<PAGE>
 
                                                                   EXHIBIT 10.15


                         AMERICAN WASTE SERVICES, INC.

                         1990 Long-Term Incentive Plan
                         -----------------------------

                            As Amended and Restated
                       Effective as of February 17, 1997

     1.    Purposes.  The principal purposes of the 1990 Long-Term Incentive
           --------                                                         
Plan (the "Plan") are:  (a) to improve individual employee performance by
providing long-term incentives and rewards to employees of the Company and its
Affiliates, (b) to assist the Company and its Affiliates in attracting,
retaining and motivating employees and non-employee directors with experience
and ability, and (c) to associate the interests of such employees and directors
with those of the Company's shareholders.

     2.  Definitions.  Unless the context clearly indicates otherwise, the
         -----------                                                      
following terms, when used in this Plan, shall have the meanings set forth
below:

     (a)  "Affiliate" means a majority-owned subsidiary, directly or indirectly,
of the Company, including a company under contract to purchase which will become
a majority owned subsidiary upon such purchase.

     (b)  "Board of Directors" means the Board of Directors of the Company.

     (c)  "Code" means the Internal Revenue Code of 1986, amended.

     (d)  "Committee" means the committee, consisting of two or more persons,
which is appointed by the Board of Directors to administer the Plan.

     (e)  "Common Stock" or "Stock" means the Class A Common Stock, no par
value, of the Company.

     (f)  "Company" means American Waste Services, Inc. and its successors.

     (g)  "Disabled" shall have the meaning set forth in the Company's long-term
disability program applicable to such employee or, if there is no such program,
as provided in Section 22(e) of the Code.
<PAGE>
 
     (h)  "Exchange Act" means the Securities Exchange Act of 1934, as amended.

     (i)  "Fair Market Value" means the amount determined by the Committee, or,
in the case of Options granted to Outside Directors pursuant to Section 6(i),
the Board of Directors, to be the fair market value of the Common Stock at the
time in question.

     (j)  "Grant Date" means the date an Option is granted under the Plan.  The
date of grant of an Option shall be the date as of which the Committee, or, in
the case of Options granted to Outside Directors pursuant to Section 6(i), the
Board of Directors, determines that such Option shall become effective.

     (k)  "Initial Public Offering" means an initial public offering of Common
Stock to the public on or before December 30, 1990.

     (l)  "Option" means a right granted under the Plan to an Optionee to
purchase a share of Common Stock at a fixed price for a specified period of
time.

     (m)  "Optionee" means an eligible employee of the Company or an Affiliate
who has received an Option granted under the Plan.

     (n)  "Option Price" means the price at which a share of Common Stock
covered by an Option granted hereunder may be purchased.

     (o)  "Outside Director" means a member of the Board of Directors or of the
board of directors of an Affiliate who is not an employee of the Company or any
Affiliate.

     (p)  "Rule 16b-3" means Rule 16b-3, as amended (17 CFR (S) 240.16b-3) or
any successor rule issued under the Exchange Act.

     (q)  "Subsidiary" means a corporation in a chain of corporations beginning
with the Company if each corporation in the chain, other than the last
corporation, owns stock possessing 50% or more of the total combined voting
power of all classes of stock in one of the other corporations in the chain.

     (r)  "Ten Percent Shareholder" means an individual owning stock possessing
10% or more of the total combined voting power of all classes of stock of the
Company or a Subsidiary.

     3.  Administration. The Plan shall be administered by the Committee, which
         --------------                                                        
shall have full power and authority to administer and interpret the Plan and to
adopt such rules, regulations, agreements, guidelines and instruments for the
administration of the Plan as the Committee deems necessary or advisable.  The
Committee's powers include, but are not limited to (subject to the

                                      -2-
<PAGE>
 
specific limitations described herein), authority to determine the employees to
be granted Options under the Plan, to determine the size and applicable terms
and conditions of grants to be made to such employees, to determine the time
when Options will be granted and to authorize grants to eligible employees.

     The Committee's interpretations of the Plan, and all actions taken and
determinations made by the Committee concerning any matter arising under or with
respect to the Plan or any Options granted hereunder, shall be final, binding
and conclusive on all interested parties, including the Company, its Affiliates,
its shareholders and all former, present and future employees of the Company.
The Committee may delegate some or all of its power and authority hereunder to
the Chairman and Chief Executive Officer of the Company or others, such
delegation to be subject to such terms and conditions as the Committee in its
discretion shall determine and to the requirements of Rule 16b-3.  The Committee
may as to all questions of accounting rely conclusively upon any determinations
made by the independent public accountants of the Company.  The Committee shall
establish procedures for conducting its business.

     The Board of Directors may exercise any of the authority conferred upon the
Committee hereunder.  In the event of such exercise of authority by the Board of
Directors, references in the Plan to the Committee shall be deemed to refer to
the Board of Directors as appropriate.

     4.  Stock Available for Options.  The shares that may be delivered or
         ---------------------------                                      
purchased under the Plan shall not exceed an aggregate of 3 million shares of
Common Stock, subject to any adjustments which may be made pursuant to Section 9
hereof.  Shares of Stock used for purposes of the Plan may be either shares of
authorized but unissued Common Stock or treasury shares or both.  Stock covered
by Options which have terminated or expired prior to exercise or have been
surrendered or canceled shall be available for further option grants hereunder.

     5.  Eligibility.  All those salaried employees of the Company or any
         -----------                                                     
Affiliates as shall be determined from time to time by the Committee shall be
eligible to participate in the Plan. Outside Directors shall participate in the
Plan only under Section 6(i).

     6.  Terms and Conditions of Options. Each Option granted hereunder shall be
         -------------------------------                                        
in writing and shall contain such terms and conditions as the Committee may
determine, subject to the following:

     (a)  Type.  All Options granted under the Plan are intended to be non-
          ----                                                            
qualified stock options for federal income tax purposes except for those Options
designated as incentive stock options which qualify under Section 422 of the
Code.  No incentive

                                      -3-
<PAGE>
 
stock options shall be granted to an Outside Director or to an employee of an
Affiliate which is not a Subsidiary.

     (b)  Price.  The Option Price shall be not less than 85% of the Fair Market
          -----                                                                 
Value of Common Stock on the Grant Date as determined by the Committee, provided
that for Options designated as incentive stock options the Option Price shall be
not less than 110% of Fair Market Value for employees who are Ten Percent
Shareholders and not less than 100% of Fair Market Value for other employees.
The Option Price of all Options granted prior to the Initial Public Offering
shall be the public offering price in such Offering.

     (c)  Maximum Grants.  No employee may be granted Options in the aggregate
          --------------                                                      
which would result in that employee receiving more than 10% of the maximum
number of shares available for issuance under the Plan.  In the case of an
Option designated as an incentive stock option, the aggregate Fair Market Value
of Common Stock (determined at the Grant Date) with respect to which incentive
stock options are exercisable for the first time by an employee during any
calendar year (under the Plan and under all other such plans of the Company or a
Subsidiary) shall not exceed $100,000.

     (d)  Term and Exercise Dates.  Options shall have a term of no longer than
          -----------------------                                              
ten years from the Grant Date except that for an Option designated as an
incentive stock option which is granted to a Ten Percent Shareholder, the Option
shall have a term no longer than five years (the date on which the Option
terminates is herein called the "Expiration Date").  No Option shall be
exercisable prior to one year after its grant, unless otherwise provided by the
Committee (but in no event before 6 months after its grant), and thereafter
Options shall become exercisable in installments, if any, as provided by the
Committee.  Options must be exercised for full shares of Common Stock.  To the
extent that Options are not exercised when they become initially exercisable,
they shall be carried forward and be exercisable until the expiration of the
term of such Options, subject to Section 6(g) hereof.  Options granted prior to
the Initial Public Offering are contingent on the consummation of such Offering.

     (e)  Exercise of Option.  To exercise an Option, the holder thereof shall
          ------------------                                                  
give notice of his or her exercise to the Secretary of the Company, specifying
the number of shares of Common Stock to be purchased and identifying the Option
being exercised. From time to time the Committee may establish procedures for
effecting such exercises.  No fractional shares shall be issued as a result of
exercising an Option.  An Option is exercisable during an Optionee's lifetime
only by the Optionee, provided, however, that in the event the Optionee is
Disabled, such Options may be exercised by such Optionee's guardian or legal
representative

                                      -4-
<PAGE>
 
designated or appointed to conduct his or her business affairs under the terms
described in Section 6(g) hereof.

     (f)  Payment of Option Price and Taxes.
          --------------------------------- 

          (i) The purchase price for the Options being exercised must be paid in
full at the time of exercise.  Such price shall be paid in cash, in Common Stock
of the Company having a Fair Market Value, as of the close of the business day
immediately preceding the date of exercise, equal to the exercise price or the
portion thereof being paid in Common Stock (provided that such Common Stock had
been owned by the Optionee for at least six months), or as the Committee may
otherwise approve.

          (ii) To enable the Company to meet any applicable federal (including
FICA), state and other withholding tax requirements, an Optionee shall also be
required to pay to the Company at the time of exercise the amount of tax which
the Company determines is to be withheld.  No share of Common Stock will be
delivered to any 0ptionee until all such amounts have been paid.  An Optionee
may satisfy such withholding tax requirement by electing to have the Company
withhold Common Stock otherwise issuable to the Optionee, or to deliver to the
Company previously acquired Common Stock, which has a Fair Market Value on the
date the tax is determined to be due (the "Tax Date") on the exercise of his or
her Option which is at least equal to the amount required to be withheld.  Such
election must be made in writing at the time prescribed by the Committee prior
to the Tax Date and shall be irrevocable.  Elections by Optionees who are
subject to Section 16(b) of the Exchange Act shall be subject to the subsequent
disapproval of the Committee and shall be subject to such further requirements
of Rule 16b-3 or other law or regulation as may be applicable.

     (g)  Effect of Termination of Employment, Disability or Death.  No
          --------------------------------------------------------     
Option may be exercised by an Optionee after the termination for any reason of
his or her employment with the Company or an Affiliate, except that:

                                      -5-
<PAGE>
 
          (i) if such termination occurs by reason of the Optionee's death or
Disability, all portions of the Option then held by the Optionee which are
exercisable on the date of termination and all portions which would have become
exercisable had the Optionee continued in employment until the third anniversary
of his or her death or Disability shall be exercisable during the six-month
period subsequent to such termination date by, in the case of death, the persons
designated in the Optionee's will or his or her legal representative designated
or appointed to conduct his or her legal affairs;

          (ii) if such termination occurs by reason other than death, Disability
or cause, all portions of the Option then held by the Optionee which are
exercisable at the date of termination shall continue to be exercisable by the
Optionee for a three-month period subsequent to such termination;

          (iii) if such termination is for cause, the Optionee shall forfeit any
portion of his or her Option which was unexercised or unexercisable at such
termination; and

          (iv) if the Optionee dies while Disabled during the six-month period
described in clause (i) or dies during the three-month period described in
clause (ii), all portions of his or her Option which were exercisable at the
time of the Optionee's death shall continue to be exercisable for a six-month
period subsequent to such date of death by the persons designated in the
Optionee's will or his or her legal representatives.

          Transfer from employment with the Company to an Affiliate, from an
Affiliate to the Company or from an Affiliate to another Affiliate shall not be
treated as a termination of employment.

          Notwithstanding the foregoing, the Option shall in no event be
exercisable by the Optionee or his or her heirs or legal representatives after
the Expiration Date.

     (h)  Nontransferability of Options.  During an Optionee's lifetime,
          -----------------------------                                 
his or her Options shall not be transferable and shall only be exercisable by
the Optionee (except as provided in Section

                                      -6-
<PAGE>
 
6(g) above) and any purported transfer shall be null and void.  No Option shall
be transferable other than by will or the laws of descent and distribution.

     (i)  Outside Directors.
          ----------------- 

          (i) Prior to February 17, 1997, an Option for 25,000 shares of Common
Stock shall be granted to each Outside Director upon his or her initial
appointment or election as a director and such Options shall become exercisable
with respect to 20% of such shares on each anniversary of such appointment or
election, provided that such person is a director of the Company or an Affiliate
on such anniversary.  Effective February 17, 1997, the Board of Directors may,
from time to time, in its discretion, grant Options to one or more Outside
Directors, subject to such terms and conditions as the Board of Directors may
determine, which such terms and conditions shall not be inconsistent with the
remaining provisions of this Section 6(i) and other applicable provisions of the
Plan.

          (ii) The Option Price shall be the Fair Market Value of the
Common Stock on the Grant Date.

          (iii)  No Option may be exercised by an Outside Director
after he or she ceases to be a director of the Company or an Affiliate by reason
of death, Disability, resignation, removal or other reason, except that:

                 (A) if such cessation occurs by reason of the Outside
Director's death or Disability, the portion of his or her Option which was
exercisable on such cessation and the portion which would become exercisable had
the Outside Director continued as a director until the third anniversary of his
or her death or Disability shall be exercisable for six months following such
cessation (but not beyond the Expiration Date), except that if such cessation
was due to Disability and the former Outside Director dies during such six-month
period, such portions of his or her Option shall be exercisable for a six-month
period following such

                                      -7-
<PAGE>
 
death by the persons designated in the Outside Director's will or his or her
legal representatives (but not beyond the Expiration Date); and

                 (B) if such cessation occurs by reason other than the Outside
Director's death or Disability, the portion of his or her Option which was
exercisable on such cessation shall be exercisable for six months following such
cessation (but not beyond the Expiration Date), except that if the former
Outside Director dies during such six-month period, such portion of his or her
Option shall be exercisable for a six-month period following such death by the
persons designated in the Outside Director's will or his or her legal
representatives (but not beyond the Expiration Date).

          (iv) The provisions of the Plan shall apply to the Options granted to
Outside Directors to the extent they are not inconsistent with the provisions of
paragraphs (i) though (iii), above.

     7.  Amendment.  The Board of Directors of the Company may, at any
         ---------                                                    
time, amend, suspend or terminate the Plan, in whole or in part, provided that
(i) no such action shall adversely affect any rights or obligations with respect
to any grants theretofore made hereunder, and (ii) any shareholder approval
required by the securities laws, stock exchange or NASDAQ rules or other
applicable law or regulation is obtained.  The Committee may amend the terms and
conditions of outstanding Options, provided, however, that (x) no such amendment
shall be adverse to the holder of an Option without the approval of such holder,
and (y) the amended terms of the Option would be permitted under the Plan.

     8.  Registration, Listing and Qualification of Shares. Each Option
         -------------------------------------------------             
shall be subject to the requirement that if at any time the Committee shall
determine that the registration, listing or qualification of the shares covered
thereby upon any securities exchange or under any federal or state securities or
other law, or the consent or approval of any governmental regulatory body, is
necessary or desirable as a condition of, or in connection with, the granting of
such Option or the purchase of shares thereunder, no such Option may be
exercised unless and until such registration, listing, qualification, consent or
approval shall have been effected or obtained free of any condition not
acceptable to the Committee.  Any person exercising an Option shall make such

                                      -8-
<PAGE>
 
representations and agreements and furnish such information as the Committee may
request to assure compliance with the foregoing or any other applicable legal
requirements.

     9.  Adjustment for Change in Stock Subject to Plan.  In the event of
         ----------------------------------------------                  
any change in the outstanding shares of Common Stock by reason of any stock
split, stock dividend, spin-off, recapitalization, merger, consolidation,
combination, exchange of shares, reorganization, sale by the Company of all or
substantially all of its assets, distribution to shareholders other than a
normal cash dividend, or other similar corporate change, such equitable
adjustments may be made in the Plan and the Options granted hereunder as the
Committee determines are necessary or appropriate, including, if necessary, an
adjustment in the number of shares and prices per share or the type or kind of
shares or property applicable to Options then outstanding and in the number of
shares which are reserved for issuance under the Plan.  Any such adjustment
shall be conclusive and binding for all purposes of the Plan.

     10.  No Rights to Options or Employment.  Except as provided in
          ----------------------------------                        
Section 6(i), no person shall have any claim or right to be granted an Option
under the Plan.  Receipt of an Option under the Plan shall not give a person any
right to receive any other grant under the Plan.  An Optionee shall have no
rights to or interest in any Option except as set forth herein.  Neither the
Plan nor any action taken hereunder shall be construed as giving any person any
right to be retained as an employee or director of the Company or any Affiliate.

     11.  Rights as a Shareholder.  An Optionee under the Plan shall have
          -----------------------                                        
no rights as a holder of Common Stock with respect to Options granted hereunder,
unless and until certificates for shares of Common Stock are issued to such
Optionee.

     12.  Other Actions.  This Plan shall not restrict the authority of the
          -------------                                                    
Committee or of the Company to grant stock options, other than under the Plan,
to or with respect to any employee or other person.

     13.  Costs and Expenses.  Except as provided in Section 6(f) hereof
          ------------------                                            
with respect to taxes, the costs and expenses of administering the Plan shall be
borne by the Company and its Affiliates and shall not be charged to any grant
nor to any person receiving a grant.

     14.  Plan Unfunded.  The Plan shall be unfunded.  Except for reserving
          -------------                                                    
a sufficient number of authorized shares Common Stock to the extent required by
law to meet the requirements of the Plan, the Company shall not be required to
establish any special or separate fund or to make any other segregation of
assets to assure the payment of any grant under the Plan.

                                      -9-
<PAGE>
 
     15.  Governing Law.  This Plan shall be governed by and construed in
          -------------                                                  
accordance with the laws of the State of Ohio.

     16.  Effective Date and Duration of Plan.  This Plan shall be
          -----------------------------------                     
effective as of August 1, 1990, conditioned upon (a) the effectiveness of the
Initial Public Offering, (b) approval of the shareholders of the Company by July
31, 1991 and (c) as to any amendments, the effective dates thereof.  No Option
shall be granted under the Plan after July 31, 2000.

                                      -10-