                   Nebraska Advance Sheets
	          BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	899
	                       Cite as 290 Neb. 899

the first workday after the 30-day appeal time ended on
Saturday, April 5. The petition was filed within the statu-
tory 30-day time period of both issuance and delivery of the
Commission’s order. Thus, the petition in error was timely
filed, and the district court erred when it dismissed the case
for lack of jurisdiction.
                          CONCLUSION
   Although, typically, decisions rendered by an inferior tribu-
nal, board, or commission are final when they are announced
on the record, the specificity in § 23-1734 overrides that
general rule. An order is not final until it meets the require-
ments in § 23-1734. Those requirements state that the order
must be in writing, “certified” to the sheriff, and delivered.
This order was not in writing until it was issued on March
6, 2014, and not delivered until March 21. March 21 is the
earliest date from which the order can be considered final
under § 23-1734(2), because the order was not delivered to
the parties until that date. The appeal was taken well within 30
days of this date. We reverse the district court’s judgment and
remand the cause for further proceedings.
	R eversed and remanded for
	                                  further proceedings.




    Bauermeister Deaver Ecology Land Use Development,
        LLC, as Successor in Interest to Dorothy L.
        Bauermeister, individually, et al., appellant,
                v. Waste M anagement Co. of
                   Nebraska, Inc., appellee.
                                  ___ N.W.2d ___

                       Filed May 15, 2015.    No. S-14-553.

 1.	 Equity: Quiet Title: Accounting. An action to quiet title and for an accounting
     sound in equity.
 2.	 Equity: Appeal and Error. On appeal from an equity action, an appellate
     court resolves questions of law and fact independently of the trial court’s
     determinations.
 3.	 Waiver: Words and Phrases. Waiver is a voluntary relinquishment of a
     known right.
    Nebraska Advance Sheets
900	290 NEBRASKA REPORTS


 4.	 Equity: Estoppel. The doctrine of equitable estoppel applies where, as a result
      of conduct of a party upon which another person has in good faith relied to his
      detriment, the acting party is absolutely precluded, both at law and in equity,
      from asserting rights which might have otherwise existed.
  5.	 ____: ____. Six elements must be satisfied for the doctrine of equitable estoppel
      to apply: (1) conduct which amounts to a false representation or concealment
      of material facts or, at least, which is calculated to convey the impression that
      the facts are otherwise than, and inconsistent with, those which the party subse-
      quently attempts to assert; (2) the intention, or at least the expectation, that such
      conduct will be acted upon by, or influence, the other party or other persons; (3)
      knowledge, actual or constructive, of the real facts; (4) lack of knowledge and the
      means of knowledge of the truth as to the facts in question; (5) reliance, in good
      faith, upon the conduct or statements of the party to be estopped; and (6) action
      or inaction based thereon of such a character as to change the position or status
      of the party claiming the estoppel.

  Appeal from the District Court for Douglas County: Gary B.
Randall, Judge. Affirmed.

  David A. Domina and Christopher A. Mihalo, of Domina
Law Group, P.C., L.L.O., for appellant.

  Thomas A. Grennan, Adam J. Wachal, and Abbie M.
Schurman, of Gross & Welch, P.C., L.L.O., for appellee.

   Heavican, C.J., Connolly, McCormack, and Miller-Lerman,
JJ., and Irwin, Judge.

      Heavican, C.J.
                       INTRODUCTION
   This case was originally docketed as an action for specific
performance and an accounting. The two actions were sev-
ered, with this court and the Nebraska Court of Appeals find-
ing for Dorothy Bauermeister and the other plaintiffs1 with
respect to the specific performance action. On remand, Waste
Management Co. of Nebraska, Inc. (WMN), was ordered to,
and did, convey title of the disputed property to the plaintiffs,
subject to specified exceptions.

 1	
      See, Bauermeister v. Waste Mgmt. Co., 280 Neb. 1, 783 N.W.2d 594
      (2010); Bauermeister v. Waste Mgmt. Co., A-09-019, 2010 WL 4009059
      (Neb. App. Oct. 12, 2010) (selected for posting to court Web site).
                 Nebraska Advance Sheets
	        BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	901
	                     Cite as 290 Neb. 899

   The accounting action then proceeded. The district court
found primarily for WMN. Bauermeister Deaver Ecology Land
Use Development, LLC (BDELUD), successor in interest to
the plaintiffs, appeals. We affirm.

                   FACTUAL BACKGROUND
   Fred and Dorothy Bauermeister and Richard and Clara
Deaver entered into an agreement with WMN on March 22,
1989, for the sale of 280 acres of farmland. WMN intended
to build a landfill on this property. This agreement provided
that WMN, as the purchaser, pay on a monthly basis to the
Bauermeisters and the Deavers, as sellers, $3,000 in base
rent and another $1, later adjusted to $1.15, per ton of refuse
added to the landfill (referred to as the “royalty fee” or “roy-
alty payment”).
   As relevant to this appeal, paragraph 6 of the agreement,
dealing with the construction of improvements, provided:
      Purchaser, at its cost, shall have the right to make any
      alternations, modifications or improvements to the
      Premises including, without limitation: (a) the demoli-
      tion of existing facilities without replacement thereof and
      renovation of existing facilities; (b) the right to construct
      roads, berms, ditches, stream diversions, embankments,
      temporary waste holding and storage facilities, office
      and garage facilities[,] laboratories, equipment shelters
      and any and all other facilities or land improvements
      necessary or required for Purchaser’s operations (includ-
      ing storage and maintenance of Purchaser’s waste col-
      lection vehicles); (c) the right to excavate, extract and,
      except as otherwise provided herein, relocate on the
      Premises for any purpose, gravel, soil, clay and all other
      minerals, materials and substances of any nature what-
      soever (whether solid, liquid or gaseous) produced at or
      under the Premises or emanating therefrom or incident
      to the utilization of the Premises as a Landfill (title to
      all of such substances being, upon extraction thereof
      from the Premises, the sole and exclusive property of
      Seller[s], except that the title to any gas generated by the
      Refuse shall remain the sole and exclusive property of
    Nebraska Advance Sheets
902	290 NEBRASKA REPORTS



     Purchaser); (d) the right to drill and establish water wells,
     install utilities, such as, but not limited to, electric lines,
     sewer lines, gas lines, underground storage tanks and
     telephone lines; (e) the right to carry out all gasification,
     waste handling, storage, treatment, disposal and similar
     operations, including, but not limited to, ponding, cover
     stock piling, fill and cover placement and compaction,
     drainage, pollution and nuisance prevention; and (f) the
     right to deposit subject to applicable permit within the
     Premises, all manner and form of solid and liquid waste
     materials. Seller[s] reserve[] for themselves, their suc-
     cessors, heirs and assigns, all insitu oil, gas and mineral
     deposits located on the Premises, and the right to extract
     from the Premises such deposits so long as such extrac-
     tion in no way interferes with the conduct of Purchaser’s
     Landfill operations.
  Paragraph 10 of the agreement, entitled “Taxes,” stated:
     Purchaser covenants that it will promptly pay, as and
     when they become due, all real estate taxes and assess-
     ments against the Premises, and all levies and impositions
     of any nature relating to or imposed upon the Premises.
     Purchaser’s obligations to pay real estate taxes shall con-
     tinue beyond closure of the Landfill site and remain until
     such time as the Premises no longer require post-closure
     monitoring as provided in Paragraph 17 hereof.
  Paragraph 14, regarding the removal of improvements,
provided:
     The parties hereto understand and agree that title to all
     buildings, equipment and other improvements (collec-
     tively, “Improvements”) installed, constructed or located
     by Purchaser upon the Premises shall remain in Purchaser
     and the same shall at all times remain Purchaser’s per-
     sonal property regardless of the nature of fixation to
     the Premises. Should Seller[s] exercise their option to
     purchase contained in Paragraph 30 hereof, Purchaser
     shall remove, unless otherwise agreed to in writing by
     Purchaser and Seller[s], all such Improvements that
     Purchaser has installed, constructed or located upon the
                 Nebraska Advance Sheets
	        BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	903
	                     Cite as 290 Neb. 899

     Premises, except those Improvements required or neces-
     sary to protect the environment, provided the same shall
     be removed within sixty (60) days after the termination or
     cancellation of this Agreement, or any extension thereof,
     for any reason. Title to any Improvements not so removed
     by Purchaser shall vest in Seller[s].
   Paragraph 16 provided for closure and postclosure monitor-
ing of the landfill:
     After termination of this Agreement and the exercise of
     Seller[s] of their option contained in Paragraph 30 hereof,
     for any reason, Seller[s] shall not disturb the integrity
     of the cover materials placed over the Premises in any
     manner, whether through excavation, cultivation, boring,
     regrading or otherwise, nor construct any structures on
     the Premises (except that paving shall be permitted), nor
     alter any venting wells, vegetation or drainage then exist-
     ing at the Premises unless Purchaser expressly consents
     to such activity until such time as the Premises no longer
     require post-closure monitoring. . . .
        After the termination of this Agreement and the exer-
     cise of Seller[s] of their option contained in Paragraph 30
     hereof, for any reason, Purchaser shall be granted access
     to the Premises to conduct such post-operation care,
     maintenance and monitoring of the Premises as it deems
     advisable, and/or shall be required by the then regulating
     government agency responsible for the oversight of the
     operation of sanitary landfills, and Purchaser shall con-
     tinue to care for, maintain and monitor the Landfill site
     for the greater of a period of ten (10) years or until such
     regulating government agency determines that such post-
     closure care is no longer required.
   Finally, paragraph 30 provided for the sellers’ option
to buy:
     If Seller(s), their successors or heirs so choose, Seller(s)
     shall have the option to repurchase all or any portion of
     the Premises from Purchaser in consideration for the sum
     of One Dollar ($1.00), at the termination, for any reason,
     of this Agreement, and Purchaser shall be obligated to
    Nebraska Advance Sheets
904	290 NEBRASKA REPORTS



      sell the Premises to Seller(s), their successors or heirs, if
      they so choose. Seller[s’] option may be exercised from
      the date of termination of the Landfill until two years
      after the date of termination of the required monitoring of
      the Landfill pursuant to Paragraph 16.
         ....
         The parties shall execute a short form memorandum of
      this option pertaining to each parcel, as deeded, in record-
      able form which shall be recorded in the official records
      (Register of Deeds) in Douglas County, Nebraska.
(Emphasis supplied.)
   WMN began receiving municipal solid waste at the site on
September 1, 1989. Municipal solid waste generates methane
gas. In the early years, this gas was collected and “flared” off,
as otherwise the gas was a nuisance, possible contaminant,
and fire hazard. But beginning in spring 2001, WMN and the
Omaha Public Power District entered into a series of agree-
ments whereby the district agreed to purchase the landfill
gases generated at the site. According to the record, WMN
had total gross revenues of $1,224,231.91 in landfill gas
sales, as well as $369,594.19 in tax credits under the federal
tax code.
   Meanwhile, on June 24, 2002, WMN and another company
entered into an agreement for a monofill to be located on the
site. A monofill is a type of landfill that accepts only one type
of waste—in this case, gypsum—from the company’s nearby
plant. WMN began accepting gypsum in January 2003. During
this time, it is undisputed that WMN made all base rent and
royalty payments.
   On November 19, 2003, WMN stopped accepting munici-
pal solid waste at the site, but continued to accept gypsum at
the monofill. WMN continued to make base rent and royalty
payments as a result of the operation of the monofill.
   On August 31, 2006, the Bauermeisters and the Deavers
attempted to exercise their option to purchase under para-
graph 30 of the agreement. On October 17, they filed suit
against WMN for specific performance and an accounting.
On October 18, 2007, they made a second attempt to exercise
                 Nebraska Advance Sheets
	        BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	905
	                     Cite as 290 Neb. 899

their option. As explained in more detail below, a trial, appeal,
remand, and eventually judgment for the Bauermeisters and
the Deavers followed. On March 17, 2011, WMN executed
deeds for the property in favor of the Bauermeisters and
the Deavers.
   In December 2009, WMN made a final base rental payment
to the Bauermeisters and the Deavers. In October 2010, WMN
made a final royalty payment to the Bauermeisters. A month
later, in November, WMN stopped accepting gypsum at the
monofill. According to the record, WMN’s net revenue for the
monofill was $4,653,313.93.
   At this point, neither the landfill nor the monofill are accept-
ing further waste. Both are now in their respective monitoring
periods as required by state law.

                 PROCEDURAL BACKGROUND
    In the action filed on October 17, 2006, the Bauermeisters
and the Deavers sought specific performance, accounting, quiet
title, and declaratory judgment. WMN asserted several affirma-
tive defenses, including that Dorothy Bauermeister and Clara
Deaver lacked standing and were not the real parties in inter-
est, and that the option to repurchase violated the common-law
rule against perpetuities.
    The district court severed the specific performance and quiet
title actions from the accounting and declaratory judgment
actions and concluded that Dorothy Bauermeister and Clara
Deaver had standing and were the real parties in interest. The
district court then concluded that they clearly intended to exer-
cise the option to repurchase and had validly done so. WMN
was ordered to convey title of the property to the Bauermeisters
and the Deavers as follows: “Defendant, [WMN], shall convey,
by warranty deed, with a covenant against liens, mortgages, or
encumbrances, except encumbrances of record as of March 22,
1989, all the following described real estate . . . .” (Emphasis
supplied.) As noted, the parties signed the purchase agreement
on March 22, 1989.
    In lieu of a supersedeas bond for an appeal, WMN sought
the court’s approval of its deposit of two warranty deeds with
    Nebraska Advance Sheets
906	290 NEBRASKA REPORTS



the court2 and served notice of its request on BDELUD. The
court approved the deposit of the warranty deeds in lieu of a
bond on January 2, 2009, and WMN filed its appeal on the
same day. Only a portion of the deeds were included in the
record of the 2009 appeal. But copies of the warranty deeds in
the 2014 transcript show that they were signed on February 4,
2009, shortly after the first appeal was docketed. The excep-
tions in the warranty deeds that the court approved were con-
sistent with its judgments against WMN:
         GRANTOR covenants with GRANTEES that
      GRANTOR:
         (1) is lawfully seized of such real estate and that it is
      free from encumbrances, except:
         a) encumbrances of record as of March 22, 1989;
         b) applicable local, state and federal ordinances, rules,
      regulations, statutes, permits and licenses;
         c) encumbrances arising by law from the use of the real
      property as a landfill and/or monofill;
         d) the Purchase Agreement executed March 22,
      1989 . . . .
   In the first appeal, the Court of Appeals reversed, conclud-
ing that the option was barred by the common-law rule against
perpetuities.3 But we reversed, concluding that the common-
law rule against perpetuities did not apply to the option
from the agreement.4 We ordered the cause remanded to the
Court of Appeals for further consideration of WMN’s appeal.
Finding no other error, the Court of Appeals affirmed the

 2	
      See Neb. Rev. Stat. § 25-1917 (Reissue 2008) (“[i]nstead of the undertaking
      prescribed in subdivision (2) of section 25-1916, the conveyance or other
      instrument may be executed and deposited with the clerk of the court in
      which the judgment was rendered or order made, to abide the judgment of
      the appellate court”).
 3	
      Bauermeister v. Waste Mgmt. Co., No. A-09-019, 2009 WL 6473172 (Neb.
      App. Dec. 8, 2009) (selected for posting to court Web site), reversed,
      supra note 1, 280 Neb. 1, 783 N.W.2d 594 (2010).
 4	
      Bauermeister v. Waste Mgmt. Co., supra note 1, 280 Neb. 1, 783 N.W.2d
      594 (2010).
                     Nebraska Advance Sheets
	            BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	907
	                         Cite as 290 Neb. 899

district court’s judgment.5 Following this affirmance, WMN
conveyed the warranty deeds to the the Bauermeisters and
the Deavers.
   The accounting portion of the underlying action was then
heard by the district court. On March 31, 2014, the district
court entered an order largely finding for WMN. First, the
district court found that the 1989 agreement had continuing
viability, because the parties both had continuing obligations
under that agreement. Second, the district court concluded that
WMN must continue to monitor the landfill for a period of
time and pay taxes on the property, per the agreement. Third,
the district court found that WMN was entitled to the profits
earned from the landfill gases and owned the pipes and under-
ground equipment used in the gasification process. Fourth, the
district court found that the Bauermeisters and the Deavers,
now BDELUD, were entitled to payment from WMN for its
failure to remove structures from the property which were
unrelated to the ongoing environmental monitoring process.
Fifth, because the Bauermeisters and the Deavers waived any
objection to the monofill, the district court concluded that
BDELUD was not entitled to any profit received by WMN
in connection with its operation of the monofill. And because
the district court concluded that the gas refuse and monofill
profits were owned by WMN, BDELUD was not entitled to
an accounting or a declaratory judgment or recovery for con-
version. The district court further declined to address any of
WMN’s affirmative defenses and declined to award prejudg-
ment interest.
   On April 16, 2014, WMN paid $88,499.80 to satisfy the
judgment against it. Meanwhile, BDELUD filed a motion for
new trial, which was denied on June 6. BDELUD appeals.
               ASSIGNMENTS OF ERROR
  On appeal, BDELUD’s assignments of error can be restated
and consolidated into two general assignments: The district

 5	
      Bauermeister v. Waste Mgmt. Co., supra note 1, No. A-09-019, 2010 WL
      4009059 (Neb. App. Oct. 12, 2010) (selected for posting to court Web
      site).
    Nebraska Advance Sheets
908	290 NEBRASKA REPORTS



court erred in (1) finding that WMN owned the landfill gases
and equipment associated with collecting and transporting the
landfill gases and that WMN was entitled to all landfill gas
revenue and (2) finding that BDELUD was not entitled to past
or future revenues from the monofill.
                  STANDARD OF REVIEW
   [1,2] An action to quiet title and for an accounting sound
in equity.6 On appeal from an equity action, an appellate court
resolves questions of law and fact independently of the trial
court’s determinations.7
                           ANALYSIS
Landfill Gases.
   BDELUD makes several assignments of error regarding the
ownership of the landfill gases, which can be restated as one:
that as of September 1, 2006, the day after the Bauermeisters
and the Deavers notified WMN of their intent to exercise their
option to purchase under the agreement, they were the owners
of record of the landfill gases. BDELUD argues that WMN
did not raise the issue of the landfill gases in the specific per­
formance action and that the ownership of those gases was
finally decided in BDELUD’s favor when the Court of Appeals
found that the Bauermeisters and the Deavers were the owners
of the real estate. In other words, BDELUD argues that the
district court’s decision was barred by res judicata or the law-
of-the-case doctrine. We disagree.
Law-of-the-Case Doctrine.
   To determine the application of the law-of-the-case doctrine,
we must necessarily review our record of the 2009 appeal. A
court may judicially notice adjudicative facts, which are not
subject to reasonable dispute, at any stage of the proceeding.8
In interwoven and interdependent cases, we can examine our
own records and take judicial notice of the proceedings and

 6	
      See, Schellhorn v. Schmieding, 288 Neb. 647, 851 N.W.2d 67 (2014);
      Robertson v. Jacobs Cattle Co., 285 Neb. 859, 830 N.W.2d 191 (2013).
 7	
      Id.
 8	
      Pennfield Oil Co. v. Winstrom, 276 Neb. 123, 752 N.W.2d 588 (2008).
                     Nebraska Advance Sheets
	            BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	909
	                         Cite as 290 Neb. 899

judgment in a former action involving one of the parties.9 We
can also take judicial notice of a document, including briefs
filed in an appeal, in a separate but related action concerning
the same subject matter in the same court.10 We turn to the
guiding principles under the law-of-the-case doctrine.
   The law-of-the-case doctrine reflects the principle that an
issue litigated and decided in one stage of a case should not
be relitigated at a later stage.11 Under this doctrine, an appel-
late court’s holdings on issues presented to it conclusively
settle all matters ruled upon, either expressly or by necessary
implication.12 The doctrine applies with greatest force when an
appellate court remands a case to an inferior tribunal.13 Upon
remand, a district court may not render a judgment or take
action apart from that which the appellate court’s mandate
directs or permits.14
   Additionally, under the mandate branch of the law-of-the-
case doctrine, a decision made at a previous stage of litiga-
tion, which could have been challenged in the ensuing appeal
but was not, becomes the law of the case; the parties are
deemed to have waived the right to challenge that decision.15
But an issue is not considered waived if a party did not have
both an opportunity and an incentive to raise it in a previ-
ous appeal.16
   Here, the court’s final order in the 2009 appeal shows that
WMN’s reservations of rights in the purchase agreement were
encumbrances on the warranty deed, and we agree. As stated,
the last sentence of paragraph 30 required the parties to record
the sellers’ purchase option “as deeded.” That term must be

 9	
      Id.
10	
      Id.
11	
      In re 2007 Appropriations of Niobrara River Waters, 283 Neb. 629, 820
      N.W.2d 44 (2012).
12	
      Id.
13	
      County of Sarpy v. City of Gretna, 276 Neb. 520, 755 N.W.2d 376 (2008).
14	
      Id.
15	
      Id.
16	
      Id.
    Nebraska Advance Sheets
910	290 NEBRASKA REPORTS



understood in the context of the entire agreement, and the
court’s judgment excluded encumbrances of record as of March
22, 1989, from its order to convey the property. This exclusion
implicitly referred to the parties’ purchase agreement.
   We conclude that the records in the 2009 appeal show that
WMN had no incentive to raise its rights under the 1989
purchase agreement, because the court had permitted it to
exclude its rights under the purchase agreement from the war-
ranty deeds that the court ordered and approved. Additionally,
we note that BDELUD has repeatedly claimed that under the
agreement, WMN has continuing obligations to pay property
taxes and to engage in environmental monitoring. These claims
illustrate that the parties understood the purchase agreement as
imposing continuing obligations and rights. It is untenable for
BDELUD to claim that it is entitled to ongoing benefits under
the agreement, but with no obligations.
   In sum, because WMN had no incentive to raise its rights
under the purchase agreement in the first appeal, and because
those issues were not presented to us on appeal and are not
required to be presented to us, neither our mandate nor the
Court of Appeals’ mandate precluded WMN from relying on
those rights in the proceedings on remand.
   Relatedly, res judicata did not preclude WMN from assert-
ing its property interests on remand, because the court spe-
cifically allowed WMN to include exceptions in the warranty
deeds for its rights under the purchase agreement.17 We reject
BDELUD’s argument that our decision in the 2009 appeal pre-
cluded the court from considering the parties’ rights under the
1998 purchase agreement.
Purchase Agreement Controls
Right to Landfill Gases.
  BDELUD concedes the purchase agreement expressly gives
WMN title to the landfill gases and to the proceeds from

17	
      See State v. York, 273 Neb. 660, 665-66, 731 N.W.2d 597, 603 (2007)
      (stating that “[d]octrine of res judicata, or claim preclusion, only bars
      the relitigation of a matter that has been directly addressed or necessarily
      included in a former adjudication if the former judgment was on the
      merits”).
                 Nebraska Advance Sheets
	        BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	911
	                     Cite as 290 Neb. 899

landfill gasification. As set out above, paragraph 6 explicitly
reserves to the seller “all insitu oil, gas and mineral deposits
located on the Premises.” BDELUD directs us to no case law,
and we find none, that definitively holds methane gas produced
by the refuse is a mineral. And we need not decide that issue
here, because paragraph 6 explicitly gave WMN title to gas
generated by refuse in the landfill:
      [WMN shall have] the right to excavate, extract and . . .
      relocate . . . all other minerals, materials and substances
      of any nature whatsoever (whether solid, liquid or gas-
      eous) produced at or under the Premises or emanating
      therefrom or incident to the utilization of the Premises
      as a Landfill (title to all of such substances being, upon
      extraction thereof from the Premises, the sole and exclu-
      sive property of Seller[s], except that the title to any gas
      generated by the Refuse shall remain the sole and exclu-
      sive property of [WMN].
(Emphasis supplied.)
   BDELUD’s only argument against applying these provisions
is that upon reconveyance, all aspects of the real estate belong
to it. We have rejected its argument that the court could not
consider restrictions in the conveyance under the 1989 pur-
chase agreement. We conclude there is no merit to BDELUD’s
assignments of error regarding the landfill gases.

Landfill Gas Fixtures.
   The same reasoning applies to BDELUD’s argument that
the district court erred in concluding that the structures on the
property used to collect the landfill gases were the property of
WMN. BDELUD contends that these structures are fixtures
and, further, that these issues were decided when this court
and the Court of Appeals adjudicated the real estate ownership
issues, as is discussed in further detail above. Because we have
rejected that argument, paragraph 14 of the purchase agreement
controls. Under that provision, whether WMN’s gas collection
system could be considered a fixture is irrelevant:
      [T]itle to all buildings, equipment and other improve-
      ments (collectively, “Improvements”) installed, con-
      structed or located by Purchaser upon the Premises shall
    Nebraska Advance Sheets
912	290 NEBRASKA REPORTS



      remain in Purchaser and the same shall at all times remain
      Purchaser’s personal property regardless of the nature of
      fixation to the Premises. Should Seller[s] exercise their
      option to purchase contained in Paragraph 30 hereof,
      Purchaser shall remove, unless otherwise agreed to in
      writing by Purchaser and Seller[s], all such Improvements
      that Purchaser has installed, constructed or located upon
      the Premises, except those Improvements required or nec-
      essary to protect the environment . . . .
(Emphasis supplied.) Additionally, paragraph 6(e) gave WMN
“the right to carry out all gasification, waste handling, storage,
treatment, disposal and similar operations.”
   Thus, prior to the exercise of the option by BDELUD’s
predecessors, the gas collection system was WMN’s personal
property, regardless of its fixation to the site. The record shows
that the collection and removal of the landfill gases is neces-
sary to protect the environment. And BDELUD has consist­
ently noted that WMN has ongoing environmental monitoring
responsibilities. We conclude that the parties did not intend for
the collection system to become a fixture of the property after
BDELUD exercised its purchase option as long as WMN was
exercising its rights under paragraph 6.

Monofill.
    In its last set of assignments of error, BDELUD assigns
that the district court erred in finding that it was not entitled
to past or future monofill revenues. The district court con-
cluded that the predecessors of BDELUD had not objected
to the construction of the monofill, had accepted royalty
payments in connection with the gypsum deposits made on
the land, and had accordingly waived and were equitably
estopped from arguing that it had any entitlement to mono-
fill revenues.
    [3-5] Waiver is a voluntary relinquishment of a known
right.18 The doctrine of equitable estoppel applies where, as

18	
      See State ex rel. Wagner v. Amwest Surety Ins. Co., 280 Neb. 729, 790
      N.W.2d 866 (2010).
                     Nebraska Advance Sheets
	            BAUERMEISTER DEAVER ECOL. v. WASTE MGMT. CO.	913
	                         Cite as 290 Neb. 899

a result of conduct of a party upon which another person
has in good faith relied to his detriment, the acting party is
absolutely precluded, both at law and in equity, from assert-
ing rights which might have otherwise existed.19 Six elements
must be satisfied for the doctrine of equitable estoppel to
apply: (1) conduct which amounts to a false representation or
concealment of material facts or, at least, which is calculated
to convey the impression that the facts are otherwise than, and
inconsistent with, those which the party subsequently attempts
to assert; (2) the intention, or at least the expectation, that such
conduct will be acted upon by, or influence, the other party
or other persons; (3) knowledge, actual or constructive, of
the real facts; (4) lack of knowledge and the means of knowl-
edge of the truth as to the facts in question; (5) reliance, in
good faith, upon the conduct or statements of the party to be
estopped; and (6) action or inaction based thereon of such a
character as to change the position or status of the party claim-
ing the estoppel.20
   In finding waiver and estoppel, the district court noted
that “[BDELUD’s] predecessors’ communications and conduct,
and [BDELUD’s] ongoing receipt of benefits under the 1989
Agreement illustrate [BDELUD] consented to the Monofill
and considered the Monofill to be part of the 1989 Agreement.
[BDELUD] cannot now ask for money [WMN] has made in
relation to the Monofill.”
   We agree. Waiver and estoppel are both evident from the
actions of BDELUD’s predecessors, the Bauermeisters and the
Deavers. At trial, BDELUD argued that the agreement did not
envision using the land as an industrial landfill and that after
it was built in 2001, it was not anticipated that the municipal
landfill would close in 2003. And indeed, there is no mention
of a monofill or industrial landfill in the agreement.
   But there is a course of action by BDELUD’s predeces-
sors that suggests acquiescence in the chain of events as they

19	
      Christiansen v. County of Douglas, 288 Neb. 564, 849 N.W.2d 493 (2014).
20	
      American Family Mut. Ins. Co. v. Regent Ins. Co., 288 Neb. 25, 846
      N.W.2d 170 (2014).
    Nebraska Advance Sheets
914	290 NEBRASKA REPORTS



occurred. When the monofill was anticipated in and around
2001, notice was sent to neighboring landowners, including
to BDELUD’s predecessors. Those predecessors were rep-
resented by counsel at meetings on the construction of the
monofill. They did not object and in fact indicated that they
had no objection so long as they continued to receive royalty
payments. In fact, in a letter to WMN regarding the monofill,
counsel acting on behalf of the Bauermeisters suggested that
the monofill was “clearly within the Purchase Agreement and
related documents” and that the Bauermeisters, among oth-
ers, were “clearly entitled to the existing royalty on waste
of any kind deposited in the [monofill] under the terms
of the Purchase Agreement.” Those royalty payments were
paid by WMN right up until the closure of the monofill and
past the August 31, 2006, date of the exercise of the option
to purchase.
   This course of action is contrary to the BDELUD’s now-
stated contention that its predecessors never intended to get
their land back with gypsum reserves on it, or that they never
intended that the monofill would operate past the operation of
the landfill. This course of action suggests waiver, and further
suggests that BDELUD should be estopped from asserting any
position contrary to this course of action.
   BDELUD’s assignments of error regarding the monofill are
also without merit.
                       CONCLUSION
  The decision of the district court is affirmed.
                                                    Affirmed.
  Wright, Stephan, and Cassel, JJ., not participating.
