<PAGE>

                                                                    EXHIBIT 10.1


                              AMENDMENT NO. 10 TO
                              -------------------
                        PURCHASE AND SALE AGREEMENT AND
                        -------------------------------
                           JOINT ESCROW INSTRUCTIONS
                           -------------------------


          THIS AMENDMENT NO. 10 TO PURCHASE AND SALE AGREEMENT AND JOINT ESCROW
INSTRUCTIONS (this "Amendment") is made and entered into and effective as of
                    ---------
April 20, 2000, by and between KAISER VENTURES INC., a Delaware corporation and
KAISER STEEL LAND DEVELOPMENT INC., a Delaware corporation (collectively,
"Seller"), and ONTARIO VENTURES I, LLC, a Delaware limited liability company
-------
("Buyer").
-------

                                    RECITALS
                                    --------

          A.   WHEREAS, Buyer and Seller have entered into that certain Purchase
and Sale Agreement and Joint Escrow Instructions dated as of October 19, 1999 as
amended by that certain Amendment No. 1 to Purchase and Sale Agreement and Joint
Escrow Instructions and Side Letter Agreement dated as of November 2, 1999,  by
that certain Amendment No. 2 to Purchase and Sale Agreement and Joint Escrow
Instructions and Side Letter Agreement dated as of November 12, 1999, by that
certain Amendment No. 3 to Purchase and Sale Agreement and Joint Escrow
Instructions and Side Letter Agreement dated as of November 19, 1999, by that
certain Amendment No. 4 to Purchase and Sale Agreement and Joint Escrow
Instructions and Side Letter Agreement dated as of November 30, 1999, by that
certain Amendment No. 5 to Purchase and Sale Agreement and Joint Escrow
Instructions And Side Letter Agreement dated as of February 4, 2000, and by that
certain Amendment No. 6 to Purchase and Sale Agreement and Joint Escrow
Instructions And Side Letter Agreement dated as of March 6, 2000, by that
certain Amendment No. 7 to Purchase and Sale Agreement and Joint Escrow
Instructions and Side Letter dated as of March 10, 2000, and by that certain
Amendment No. 8 to Purchase and Sale Agreement and Joint Escrow Instructions and
Side Letter dated as of March 13, 2000, and by that certain Amendment No. 9 to
Purchase and Sale Agreement and Joint Escrow Instructions and Side Letter dated
as of March 14, 2000 (collectively, the "Purchase Agreement"); and
                                         ------------------

          B.   WHEREAS, Buyer and Seller desire to again amend and the Purchase
Agreement and Side Letter Agreement, as more particularly set forth herein.

          NOW, THEREFORE, in consideration of the mutual covenants and
agreements herein contained and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, Buyer and Seller
hereby agree as follows:

                                   AGREEMENT
                                   ---------

          1.   Amendments.  The Purchase Agreement and Side Letter Agreement are
               ----------
hereby amended as follows:

          A.  The "Contingency Date" (as defined in Section 1.11 of the Purchase
                   ----------------
          Agreement) shall be extended further to May 12, 2000. On or prior to
May 12, 2000, Buyer shall have exercised its right to terminate Escrow pursuant
to Section 4.7 of the Purchase Agreement with respect to all contingencies
except the DTSC Issues (defined below), or such right to terminate Escrow shall
be deemed waived by Buyer. On or prior to May 12, 2000, Seller shall have
exercised its right to
<PAGE>

terminate Escrow pursuant to Section 4.8 of the Purchase Agreement, or such
right to terminate Escrow shall be deemed waived by Seller.

          If the DTSC Issues (as defined below) have not been resolved (as
herein described) and approved by Buyer on or prior to May 12, 2000, then the
Contingency Date shall be extended automatically to May 19, 2000 solely with
respect to Buyer's approving or disapproving the DTSC Issues provided that the
May 12 Deposit is timely made as provided in Paragraph B below.   As used in
this Amendment, the term "DTSC Issues" means the DTSC's determination of the
                          -----------
nature and scope of any material closure requirements for any RCRA units
identified on the Real Property, the CSI Property and the Speedway Property, as
more particularly set forth in the three following memoranda: (i) a memorandum
from Kathy San Miguel to Files via Robert M. Senga, Unit Chief dated April 13,
2000; (ii) a memorandum from Kathy San Miguel to Files via Robert M. Senga, Unit
Chief dated April 10, 2000; and (iii) a memorandum from Thomas M. Seckington to
Greg Holmes dated April 12, 2000 and Buyer's approval or disapproval of the
impact of such requirements on the Property, the IT Contract and the Insurance
Policies.  The foregoing DTSC Issues shall be deemed to be "resolved" upon
Buyer's receipt of a letter or memorandum from the DTSC to Buyer which sets
forth the DTSC's final characterization of the nature and scope of the material
closure requirements for all defined RCRA units which must be assumed and
performed by Buyer following the Close of Escrow.  Buyer shall thereafter have
the right to approve of the manner in which such requirements have been
incorporated into the final Consent Order and the impact of such requirements on
the Property, including, without limitation, the IT Contract and the insurance
policies.  Buyer's approval shall be given or withheld, in Buyer's sole and
absolute discretion, on or before the earlier of the fifth (5th) business day
after Buyer's receipt of the letter described above or the Contingency Date (as
it may have been extended pursuant to this paragraph).  If Buyer timely
determines that the DTSC Issues have not been resolved as provided above and
approved by Buyer, then Buyer shall have the right to terminate Escrow in
accordance with Section 4.7 of the Purchase Agreement.  Buyer's failure to
notify Seller and Escrow Holder on or prior to the earlier of the fifth (5th)
business day after Buyer's receipt of the letter described above or the
Contingency Date (as it may have been extended pursuant to this paragraph) of
Buyer's election to terminate Escrow in accordance with Section 4.7 of the
Purchase Agreement based upon the DTSC Issues shall constitute a waiver of
Buyer's right to terminate the Purchase Agreement pursuant to Section 4.7 based
upon the DTSC Issues.

          B.   As consideration for the extension of the Contingency Date,
concurrent with the execution of this Amendment, Buyer shall deliver to Escrow
Holder a nonrefundable deposit in the amount of Fifty Thousand Dollars ($50,000)
(the "April 20 Deposit"), which April 20 Deposit shall be released to Seller as
      ----------------
set forth in Section 3.1.2 of the Purchase Agreement.  If the DTSC Issues have
not been resolved and approved on or prior to May 12, 2000 and Escrow has not
been terminated by Buyer or Seller pursuant to their respective rights in
Article 4 of the Purchase Agreement, then on May 12, 2000,  Buyer shall deliver
to Escrow Holder a refundable deposit in the amount of Fifty Thousand Dollars
($50,000) (the "May 12 Deposit"), which deposit shall be held by Escrow Holder
                --------------
as provided in Section 3.1.2 of the Purchase Agreement.  If the Contingency Date
is extended to May 19, 2000 pursuant to Paragraph A above and Buyer does not
exercise its right to terminate Escrow on or prior to the extended Contingency
Date based upon the DTSC Issues, then Buyer shall deliver to Escrow Holder on
May 19, 2000 a nonrefundable deposit in the amount of (i) One Hundred Thousand
Dollars ($100,000) if Buyer and DTSC have reached an agreement on a final
Consent Order for the former Kaiser Steel Mill, or (ii) Two Hundred Thousand
Dollars ($200,000) if Buyer and DTSC have not reached agreement on a final
Consent Order for the former Kaiser Steel Mill by such date (either sum

                                       2
<PAGE>

shall be herein referred to as the "Final Deposit"). The May 12 Deposit and the
                                    -------------
Final Deposit shall be released to Seller as provided in Section 3.1.2 below.
Whether the DTSC and Buyer have agreed upon a final Consent Order shall be
evidenced by (x) a letter executed and delivered by the DTSC stating that the
DTSC is willing to execute an attached Consent Order, without any change,
modification or any contingency, subject only to Buyer or its permitted assignee
taking title to the Real Property, and (y) a letter from Buyer to Seller stating
that Buyer or its permitted assignee will execute and deliver the Consent Order
attached to the DTSC's letter without any change, modification or amendment or
any contingency other than Buyer or its permitted assignee taking title to the
Real Property.

          C.   The "Closing Date" (as defined in Section 1.9 of the Purchase
                    ------------
Agreement) shall be revised to mean June 29, 2000, unless Buyer and Seller
mutually agree to an earlier date.

          D.   Notwithstanding any other provision of this Amendment, in the
event the DTSC Issues are resolved and approved of or disapproved of on or prior
to May 12, 2000, then the Contingency Date shall not be extended beyond May 12,
2000.  In such case, if the Purchase Agreement is not terminated by Buyer or
Seller in accordance with Article 4 thereof on or prior to May 12, 2000, the
Final Deposit shall be delivered to Escrow Holder together with the May 12
Deposit, and the Closing Date shall be revised to be one business day earlier
for each business day prior to May 19, 2000 that the DTSC Issues are resolved
and approved of.

          E.   Section 3.1.2 of the Purchase Agreement is hereby revised to read
in full as follows:

          3.1.2    Disposition of Deposit.  To date, Buyer has delivered to
                   ----------------------
          Escrow Holder, which has in turn released to Seller, the total sum of
          Two Hundred Fifty Thousand Dollars ($250,000.00), which is the sum of
          Seventy-Five Thousand Dollars ($75,000.00) which was released to
          Seller on December 17, 1999, the sum of Seventy-Five Thousand Dollars
          ($75,000.00) which was released to Seller on February 4, 2000,  and
          the sum of One Hundred Thousand Dollars ($100,000.00) which was
          released to Seller on March 13, 2000 (collectively, the "Initial
                                                                   -------
          Deposit"). Any portion of the Initial Deposit, the April 20 Deposit,
          -------
          the May 12 Deposit, and the Final Deposit which has been released to
          Seller prior to the termination of the Agreement shall be retained by
          Seller and become non-refundable to Buyer, so long as Seller has not
          materially defaulted, including, without limitation, by not delivering
          the Deed.  Notwithstanding the foregoing, the May 12 Deposit shall be
          retained by Escrow Holder until (a) the termination of Escrow by Buyer
          based upon the unresolved DTSC Issues, in which case the May 12
          Deposit and all interest thereon shall be returned to Buyer promptly
          following such termination, or (b) Buyer's waiver or approval of the
          DTSC Issues, in which case the May 12 Deposit and all interest thereon
          shall be delivered to Seller together with the Final Deposit.
          Following the Contingency Date, in the event this Agreement is
          terminated or the Close of Escrow fails to occur by reason of Buyer's
          default hereunder, the entire Initial Deposit, the entire April 20
          Deposit, the entire May 12 Deposit, and, if required to be delivered
          to Escrow Holder pursuant to this Agreement,  the entire Final Deposit
          (including all interest accrued on each of them prior to delivery to
          Seller) shall constitute liquidated damages pursuant to Section 6.2
          below.  In the event this Agreement is terminated by reason of
          Seller's material default or the Close of Escrow fails to occur by
          reason of Seller's material default hereunder, the entire Initial
          Deposit, the entire April 20 Deposit, the

                                       3
<PAGE>

          entire May 12 Deposit, and, if delivered to Escrow Holder pursuant to
          this Agreement, the entire Final Deposit (including all interest
          accrued on each of them prior to delivery to Seller) shall be returned
          to Buyer. Upon the Close of Escrow, the entire Deposit, the entire
          April 20 Deposit, the entire May 12 Deposit and the entire Final
          Deposit (including all interest thereon) shall be credited towards the
          payment of the Purchase Price.

          F.   As used in any other provision of the Purchase Agreement that is
not expressly modified by this Amendment, the term "Deposit" shall refer to the
                                                    -------
Initial Deposit, the April 20 Deposit, the May 12 Deposit and the Final Deposit
and any interest which has accrued thereon.

          G.   Section 4.7 of the Agreement is hereby replaced with the
following:

               4.7  Termination by Buyer Prior to Contingency Date.  Buyer shall
                    ----------------------------------------------
     have the right, exercisable in Buyer's sole and absolute discretion at any
     time on or prior to the Contingency Date, to terminate this Agreement for
     any reason or no reason whatsoever; provided, however that following May
                                         --------  -------
     12, 2000, Buyer shall have the right, exercisable in Buyer's sole and
     absolute discretion, to terminate this Agreement only based upon the DTSC
     Issues, in accordance with Section 4.9 below.  If Buyer shall, on or prior
     to the Contingency Date, deliver written notice of termination of this
     Agreement to Seller and Escrow Holder, then this Agreement shall terminate,
     Seller shall retain any portion of the Initial Deposit and  the April 20
     Deposit which has been released to Seller prior to the date of such
     termination, the May 12 Deposit shall be returned to Buyer, Escrow shall be
     canceled, Seller and Buyer shall each pay one-half (1/2) of all Title
     Company and Escrow cancellation fees, and Buyer and Seller shall have no
     further obligations to each other hereunder, except as otherwise expressly
     set forth herein.  In that event, Buyer shall return to Seller all
     documents delivered to Buyer at the request of Seller.  Buyer's failure to
     deliver written notice of Buyer's election to terminate this Agreement in
     accordance with this Section 4.7 shall constitute a waiver of Buyer's right
     to disapprove any matters set forth in this Article 4, except as expressly
     provided in Section 4.1, above.

          H.   Section 4.8 of the Purchase Agreement is hereby revised to read
in full as follows:

          4.8  Termination by Seller.   If Buyer disapproves any of (i) the
               ---------------------
          Adjacent Property Indemnification and Other Agreements or (ii) the
          Permits or (iii) any of the Other Assumed Obligations and Liabilities,
          then Seller shall have the right, within fourteen (14) days after
          Buyer gives notice of such disapproval but in no event later than May
          12, 2000, to terminate this Agreement, in which event the Seller shall
          retain any portion of the Initial  Deposit and the April 20  Deposit
          which has been released to Seller prior to the termination of the
          Agreement as set forth in Section 3.1.2 hereof. Notwithstanding
          anything to the contrary, with respect to the following railroad
          obligation only, Buyer shall only be obligated to assume Kaiser
          Venture Inc.'s guaranty of and the obligation of Kaiser Recycling
          Corporation ("KRC") to "provide space for a rail storage yard
                        ---
          sufficient to meet the needs of the Company," as required by Section
          2.2(A) of the Members Operating Agreement of West Valley MRF, LLC
          ("MRF") dated as of June 19, 1997 in accordance with and to the extent
           ----
          of the matters set forth below in this Section.  Such agreement is as
          follows:  (a) MRF must use the Tar Pits Parcel for rail storage
          purposes to the extent set forth below; (b) Buyer will, without
          charge, grant to MRF through Escrow at the Close of Escrow, a
          nonexclusive easement, to be used by MRF to the extent the Tar Pits
          Parcel is

                                       4
<PAGE>

          not available for MRF's rail storage purposes, drafted by Buyer to MRF
          (but MRF shall pay any recording costs), KRC, or Seller granting to
          MRF the nonexclusive right to use the existing rail tracks on Parcel 5
          of the Land (APN No. 229-291-29) for MRF's rail storage purposes (x)
          for a storage period not exceeding 48 hours, except that on weekends
          and holidays such period shall be extended to 72 hours, (y) for
          storage of rail cars being delivered to or picked up from MRF, and (z)
          for an aggregate use at any one time not to exceed one and one-half
          (1-1/2) trains (hereinafter called "Rail Storage"), all subject to the
                                              ------------
          conditions set forth below (the "Existing Track Easement"), (c) Buyer
                                           -----------------------
          shall, without charge, through Escrow at the Close of Escrow, grant to
          MRF a new, nonexclusive blanket easement pursuant to which MRF may, at
          its sole cost and expense, construct on such portions of the area of
          said Parcel 5 of the Land on which there is no existing track as Buyer
          may reasonably approve, additional railroad track to be used for Rail
          Storage or spur line purposes, subject to the conditions set forth
          below (the "Additional Track Easement"), so long as such tracks are
                      -------------------------
          (aa) in a location reasonably approved by Buyer or its assigns after
          consultation with the MRF, (bb) available for use by Buyer and its
          assignees if not in use by or necessary for the operations of MRF, and
          (cc) are consistent with any and all rights granted to any party prior
          to the date of notification by MRF to Buyer or its assigns that MRF
          intends to construct such additional railroad track, including,
          without limitation, rights granted to Speedway Development Corporation
          or The California Speedway Corporation; and (d) Buyer shall, without
          charge, through Escrow at the Close of Escrow, grant to MRF, subject
          to the easement granted for the San Sevaine Channel, and subject to
          there being property which satisfies the condition set forth in this
          (d), a nonexclusive easement to construct (at MRF's sole cost and
          expense) additional railroad track to be used for Rail Storage or spur
          line purposes, subject to the conditions described below (the "San
                                                                         ---
          Sevaine Track Easement"), so long as Buyer and its assigns may use
          ----------------------
          such track if not in use by or necessary for the operations of MRF.
          Such easement shall only be used to the extent that the ultimate
          location and construction of the San Sevaine Channel is such that
          there exists, after such location and construction, a portion of the
          Land which lies east of the San Sevaine Channel and west of the
                          ----                                ----
          easterly boundary of the Land. Buyer (at its cost) and Seller (at its
          cost) shall negotiate in good faith the final form of each of such
          above-referenced easements on or prior to May 12, 2000.

          Buyer shall have the right to establish reasonable rules for the use
          and conduct of operations of the railroad and on the rail storage
          facilities, including provisions to ensure that no activity or
          construction undertaken by MRF shall cause Buyer or its assigns to
          incur any out-of-pocket third party cost or expense.

          At such time as the MRF begins to use any easement for Rail Storage,
          Buyer shall request that CSI and The California Speedway agree to
          increase the size of the Rail Transportation Committee to include a
          representative of the MRF.

          With respect to the Additional Track Easement and the San Sevaine
          Track Easement, such easements shall provide that they will not be
          exercised and used by the MRF if it is commercially reasonable to use
          the Tar Pits Parcel for Rail Storage.  The Parties agree that it shall
          be commercially unreasonable, among other things, to require the
          remediation of the Tar Pits Parcel in a manner other than the use of a
          capping strategy.  In addition, Buyer and the MRF shall in good faith
          determine the final location of the additional track and

                                       5
<PAGE>

          switches to be constructed pursuant to the exercise of the rights
          granted pursuant to the Additional Track Easement and/or the San
          Sevaine Track Easement. Other than providing the Existing Track
          Easement, the Additional Track Easement and the San Sevaine Channel
          Easement, Buyer shall have no obligation to grant or convey any other
          real property or interest therein to Seller, the MRF or KRC pursuant
          to Section 2.2 (A).

          Seller hereby agrees that in no event shall Buyer assume any
          obligation of Seller or any related entity to expend money pursuant to
          any agreement relating to the MRF for any capital or operational cost
          relating to the rail operations of the MRF.  Buyer shall have no
          obligation to contribute, grant or convey any other real property or
          interest therein to MRF or KRC pursuant to such Section 2.2(A).

          I.   Section 6.2. of the Purchase Agreement is hereby revised to read
          in full as follows:

          6.2  Default by Buyer.  IN THE EVENT THAT BUYER FAILS IN THE
               ----------------
          PERFORMANCE OF ANY OF ITS OBLIGATIONS HEREUNDER FOLLOWING THE
          CONTINGENCY DATE BUT PRIOR TO THE CLOSE OF ESCROW, OR IN THE EVENT
          THAT THE CLOSE OF ESCROW SHALL FAIL TO OCCUR BY REASON OF A DEFAULT IN
          BUYER'S OBLIGATIONS HEREUNDER, THE PARTIES AGREE THAT IT WOULD BE
          IMPRACTICAL OR EXTREMELY DIFFICULT TO FIX, PRIOR TO SIGNING THIS
          AGREEMENT, THE ACTUAL DAMAGES WHICH WOULD BE SUFFERED BY SELLER IF
          BUYER FAILS TO PERFORM ITS OBLIGATIONS UNDER THIS AGREEMENT.
          THEREFORE, IN THE EVENT THAT THE CLOSE OF ESCROW SHALL FAIL TO OCCUR
          BY REASON OF A DEFAULT IN BUYER'S OBLIGATIONS HEREUNDER, SELLER SHALL
          BE ENTITLED, AS ITS SOLE AND EXCLUSIVE REMEDY FOR SUCH DEFAULT, TO
          IMMEDIATELY TERMINATE THIS AGREEMENT UPON SUCH DEFAULT, IN WHICH CASE
          THE SELLER SHALL RETAIN ANY PORTION OF THE INITIAL DEPOSIT, THE APRIL
          20 DEPOSIT, THE MAY 12 DEPOSIT AND/OR THE FINAL DEPOSIT ALREADY
          RELEASED TO SELLER AS LIQUIDATED DAMAGES AND BUYER SHALL NOT BE
          ENTITLED TO RECOVER ANY OF ITS DUE DILIGENCE EXPENSES PURSUANT TO
          ARTICLE 4 ABOVE.  THE PARTIES ACKNOWLEDGE THAT THE PAYMENT OF SUCH
          LIQUIDATED DAMAGES IS NOT INTENDED AS A FORFEITURE OR PENALTY WITHIN
          THE MEANING OF CALIFORNIA CIVIL CODE SECTION 3275 OR 3369, BUT IS
          INTENDED TO CONSTITUTE LIQUIDATED DAMAGES TO SELLER PURSUANT TO
          CALIFORNIA CIVIL CODE SECTIONS 1671, 1676, AND 1677.  THE PARTIES HAVE
          SET FORTH THEIR INITIALS BELOW TO INDICATE THEIR AGREEMENT WITH THE
          LIQUIDATED DAMAGES PROVISION CONTAINED IN THIS SECTION.  SELLER WAIVES
          ALL OTHER REMEDIES AGAINST BUYER FOR BUYER'S FAILURE TO CLOSE ESCROW,
          INCLUDING ANY RIGHT TO SPECIFIC PERFORMANCE UNDER CALIFORNIA CIVIL
          CODE SECTION 1680 OR ANY OTHER APPLICABLE LAW.

                                       6
<PAGE>

          BUYER AND SELLER ACKNOWLEDGE THAT THEY HAVE READ AND UNDERSTOOD THE
          PROVISIONS OF THIS SECTION 6.2 AND BY THEIR INITIALS BELOW AGREE TO BE
          BOUND BY ITS TERMS.

                      SLM                            TLC
               -----------------                ----------------

               Buyer's Initials                  Seller's Initials

          J.   The Purchase Agreement and the Side Letter are hereby amended to
provide that the date by which Buyer and Seller shall negotiate in reasonable
good faith to finalize the remaining provisions of Exhibits E, G, K, L, M, M-I,
Q, Y and CC and attach them to the Purchase Agreement shall be May 12, 2000.  In
addition, Buyer and Seller shall negotiate in reasonable good faith to finalize
the following new and revised Exhibits on or prior to May 12, 2000: (i) Exhibit
F (to replace existing Exhibit F), (ii) Exhibit H (to replace existing Exhibits
H and U), (iii) Exhibit J (to replace existing Exhibit J), (iv) Exhibit O (to
replace existing Exhibit O), (v) Exhibit P (to replace existing Exhibit P), (vi)
Exhibit R (to replace existing Exhibit R), (vii) Exhibit S (to replace existing
Exhibit S), (viii) Exhibit V (to replace existing Exhibit V), (ix) Exhibit W (to
replace existing Exhibit W), (x) Exhibit Z (to replace existing Exhibit Z), (xi)
Exhibits AA and BB (to replace existing Exhibits AA and BB), and (xii) a new
Exhibit EE, which shall set forth the form of any agreement between Buyer and
KVI, KRC, WVRT and West Valley MRF, LLC regarding certain environmental and
other covenants and indemnities affecting the Tar Pits Parcel, the Household
Hazardous Waste Parcel and the MRF Parcel.  During the time between the date
hereof and May 12, 2000, the Parties shall diligently and in reasonable good
faith attempt to finalize such Exhibits, and new and revised Exhibits.  In the
event that all of such Exhibits, and such new and revised Exhibits are not so
agreed upon on or prior to May 12, 2000, then either Buyer or Seller may
terminate the Purchase Agreement, in which event the provisions of Section 4.7
thereto shall apply as if Buyer had terminated the Purchase Agreement and thus,
any portion of the Initial Deposit and the April 20 Deposit theretofore released
to Seller shall not be refunded to Buyer.

          K.   Section 4.9 of the Purchase Agreement is hereby amended by
extending the date by which Buyer and Seller shall negotiate in good faith to
finalize the IT Contract and performance bond therefor or each of the Insurance
Policies so that they are acceptable to Seller to May 12, 2000 (or May 19, 2000,
in the event that the DTSC Issues remain unresolved and not approved or
disapproved on May 12, 2000 and the Contingency Date is extended to May 19,
2000).  If all of such Insurance Policies, the IT Contract and the performance
bond therefor are not so agreed upon on or prior to such date, then either Buyer
or Seller may terminate the Purchase Agreement, in which event the provisions of
Section 4.7 thereto shall apply as if Buyer had terminated the Purchase
Agreement and thus, any portion of the Initial Deposit and the April 20 Deposit
theretofore released to Seller shall not be refunded to Buyer.

          L.   Section 4.1 of the Purchase Agreement is hereby amended to
provide that: (i) Buyer has received an updated Survey from Seller and an
updated PTR from the Title Company; (ii) Seller shall have until and including
May 1, 2000 to notify Buyer of Seller's election to cure or not cure any title
and survey objections set forth in any objection letters delivered by Buyer to
Seller on or before April 27, 2000; and (iii) if Seller cannot or refuses to
cure any title or survey objections set forth in any objection letters delivered
by Buyer to Seller on or before April 27, 2000, Buyer shall have the right to
terminate the Agreement and to cancel Escrow by delivering written notice to
Seller and Escrow Holder on or prior to May 12, 2000,  in which case the
Parties' rights shall be as set forth in Section 4.7 of the

                                       7
<PAGE>

Agreement as if Buyer had terminated the Purchase Agreement and thus any portion
of the Initial Deposit and the April 20 Deposit theretofore released to Seller
shall not be refunded to Buyer. Unless Seller elects otherwise, in no event
shall Seller be required to cure any title objection other than a monetary
encumbrance, as provided in Section 4.1 of the Purchase Agreement.

     2.   No Other Amendments.  Except as expressly amended hereby, the Purchase
          -------------------
Agreement is unchanged and in full force and effect.

     3.   Counterparts.  This Amendment may be executed in counterparts, each of
          ------------
which shall be an original and all of which taken together shall constitute the
same instrument.

          IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the dates written below.

Buyer:                        ONTARIO VENTURES I, LLC, a Delaware limited
-----
                              liability company

                              By:  LandBank Environmental Properties, LLC,
                                   a Delaware limited liability company, its
                                   Manager

                                   By:  LandBank, Inc., a Delaware corporation,
                                        its managing member


                                   By: /s/ Stuart L. Miner
                                      ---------------------------------------

Date Executed: 4/25/00             Its: Vice President
              ------------             --------------------------------------


Seller:                       KAISER VENTURES INC., a Delaware corporation
------

                              By: /s/ Terry L. Cook
                                 -------------------------------------------

Date Executed: 4/25/00        Its: Executive Vice President
              ------------        ------------------------------------------

                              KAISER STEEL LAND DEVELOPMENT INC., a Delaware
                              corporation



                              By: /s/ Terry L. Cook
                                 ------------------------------------------

Date Executed: 4/25/00        Its: Vice President
              ------------        -----------------------------------------

                                       8
<PAGE>

RECEIVED AND ACCEPTED THIS ____ DAY OF_____________, 2000.


ESCROW HOLDER:

CHICAGO TITLE INSURANCE COMPANY



By:____________________________

Its:___________________________

                                       9