Exhibit (10)(hh)
                                             Rider to 2/1/01 AA Letter Agreement
                                                 re Company Process Improvements

                                                                        ANDERSEN
RIDER #1 TO THE FEBRUARY 1, 2001
ARRANGEMENT LETTER                                      Arthur Andersen LLP
                                                        Suite 3800
                                                        100 North Tryon Street
December 5, 2001                                        Charlotte NC 28202-4000

Mr. Larry Singleton                                     Tel 704 332 0092
Chief Financial Officer
Safety-Kleen Corp.                                      www.andsersen.com
1301 Gervais Street
Columbia, South Carolina 20201

Dear Mr. Singleton:

This Rider #1, including any appendices, schedules, and/or attachments,
documents the understanding between Arthur Andersen LLP ("Andersen") and
Safety-Kleen ("Client") with respect to certain services to be provided by
Andersen related to program management for the Client's finance Process
Improvement Initiatives. In addition, Client has requested services to be
provided by Andersen in conjunction with the execution of various process
improvement projects included in the Process Improvement Initiatives and
assistance, as needed, with implementation of the recommendations (collectively
the "Services"). Andersen shall provide the Services pursuant to the provisions
of this Rider #1 and the Arrangement Letter dated February 1, 2001, entered into
by and between Andersen and Client, which is attached hereto and incorporated
herein by this reference, which, together, describe our understanding with
respect to the Services ("Agreement").


PROJECT SCOPE AND OBJECTIVES

The Client has undertaken a series of projects designed to address previously
identified material internal control weaknesses and business process improvement
opportunities ("Process Improvement Initiatives"). The objective of the Process
Improvement Initiatives is to assess the Client's core finance processes and
focus on "quick hit" (to be implemented within 3 months) improvement
recommendations and intermediate solutions (to be implemented within 3 to 6
months) to allow the Client's material internal control weaknesses to be
mitigated by May 31, 2002.


<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 2 of 10

The Process Improvement Initiatives, which have been identified and launched to
date, address the following finance and support processes:

o        Order entry and billing
o        Collections and cash accounting
o        Accounts receivable accounting
o        Procurement-to-payment

o        Payroll and benefits accounting
o        Intercompany accounting
o        Inventory and equipment-at-customers
o        Account Analysis and close-the-books

Some of the above initiatives may be terminated and/or combined and other
initiatives may be initiated as part of the overall project. The Client will
ultimately be responsible for the approval of any changes.

The Client seeks to better manage the Process Improvement Initiatives by
organizing and managing them as a collective "program". Andersen has been
engaged to provide assistance in designing and administering a Program
Management Office (PMO) through which the program will be managed and
administered. In addition, Andersen will provide experienced resources to
perform and administer the individual process improvement initiatives included
in the overall program.

Andersen will work jointly with resources from Jefferson Wells International
(JWI), a third party consulting firm hired by the Client to perform outsourced
internal audit services and to assist with the Process Improvement Initiatives.
In executing their role as internal auditors, JWI will serve as a component of
the Client's quality assurance function by evaluating the effectiveness of any
internal control recommendations proposed during the Process Improvement
Initiatives, which are ultimately selected and implemented by the Client.


ANDERSEN SERVICES AND RESPONSIBILITIES

Andersen has responsibility to recommend a design and provide appropriate
staffing for the PMO for the Process Improvement Initiatives. The PMO will be
responsible for the planning and administration of all the finance process
improvement initiatives. The services the PMO will perform include program
control for all initiatives, change management, and all required communications,
including recurring project status reports, Steering Committee meetings and
reports for the Client's senior management, Audit Committee and Board of
Directors. The PMO will track the progress of all process improvement
initiatives and work with the Client's senior management team and Steering
Committee to address the

<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 3 of 10

timely resolution of issues, the resource allocations  necessary to meet project
timelines and to develop the necessary training and implementation plans to
address material control weaknesses.  However, while Andersen may assist in the
implementation of resulting recommendations, Andersen will not determine which
internal control recommendations will be implemented.  The Client's management
will make those decisions.

Additionally, Andersen has the responsibility to administer and provide
resources to many of the process improvement initiatives. In that regard,
Andersen will work jointly with resources from JWI in these process improvement
initiatives. Individual process improvement teams will be staffed with an
appropriate complement of skilled resources, considering Andersen and JWI
resources along with dedicated resources committed by the Client. These teams
will assess and document the current procedures in place at the Client, provide
recommendations for improvement, develop implementation plans for those
recommendations which are approved by the Client, and provide resources to
assist in the implementation, as necessary and requested by the Client.


DELIVERABLES

The design and establishment of the PMO will result in the production of some
deliverables including the following:

o    PMO  organization  structure -  including  roles and  responsibilities  for
     Andersen, JWI and Client resources.
o    Program Management repository - likely a Lotus Notes-based database for use
     by the  PMO  and  all of  the  Process  Improvement  Initiative  teams  for
     communication of status, issues, deliverables, etc.

Other PMO deliverables will arise primarily from the day-to-day operation of the
PMO. Examples of deliverables include:

o    Program status reports
o    Stakeholder assessment and related program communication strategy
o    Steering committee program, senior management, Audit Committee and Board of
     Directors summary reports

Andersen shall retain all right, title and interest in and to: (i) the
Deliverables, including but not limited to all patent, copyright, trademark and
other intellectual property rights therein; and (ii) all methodologies,
processes, techniques, ideas, concepts, trade secrets and know-how embodied in
the Deliverables or that Andersen may develop or supply in connection with this
Agreement (the "Andersen Knowledge"). Subject to the confidentiality
restrictions contained below, Andersen may use the Deliverables and the Andersen
Knowledge for any purpose.

<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 4 of 10

The deliverables arising from the individual process improvement initiatives
will vary depending on the specific scope and duration of the individual process
improvement initiatives. Examples of deliverables for individual process
improvement initiatives will include:

o    Project work plans
o    Project status reports
o    Issues lists requiring Client management decisions
o    Recommendations  for improvements,  including:
       o   Quick Hit recommendations (implementable within 3 months)
       o   Intermediate solution recommendations (implementable in 3-6 months)
o    High-level implementation and training plans

ACCEPTANCE

All major deliverables will be reviewed and approved by Client senior management
and the Program Steering Committee.


Client shall accept Deliverables which (i) conform to the requirements of this
Rider #1 or (ii) where applicable, successfully complete the acceptance test
plan described in this Rider #1. Client will promptly give Andersen notification
of any non-conformance of the Deliverables with such requirements
("Non-conformance"), and Andersen shall have a reasonable period of time, based
on the severity and complexity of the Non-conformance, to correct the
Non-conformance. If Client uses the Deliverable before acceptance, fails to
promptly notify Andersen of any Non-conformance, or unreasonably delays the
beginning of acceptance testing, then the Deliverable shall be considered
accepted by the Client.


Client Responsibilities and Project Assumptions

1.   Client Responsibilities

     In connection with Andersen's provision of the Services, Client will
     perform the tasks, furnish the personnel, provide the resources, or
     undertake the responsibilities specified below ("Client Responsibilities").

     o    Provide access to appropriate personnel throughout the project

     o    Provide access to data required to support the  successful  completion
          of these process improvement initiatives

<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 5 of 10


     o    Provide the  appropriate  information  technology  resources  (people,
          hardware,  software, Notes / network access, etc.) necessary to set up
          the PMO  repository  and to allow all process  improvement  initiative
          team members access to the repository

     o    Provide  Andersen with sufficient  workspace  (including work areas to
          enable entire process improvement initiative teams to work in the same
          place) and other resources to support our ability to competently  work
          with the Client team

     o    Designate a senior  management  sponsor  who will make all  management
          decisions with respect to this engagement.

     o    Designate  an "owner"  for each team who will serve as the key contact
          point for the team in terms of content  regarding  the team's  area of
          focus and who will also  arrange  for access to data,  resources,  and
          other assistance for their team.

     o    Provide  necessary  personnel to serve as part of the various teams as
          needed  and as  directed  by the  Client's  team owner  and/or  senior
          management sponsor.


     To the extent that the  Services  or  Andersen's  deliverables  include the
     design  or  implementation  of  hardware  or  software  systems,   Client's
     management  shall be  responsible  for  making  all  management  decisions,
     including but not limited to, decisions  concerning systems to be evaluated
     and selected; the design of such systems; controls and system procedures to
     be implemented; scope and timetable of system implementation;  and testing,
     training, and conversion plans. To the extent that Andersen's  deliverables
     include surveys, analyses, reports,  evaluations,  recommendations or other
     management  consulting  services,  Client's management shall be responsible
     for all implementation  decisions and for any future action with respect to
     the matters  addressed  in the  deliverables.  In  conjunction  with Client
     acceptance,  Client's  management will evaluate the adequacy and results of
     the design and implementation of Andersen's deliverables.


     Notwithstanding the scope of Andersen's services or deliverables hereunder,
     Client  acknowledges that it remains Client's  responsibility to devise and
     maintain  a system of  internal  accounting  controls  in  compliance  with
     Section 13(b)(2) of the U.S. Securities Exchange Act of 1934, which Section
     provides that such controls be sufficient to provide reasonable  assurances
     that: (i) transactions are executed in accordance with management's general
     or specific authorization;  (ii) transactions are recorded as necessary (a)
     to permit preparation of financial  statements in conformity with generally
     accepted  accounting  principles or any other  criteria  applicable to such
     statements,  and (b) to maintain accountability for assets; (iii) access to
     assets  is  permitted  only in  accordance  with  management's  general  or
     specific authorization;  and (iv) the recorded accountability for assets is
     compared with the existing  assets at reasonable  intervals and appropriate
     action is taken  with  respect  to any  differences.  In  addition,  Client
     represents  and warrants to Andersen that Client's  management  will,  upon
     execution,  provide a copy of this Rider #1 to the Audit Committee.  Client
     will  determine  the  adequacy  of its  internal  accounting  controls  and
     financial reporting systems without relying on

<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 6 of 10


     Andersen's  services or  deliverables  as the primary basis for making such
     determination. Finally, Client acknowledges to Andersen that it is Client's
     responsibility  to make such  disclosures  with respect to this  engagement
     that are required by applicable laws and regulations.

     Client acknowledges that: (i) Andersen and Client may correspond or convey
     documentation via Internet e-mail unless Client expressly requests
     otherwise, (ii) neither party has control over the performance,
     reliability, availability, or security of Internet e-mail, and (iii)
     Andersen shall not be liable for any loss, damage, expense, harm or
     inconvenience resulting from the loss, delay, interception, corruption, or
     alteration of any Internet e-mail due to any reason beyond Andersen's
     reasonable control.

2.   Project Assumptions

     The Services, fees and delivery schedule for this engagement are based upon
     the following assumptions, representations or information supplied by
     Client ("Assumptions").

     o    The quality of any analysis,  documentation, or other work contributed
          by or produced by any of the non-Andersen parties contracted by Client
          to play a role  in the  PMO  and/or  Process  Improvement  Initiatives
          (e.g.,  JWI personnel,  independent  contractors,  etc.) will meet the
          quality  expectations  of  Andersen  and the  quality  and  timeliness
          required by the Client via their needs and timelines.

     o    Information required for the completion of this work that is requested
          from,  agreed to by the Client and  prepared / supplied  by the Client
          will meet the  requirements of the project  timelines and will be of a
          sufficient  quality and reliability  level as to not delay the project
          (for re-work, excessive validation, interpretation, etc.)

     o    Data extracts needed from Client's  systems will be supplied by Client
          or  outside  contractors  (Andersen  or others)  will be  allowed  and
          enabled to supply it.

Andersen's delivery of the Services and the fees charged are dependent on (i)
the Client's timely and effective completion of the Client Responsibilities,
(ii) the accuracy and completeness of the Project Assumptions, and (iii) timely
decisions and approvals by Client's management. Client shall be responsible for
any delays, additional costs, or other liabilities caused by or associated with
any deficiencies in the Client Responsibilities and Project Assumptions.

<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 7 of 10


Project Approach and Staffing

1.   Project Approach

     Program Management Office - The key tasks performed by the PMO will include
the following:

     o    Develop  a  structure  for  all  Process   Improvements   Initiatives,
          including project scope, approach, timeline, resources, budgets, etc.
     o    Mobilize process improvement teams comprised of Client, Andersen, JWI,
          and other resources.
     o    Develop stakeholder analyses and related change enablement  strategies
          and plans (e.g.,  communication  strategy,  skills  enhancement plans,
          organization analysis and design, etc.)
     o    Review  project  deliverables  and  prepare  summary   program/project
          summary reports for senior management,  the Steering Committee,  Audit
          Committee and Board of Directors.
     o    Ongoing  review of status  and  progress  of all  process  improvement
          initiatives  focusing on timeline adherence,  milestone  achievements,
          issue resolution, budget tracking, and risk management and mitigation.

     Process Improvement Initiatives - The key tasks and typical approach
     employed by each Process Improvement team is as follows:

     o    Develop detailed  project plans for all assigned  process  improvement
          initiatives  and  related   sub-projects,   including  project  scope,
          approach, timeline, resources, budgets, etc.

     o    Review existing processes and previously  identified  material control
          weaknesses  and work  with  Client  management  to  develop  quick hit
          recommendations  and  intermediate   solutions  to  mitigate  material
          control weaknesses.

     o    Develop plans by which to implement recommendations.

     o    Assist with  implementation of recommendations  selected by Client and
          as requested by Client.

     o    Prepare   recurring   project  status  reports  and  summarize  issues
          requiring Client management decisions.

     The project will begin immediately. We estimate that the project duration
     will be approximately six to nine months.


<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 5 of 10


2.   Staffing

     The leadership and advisory team for the PMO and Process Improvement
     Initiatives will be structured and Andersen resources assigned as shown in
     the charts separately provided to Client on December 5, 2001. Andersen
     Process Improvement Initiative management leads and supporting resources
     were determined based upon Client's initial prioritization of Process
     Improvement Initiatives.

     Andersen will assign other competent and appropriately experienced
     personnel to the PMO, advisory, and initiative teams as required by the
     project plans and as requested by the Client.

     Other PMO resources will be determined after assessing the overall scope of
     the Process Improvement Initiatives and the availability of appropriate
     Client, JWI, and other resources.


MUTUAL RESPONSIBILITIES

With respect to this Agreement and any information supplied in connection with
this Agreement and designated by the disclosing party as confidential, the
recipient agrees to: (i) protect the confidential information in a reasonable
and appropriate manner or in accordance with applicable professional standards;
(ii) use confidential information only to perform its obligations under this
Agreement; and (iii) reproduce confidential information only as required to
perform its obligations under this Agreement. This section shall not apply to
information which is (i) publicly known, (ii) already known to the recipient;
(iii) disclosed to a third party without restriction; (iv) independently
developed; or (v) disclosed pursuant to legal requirement or order. Subject to
the foregoing, Andersen may disclose Client's confidential information to its
subcontractors and affiliates.

Neither party shall use the other party's name, trademarks, service marks,
logos, trade names and/or branding without such party's prior written consent.
Notwithstanding anything herein to the contrary, Andersen may reference or list
Client's name and/or a general description of the Services/project. Client also
agrees that upon reasonable prior notice from Andersen, Client will be willing
to provide a reference for Andersen (e.g. in the form of analyst telephone
calls, client telephone calls, presentations, and the like).


<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 9 of 10



FEES & Expenses

Andersen's fees for the scope of Services described in this Rider #1 will be
based upon actual time and materials at the rates included in the February 1,
2001 Arrangement Letter issued by the Bankruptcy Court and are estimated to be
in the range of $10 million to $15 million, plus actual out of pocket expenses.
Client shall pay Andersen the professional fees and the related expenses in
accordance with Rider #1. Upon a request for a revision in the scope of the
Services under this Rider #1, Andersen shall submit a proposal describing the
impact of such revisions in scope on the fees and expenses.

This fee is based on Client fulfilling the Client Responsibilities and
Assumptions described in this Rider #1.


The payment schedule will be as ordered by the Bankruptcy Court.


REVISION OF SCOPE

In the event either party seeks additions, deletions, or modifications to the
scope or nature of the Services described in this Rider #1, Andersen shall
prepare an additional rider to the February 1, 2001, Arrangement Letter
outlining such additions, deletions or modifications to the scope or nature of
the Services and provide such rider to Client for its review. Andersen shall
have no obligation to begin performing any such scope change until such rider
has been signed by both parties.

MISCELLANEOUS

If any term or provision of this Agreement is determined to be illegal or
unenforceable, such term or provision shall be deemed stricken, and all other
terms and provisions shall remain in full force and effect.

This Agreement may not be assigned or otherwise transferred without the prior
express written consent of the other party. Andersen may assign this Agreement
to an affiliate of its international organization or use subcontractors to
provide Services.

No term of this Agreement shall be deemed waived, and no breach of this
Agreement excused, unless the waiver or consent is in writing signed by the
party granting such waiver or consent.

<PAGE>

Mr. Larry Singleton
December 5, 2001
Page 10 of 10


Notwithstanding the completion of the Services or termination of this Agreement,
the parties shall continue to be bound by those provisions of this Agreement
which by their nature survive such completion or termination.

We appreciate the opportunity to be of service to you and look forward to
working with you on this challenging project. You can be assured that it will
receive our close attention. Please indicate your agreement to these
arrangements by signing and returning to Andersen the enclosed copy of this
Agreement.

Very truly yours,

ARTHUR ANDERSEN LLP

   /s/ Tom Eiselt

By:
     Thomas D. Eiselt


Acknowledged and accepted:

Safety-Kleen Corp.

By:      /s/ Larry W. Singleton
        -------------------------------------
Title:  CFO
        -------------------------------------
Date:    1-8-2002
        -------------------------------------