002
    ___________
    Before WOLLMAN, Chief Judge, BOWMAN and HAMILTON,1 Circuit Judges.
    ___________
    BOWMAN, Circuit Judge.
    Basin Electric Power Cooperative, Dakota Coal Co., and The Coteau Properties
    Co. sued ANR Western Coal Development Co. (WCDC) in a dispute arising out of
    the development of coal fields to supply a gasification plant (Gas Plant) near Beulah,
    1
    The Honorable Clyde H. Hamilton, United States Circuit Judge for the United
    States Court of Appeals for the Fourth Circuit, sitting by designation.
    North Dakota.2 Basin, Coteau, and Dakota Coal sued WCDC in North Dakota state
    court in 1992; WCDC removed to the District Court and filed counterclaims. The
    District Court granted summary judgment to Basin, Dakota Coal, and Coteau; we
    reversed and remanded for trial. Basin Elec. Power Coop. v. ANR W. Coal Dev. Co.,
    
    105 F.3d 417
    (8th Cir. 1997) (Basin I). After our remand the District Court assigned
    the case to a Magistrate Judge who realigned the parties, positioning WCDC as the
    plaintiff, and tried WCDC's counterclaims. The Magistrate Judge entered judgment
    for WCDC on its claim for breach of implied duty to reasonably develop and against
    WCDC on its claim for tortious interference with contract.
    WCDC appeals and Basin, Coteau, and Dakota Coal cross-appeal from the
    judgment of the Magistrate Judge. The case, in federal court on diversity jurisdiction,
    is governed by North Dakota law. We affirm on the cross-appeal, but on the appeal
    we reverse and remand for further proceedings.
    I.
    Our previous opinion in this litigation sets forth its long and complicated
    history. 
    Id. at 420-22.
    We recount much of it here to clarify the issues presented in
    the current appeal and cross-appeal.
    In the early 1970s, WCDC's predecessor-in-interest3 began pursuing a plan to
    construct several coal-gasification plants in North Dakota. The initial stages of the
    2
    This plant, the Great Plains Synfuels Plant, converts coal into synthetic gas.
    See Basin Elec. Power Coop. v. ANR W. Coal Dev. Co., 
    105 F.3d 417
    , 420 & n.2
    (8th Cir. 1997) (Basin I).
    3
    WCDC is the successor-in-interest to ANR Pipeline Company, formerly
    known as the Michigan-Wisconsin Pipeline Co., which was the pipeline subsidiary
    of the American Natural Resources Company (ANR). ANR and its business partners
    initiated the Gas Plant project.
    -2-
    project required the acquisition of coal reserves dedicated to supplying the coal needs
    of the gasification plants. Thus, in 1972 WCDC's predecessor entered into an
    agreement with Coteau's parent company, the North American Coal Co. (NACCO),
    which required NACCO to set aside coal reserves under its control to be used
    exclusively to supply the future needs of the proposed plants. Specifically, the 1972
    Basic Agreement obligated NACCO to dedicate certain coal reserves to WCDC and
    in return obligated WCDC to finance the acquisition and carrying costs of additional
    coal reserves necessary to meet the anticipated needs of the proposed plants. The
    parties to the 1972 agreement envisioned that Coteau would mine the dedicated
    reserves and supply the coal from them to the proposed plants.
    After the 1972 agreement, plans for the construction and operation of the
    gasification plants moved forward. In 1979, WCDC and NACCO entered the first of
    three agreements implicated in this lawsuit. The 1979 Restatement of Basic
    Agreement superseded the 1972 agreement, but retained most of the major provisions
    of the original contract. It again obligated WCDC to fund the acquisition and
    carrying costs of the coal reserves near Beulah.4 In return, the agreement entitled
    WCDC to receive an overriding royalty of forty cents per ton, to be adjusted for
    inflation, on all coal mined from the WCDC-funded reserves (royalty-bearing
    reserves). The agreement imposed upon Coteau the duty to pay this overriding
    royalty to WCDC. It also provided that WCDC would receive a delay-rental-payback
    4
    WCDC agreed to pay acquisition costs including "salaries of employees
    directly engaged in acquisition, the purchase price of coal land acquired in fee,
    bonuses for leases, legal and other expense in establishing and reviewing titles,
    closing expenses, transfer taxes and, to the extent approved by [WCDC], drilling,
    engineering and testing costs." 1979 Restatement of Basic Agreement ¶ 5. The
    carrying charges WCDC agreed to pay included "delay royalties on coal and ad
    valorem taxes." 
    Id. -3- payment
    of five cents per ton,5 also to be adjusted for inflation, on a defined amount
    of coal produced from these reserves, as consideration for WCDC's fronting an
    amount that eventually totaled over $11 million dollars to NACCO to hold the coal
    reserves from the time of the 1972 agreement until the Gas Plant and its
    accompanying power plant (the Antelope Valley Station or AVS) were completed.6
    See 1979 Restatement of Basic Agreement ¶ 10(a). Moreover, the 1979 Restatement
    designated Coteau as holder of all deeds and leases on the dedicated coal reserves and
    limited Coteau's business activities to those set forth in the agreement. 
    Id. at ¶¶
    4, 3.
    It is under this agreement that WCDC argues Coteau's implied duty to reasonably
    develop WCDC's royalty-bearing reserves first arose.
    Basin and WCDC signed the second agreement central to this dispute in 1982.
    At the time, Basin was involved with the Gas Plant project through its construction
    5
    Delay rentals are amounts paid to the holder of mining rights on an area of
    coal "for the privilege of deferring development of the property." 3 American Law
    of Mining §85.03[4], at 85-32 (The Rocky Mountain Mineral Law Found. eds., 2d ed.
    Supp. 1985). The parties' agreement thus provided that WCDC would eventually
    recover, in the form of a "delay-rental payback," the delay rentals it paid.
    6
    Only the Gas Plant and AVS were ever completed. Because changing
    economic circumstances made the cost of producing the synthetic gas uneconomical,
    plans to build additional coal-gasification plants were abandoned. ANR eventually
    defaulted on its loans and, in 1986, the Department of Energy foreclosed on the plant.
    For a review of the litigation surrounding the foreclosure, see Dakota Gasification
    Co. v. Natural Gas Pipeline Co. of America, 
    964 F.2d 732
    (8th Cir. 1992), cert.
    denied, 
    506 U.S. 1048
    (1993); United States v. Great Plains Gasification Associates,
    
    819 F.2d 831
    (8th Cir. 1987); and United States v. Great Plains Gasification
    Associates, 
    813 F.2d 193
    (8th Cir.), cert. denied, 
    484 U.S. 924
    (1987). By the time
    of the foreclosure, the plant had entered into long-term supply contracts with
    purchasers of gas extending through 2009. The plant is still in operation, although
    the purchasers of the gas it produces are paying a fixed rate that is often higher than
    the market price for natural gas. Whether the plant will continue to operate after the
    expiration of these contracts in 2009 is unknown.
    -4-
    and operation of AVS. Basin negotiated a deal directly with WCDC whereby it paid
    $40 million to WCDC as a prepayment on the overriding royalty due on all coal
    mined by Coteau from the WCDC royalty-bearing reserves and delivered to AVS.
    The agreement, known as the 1982 Purchase Agreement, specified that this
    prepayment would exempt from WCDC's overriding royalty 5.2 million tons per year
    of coal mined from royalty-bearing reserves and "delivered to Basin Electric for the
    Antelope Valley Station," up to a maximum of 210 million tons over the life of the
    agreement. 1982 Purchase Agreement ¶¶ 1, 2. Basin's later imposition of a particular
    accounting method in an attempt to get full credit for coal delivered to AVS against
    the 5.2 million tons per year under the 1982 Purchase Agreement forms the basis for
    WCDC's claim of tortious interference with contract.
    In 1987 the parties entered into the Coal Reserve Agreement, the final
    agreement implicated in this lawsuit. By 1987, WCDC no longer had an ownership
    interest in the Gas Plant, see supra note 6, and had little need for the vast coal
    reserves acquired as a result of and protected by the 1972 and 1979 agreements.
    Through other agreements, WCDC had already narrowed its obligations under the
    1979 agreement to encompass only Mine Areas 1 through 4, also known as the
    Freedom Mine. The Coal Reserve Agreement superseded the 1979 agreement. It
    relieved WCDC of the obligation to fund any further carrying costs or acquisition of
    Freedom Mine reserves and relieved Coteau of the obligation to pay the overriding
    royalty to WCDC on any coal reserves acquired after March 2, 1987, the date of the
    agreement. Moreover, the agreement transferred to a third party (whose rights were
    eventually assumed by appellee Dakota Coal) all rights held by WCDC to direct
    Coteau in the acquisition and mining of the Freedom Mine and other reserves. Thus,
    WCDC retained only its right to receive the overriding royalty on coal Coteau held
    prior to March 2, 1987 and for which WCDC had paid carrying and acquisition costs.
    WCDC argues that Coteau's implied duty to reasonably develop WCDC's royalty-
    bearing reserves continued under the 1987 agreement.
    -5-
    In 1988, Basin purchased the Gas Plant from the Department of Energy (DOE)
    and created Dakota Coal to manage the Gas Plant's coal resources. At this time,
    Basin held the rights to the Dakota Star reserves, an area of coal contiguous to Mine
    Areas 1 through 4. Basin also operated the Leland Olds Station (LOS), a power plant
    located at another mine. Before purchasing the Gas Plant, Basin maintained a
    business relationship with Coteau based upon Basin's operation of AVS and Coteau's
    mining of the coal used to fuel AVS's operations. Once Basin learned it was the
    successful purchaser of the Gas Plant, and after discussing its plans with Coteau,
    Basin determined that it would incorporate the Dakota Star reserves into the Freedom
    Mine. Thus, Coteau arranged to purchase Dakota Star from Basin, incorporate it into
    the Freedom Mine, and supply coal to LOS and to the UPA Stanton Station (UPA)
    (which had been supplied with coal from soon-to-be-exhausted reserves also owned
    by Basin). Basin, pursuant to the rights it had obtained as owner of the Gas Plant to
    direct Coteau's mining through its newly created subsidiary Dakota Coal, directed
    Coteau to preferentially mine the Dakota Star reserves to supply LOS, UPA, and the
    Gas Plant. In Basin's notes from an April 1990 meeting between representatives of
    Basin and Coteau, the discussion summary states, "Meeting participants were also
    informed that the Dakota Star reserves should be utilized as much as practical to
    minimize overriding royalty payments to WCDC." Conference Notes prepared by
    Karl Lemmerman ¶ 2 (Apr. 17, 1990). WCDC points to this evidence as part of the
    basis for its claim that Coteau breached an implied duty to reasonably develop
    WCDC royalty-bearing reserves.
    By 1993, Coteau was mining coal from the Freedom Mine and the Dakota Star
    reserves, commingling it, and delivering commingled coal to AVS, the Gas Plant,
    LOS, and UPA (collectively, the end users). Coteau could determine what percentage
    of the coal mined came from royalty-bearing reserves but could not identify how
    much royalty-bearing coal was actually delivered to each end user. Up to 5.2 million
    tons of royalty coal delivered to AVS per year were exempt from WCDC royalties
    under the 1982 Purchase Agreement, so the parties had to devise a method to
    -6-
    calculate the royalties owed to WCDC. After some discussion between WCDC and
    Coteau, and among Coteau, Basin, and Dakota Coal, Basin and Dakota Coal directed
    Coteau to use a deeming accounting method. Under the deeming method, all coal
    delivered to AVS would be deemed to have been mined from royalty-bearing
    reserves, regardless of its actual origin. The use of this accounting method
    substantially reduced WCDC's royalty payments on coal delivered to the Gas Plant,
    LOS, and UPA because Basin received credit against its royalty pre-payment on more
    royalty-bearing coal than was physically being delivered to AVS.
    The decision to implement the deeming accounting method led Basin, Dakota
    Coal, and Coteau to file for a declaratory judgment in state court in 1992, seeking
    approval of their proposed method. WCDC removed the case to the District Court
    and filed counterclaims. The District Court granted summary judgment to Basin,
    Dakota Coal, and Coteau, essentially approving the deeming method. We reversed,
    and held that a pro-rata accounting method should have been employed. Basin 
    I, 105 F.3d at 424
    . Under the pro-rata method, WCDC's royalties are calculated by
    assuming that the percentage of royalty-bearing coal eventually delivered to each end
    user is the same as the ratio of coal mined from the royalty-bearing reserves to all coal
    mined by Coteau. Thus, if fifty percent of all coal mined by Coteau comes from
    royalty-bearing reserves, then fifty percent of all coal delivered to each end user is
    assumed to be royalty-bearing coal.
    After our remand in Basin I, Coteau paid WCDC for the past unpaid royalties
    on the coal wrongly deemed delivered to AVS.7 The District Court assigned the case
    to a Magistrate Judge who then realigned the parties, positioning WCDC as the
    plaintiff, granted summary judgment in favor of WCDC on its claim that Coteau had
    7
    Under the parties' agreements, Coteau has the ultimate responsibility for
    paying the overriding royalty to WCDC, but Coteau is able to pass the cost of the
    royalty through to each end-use purchaser.
    -7-
    an implied duty to reasonably develop the royalty-bearing reserves, and tried the
    remaining issues.8 The Magistrate Judge found that Coteau had breached its duty to
    develop WCDC royalty-bearing reserves by preferentially mining the Dakota Star
    reserves and found that WCDC was entitled to interest-only damages on a certain
    portion of the displaced coal.9 The Magistrate Judge also held that WCDC's tortious-
    interference claim failed because WCDC did not prove that Basin and Dakota Coal
    acted with actual malice when they directed Coteau to implement the deeming
    accounting method.
    WCDC appeals from the judgment, arguing that the Magistrate Judge
    erroneously interpreted the "prudent-operator standard" applicable to WCDC's claim
    for breach of implied duty to develop, erred in awarding interest-only damages,
    8
    The parties consented to try the case before a magistrate judge pursuant to 28
    U.S.C. §636(c). The Magistrate Judge described the four trial issues as
    (1) whether Basin and Dakota Coal acted with the requisite intent in
    inducing Coteau to breach its contract with WCDC by implementing the
    deeming method, and whether their acts were justified; (2) whether
    Coteau breached its implied duty of reasonable development by
    preferentially mining the Dakota Star reserves; (3) whether Basin and
    Dakota Coal intentionally interfered with WCDC's contract by directing
    Coteau to preferentially mine the Dakota Star reserves; and (4) whether
    Basin and Dakota Coal are liable for punitive damages.
    ANR W. Coal Dev. Co. v. Basin Elec. Power Coop., Civil No. A1-92-105,
    Memorandum and Order for Judgment at 11 (D.N.D. Aug. 12, 1999). WCDC does
    not appeal the Magistrate Judge's adverse judgment on WCDC's claim that Basin and
    Dakota Coal intentionally interfered with WCDC's contract by ordering Coteau to
    preferentially mine the Dakota Star reserves.
    9
    Rather than award the full value of the royalties on the portion of the coal she
    determined had been displaced, the Magistrate Judge awarded only the interest that
    would have accrued on the full payment of the displaced royalties.
    -8-
    misinterpreted North Dakota law in concluding that Dakota Coal and Basin did not
    tortiously interfere with WCDC's contract with Coteau, and calculated WCDC's
    damages using the deeming method rejected in Basin I. WCDC further argues that
    the Magistrate Judge's damage calculations employ the wrong interest and discount
    rates, that the court should have awarded delay-rental-payback damages, and that the
    court abused its discretion in denying WCDC's Federal Rule of Civil Procedure 59(e)
    motion.
    Basin, Dakota Coal, and Coteau cross-appeal, urging three grounds for
    reversal. They argue that the court erroneously found that Coteau owed WCDC an
    implied duty to reasonably develop WCDC's royalty-bearing reserves; that, if a duty
    to develop applied, the court erred in finding that Coteau breached that duty; and
    finally that even if there were a duty and a breach, it was error to award WCDC
    damages for that breach.
    II.
    Coteau, Basin, and Dakota Coal together filed a notice of cross-appeal from the
    Magistrate Judge's judgment. In their brief the cross-appellants only address alleged
    errors related to the Magistrate Judge's judgment against Coteau on WCDC's claim
    that Coteau breached an implied covenant of reasonable development and mining.
    Because Coteau was the only entity found to owe a duty to WCDC, we will treat
    Coteau as the cross-appellant. We address the cross-appeal first.
    A.
    WCDC's complaint alleged that Coteau breached an implied covenant of
    reasonable development and mining by preferentially mining the Dakota Star
    reserves. The Magistrate Judge, in a pretrial summary judgment ruling, held that
    Coteau owes to WCDC an implied duty to reasonably develop the coal reserves that
    -9-
    were subject to WCDC's overriding royalty.10 In its cross-appeal, Coteau argues that,
    although with respect to oil and gas leases North Dakota law implies a duty to
    reasonably develop, North Dakota courts have not and would not impose such a duty
    in favor of an overriding-royalty owner whose interest is created in a mineral lease.
    Coteau claims that the rationales usually invoked for implying such a duty simply do
    not apply to the contractual relationship between Coteau and WCDC. We have not
    found any North Dakota case addressing this precise issue; therefore, "our duty is to
    predict how the North Dakota Supreme Court would resolve" this claim. Basin 
    I, 105 F.3d at 422
    .
    The Magistrate Judge held that the implied duty exists between WCDC and
    Coteau, basing its finding in part on the North Dakota Supreme Court's recognition
    of the implied duty in oil and gas leases, see Feland v. Placid Oil Co., 
    171 N.W.2d 829
    , 835 (N.D. 1969), and its conclusion that "the legal theories involved with
    leaseholds and royalties are basically the same whether they are for extraction of gold,
    iron, or some other mineral," Finstrom v. First State Bank of Buxton, 
    525 N.W.2d 675
    , 677 n.1 (N.D. 1994).
    Having reviewed this question of state law de novo, we agree with the
    Magistrate Judge (for slightly different reasons) that on the facts of this case the
    Supreme Court of North Dakota likely would imply the duty of reasonable
    development in Coteau's contract with WCDC.
    First, the parties do not dispute that North Dakota implies the duty of
    reasonable development in oil and gas leases. See, e.g., Olson v. Schwartz, 
    345 N.W.2d 33
    , 38 (N.D. 1984) ("It is well settled that the lessee of an oil and gas lease
    has an implied obligation to the lessor to do everything that a reasonably prudent
    10
    We review this question of North Dakota law de novo. Salve Regina Coll.
    v. Russell, 
    499 U.S. 225
    , 239 (1991).
    -10-
    operator would do in operating, developing, and protecting the property . . . .");
    
    Feland, 171 N.W.2d at 835
    ; Hermon Hanson Oil Syndicate v. Bentz, 
    40 N.W.2d 304
    ,
    308 (N.D. 1949). Second, that this case is about coal reserves, rather than oil and gas
    leases, does not appear to limit the implied duty under North Dakota law. The North
    Dakota Supreme Court has suggested that cases concerning oil and gas leases and
    royalties should, and do, apply to coal and other minerals. In Finstrom, the court
    cited with approval a case from our own court, Superior Oil Co. v. Devon Corp., 
    604 F.2d 1063
    , 1068-69 (8th Cir. 1979), in which we "applied, to an oil and gas lease, the
    doctrine of an implied covenant to reasonably develop, even though that doctrine had
    originated in Nebraska in a gravel lease case." 
    Finstrom, 525 N.W.2d at 677
    n.1. The
    court in Finstrom equated the gravel royalties at issue with petroleum royalties,
    applying prior case law defining unaccrued oil and gas royalties as real property11 and
    concluding that the gravel royalty at issue in Finstrom was, before accrual (that is,
    severance of the gravel), an interest in real property as well. 
    Id. at 677.
    Thus, the
    trend in North Dakota law strongly suggests that to protect royalty owners, an implied
    duty to develop would be found in mineral cases as well as in oil and gas cases.
    Coteau, seeking to distinguish lease cases from non-lease overriding-royalty
    cases like this one, argues that lessors usually seek to develop their mineral rights and
    that the overriding royalty at issue here is unrelated to any development of mineral
    rights under a lease. Therefore, Coteau argues, because WCDC is not the lessor or
    owner of the coal fields at issue, the policy reasons recognized in North Dakota for
    implying a covenant of development do not support the result WCDC seeks.
    11
    Unaccrued royalties are royalties that will be earned on minerals that have not
    yet been severed from the ground; thus, under North Dakota law, they are considered
    real property. Accrued royalties are royalties due on minerals that have been severed.
    At the point the mineral is severed from the ground, the right to the royalty becomes
    a personal property interest under North Dakota law. GeoStar Corp. v. Parkway
    Petroleum, Inc., 
    495 N.W.2d 61
    , 67 (N.D. 1993). The royalty-bearing coal at issue
    here has not yet been severed.
    -11-
    We disagree. The North Dakota Supreme Court has recognized that, as a
    policy rationale for implying in oil and gas leases a duty to develop, lessors have a
    property interest in the oil and gas and a right to receive compensation that should be
    protected. See 
    Olson, 345 N.W.2d at 39
    . Under North Dakota law, royalty holders
    appear to have the same type of interest as lessors. In GeoStar Corp. v. Parkway
    Petroleum, Inc., 
    495 N.W.2d 61
    , 67 (N.D. 1993), the court considered the nature of
    a royalty interest in the context of a dispute over whether GeoStar was entitled to
    specific performance of a contract for the conveyance of an overriding-royalty
    interest in oil and gas wells. The court explained, in no uncertain terms, that under
    North Dakota law "a royalty interest is real property." 
    Id. at 67.
    As a result, GeoStar
    was entitled to specific performance under a North Dakota remedies statute. The
    Magistrate Judge reasoned, and we agree, that the rationale for implying the duty in
    regard to lessors holds equally true in regard to overriding-royalty holders.
    Overriding-royalty holders have an interest that is a form of real property under North
    Dakota law and, without the implied duty, have "no mineral rights to fall back on" if
    the coal reserves are not developed. ANR W. Coal Dev. Co. v. Basin Elec. Power
    Coop., Civil No. A1-92-105, Memorandum and Order at 19 (D.N.D. Oct. 23, 1998).
    Thus, implying the duty to develop in favor of overriding-royalty holders protects the
    same interests deemed worthy of protection in regard to lessors in Olson.
    Moreover, other jurisdictions have implied the duty of reasonable development
    in favor of royalty holders. See Garman v. Conoco, Inc., 
    886 P.2d 652
    , 659 & n.23
    (Colo. 1994) (en banc) (discussing implied duty to market, a corollary under
    Colorado law to the implied duty to develop), cited in Rogers v. Westerman Farm
    Co., 
    29 P.3d 887
    , 902 n.16 (Colo. 2001) (en banc); United States Steel Corp. v.
    Whitley, 
    636 S.W.2d 465
    , 473 (Tex. Ct. App. 1982) (recognizing implied duty in
    favor of overriding-royalty owner to produce uranium with due diligence); Cont'l
    Potash, Inc. v. Freeport-McMoran, Inc., 
    858 P.2d 66
    , 82 (N.M. 1993) ("There are
    occasions . . . when courts will imply covenants to protect the interests of an owner
    of an overriding royalty . . . ."), cert. denied, 
    510 U.S. 1116
    (1994); 2 Howard R.
    -12-
    Williams & Charles J. Meyers, Oil and Gas Law § 420.1 (rev. 2000). But cf. XAE
    Corp. v. SMR Prop. Mgmt. Co., 
    968 P.2d 1201
    , 1207 (Okla. 1998) (refusing to allow
    overriding-royalty holder to enforce implied duty to market).
    Therefore, in light of the North Dakota Supreme Court's holdings in Finstrom
    and GeoStar, as well as recent cases from other jurisdictions recognizing the implied
    duty to develop in favor of the overriding-royalty owner, we believe the North Dakota
    Supreme Court, were the issue presented to it, would imply a duty of reasonable
    development in favor of WCDC. We affirm the Magistrate Judge's grant of summary
    judgment to WCDC on this aspect of its claim.
    B.
    Coteau further argues that the Magistrate Judge erred in finding that Coteau
    breached the implied duty of reasonable development by preferentially mining the
    Dakota Star reserves. The Magistrate Judge tried this issue and found that Coteau
    had committed a breach. We review the Magistrate Judge's factual findings for clear
    error. See Slaaten v. Amerada Hess Corp., 
    459 N.W.2d 765
    , 769 (N.D. 1990)
    (explaining that under North Dakota law breach is a finding of fact reviewed for clear
    error).
    To determine whether a breach occurred, the Magistrate Judge applied the
    "prudent-operator" standard outlined in 
    Olson, 345 N.W.2d at 39
    . In Olson, the
    North Dakota Supreme Court explained that "[i]t is impossible to state a formula by
    which a court can determine whether a particular lessee has developed a particular
    lease in conformity with the prudent operator standard. Each case must be decided
    -13-
    on the facts peculiar to it and the burden of proving a breach of the implied covenant
    is on the party asserting it." Id.12
    The Magistrate Judge concluded that when WCDC entered the 1987 Coal
    Reserve Agreement, its expectation was that Coteau would continue to mine royalty-
    bearing reserves to supply the Gas Plant and AVS for as long as those facilities
    remained in operation. Moreover, the court found that cost savings and quality
    concerns did not indicate a need to add other reserves to the Freedom Mine. Coteau's
    own mine plan showed that by adding the Dakota Star reserves there would be a
    significant reduction in production from WCDC's reserves through 2009 (the year the
    Gas Plant's long-term supply contracts expire). ANR W. Coal Dev. Co. v. Basin Elec.
    Power Coop., Civil No. A1-92-105, Memorandum and Order for Judgment at 28-29
    (D.N.D. Aug. 12, 1999). Basin had requested Coteau to produce as much coal as
    possible from Dakota Star. When Coteau's plan to preferentially mine Dakota Star
    resulted in "substantial tons of Dakota Star coal being delivered to the Gas Plant and
    AVS, thus significantly delaying development of WCDC's reserves," Coteau failed
    to act as a prudent operator and thus breached its duty to WCDC, failing entirely to
    12
    In Olson, the court outlined factors relevant to applying the prudent-operator
    standard in the context of an oil and gas lease, relying on a decision of the Kansas
    Supreme Court. 
    Olson, 345 N.W.2d at 39
    -40. Of the non-exclusive factors outlined
    in Olson, those relevant to mineral leases include (1) the quantity of mineral capable
    of being produced as indicated by prior exploration and development; (2) the local
    market and demand for that mineral; (3) the extent and results of operations, if any,
    on adjacent lands; (4) the usages of the business; (5) the cost of the mining
    operations; (6) the cost of transportation and storage, and the prevailing price of the
    mineral; (7) general market conditions as influenced by supply and demand or by
    government regulation of production; (8) evidence of the willingness of another
    operator to mine the tract in question; (9) the attitude of the lessee toward further
    development; and (10) the time elapsed since mining operations were last conducted.
    See id.; see also Johnson v. Hamill, 
    392 N.W.2d 55
    , 57-58 (N.D. 1986). Not all of
    the factors identified in Olson are relevant to this case.
    -14-
    consider "WCDC's interests or expectation that its coal would be used for the Gas
    Plant and AVS." 
    Id. at 28.
    Coteau's arguments fail to convince us that the Magistrate Judge committed
    clear error. The Magistrate Judge found several facts relevant to the prudent-operator
    inquiry as outlined in 
    Olson. 345 N.W.2d at 39-40
    . For example, the court
    recognized that the potential closure of the Gas Plant in 2009 significantly limits the
    market for Freedom Mine coal. The court also found that Coteau's mine plan before
    adding the Dakota Star reserves, designated as Engineering Report (ER) 802, has the
    same quality parameters as ER 803, which included the Dakota Star Reserves. In
    other words, the royalty-bearing coal met the quality parameters of both plans.
    Coteau's projected cost savings from adding Dakota Star were only twelve cents per
    ton (only a 1.7% reduction in cost, according to Coteau's expert), a savings deemed
    negligible by the Magistrate Judge in relation to the losses incurred by WCDC from
    Coteau's preferential mining of Dakota Star.
    The Magistrate Judge also made findings regarding the parties' motivations and
    expectations. The court found that Basin wanted to produce as much coal from
    Dakota Star as possible because Coteau's payments to Basin for the purchase of the
    reserves were based in part on the tons of coal mined and delivered from them.
    Moreover, the court's assessment of WCDC's expectations indicated that after the
    1987 Coal Purchase Agreement, WCDC expected that Coteau would mine the
    Freedom Mine royalty-bearing reserves for as long as the Gas Plant and AVS
    remained in production. The agreement placed upon Coteau the risk that Basin and
    Dakota could essentially force Coteau into a breach with WCDC by exercising
    Dakota's right to disapprove of Coteau's mine plans and direct Coteau to adopt
    revisions thereto, such as adding the Dakota Star Reserves.
    Coteau's challenge to the Magistrate Judge's findings would have this Court
    focus on two sets of facts: the amount of royalties already collected by WCDC and
    -15-
    Coteau's "development and adherence to mining plans" at the Freedom Mine.
    Although Coteau insists that WCDC has done extremely well financially with respect
    to its initial investment in the Freedom Mine, the agreements of the parties set no
    upper limit on the amount of the overriding-royalty payments WCDC might earn for
    that investment. Moreover, Coteau has not cited any North Dakota cases, and we
    have found none, that would suggest we should so exclusively focus on the amount
    WCDC has earned in this transaction. The Magistrate Judge made a finding
    regarding the nature of WCDC's "reasonable expectations"—that mining of the
    Freedom Mine would continue as long as the Gas Plant and AVS continued to
    operate—and Coteau has not pointed us to any evidence in the record demonstrating
    that this finding is clearly erroneous. In fact, the finding reflects a determination that
    can reasonably be reached rather easily by reading the agreements in question.
    Coteau's argument based on its "development and adherence to mining plans"
    at the Freedom Mine suffers similar defects. Coteau may be technically correct in
    asserting that "[n]o mine plan investigated is economically nor qualitatively superior
    to plans actually implemented by Coteau which incorporated mining of the Dakota
    Star reserve beginning in 1993," Appellee's Br. at 39, but only in the sense that ER
    802 cost just slightly more than and contained quality parameters equal to those found
    in its later mine plans that included Dakota Star. In any case, as the Magistrate Judge
    determined, this assertion misses the mark in regard to the prudent-operator standard.
    Under that standard, Coteau is obligated to consider both its own interests and those
    of WCDC as the overriding-royalty holder. 
    Olson, 345 N.W.2d at 38
    . We see no
    clear error in the court's findings regarding Coteau's mine plans, the economics of
    adding the Dakota Star reserves, and Coteau's failure to consider WCDC's interests
    in implementing its mine plans calling for the preferential development of the Dakota
    Star reserves.
    Because Coteau has not shown any clear error in the Magistrate Judge's
    findings, WCDC has, as a matter of law, sustained its burden of proof regarding
    -16-
    Coteau's breach of the implied duty of reasonable development. We affirm the
    Magistrate Judge's judgment for WCDC on this claim.
    III.
    We turn now to the issues raised by WCDC's appeal. WCDC asserts error in
    the Magistrate Judge's calculation of damages, in her refusal to award delay-rental-
    payback damages, and in her rejection of WCDC's tortious-interference claim. We
    first address the question of damages.
    A.
    WCDC appeals from the Magistrate Judge's award of damages on its claim for
    breach of duty to develop. As an initial matter, WCDC urges us to find error in the
    Magistrate Judge's conclusion that some portion of the Dakota Star reserves could
    reasonably have been mined by Coteau to supply LOS and UPA. We see no clear
    error in the Magistrate Judge's conclusion that it was not a breach of the implied duty
    to reasonably develop merely to add Dakota Star to the reserves mined by Coteau,
    because the 1987 Coal Reserve Agreement clearly contemplates Dakota's authority
    to add to and subtract from the reserves being mined by Coteau. See 1987 Coal
    Reserve Agreement ¶ 9(a). Thus, the Magistrate Judge's holding that some portion
    of Dakota Star could be mined to supply LOS and UPA stands. Although this
    conclusion is helpful to Coteau, it is not entirely dispositive of the damages issue.
    WCDC argues that even if Coteau could reasonably mine some portion of
    Dakota Star, the Magistrate Judge nevertheless erred in figuring damages. In
    calculating the tons of coal per year on which WCDC reasonably expected to receive
    a royalty (the coal that was unreasonably displaced by the preferential mining of
    Dakota Star), the Magistrate Judge concluded that WCDC could only reasonably
    expect to receive royalties on the coal supplied to the Gas Plant and AVS (about 11.5
    -17-
    million tons per year). Thus, she completely excluded coal supplied to LOS and UPA
    from the calculation of WCDC's damages. Coal from Renners Cove, another non-
    royalty-bearing field mined by Coteau, was also deemed to supply only the Gas Plant
    and AVS, thus further reducing the amount of royalty coal the Magistrate Judge
    found to have been wrongfully displaced.
    WCDC contends that the Magistrate Judge's calculation employs the very same
    deeming accounting method that we rejected in Basin I. We said in Basin I that the
    parties could not deem certain coal as delivered to certain markets, and we directed
    application of the pro-rata method to determine the amount of coal that had been
    delivered to each 
    location. 105 F.3d at 424
    . The pro-rata method is the law of the
    case and must be applied to the damages calculations here. See United States v.
    Bartsh, 
    69 F.3d 864
    , 866 (8th Cir. 1995). WCDC correctly concludes that under our
    decision in Basin I, "production from Mine Areas 1-4, Renners Cove, and Dakota Star
    must be proportionally allocated to all markets" for the purpose of determining the
    quantum of coal displaced by Coteau's preferential mining of Dakota Star.
    Appellant's Br. at 35. Thus, the Magistrate Judge must make a pro-rata allocation of
    royalty-bearing coal delivered to each customer (LOS, UPA, AVS, and the Gas Plant)
    before calculating WCDC's damages.13
    B.
    WCDC argues it is entitled to more damages than simply the interest it would
    have earned on the royalties of which it has been deprived by Coteau's preferential
    mining of Dakota Star. The Magistrate Judge concluded that "WCDC has not
    13
    Based upon our conclusion, WCDC's post-trial motion to alter or amend the
    judgment under Federal Rule of Procedure 59(e) was well-founded, and it was an
    abuse of discretion for the Magistrate Judge to deny that motion. See Innovative
    Home Health Care, Inc. v. P.T.-O.T. Assocs. of the Black Hills, 
    141 F.3d 1284
    , 1286
    (8th Cir. 1998) (standard of review).
    -18-
    actually lost any royalties, just the time value of the underpaid royalty amount, and
    thus WCDC is not entitled to recover the actual royalty underpayment as damages,"
    but only the interest income. ANR W. Coal Dev. Co., Memorandum and Order for
    Judgment at 33 (Aug. 12, 1999). Coteau urges us to accept the Magistrate Judge's
    damage calculation, arguing that even though other courts have rejected this interest-
    only rule, it is appropriate here because the "case is unique in not only its complexity,
    but the manner in which the alleged damages to WCDC arose." Appellee's Br. at 55.
    Coteau maintains that to apply any other rule would result in overcompensating
    WCDC, because the coal in the ground is still available to mine and to generate
    royalties for WCDC.
    As WCDC notes, North Dakota has not addressed the measure of damages for
    breach of the implied covenant of development on facts similar to this case. Some
    courts that have considered the issue agree, with certain caveats, that the measure of
    damages for such a breach should be the royalty that would have been received had
    the mining been diligently pursued. See 
    76 A.L.R. 2d 721
    , 748 §6. Courts refer to
    this measure of damages as the "royalty rule."
    The Texas Supreme Court is among those courts that have adopted the royalty
    rule, explaining,
    [T]he award of interest only does not give the lessor what he would have
    received had the lessee performed his obligation.
    The purpose of the law to give compensation for breach of
    contract is subserved by allowing the injured party to have the value to
    him of the contract's performance. . . . Therefore, to allow the lessor the
    value of royalty wrongfully withheld from him complies with the law's
    fundamental purpose of adequate compensation. The lessor is put in the
    same position as though the contract had been performed.
    -19-
    Tex. Pac. Coal & Oil Co. v. Barker, 
    6 S.W.2d 1031
    , 1037 (Tex. 1928). California
    courts adopted the same rule in Gold Mining & Water Co. v. Swinerton, 
    142 P.2d 22
    ,
    34 (Cal. 1943), stating,
    True, plaintiff still has the mining property and may lease it again on a
    royalty basis, but even if it does so and receives a royalty on all of the
    gold extracted from the 300,000 cubic yards of gravel which defendants
    agreed to extract, plaintiff will not thereby recover double damages or
    receive as royalty the amount it is entitled to recover from defendants as
    damages. In other words, what plaintiff is entitled to recover from
    defendants under the rule here announced is damages for the failure of
    defendants to perform their agreement under the lease to mine the
    property, extract the mineral therefrom and pay plaintiff a royalty
    thereon. Since defendants have failed to perform, plaintiff may recover
    from them as damages an amount equal the amount of royalty which
    plaintiff would have received had defendants operated the property in
    accordance with the provisions of the lease.
    See also Fisher v. Hampton, 
    118 Cal. Rptr. 811
    , 814 (Ct. App. 1975) (reaffirming
    California's adherence to the royalty rule); see also, e.g., Cotiga Dev. Co. v. United
    Fuel Gas Co., 
    128 S.E.2d 626
    , 638-39 (W. Va. 1962) (applying royalty rule, but
    concluding that defendant would be entitled to offset the present payment of royalty
    damages against royalties due when the wrongly delayed production of minerals is
    finally completed); Cawood v. Hall Land & Mining Co., 
    168 S.W.2d 366
    , 369-70
    (Ky. 1943) (approving royalty rule and awarding interest for period of unreasonable
    delay in development on the lost royalties). But see 3 American Law of Mining §
    82.04(2), at 82-22 ("Development clauses are presumptively covenants and not
    conditions. For nonperformance by the grantee, the grantor will normally be limited
    to damages equal to interest on the royalties or other payments he would have
    received if production had been obtained in a timely manner." (footnote omitted and
    emphasis added)).
    -20-
    Coteau argues that North Dakota would not apply the royalty rule, particularly
    on these facts, owing to the likelihood of overcompensating WCDC. We think that
    Coteau's "double-recovery" argument is not well-founded. It is true, as Coteau
    argues, that WCDC took on some risk that not all the royalty-bearing reserves would
    eventually be mined. Coteau points to this as a reason to reject WCDC's contention
    that it is highly likely that after the Gas Plant's supply contracts expire in 2009, its
    royalty-bearing reserves will cease to be mined. WCDC may have assumed some
    risk, but it certainly did not assume the risk that came to pass in this case—that
    Coteau would wrongly refuse to mine an appropriate amount of royalty-bearing
    reserves. The only way WCDC can be made whole in this instance is to award the
    full value of the displaced royalties. We reverse and remand for recalculation of
    damages based on the full royalties owed on the displaced coal. Because we remand
    for an award of full royalties, we see no need to address WCDC's interest-rate and
    discount-rate arguments.
    IV.
    WCDC advanced over $11 million to NACCO for delay rentals, which were
    paid to maintain the coal leases needed by WCDC for development of the Gas Plant
    and to hold those leases from 1972 until construction of the plant and AVS was
    finished. WCDC was owed a delay-rental payback on all coal mined, sold, and
    delivered, up to an aggregate amount of approximately 233 million tons, from the
    Freedom Mine leases held by Coteau at the time of the 1987 agreement. The delayed
    development of these reserves resulting from the preferential mining of Dakota Star
    has in turn wrongly reduced the delay-rental payback received by WCDC.
    The Magistrate Judge reasoned that because she rejected WCDC's proffered
    expert testimony that removed all Dakota Star production from the calculation of
    WCDC's damages, WCDC failed to carry its burden of proof on this issue. Under
    North Dakota law, however,
    -21-
    When the fact of injury has been proved with reasonable certainty, the
    fact that the amount of damages may be hard to prove does not prevent
    the jury from awarding damages.
    ....
    Uncertainty as to the amount of damages does not preclude
    recovery, and mathematical certainty as to the amount of recovery is not
    necessary. If a reasonable basis for computing an approximate amount
    of damages is provided, that is all that the law requires.
    N. Am. Pump Corp. v. Clay Equip. Corp., 
    199 N.W.2d 888
    , 895-96 (N.D. 1972),
    quoted in Symington v. Mayo, 
    590 N.W.2d 450
    , 454 (N.D. 1999). WCDC has
    offered sufficient proof that the delayed development was wrongful, and because the
    delay-rental-payback payments are tied to the rate of coal development, WCDC has
    sustained damages. Moreover, the pro-rata method, applied to the tonnage of WCDC
    royalty-bearing coal wrongfully displaced by Coteau's preferential mining of Dakota
    Star, provides a reasonable basis for computing WCDC's delay-rental-payback
    damages. The Magistrate Judge clearly erred, therefore, in concluding that WCDC
    failed to carry its burden of proof on this element of damages. Because we reverse
    and remand on the damages calculation for breach of implied duty to reasonably
    develop, based on the Magistrate Judge's erroneous deeming of all Dakota Star
    reserves to LOS and UPA, we must also reverse the Magistrate Judge's rejection of
    delay-rental-payback damages and remand for further proceedings.
    V.
    Finally, we consider WCDC's appeal from the Magistrate Judge's adverse
    judgment on WCDC's claim of tortious interference with contract. WCDC alleges
    that Basin and Dakota Coal tortiously interfered with WCDC's contract with Coteau
    by directing Coteau to implement the deeming accounting method. The Magistrate
    Judge found that WCDC's evidence failed to establish all the elements of tortious
    -22-
    interference required by North Dakota law. Specifically, the court found that the
    "evidence indicates that defendants' motive and purpose behind the deeming method
    was to get the full benefit of the $40 million 'prepurchase,' to which they in good faith
    believed they were entitled." ANR W. Coal Dev. Co., Memorandum and Order for
    Judgment at 15 (Aug. 12, 1999). Thus, the Magistrate Judge held that WCDC failed
    to establish the intent element of its claim. WCDC argues that this justification is a
    pretext that the court must reject because the 1982 Purchase Agreement states in plain
    language that the royalty prepayment solely applies to coal actually delivered to AVS.
    See 1982 Purchase Agreement ¶ 2.
    Under North Dakota law, the tort of interference with contract requires a
    showing of five elements. Plaintiff must prove the existence of a contract, a breach
    of that contract, that the defendant instigated the breach, that the defendant instigated
    the breach without justification, and that the defendant acted intentionally. Peterson
    v. Zerr, 
    477 N.W.2d 230
    , 234 (N.D. 1991); Bismarck Realty Co. v. Folden, 
    354 N.W.2d 636
    , 642 (N.D. 1984). The intent required "goes beyond the traditional tort
    concept of intent"; WCDC must show that the defendants "specifically intended to
    interfere" with WCDC's contractual rights, or that the defendants "acted with
    knowledge that the interference would result." 
    Peterson, 477 N.W.2d at 234
    . In
    Peterson, the court further explains that the intent requirement
    "applies also to intentional interference . . . in which the actor does not
    act for the purpose of interfering with the contract or desire it but knows
    that the interference is certain or substantially certain to occur as a result
    of his action. The rule applies, in other words, to an interference that is
    incidental to the actor's independent purpose and desire but known to
    him to be a necessary consequence of his action."
    -23-
    
    Id. (quoting Restatement
    (Second) of Torts § 766 cmt. j. (1979)).14 The Magistrate
    Judge found that WCDC had unquestionably carried its burden of proof on the first
    three elements. The Magistrate Judge's opinion analyzes justification and intent
    together, discussing the facts as presenting a justification that negates any ill intent
    on the part of Basin or Dakota Coal.
    The Magistrate Judge found that Basin and Dakota Coal prompted Coteau to
    impose the deeming method. The court accepted as true Dakota Coal's contentions
    that using the pro-rata method would result in significantly larger royalty payments
    to WCDC and would also result in significantly fewer tons of coal being written off
    under Basin's 1982 prepayment of the overriding royalty for certain tons of coal
    delivered to AVS. Moreover, the court found that the studies on which these
    contentions were based, completed by Dakota Coal in November 1991, "show that
    defendants were aware that using the deeming method would significantly reduce the
    royalty paid to WCDC for coal delivered to the Gas Plant, LOS and UPA." ANR W.
    Coal Dev. Co., Memorandum and Order for Judgment at 16 (Aug. 12, 1999). The
    court concluded from these facts that the inference to be drawn was that defendants
    were not motivated by a desire to "'cheat' WCDC out of the royalty it was due." 
    Id. Despite the
    Magistrate Judge's conclusion to the contrary, we conclude that
    under North Dakota law, Basin and Dakota Coal's motive and purpose are not
    material in this instance. In Peterson, the North Dakota Supreme Court adopted
    comment j to section 766 of the Restatement. Under that comment, even if an actor
    has a legitimate motive or purpose for its actions, if the actor has knowledge of the
    14
    Basin and Dakota Coal cite language from Blair v. Boulger, 
    336 N.W.2d 337
    (N.D.), cert. denied, 
    464 U.S. 995
    (1983), and Hennum v. City of Medina, 
    402 N.W.2d 327
    (N.D. 1987), in support of the Magistrate Judge's interpretation of North
    Dakota law on tortious interference. We rely on Peterson instead because it is the
    most recent statement of the North Dakota Supreme Court regarding the elements of
    this claim.
    -24-
    consequences of its acts, then it may be liable for tortious interference with contract.
    The Magistrate Judge found that Basin and Dakota Coal had the requisite knowledge
    of the inevitable effect of the deeming accounting method—that it would undercut
    WCDC's position in relation to its royalty agreement with Coteau regarding the
    royalty-bearing reserves. That finding is enough, under North Dakota law, to
    establish tortious interference as a matter of law. Therefore, we hold that the
    Magistrate Judge erred as a matter of law in rejecting WCDC's tortious-interference-
    with-contract claim on the basis of its finding that Basin and Dakota Coal did not act
    with the purpose and intent of interfering with WCDC's contractual right to royalty
    payments when they directed Coteau to implement the deeming accounting method.
    We reverse the judgment for Basin and Dakota Coal, and remand for further
    proceedings. On remand, WCDC should have the opportunity to prove its damages
    recoverable on this claim.15
    VI.
    For the reasons stated, the portion of the judgment appealed by Basin, Dakota
    Coal, and Coteau is affirmed, and the portion of the judgment appealed by WCDC is
    reversed. The case is remanded for further proceedings consistent with this opinion.
    WCDC's motion to file its tendered supplemental brief is denied.
    15
    Issues concerning the damages recoverable on the tortious-interference claim
    have not been raised in this appeal and must be addressed initially on remand. We
    note the possibility that redundancy, in whole or in part, may exist between WCDC's
    tortious-interference damages and its preferential-development damages.
    -25-
    A true copy.
    Attest:
    CLERK, U.S. COURT OF APPEALS, EIGHTH CIRCUIT.
    -26-