PNC Bank, N.A.
1600 Market Street
Philadelphia, PA 19103
215 585 5000 Tel



February 3, 2000                                                        PNC BANK


Peter W. Knipe
Vice President and Chief Financial Officer
STV GROUP, INCORPORATED
205 West Welsh Drive
Douglassville, Pennsylvania 19518

Re:      $12,000,000 Committed Line of Credit

Dear Pete:

         We are pleased to inform you that PNC Bank,  National  Association (the
"Bank"),  has approved your request for a committed  line of credit (the "Loan")
to STV Group,  Incorporated and STV Incorporated and its subsidiaries  listed on
the attached Schedule A (individually and collectively, the "Borrower"). We look
forward  to this  opportunity  to help  you  meet  the  financing  needs of your
business.  All the details  regarding  your Loan are  outlined in the  following
sections of this  letter.  If these terms are  satisfactory,  please  follow the
instructions for proceeding with your Loan provided at the end of this letter.

1. Facility and Use of Proceeds.  This is a committed  revolving  line of credit
under which the  Borrower  may  request  and the Bank,  subject to the terms and
conditions of this letter,  will make advances to the Borrower from time to time
until the Expiration Date, in an amount in the aggregate at any time outstanding
not to exceed  $12,000,000 (the "Line of Credit").  The "Expiration  Date" means
December  31,  2001,  or such  later  date as may be  designated  by the Bank by
written  notice to the Borrower.  Advances under the Line of Credit will be used
for working  capital,  acquisitions  or other general  business  purposes of the
Borrower.

         The Borrower may request that the Bank, in lieu of cash advances, issue
standby letters of credit  (individually,  a "Letter of Credit" and collectively
the "Letters of Credit") under the Line of Credit having expiration dates not to
exceed the earlier of one (1) year from the date of issuance and the  Expiration
Date; provided,  however, that the total amount of outstanding Letters of Credit
issued  hereunder (in the Bank's sole  discretion  and subject to  documentation
satisfactory to the Bank) shall not exceed  $2,000,000.00.  The  availability of
advances  under the Line of Credit  shall be reduced by the face  amount of each
Letter of Credit issued and outstanding  (whether or not drawn). Each payment by
the Bank under a Letter of Credit shall in the Bank's  discretion  constitute an
advance of principal under the Line of Credit and shall be

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STV Group, Incorporated
February 3, 2000
Page 2



evidenced  by the Note (as  defined  below).  The  Letters  of  Credit  shall be
governed by one or more reimbursement  agreements  executed by the Borrower (the
"Reimbursement Agreement").  Each request for the issuance of a Letter of Credit
must be accompanied by the Borrower's  execution of an application on the Bank's
standard  forms,  together  with all  supporting  documentation.  Each Letter of
Credit will be issued in the Bank's sole  discretion and in a form acceptable to
the Bank.  The Borrower shall pay the Bank a per annum issuance fee in an amount
equal to 1.5% of the face amount of each Letter of Credit,  payable quarterly in
arrears on a basis of a year of 360 days,  together  with such  other  customary
fees,  commissions and expenses  therefor as shall be required by the Bank. This
letter is not a  pre-advice  for the  issuance  of a letter of credit and is not
irrevocable.

2. Note.  The  obligation  of the Borrower to repay  advances  under the Line of
Credit shall be evidenced by a promissory  note (the "Note") in form and content
satisfactory to the Bank.

         This  letter  (the  "Letter  Agreement"),  the Note and the other  loan
documents  delivered  pursuant  hereto  will  constitute  the "Loan  Documents."
Capitalized  terms not defined herein shall have the meaning ascribed to them in
the Loan Documents.

3. Interest Rate.  Interest on the unpaid balance of the Line of Credit advances
will be charged at the rates,  and be payable on the dates and times,  set forth
in the Note evidencing the Loan.

4. Repayment.  Subject to the terms and conditions of this letter,  the Borrower
may borrow,  repay and reborrow  under the Line of Credit  until the  Expiration
Date, on which date the outstanding principal balance and any accrued but unpaid
interest shall be due and payable.

5. Security.  The Borrower must cause or has previously  caused the following to
be executed and  delivered to the Bank in form and content  satisfactory  to the
Bank as security for the Loan:

         (a) a security  agreement  granting the Bank a first priority perfected
lien on the Borrower's existing and future personal property,  including but not
limited to accounts, inventory,  equipment, general intangibles,  chattel paper,
documents and instruments.

         If all or any portion of the tangible collateral is located on property
which is not owned by the Borrower or which is subject to a mortgage in favor of
another lender,  the Borrower will deliver to the Bank Landlord's or Mortgagee's
Waivers,  as  applicable,  acceptable in form and substance to the Bank for each
such location.


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STV Group, Incorporated
February 3, 2000
Page 3



         Hazard insurance must be maintained on all inventory, equipment or real
property  securing  the Loan in such  amounts  and with  such  coverages  as are
acceptable to the Bank,  containing a standard  lender loss payable or mortgagee
clause in favor of the Bank.

         The Loan  will be  cross-collateralized  and  cross-defaulted  with all
other present and future Obligations of the Borrower to the Bank.

6.  Covenants.  Unless  compliance  is  waived in  writing  by the Bank or until
payment in full of the Loan and  termination  of the  commitment for the Line of
Credit:

         (a) The  Borrower  will  promptly  submit to the Bank such  information
relating  to the  Borrower's  affairs  (including  but  not  limited  to  annual
financial  statements for the Borrower) or any security for the Loan as the Bank
may reasonably request.

         (b) The Borrower  will notify the Bank in writing of the  occurrence of
an Event of Default or an act or condition which,  with the passage of time, the
giving of notice or both might become an Event of Default.

         (c) The Borrower  will comply with the  financial  and other  covenants
included in Exhibit "A" hereto.

7.  Representations  and  Warranties.  To induce the Bank to extend the Loan and
upon the making of any  advance to the  Borrower  under the Line of Credit,  the
Borrower represents and warrants as follows:

         (a) The Borrower's latest consolidated financial statements provided to
the Bank are true,  complete and  accurate in all  material  respects and fairly
present  the  financial  condition,  assets and  liabilities,  whether  accrued,
absolute,  contingent or otherwise, and the results of the Borrower's operations
for  the  period  specified  therein.  The  Borrower's   consolidated  financial
statements  have been prepared in accordance  with GAAP (as defined in Exhibit A
hereto)  consistently  applied  from  period  to period  subject  in the case of
interim statements to normal year-end adjustments.  Since the date of the latest
financial  statements  provided to the Bank,  the  Borrower has not suffered any
damage,  destruction  or  loss  which  has  materially  adversely  affected  its
business, assets, operations, financial condition or results of operations.

         (b)  There  are  no  actions,   suits,   proceedings  or   governmental
investigations pending or, to the knowledge of the Borrower,  threatened against
the  Borrower,  including  without  limitation  those  described on the attached
Exhibit B, which  could  result in a material  adverse  change in its  business,
assets, operations, financial condition or results of operations and there is

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STV Group, Incorporated
February 3, 2000
Page 4


no basis known to the Borrower or its officers,  directors or  shareholders  for
any such action, suit, proceedings or investigation.

         (c) The Borrower has filed all returns and reports that are required to
be filed by it in  connection  with any  federal,  state or local  tax,  duty or
charge levied, assessed or imposed upon the Borrower or its property,  including
unemployment,  social security and similar taxes and all of such taxes have been
either paid or adequate reserve or other provision has been made therefor.

         (d)  The  Borrower  is duly  organized,  validly  existing  and in good
standing under the laws of the state of its  incorporation  or organization  and
has the power and  authority  to own and  operate  its assets and to conduct its
business as now or proposed  to be carried on, and is duly  qualified,  licensed
and in good standing to do business in all jurisdictions  where its ownership of
property or the nature of its business requires such qualification or licensing.

         (e) The  Borrower  has full  power  and  authority  to  enter  into the
transactions  provided for in this Letter Agreement and has been duly authorized
to do so by all necessary and appropriate action and when executed and delivered
by the  Borrower,  this  Letter  Agreement  and the other  Loan  Documents  will
constitute the legal, valid and binding obligations of the Borrower, enforceable
in accordance with their terms.

         (f) There does not exist any default or violation by the Borrower of or
under any of the terms,  conditions or  obligations  of: (i) its  organizational
documents;  (ii) any  indenture,  mortgage,  deed of trust,  franchise,  permit,
contract,  agreement,  or other instrument to which it is a party or by which it
is bound;  or (iii) any law,  regulation,  ruling,  order,  injunction,  decree,
condition or other requirement applicable to or imposed upon the Borrower by any
law or by any governmental authority, court or agency.

         (g) The  Borrower  has  reviewed  the areas  within  its  business  and
operations  which  could be  adversely  affected  by,  and has  developed  or is
developing a program to address on a timely basis the risk that certain computer
applications  used by the  Borrower  may be  unable  to  recognize  and  perform
properly  date-sensitive  functions  involving dates prior to and after December
31, 1999 (the "Year 2000 Problem").  The Year 2000 Problem will not result,  and
is not  reasonably  expected to result,  in any material  adverse  effect on the
business,  properties,  assets,  financial  condition,  results of operations or
prospects of the Borrower, or the ability of the Borrower to duly and punctually
pay or perform its obligations hereunder and under the other Loan Documents.

8. Fees.  Beginning  on the first day of the quarter  after the date of the Note
and continuing on the first day of each quarter  thereafter until the Expiration
Date, the Borrower shall pay a

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STV Group, Incorporated
February 3, 2000
Page 5



commitment fee to the Bank, in arrears,  at the rate of .375 percent (.375%) per
annum on the average  daily  balance of the Line of Credit which is  undisbursed
and uncancelled during the preceding quarter. For the purpose of calculating the
commitment  fee,  the face amount of any  outstanding  Letters of Credit  issued
under the Line of Credit shall be deemed to be  disbursed.  The  commitment  fee
shall be  computed  on the  basis  of a year of 360 days and paid on the  actual
number of days elapsed.

9.  Expenses.  The Borrower will  reimburse  the Bank for the Bank's  reasonable
out-of-pocket  expenses  incurred or to be incurred in conducting UCC, title and
other  public  record  searches,  and in filing and  recording  documents in the
public records to perfect the Bank's liens and security interests.  The Borrower
shall also reimburse the Bank for the Bank's expenses  (including the reasonable
fees and expenses of the Bank's outside and in-house counsel) in documenting and
closing this  transaction,  in connection with any amendments,  modifications or
renewals  of the  Loan,  and in  connection  with the  collection  of all of the
Borrower's  obligations  to the Bank,  including but not limited to  enforcement
actions relating to the Loan.

10.  Depository.  The  Borrower  will  establish  and  maintain  at the Bank the
Borrower's primary depository accounts.

11. Additional Provisions. Before the first advance under the Loan, the Borrower
shall execute and deliver to the Bank the Note and other required Loan Documents
and such other  instruments  and documents as the Bank may  reasonably  request,
such as certified  resolutions,  incumbency  certificates  or other  evidence of
authority.  The Bank will not be obligated to make any advance under the Line of
Credit  if any  Event of  Default  or event  which  with  the  passage  of time,
provision  of notice or both would  constitute  an Event of  Default  shall have
occurred and be continuing.

12.  Other  Conditions  to  Advances.  The Bank will not be obligated to make an
advance under the Line of Credit until the Borrower has provided the  following,
all in form and content  satisfactory  to the Bank:  evidence of cancellation of
all  commitments  from and evidence of repayment in full of all  indebtedness to
First Union  National  Bank except for  obligations  relating to four letters of
credit outstanding on the date hereof, which are listed on the attached Schedule
B, which shall be replaced no later than June 30, 2000;  evidence of termination
of all  existing  liens in  favor of First  Union  National  Bank;  transfer  of
Borrower's primary operating accounts to the Bank.

         Prior to execution of the final Loan Documents,  the Bank may terminate
this Letter  Agreement if a material  adverse  change occurs with respect to the
Borrower,  any  guarantor,  any  collateral  for the Loan or any other person or
entity connected in any way with the Loan, or if the

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STV Group, Incorporated
February 3, 2000
Page 6



Borrower  fails to comply  with any of the terms and  conditions  of this Letter
Agreement,  or if the Bank  reasonably  determines  that  any of the  conditions
cannot be met.

         This Letter  Agreement is governed by the laws of the  Commonwealth  of
Pennsylvania.  No modification,  amendment or waiver of any of the terms of this
Letter  Agreement,  nor any consent to any departure by the Borrower  therefrom,
will be  effective  unless made in a writing  signed by the party to be charged,
and then such waiver or consent shall be effective only in the specific instance
and for the purpose for which given.  When accepted,  this Letter  Agreement and
the other Loan Documents will constitute the entire  agreement  between the Bank
and  the   Borrower   concerning   the  Loan,   and  shall   replace  all  prior
understandings,  statements,  negotiations and written materials relating to the
Loan.

         THE BORROWER AND THE BANK IRREVOCABLY WAIVE ANY AND ALL RIGHTS THEY MAY
HAVE TO A TRIAL BY JURY IN ANY ACTION, PROCEEDING OR CLAIM OF ANY NATURE ARISING
OUT OF THIS  LETTER  AGREEMENT  AND THE  TRANSACTIONS  CONTEMPLATED  HEREBY  AND
ACKNOWLEDGE THAT THE FOREGOING WAIVER IS KNOWING AND VOLUNTARY.

         If and when a loan closing occurs,  this Letter  Agreement (as the same
may be amended  from time to time)  shall  survive the closing and will serve as
our loan agreement throughout the term of the Loan.

         To accept  these terms,  please sign the  enclosed  copy of this Letter
Agreement as set forth below and the Loan  Documents and return them to the Bank
within  ten (10) days from the date of this  Letter  Agreement,  or this  Letter
Agreement may be terminated  at the Bank's option  without  liability or further
obligation of the Bank.

         Thank  you for  giving  PNC Bank  this  opportunity  to work  with your
business.  We look  forward  to other ways in which we may be of service to your
business or to you personally.

Very truly yours,

PNC BANK, NATIONAL ASSOCIATION


By:      /s/ Amy T. Petersen

Title:   Vice President



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STV Group, Incorporated
February 3, 2000
Page 7



                                   ACCEPTANCE

With the intent to be legally bound hereby,  the above terms and  conditions are
hereby agreed to and accepted as of this 3rd day of February, 2000.

                                    BORROWER:

                                    STV GROUP, INCORPORATED

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title: CFO


                                    STV INCORPORATED

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title: CFO


                                    STV CONSTRUCTION SERVICES, INC.

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title: CFO


                                    STV INTERNATIONAL, INC.

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title: CFO



                [SIGNATURES ARE CONTINUED ON THE FOLLOWING PAGE]


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STV Group, Incorporated
February 3, 2000
Page 8



                                    STV/ENVIRONMENTAL, INC.

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title: CFO


                                    STV SURVEYING, INC.

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title: CFO


                                    STV CONSTRUCTION, INC.

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title: CFO


                                    STV ARCHITECTS, INC.

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title:  Secretary


                                    STV SILVER & ZISKIND ARCHITECTS, P.C.

                                    By:  /s/ Peter W. Knipe   (SEAL)
                                    Print Name:  Peter W. Knipe
                                    Title:  Secretary



                [SIGNATURES ARE CONTINUED ON THE FOLLOWING PAGE]

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STV Group, Incorporated
February 3, 2000
Page 9



                                    STV ARCHITECTS, P.C.

                                    By:  /s/ Michael D. Garz  (SEAL)
                                    Print Name:  Michael D. Garz
                                    Title:  President