<PAGE>

                                                                     EXHIBIT 2.2

            FIRST AMENDMENT TO MEMBERSHIP INTEREST PURCHASE AGREEMENT

      THIS FIRST AMENDMENT TO MEMBERSHIP INTEREST PURCHASE AGREEMENT (this
"Amendment") is made and entered into as of the 30th day of March, 2005, between
WCA of North Carolina, L.P., a Delaware limited partnership ("WCA NC"), MRR
Southern, LLC, a North Carolina limited liability company ("Seller"), WCA Waste
Corporation, a Delaware corporation ("WCA") and WCA of Wake County, L.P., a
Delaware limited partnership ("WCA Wake").

                              STATEMENT OF PURPOSE

      WCA NC, Seller, WCA and the other parties thereto have entered into that
certain Membership Interest Purchase Agreement dated as of January 14, 2005 (the
"Purchase Agreement"), pursuant to which Seller has agreed to sell, and WCA NC
has agreed to purchase, Seller's entire membership interest in each of Material
Reclamation, LLC ("Reclamation"), Material Recovery, LLC ("Recovery"), MRR of
High Point, LLC ("High Point") and MRR Wake Transfer Station, LLC ("Wake"), each
a North Carolina limited liability company. WCA NC and Seller desire to amend
the Purchase Agreement in order to (a) substitute WCA Wake as the purchaser of
Seller's entire membership interest in each of Reclamation, Recovery and Wake,
with WCA NC continuing as the purchaser of Seller's entire membership interest
in High Point, and (b) permit Seller or any Company, as the case may be, to
distribute and assign any Excluded Asset to such designee as Seller or any such
Company may designate. Capitalized terms used herein shall have the meanings
ascribed thereto in the Purchase Agreement unless otherwise defined herein.

      NOW, THEREFORE, in consideration of the mutual promises contained herein,
and for other good and valuable consideration, the receipt, sufficiency and
adequacy of which are hereby acknowledged, the parties agree as follows:

      1. AMENDMENT WITH RESPECT TO WCA WAKE. The parties hereto hereby agree
that the Purchase Agreement is hereby amended in order to substitute WCA Wake as
the purchaser of Seller's entire membership interest in each of Reclamation,
Recovery and Wake, with WCA NC continuing as the purchaser of Seller's entire
membership interest in High Point. To that end, all references to "Buyer" in the
Purchase Agreement shall mean (a) WCA NC with respect to Seller's entire
membership interest in High Point and (b) WCA Wake with respect to Seller's
entire membership interest in Reclamation, Recovery and Wake. WCA Wake agrees to
be bound by all of the terms and conditions of the Purchase Agreement as if it
were a signatory thereto and to assume all of the obligations of WCA NC
thereunder with respect to the purchase of Seller's entire membership interest
in Reclamation, Recovery and Wake. All obligations of WCA under the Purchase
Agreement, including, without limitation, WCA's obligations under Article 7
thereunder, shall apply to WCA Wake in the same manner as such obligations apply
to WCA NC.

      2. AMENDMENT WITH RESPECT TO SELLER DESIGNEE AS ASSIGNEE OF EXCLUDED
ASSETS. The parties hereto hereby agree that the Purchase Agreement is hereby
amended in order to permit Seller or any Company, as the case may be, to
distribute and assign to MRR High Point

<PAGE>

Real Estate, LLC immediately prior to Closing (a) the grinder described in
Section 2.4(a) of the Purchase Agreement and (b) the land described in Section
2.4(b) of the Purchase Agreement.

      3. CLOSING DATE. The parties hereto agree that the Closing shall take
place at, and the Purchase Agreement is hereby amended in order to define the
"Closing Date" as, 10:00 a.m. EST on April 1, 2005 or such other time as Seller
and Buyer may mutually agree upon.

      4. MISCELLANEOUS.

            (a) Effect of Amendment. Except as specifically amended hereby or
      otherwise agreed, the Purchase Agreement and the documents related thereto
      are hereby ratified and confirmed and shall remain in full force and
      effect according to their terms. This Amendment shall be deemed to be
      incorporated into the Purchase Agreement and made a part thereof.

            (b) Governing Law. This Amendment shall be construed, interpreted,
      enforced and governed by and under the laws applicable to the Purchase
      Agreement. The jurisdiction, venue and service of process provisions set
      forth in Section 12.7 of the Purchase Agreement are hereby incorporated by
      reference.

            (c) Counterparts. This Agreement may be executed in any number of
      counterparts, each of which so executed shall be deemed to be an original,
      and such counterparts together shall constitute but one and the same
      instrument.

                            [SIGNATURE PAGE FOLLOWS]

                                        2
<PAGE>

      IN WITNESS WHEREOF, the undersigned have caused this Amendment to be
executed by their duly authorized corporate officers, as of the date first set
forth above.

                                    MRR SOUTHERN, LLC

                                    By: /s/ F. Norbert Hector, Jr.
                                        ---------------------------------------
                                    Name: F. Norbert Hector, Jr.
                                    Title: Manager

                                    WCA OF NORTH CAROLINA, L.P.

                                    By: WCA NC General, Inc.

                                    By: /s/ J. Edward Menger
                                        ----------------------------------------
                                    Name: J. Edward Menger
                                          --------------------------------------
                                    Title: Vice President
                                           -------------------------------------
                                    ITS: General Partner

                                    WCA WASTE CORPORATION

                                    By: /s/ J. Edward Menger
                                        ----------------------------------------
                                    Name: J. Edward Menger
                                          --------------------------------------
                                    Title: Vice President & General Counsel
                                           -------------------------------------

                                    WCA OF WAKE COUNTY, L.P.

                                    By: WCA Wake County Management General, Inc.

                                    By: /s/ J. Edward Menger
                                        ----------------------------------------
                                    Name: J. Edward Menger
                                          --------------------------------------
                                    Title: Vice President
                                           -------------------------------------
                                    ITS: General Partner

[First Amendment to Membership Interest Purchase Agreement]