<PAGE>

                                                                    EXHIBIT 4.15

                                 NINTH AMENDMENT
             TO THIRD AMENDED AND RESTATED SECURED CREDIT AGREEMENT

         THIS NINTH AMENDMENT TO THIRD AMENDED AND RESTATED SECURED CREDIT
AGREEMENT (this "Amendment"), dated as of December 20, 2002, is entered into
among QUANTA SERVICES, INC., a Delaware corporation (the "Borrower"), the
Lenders (defined below) who are signatories hereto, and BANK OF AMERICA, N.A.,
as administrative agent for the Lenders (in such capacity, the "Agent").
Capitalized terms used but not defined in this Amendment have the meaning given
them in the Credit Agreement (defined below).

                                   BACKGROUND

         A.       The Borrower is party to that certain Third Amended and
Restated Secured Credit Agreement dated as of June 14, 1999 (as amended through
the date hereof and as may be further amended, restated or supplemented from
time to time, the "Credit Agreement"), among the Borrower, the Agent, and the
lenders from time to time party to the Credit Agreement (each a "Lender" and
collectively, the "Lenders").

         B.       The Borrower, Majority Lenders and the Agent desire to make
certain amendments to the Credit Agreement.

         NOW, THEREFORE, in consideration of the covenants, conditions and
agreements hereinafter set forth, and for other good and valuable consideration,
the receipt and adequacy of which are all hereby acknowledged, the Borrower,
Majority Lenders and the Agent covenant and agree as follows:

         1.       AMENDMENTS TO CREDIT AGREEMENT. The Credit Agreement is hereby
amended as follows:

                  (a)      Amendments to Section 1.1. Section 1.1 is amended by
         adding or entirely amending the following defined terms:

                           "COMMITMENT AMOUNT" means an amount equal to (a) from
                  the Effective Date through August 11, 2002, $350,000,000, (b)
                  from August 12, 2002, through December 19, 2002, $275,000,000,
                  (c) from December 20, 2002, through March 31, 2003,
                  $250,000,000, (d) from April 1, 2003 through December 31,
                  2003, $225,000,000, and (e) from January 1, 2004 through the
                  Commitment Termination Date, $200,000,000, in each case as
                  such amount may be reduced from time to time pursuant to the
                  terms of this Agreement. Notwithstanding the foregoing, the
                  Borrower shall not be permitted to borrow $25,000,000 of the
                  Commitment Amount commencing on December 19, 2002, and
                  continuing at all times thereafter until the occurrence of a
                  Reinstatement Event.

                           "INITIAL ACQUISITION BASKET" means 75% of the net
                  cash proceeds realized by the Borrower from the sale or
                  issuance of the Borrower's capital stock between September 30,
                  2002 and December 31, 2002.

<PAGE>

                           "MATERIAL ADVERSE EFFECT" means an effect that
                  results in a material adverse change since December 31, 2001,
                  in (i) the business, properties, assets, financial condition
                  or, prior to December 31, 2001, prospects of the Borrower and
                  its Subsidiaries taken as a whole, or (ii) in the ability of
                  the Borrower, or Borrower or the Guarantors taken as a whole,
                  to perform the Obligations under the Credit Documents to which
                  they are a party.

                           "QUARTERLY EBITDA" means, for the one fiscal quarter
                  ending on the date of determination, the sum of Consolidated
                  Net Income plus, without duplication, each of the following to
                  the extent actually deducted in determining Consolidated Net
                  Income, (a) Consolidated Interest Expense; (b) provisions for
                  taxes based on income or revenues; (c) the amount of all
                  depreciation and amortization expense deducted in determining
                  Consolidated Net Income; (d) charges taken in accordance with
                  SFAS 142 and SFAS 144, which when taken together with all
                  other charges previously taken in connection with SFAS 142 and
                  SFAS 144, do not, in the aggregate, exceed $850,000,000; (e)
                  without duplication, Quarterly Permitted Charges; and (f)
                  without duplication, Non-Cash Charges, all calculated on a
                  consolidated basis for the Borrower and its Subsidiaries and
                  as determined in accordance with GAAP. For purposes of this
                  definition, the calculation shall not include the historical
                  financial results of (i) any business acquired in connection
                  with an Acquisition during such period, or (ii) any business
                  or division disposed of by the Borrower during such period.

                           "QUARTERLY PERMITTED CHARGES" means, for the one
                  fiscal quarter ending on the date of determination, expenses,
                  write-offs or losses incurred in such quarter, which in each
                  case have been (a) paid, incurred or realized on or before
                  June 30, 2003, (b) disclosed to the Agent in such detail as
                  the Agent deems acceptable, and (c) determined in accordance
                  with GAAP, and which relate to:

                           (a)      employee terminations, equipment sales,
                  operating lease termination expenses, and real estate lease
                  terminations (including related clean-up and moving charges)
                  which, in the aggregate do not exceed $29,000,000, provided
                  that, cash payments in connection with the items under this
                  clause (a), may not, in the aggregate, exceed $20,000,000;

                           (b)      accounts receivable, notes receivable,
                  retainage, costs and earnings in excess of billing, and other
                  amounts which (i) are either (A) set out in the consolidated
                  balance sheet of the Borrower and its Subsidiaries for the
                  fiscal quarter ended September 30, 2002 as net of allowances
                  or (B) disclosed in writing to the Agent on December 20, 2002,
                  or (ii) relate to the contractual obligations of Borrower or
                  its Subsidiaries existing on September 30, 2002 as disclosed
                  in writing to the Agent on December 20, 2002, and which have
                  been reserved as doubtful for collection, provided that, all
                  such amounts under clauses (i) and (ii) may not, in the
                  aggregate, exceed $77,000,000;

                           (c)      the proxy contest with Utilicorp, and which
                  do not, in the aggregate, exceed $13,000,000; and

                                        2

<PAGE>

                           (d)      without duplication, (i) advisory, legal,
                  and bank fees and expenses in connection with the negotiation,
                  execution and delivery of the Eighth Amendment to this
                  Agreement (including any related amendment to the Senior Notes
                  in connection therewith) and related third party due diligence
                  conducted on behalf of the Agent in connection therewith, and
                  which do not, in the aggregate, exceed $4,100,000, (ii)
                  advisory and legal fees and expenses in connection with the
                  negotiation, execution and delivery of the Ninth Amendment to
                  this Agreement (including any related amendment to the Senior
                  Notes in connection therewith) and the raising of capital
                  completed on or about the date of such amendment, which do
                  not, in the aggregate, exceed $4,400,000, (iii) all amendment
                  fees paid to the Agent, the Lenders and the holders of the
                  Senior Notes and all other out-of-pocket fees and expenses
                  incurred by the Agent and paid by the Borrower as a condition
                  to the closing of the Ninth Amendment to this Agreement and
                  any contemporaneous amendment to the Note Purchase Agreement,
                  and (iv) non-cash expenses related to prior financing
                  transaction costs which have been capitalized and are required
                  to be expensed in accordance with GAAP.

                           "RESIDUAL ACQUISITION BASKET" means, (a) with respect
                  to mergers, consolidations, purchases or Acquisitions in which
                  (i) no greater than 33.33% of the aggregate amount of
                  consideration paid by the Borrower is in the form of cash, and
                  (ii) no less than 66.67% of the aggregate amount of
                  consideration paid by the Borrower is in the form of the
                  Borrower's common stock, an amount equal to 25% of the net
                  cash proceeds realized by the Borrower from the sale or
                  issuance of the Borrower's capital stock between September 30,
                  2002 and December 31, 2002, and (b) with respect to all other
                  mergers, consolidations, purchases or Acquisitions, $0.00.

                           "REINSTATEMENT EVENT" means, so long as no Default or
                  Event of Default exists at such time, the Borrower's
                  achievement, for two consecutive fiscal quarters, of Quarterly
                  EBITDA no less than the amount set forth below for the one
                  fiscal quarter ending on the applicable date set forth beside
                  such amount below:

<TABLE>
<CAPTION>
Fiscal Quarter Ending:              Minimum Quarterly EBITDA
---------------------               ------------------------
<S>                                 <C>
December 31, 2002                         $29,000,000
March 31, 2003                            $28,000,000
June 30, 2003                             $39,000,000
September 30, 2003                        $45,000,000
December 31, 2003, and                    $38,000,000
each fiscal quarter thereafter
</TABLE>

                           "SECONDARY ACQUISITION BASKET" means an amount equal
                  to the difference of (a) the Initial Acquisition Basket, minus
                  (b) the aggregate amount of the cash portion of the
                  consideration paid by the Borrower in respect of all mergers,

                                        3

<PAGE>

                  consolidations, purchases or Acquisitions consummated on or
                  prior to December 31, 2003.

                  (b)      Further Amendments to Section 1.1. Section 1.1 is
         further amended by amending (i) the definitions of "EBIT" and "EBITDA"
         to delete each reference to "SFAS 142" that appears therein and replace
         it with "SFAS 142 or SFAS 144" and to delete each reference to
         "$800,000,000" that appears therein and replace it with "$850,000,000",
         and (ii) the definition of "MINIMUM INTEREST COVERAGE RATIO" to delete
         the phrase "or Modified Make-Whole Amount (as defined in the Note
         Purchase Agreement), as applicable" in the fourth and fifth lines
         thereof, and (iii) clauses (b) and (d) of the definition of "PERMITTED
         CHARGES", so that such definition reads in its entirety as follows:

                           "PERMITTED CHARGES" means, for any period, on a
                  trailing four fiscal quarter basis, expenses, write-offs or
                  losses, which in each case have been (a) paid, incurred or
                  realized on or before June 30, 2003, (b) disclosed to the
                  Agent in such detail as the Agent deems acceptable, and (c)
                  determined in accordance with GAAP, and which relate to:

                           (a)      employee terminations, equipment sales,
                  operating lease termination expenses, and real estate lease
                  terminations (including related clean-up and moving charges)
                  which, in the aggregate do not exceed $29,000,000, provided
                  that, cash payments in connection with the items under this
                  clause (a), may not, in the aggregate, exceed $20,000,000;

                           (b)      accounts receivable, notes receivable,
                  retainage, costs and earnings in excess of billing, and other
                  amounts which (i) are either (A) set out in the consolidated
                  balance sheet of the Borrower and its Subsidiaries for the
                  fiscal quarter ended September 30, 2002 as net of allowances
                  or (B) disclosed in writing to the Agent on December 20, 2002,
                  or (ii) relate to the contractual obligations of Borrower or
                  its Subsidiaries existing on September 30, 2002 as disclosed
                  in writing to the Agent on December 20, 2002, and which have
                  been reserved as doubtful for collection, provided that, all
                  such amounts under clauses (i) and (ii) may not, in the
                  aggregate, exceed $77,000,000;

                           (c)      the proxy contest with Utilicorp, and which
                  do not, in the aggregate, exceed $13,000,000; and

                           (d)      without duplication, (i) advisory, legal,
                  and bank fees and expenses in connection with the negotiation,
                  execution and delivery of the Eighth Amendment to this
                  Agreement (including any related amendment to the Senior Notes
                  in connection therewith) and related third party due diligence
                  conducted on behalf of the Agent in connection therewith, and
                  which do not, in the aggregate, exceed $4,100,000, (ii)
                  advisory and legal fees and expenses in connection with the
                  negotiation, execution and delivery of the Ninth Amendment to
                  this Agreement (including any related amendment to the Senior
                  Notes in connection therewith) and the raising of capital
                  completed on or about the date of such amendment, which do
                  not, in the aggregate, exceed $4,400,000, (iii) all

                                        4

<PAGE>

                  amendment fees paid to the Agent, the Lenders and the holders
                  of the Senior Notes and all other out-of-pocket fees and
                  expenses incurred by the Agent and paid by the Borrower as a
                  condition to the closing of the Ninth Amendment to this
                  Agreement and any contemporaneous amendment to the Note
                  Purchase Agreement, and (iv) non-cash expenses related to
                  prior financing transaction costs which have been capitalized
                  and are required to be expensed in accordance with GAAP.

                  (c)      Amendment to Section 2.10. Clause (c) of Section 2.10
         is amended and restated in its entirety, as follows:

                           (c)      If, on or after December 21, 2002, the
                  Borrower or any of its Subsidiaries issues any (i) Funded Debt
                  which, in the aggregate, exceeds $15,000,000, other than the
                  Indebtedness referenced in SUBSECTION (b) above (and, for the
                  avoidance of doubt, increases in the Commitments hereunder or
                  borrowings hereunder), or (ii) common or preferred stock or
                  other equity interests, then the Borrower shall promptly,
                  without notice or demand, pay all net cash proceeds from any
                  such issuance (net of usual and customary transaction costs
                  and expenses actually incurred in connection with such
                  issuance) to the Agent for the ratable benefit of the Lenders
                  and the holders of the Senior Notes (based on the proportion
                  of the Commitment Amount under this Agreement and the
                  proportion of the outstanding principal amount of the Senior
                  Notes to the sum of both) as a prepayment respectively of (A)
                  the Loans, and if all Loans have been paid, a pre-funding of
                  Letters of Credit pursuant to the provisions of SECTION 7.4,
                  and upon such issuance, the Committed Amount shall be
                  automatically and permanently reduced by an amount equal to
                  the amount of the proceeds of such issuance required to be
                  paid to the Agent under this SECTION 2.10(c)(i), and (B) the
                  Senior Notes.

                  (d)      Amendment to Section 2.10. Clause (d) of Section 2.10
         is hereby amended by deleting the phrase "doubtful for collection" as
         it appears in the third line thereof and replacing it with the word
         "uncollectible".

                  (e)      Amendment to Section 5.10. Section 5.10 is hereby
         amended by deleting the date "December 31, 1998" in the first line
         thereof and inserting the date "December 31, 2001".

                  (f)      Amendment to Section 6.5. The last sentence of
         Section 6.5 is hereby deleted.

                  (g)      Amendment to Section 6.6. Clause (a)(iii) of Section
         6.6 is hereby amended by deleting the text, "audited by an independent
         nationally-recognized accounting firm acceptable to the Agent" and
         replacing it with the text, "audited by an independent
         nationally-recognized accounting firm acceptable to the Agent, whose
         opinion shall be in scope and substance in accordance with generally
         accepted auditing standards and, with respect to the audited financial
         statements for the Borrower's fiscal year 2002, shall not contain a
         going concern or other like qualification".

                                        5

<PAGE>

                  (h)      Addition to Section 6.6. New clauses (c) and (d) are
         hereby added to Section 6.6 immediately following clause (b) thereof,
         as follows:

                           (c)      within forty-five (45) days after the end of
                  each month of each fiscal year of the Borrower, a projected
                  balance sheet, income statement and cash flow statement of the
                  Borrower and its Subsidiaries for the three month period
                  commencing on the day immediately following the last day of
                  such month, presented on a month by month basis and otherwise
                  in form and detail reasonably acceptable to the Agent.

                           (d)      at any time after the occurrence and during
                  the continuation of a Weekly Reporting Trigger, no later than
                  Friday of each week, a forecast of projected cash flows of the
                  Borrower and its Subsidiaries for the 13-week period
                  commencing on the Monday immediately preceding the Friday on
                  which delivery is required, presented on a week by week basis
                  and otherwise in form and detail reasonably acceptable to the
                  Agent. For purposes of this SECTION 6.6(d), "WEEKLY REPORTING
                  TRIGGER" shall mean the occurrence of either of the following
                  events: (i) the aggregate principal amount of all Revolving
                  Loans and L/C Obligations outstanding shall exceed
                  $160,000,000; or (ii) the Minimum Interest Coverage Ratio for
                  the period of four fiscal quarters ending on the date set
                  forth below, as reported in the financial statements most
                  recently delivered under SECTION 6.6(a), shall be less than
                  the ratio set out below for the applicable period:

<TABLE>
<CAPTION>
For The Period Ending:
---------------------
<S>                             <C>
December 31, 2002:              1.86 to 1.00
March 31, 2003:                 1.48 to 1.00
June 30, 2003:                  1.66 to 1.00
September 30, 2003:             2.18 to 1.00
December 31, 2003 and
thereafter:                     2.49 to 1.00
</TABLE>

                  (i)      Amendment to Section 6.10. Clause (a) of Section 6.10
         is amended and restated in its entirety, as follows:

                           (a)      The Borrower shall not pay any dividends or
                  other distributions on its capital stock other than (i) when
                  no Default or Event of Default exists or will result
                  therefrom, cash dividends in respect of the Preferred Stock
                  not to exceed $1,000,000 during any fiscal year of the
                  Borrower, (ii) dividends made wholly in the form of additional
                  shares of the Borrower's capital stock, provided that, in
                  respect of any stock split, the Borrower may make cash
                  distributions in lieu of issuing fractional shares of capital
                  stock which would otherwise result from such stock split, and
                  (iii) repurchases of common stock of the Borrower from
                  officers, directors and employees pursuant to the Borrower's
                  restricted stock option or compensation programs, to pay
                  withholdings in respect of taxes owed as a result of grants of
                  stock options and stock compensation thereunder, so long as
                  the Borrower's performance of its obligations under such
                  restricted stock option or

                                        6

<PAGE>

                  compensation programs cannot reasonably be expected to have a
                  material negative impact on projected cash flows.

                  (j)      Section 6.11 is amended and restated in its entirety,
         as follows:

                           Section 6.11 Restrictions on Fundamental Changes.
                  Neither the Borrower nor any of its Subsidiaries shall be a
                  party to any merger into or consolidation with, make an
                  Acquisition or otherwise purchase or acquire all or
                  substantially all of the assets or stock of, any other Person,
                  or sell all or substantially all of its assets or stock (other
                  than as permitted under SECTION 6.16), except:

                           (a)      at any time after May 15, 2003 and the
                  delivery of the required financial statements, Compliance
                  Certificate and other reports for the fiscal quarter of
                  Borrower ending March 31, 2003, required to be delivered under
                  SECTION 6.6, the Borrower or any of its Subsidiaries may merge
                  into or consolidate with, make an Acquisition or otherwise
                  purchase or acquire all or substantially all of the assets or
                  stock of any other Person, so long as (i) the Borrower is the
                  surviving entity to any such merger or consolidation to which
                  the Borrower is a party, or, if the Borrower is not a party to
                  such transaction, a domestic Subsidiary is the surviving
                  entity to any such merger or consolidation or the other Person
                  will thereby become a domestic Subsidiary (unless no party to
                  such transaction is a domestic Subsidiary, in which case the
                  applicable foreign Subsidiary must be the surviving entity to
                  any such merger or consolidation or the other Person must
                  thereby become a foreign Subsidiary), (ii) the nature of the
                  business of such acquired Person is a Permitted Business,
                  provided that, Acquisitions consummated after December 20,
                  2002 will be primarily focused on acquiring Persons whose
                  business activities are restricted to the specialty electric
                  and infrastructure contracting service business and utility
                  outsourcing business, (iii) no Default or Event of Default
                  shall have occurred and be continuing or would otherwise be
                  existing as a result of such merger, consolidation, purchase
                  or Acquisition, (iv) such merger, consolidation, purchase or
                  Acquisition is non-hostile in nature, (v) with respect to all
                  such mergers, consolidations, purchases or Acquisitions
                  consummated on or after December 20, 2002, the aggregate
                  amount of the cash portion of the consideration paid by the
                  Borrower and its Subsidiaries in respect thereof, does not
                  exceed the excess of $85,000,000 over Indebtedness outstanding
                  under SECTION 6.14(c), (vi) with respect to all such mergers,
                  consolidations, purchases or Acquisitions consummated on or
                  prior to December 31, 2003, the aggregate amount of the cash
                  portion of the consideration paid by the Borrower and its
                  Subsidiaries in respect thereof, does not exceed the Initial
                  Acquisition Basket, (vii) with respect to any such mergers,
                  consolidations, purchases or Acquisitions consummated after
                  December 31, 2003, the aggregate amount of the cash portion of
                  the consideration paid by the Borrower and its Subsidiaries in
                  respect thereof, does not exceed (A) the Secondary Acquisition
                  Basket, and (B) at any time after the Secondary Acquisition
                  Basket has been fully utilized, the Residual Acquisition
                  Basket, and (viii) prior to the consummation of any such
                  merger, consolidation, purchase or Acquisition, the Borrower
                  shall have

                                        7

<PAGE>

                  delivered to the Agent (which the Agent shall promptly provide
                  to each Lender) (A) updated consolidated financial
                  projections, in form and detail reasonably satisfactory to the
                  Agent, for the then-current fiscal year of the Borrower and
                  the immediately following fiscal year of the Borrower, which
                  projections shall give pro forma effect to such merger,
                  consolidation, purchase or Acquisition and shall be in
                  compliance with SEC regulations and requirements regarding the
                  preparation and presentation of pro forma financial
                  information, and (B) to the extent available, the audited
                  annual financial statements of the Person being acquired (or
                  the Person from whom the assets, securities or other equity
                  interests were acquired for the most recently ended fiscal
                  year of such Person, including a balance sheet and statements
                  of income, retained earnings, and cash flows of such Person;
                  and

                           (b)      the Borrower may purchase or otherwise
                  acquire all or substantially all of the stock or assets of, or
                  otherwise acquire by merger or consolidation, any of its
                  Subsidiaries, and any such Subsidiary may merge into, or
                  consolidate with, or purchase or otherwise acquire all or
                  substantially all of the assets or stock of or sell all or
                  substantially all of its assets or stock to, any other
                  Subsidiary of the Borrower or the Borrower, in each case so
                  long as (i) if the transaction is with the Borrower, the
                  Borrower shall be the surviving entity to any such merger or
                  consolidation, or (ii) if the transaction is not with the
                  Borrower, a domestic Subsidiary shall be the surviving entity
                  to any such merger or consolidation (unless no party to such
                  transaction is a domestic Subsidiary).

                           Except as otherwise permitted in this SECTION 6.11
                  and SECTION 6.16, the Borrower shall not sell or dispose of
                  any capital stock of or its ownership interest in any of the
                  Guarantors or any other Subsidiaries which it may form.
                  Borrower shall give the Agent the notice required under
                  SECTION 6.9.

                  (k)      Amendment to Section 6.16. Clause (e) of Section 6.16
         is amended and restated in its entirety, as follows:

                           (e)      to the extent not included in clauses (a)
                  through (d) above, dispositions of assets (including for the
                  avoidance of doubt, the capital stock of any Subsidiary
                  provided that all of the capital stock owned by the Borrower
                  and/or any of its other Subsidiaries is sold or disposed), for
                  fair and adequate consideration and for cash, provided that,
                  dispositions under this SUBSECTION (e) may not, in the
                  aggregate, exceed $50,000,000 in book value during the term of
                  this Agreement, and all proceeds from the disposition of such
                  assets (net of usual and customary transaction costs and
                  expenses actually incurred in connection with such
                  disposition) in excess of $5,000,000 received during any
                  fiscal year of the Borrower shall be paid to the Agent, for
                  the ratable benefit of the Lenders and the holders of the
                  Senior Notes (based on the proportion of the Commitment Amount
                  under this Agreement and the proportion of the outstanding
                  principal amount of the Senior Notes to the sum of both) as a
                  prepayment respectively of (i) the Loans, and if all Loans
                  have been paid, a pre-funding of Letters of Credit pursuant to
                  the provisions of SECTION 7.4, and upon such disposition, the
                  Commitment

                                        8

<PAGE>

                  Amount shall be automatically and permanently reduced by an
                  amount equal to the amount of such proceeds required to be
                  paid to the Agent pursuant to this SECTION 6.16(e)(i), and
                  (ii) the Senior Notes. Amounts required to be paid to the
                  Lenders and the holders of the Senior Notes under this SECTION
                  6.16(e) shall be made on the date the Compliance Certificate
                  and financial statements are required to be delivered under
                  SECTION 6.6(b), provided that, with respect to any asset sale
                  from which the amount required to be paid to the Lenders and
                  the holders of the Senior Notes pursuant to this SECTION
                  6.16(e) is equal to or greater than $10,000,000, the amount
                  required to be paid hereunder shall be paid within 15 days
                  after such proceeds are received by the Borrower or the
                  applicable Subsidiary.

                  (l)      Amendment to Section 6.19. Section 6.19 is amended
         and restated in its entirety, as follows:

                           Section 6.19 Capital Expenditures.

                           (a)      Neither the Borrower nor any of its
                  Subsidiaries shall make or commit to make Capital Expenditures
                  greater than (i) for fiscal year 2002, $60,000,000, (ii) for
                  fiscal year 2003, $60,000,000, and (iii) for fiscal year 2004
                  and each fiscal year thereafter, $50,000,000. No portion of
                  any annual limit may be carried forward to a subsequent fiscal
                  year.

                           (b)      In addition to the annual limits under
                  Section 6.19(a), if the Borrower executes an eligible
                  contract, then the Borrower may make Capital Expenditures in
                  respect of such contract in an amount equal to the lesser of
                  (i) the actual amount required by such contract, and (ii)
                  $30,000,000, provided that, (A) in respect of each such
                  contract, Capital Expenditures not made within 12 months after
                  the date of such contract shall be applied against the annual
                  limits under SECTION 6.19(a), and (B) the amount of Capital
                  Expenditures under this SECTION 6.19(b) for all such contracts
                  may not, in the aggregate, exceed $30,000,000 in any fiscal
                  year. Upon execution of each eligible contract, the Borrower
                  shall promptly deliver a copy of such contract to the Agent,
                  together with a summary of the Capital Expenditures required
                  by such contract in form and detail acceptable to the Agent.
                  As used in this SECTION 6.19(b), "ELIGIBLE CONTRACT" means, a
                  utility outsourcing contract with quantifiable revenues to the
                  Borrower of at least $30,000,000 during any 12 consecutive
                  month period prior to 18 months after execution of such
                  contract."

                  (m)      Amendment to Section 6.20. Clause (b)(v) of Section
         6.20 is amended and restated in its entirety, a new clause (b)(vi) is
         added to Section 6.20, and the sentence immediately following clause
         (b)(v) in Section 6.20 shall now immediately follow the new clause
         (b)(vi) and is amended and restated in its entirety, all as follows:

                           (v) without duplication, charges taken in accordance
                  with SFAS 142 and SFAS 144 in accordance with GAAP, which when
                  taken together with all other charges previously taken in
                  connection with SFAS 142 and SFAS 144, do not, in

                                        9

<PAGE>

                  the aggregate, exceed $850,000,000, and minus (vi) without
                  duplication, all non-cash charges related to the Borrower's
                  stock option program or stock compensation plan as required to
                  be taken pursuant to GAAP. Increases in Consolidated Net Worth
                  after June 30, 2002 shall be appropriately adjusted to
                  eliminate any adverse effects occasioned by the expensing of
                  Make-Whole Amounts (as defined in the Note Purchase Agreement)
                  paid pursuant to Section 8.8 of the Note Purchase Agreement.

                  (n)      Amendment to Section 6.21. Section 6.21 is amended
         and restated in its entirety, as follows:

                           Section 6.21 Minimum Interest Coverage Ratio. The
                  Borrower will maintain a Minimum Interest Coverage Ratio not
                  less than the ratio set out below for the applicable period:

<TABLE>
<S>                                                  <C>
For the period ending September 30, 2002:            2.40 to 1.00
For the period ending December 31, 2002:             1.80 to 1.00
For the period ending March 31, 2003:                1.35 to 1.00
For the period ending June 30, 2003:                 1.55 to 1.00
For the period ending September 30, 2003:            2.10 to 1.00
For the period ending December 31, 2003
and thereafter:                                      2.30 to 1.00
</TABLE>

                  (o)      Amendment to Section 6.22. Section 6.22 is amended
         and restated in its entirety, as follows:

                           Section 6.22 Funded Debt to EBITDA Ratio. The
                  Borrower will maintain a maximum Funded Debt to EBITDA Ratio
                  not greater than the ratio set out below for the applicable
                  period:

<TABLE>
<S>                                                  <C>
For the period ending September 30, 2002:            4.30 to 1.00
For the period ending December 31, 2002:             4.25 to 1.00
For the period ending March 31, 2003:                4.70 to 1.00
For the period ending June 30, 2003:                 4.40 to 1.00
For the period ending September 30, 2003:            3.90 to 1.00
For the period ending December 31, 2003
and thereafter:                                      3.60 to 1.00
</TABLE>

                  (p)      Amendment to Section 6.23. Section 6.23 is amended
         and restated in its entirety, as follows:

                           Section 6.23 Senior Debt to EBITDA. The Borrower will
                  maintain a maximum Senior Debt to EBITDA Ratio not greater
                  than the ratio set out below for the applicable period:

<TABLE>
<S>                                                  <C>
For the period ending September 30, 2002:            3.10 to 1.00
For the period ending December 31, 2002:             2.65 to 1.00
For the period ending March 31, 2003:                2.95 to 1.00
</TABLE>

                                       10

<PAGE>

<TABLE>
<S>                                                  <C>
For the period ending June 30, 2003:                 2.75 to 1.00
For the period ending September 30, 2003:            2.45 to 1.00
For the period ending December 31, 2003
and thereafter:                                      2.30 to 1.00
</TABLE>

                  (q)      The first sentence of Section 10.13 is amended and
         restated in its entirety, as follows:

                           The Borrower, upon demand by the Agent, the Lead
                  Arranger and Book Manager, the Documentation Agents, Managing
                  Agents, any Co-Agent or any Lender, agrees to pay the
                  reasonable fees and disbursements of legal counsel and
                  financial advisors to the Agent, the Lead Arranger and Book
                  Manager, the Documentation Agents, Managing Agents, any
                  Co-Agent or any Lender in connection with (a) the preparation
                  and execution of the Credit Documents, any amendment, waiver
                  or consent related thereto, whether or not the transactions
                  contemplated therein are consummated, (b) any Default or Event
                  of Default by the Borrower hereunder and any enforcement
                  (including, without limitation, all workout and bankruptcy
                  proceedings) of any of the Credit Documents or collection of
                  any Obligations, and (c) any refinancings, restructures or
                  "work out" of the transactions contemplated by the Credit
                  Documents; provided that the Borrower shall only have to pay
                  the reasonable fees and disbursements of one law firm and one
                  financial advisory firm in connection therewith unless the
                  Agent, the Lead Arranger and Book Manager, the Documentation
                  Agents, Managing Agents, any Co-Agent, any Lender or their
                  counsel is of the reasonable opinion that representation by
                  one law firm or one financial advisory firm, as applicable,
                  would not be feasible or that a conflict of interest would
                  exist.

                  (r)      Addition of Section 10.21. Section 10.21 is hereby
         added to the Credit Agreement to read in its entirety as follows:

                           Section 10.21 Certain Amendments. No amendment or
                  waiver with respect to this Agreement shall modify this
                  Section 10.21 or the definitions of "REINSTATEMENT EVENT,"
                  "QUARTERLY EBITDA" or "QUARTERLY PERMITTED CHARGES", or the
                  last sentence of the definition of "COMMITMENT AMOUNT" without
                  the consent of Lenders then holding in the aggregate more than
                  66 2/3% of the aggregate of the Commitments, or if the
                  Commitments have terminated pursuant to the terms hereof, the
                  aggregate Obligations.

                  (s)      Exhibit 6.6 is amended and restated in the form of,
         and all references to Exhibit 6.6 are hereby deemed to be references
         to, Amended Exhibit 6.6 attached hereto.

         2.       REPRESENTATIONS AND WARRANTIES. Each of the Borrower and the
Guarantors represents and warrants to the Lenders that (a) it possesses all
requisite power and authority to execute, deliver and comply with the terms of
this Amendment, (b) this Amendment has been duly authorized and approved by all
requisite corporate, partnership or limited liability company action, as
applicable, by it, (c) no consent of any Person is required for its execution
and delivery of this Amendment, (d) its execution and delivery of this Amendment
will not

                                       11

<PAGE>

violate its organizational documents, (e) the representations and warranties in
each Credit Document to which it is a party are true and correct in all material
respects on and as of the date of this Amendment as though made on the date of
this Amendment (except to the extent that such representations and warranties
speak to a specific date), (f) it is in full compliance with all covenants and
agreements contained in each Credit Document to which it is a party, and (g) no
Default or Event of Default exists as of the date of this Amendment.

         3.       RELEASE.

                  (a)      The Borrower and each Guarantor hereby
         unconditionally and irrevocably remises, acquits, and fully and forever
         releases and discharges the Agent and the Lenders and all respective
         affiliates and subsidiaries of the Agent and the Lenders, their
         respective officers, servants, employees, agents, attorneys, financial
         advisors, principals, directors and shareholders, and their respective
         heirs, legal representatives, successors and assigns (collectively, the
         "Released Lender Parties") from any and all claims, demands, causes of
         action, obligations, remedies, suits, damages and liabilities
         (collectively, the "Borrower Claims") of any nature whatsoever, whether
         now known, suspected or claimed, whether arising under common law, in
         equity or under statute, which the Borrower or any Guarantor ever had
         or now has against the Released Lender Parties which may have arisen at
         any time on or prior to the date of this Amendment and which were in
         any manner related to any of the Credit Documents or the enforcement or
         attempted enforcement by the Agent or the Lenders of rights, remedies
         or recourses related thereto.

                  (b)      The Borrower and each Guarantor covenants and agrees
         never to commence, voluntarily aid in any way, prosecute or cause to be
         commenced or prosecuted against any of the Released Lender Parties any
         action or other proceeding based upon any of the Borrower Claims which
         may have arisen at any time on or prior to the date of this Amendment
         and were in any manner related to any of the Credit Documents.

                  (c)      The agreements of the Borrower and each Guarantor set
         forth in this Section 3 shall survive termination of this Amendment and
         the other Credit Documents.

         4.       AMENDMENT FEE. The Borrower agrees to pay to Agent for the
benefit of each Lender that executes and delivers this Amendment on or before
4:00 p.m. Central Time, December 20, 2002, an amendment fee (the "Amendment
Fee") equal to .375% of such Lender's Commitment (after giving effect to this
Amendment) minus such Lender's pro rata portion of the amount of the Commitment
being blocked pursuant to the Credit Agreement, as amended by this Amendment.
Such Amendment Fee shall be paid in immediately available funds.

         5.       CONDITIONS OF EFFECTIVENESS. This Amendment shall be effective
only after each of the following conditions precedent shall have been satisfied
and only if all conditions precedent to effectiveness are satisfied on or prior
to December 31, 2002:

                  (a)      the Agent shall receive counterparts of this
         Amendment executed by the Majority Lenders, the Borrower and the
         Guarantors;

                                       12

<PAGE>

                  (b)      the representations and warranties set forth in
         Section 2 of this Amendment shall be true and correct;

                  (c)      all reasonable out-of-pocket fees and expenses of the
         Agent in connection with the Credit Documents, including its reasonable
         out-of-pocket legal and other professional fees and expenses by the
         Agent, including, without limitation, such fees and expenses of
         Winstead Sechrest & Minick P.C., Porter & Hedges, L.L.P. and Ernst
         &Young Corporate Finance LLC, shall have been paid;

                  (d)      the Amendment Fee shall have been paid;

                  (e)      the Agent shall receive evidence reasonably
         satisfactory to the Agent that (i) the Borrower has received on or
         about the date hereof, no less than $72,900,000 in gross cash proceeds
         as a result of new equity issued to certain existing shareholders upon
         substantially the terms and conditions previously disclosed in writing
         to the Agent and the Lenders, (ii) the Borrower has received no less
         than $98,500,000 in aggregate gross cash proceeds as a result of new
         equity issued to certain existing shareholders from September 30, 2002
         through and including the date of the issuance referenced in clause (i)
         above, and (iii) the net cash proceeds thereof shall have been paid to
         the Agent for the ratable benefit of the Lenders (based on the
         proportion of the Commitment Amount under this Agreement) as a
         prepayment of the Loans (which prepayment shall not result in a
         permanent reduction of the Commitment Amount);

                  (f)      the Agent shall receive evidence reasonably
         satisfactory to the Agent that the Borrower has entered into an
         amendment to the Note Purchase Agreement in form and substance
         reasonably satisfactory to the Agent;

                  (g)      the Agent shall receive a written certificate signed
         by an officer of the Borrower acceptable to the Agent as to (i) the
         absence of any action, suit, investigation or proceeding pending or, to
         the knowledge of the Borrower, threatened in any court or before any
         arbitrator or governmental authority that could reasonably be expected
         to materially and adversely affect (A) the financial condition of the
         Borrower and its Subsidiaries, taken as a whole, or (B) the ability of
         the Borrower and its Subsidiaries to perform their respective
         obligations under the Credit Documents, as amended by the Amendment,
         (ii) the absence of a material breach of any representation or warranty
         of the Borrower set out in the Credit Documents, and (iii) the
         existence of no Default or Event of Default, after giving effect to
         this Amendment; and

                  (h)      the Agent shall receive, in form and substance
         satisfactory to the Agent and its counsel, such other documents,
         certificates and instruments as the Agent shall reasonably require.

         6.       CREDIT DOCUMENT: REFERENCE TO CREDIT AGREEMENT. This Amendment
is a Credit Document. Upon the effectiveness of this Amendment, each reference
in the Credit Agreement to "this Agreement," "hereunder," or words of like
import shall mean and be a reference to the Credit Agreement, as affected and
amended by this Amendment.

                                       13

<PAGE>

         7.       COUNTERPARTS; EXECUTION VIA FACSIMILE. This Amendment may be
executed in one or more counterparts, each of which shall be deemed an original,
but all of which together shall constitute one and the same instrument. This
Amendment may be validly executed and delivered by facsimile or other electronic
transmission.

         8.       GOVERNING LAW: BINDING EFFECT. This Amendment shall be
governed by and construed in accordance with the laws of the State of Texas and
shall be binding upon the Borrower, the Agent, each Lender and their respective
successors and assigns.

         9.       HEADINGS. Section headings in this Amendment are included
herein for convenience of reference only and shall not constitute a part of this
Amendment for any other purpose.

         10.      NO ORAL AGREEMENTS. THIS WRITTEN AGREEMENT AND THE OTHER
CREDIT DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT
BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE
PARTIES.

                     REMAINDER OF PAGE INTENTIONALLY BLANK.
                             SIGNATURE PAGES FOLLOW.

                                       14

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their proper and duly authorized officers as of
the day and year first above written.

BORROWER:

QUANTA SERVICES, INC.

By: /s/ James H. Haddox
    ----------------------------------
Name:  James H. Haddox

Title: Cheif Financial officer


AGENT:

BANK OF AMERICA, N.A., AS AGENT AND A LENDER

By: /s/Suzanne M.Paul
    -------------------------------
    Suzanne M.Paul, Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                      AND RESTATED SECURED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

                        GUARANTORS' CONSENT AND AGREEMENT

As an inducement to the Lenders to execute, and in consideration of the Lenders'
execution of this Amendment, each of the undersigned hereby consents to this
Amendment and agrees that the same shall in no way release, diminish, impair,
reduce or otherwise adversely affect the obligations and liabilities of the
undersigned under their respective Guaranties described in the Credit Agreement
executed by the undersigned, or any agreements, documents or instruments
executed by any of the undersigned, all of which obligations and liabilities
are, and shall continue to be, in full force and effect. This consent and
agreement shall be binding upon the undersigned, and their respective successors
and assigns, and shall inure to the benefit of the Lenders, and their respective
successors and assigns.

                           ADVANCED TECHNOLOGIES AND INSTALLATION CORPORATION
                           ALLTECK LINE CONTRACTORS (USA), INC.
                           ARBY CONSTRUCTION, INC.
                           AUSTIN TRENCHER, INC.
                           BRADFORD BROTHERS, INC.
                           CCLC, INC.
                           COMMUNICATION MANPOWER, INC.
                           COMPUTAPOLE, INC.
                           CONTI COMMUNICATIONS, INC.
                           CROCE ELECTRIC COMPANY, INC.
                           CROWN FIBER COMMUNICATIONS, INC.
                           DILLARD SMITH CONSTRUCTION COMPANY
                           DRIFTWOOD ELECTRICAL CONTRACTORS, INC.
                           ENVIRONMENTAL PROFESSIONAL ASSOCIATES, LIMITED
                           FIVE POINTS CONSTRUCTION CO.
                           GLOBAL ENERCOM MANAGEMENT, INC.
                           GOLDEN STATE UTILITY CO.
                           H. L. CHAPMAN PIPELINE CONSTRUCTION, INC.
                           HAINES CONSTRUCTION COMPANY
                           INTERMOUNTAIN ELECTRIC, INC.
                           IRBY CONSTRUCTION COMPANY
                           LINE EQUIPMENT SALES CO., INC.
                           MANUEL BROS., INC.
                           MEARS GROUP, INC.
                           MEJIA PERSONNEL SERVICES, INC.
                           METRO UNDERGROUND SERVICES, INC.
                           MUSTANG LINE CONTRACTORS, INC.
                           NETWORK ELECTRIC COMPANY
                           NORTH PACIFIC CONSTRUCTION CO., INC.
                           NORTH SKY COMMUNICATIONS, INC.
                           NORTHERN LINE LAYERS, INC.
                           PAR ELECTRICAL CONTRACTORS, INC.
                           PARKSIDE SITE & UTILITY COMPANY CORPORATION
                           PARKSIDE UTILITY CONSTRUCTION CORP.
                           P.D.G. ELECTRIC COMPANY
                           POTELCO, INC.
                           PROFESSIONAL TELECONCEPTS, INC.
                           PROFESSIONAL TELECONCEPTS, INC.
                           PWR FINANCIAL COMPANY
                           QPC, INC.
                           QSI, INC.
                           QUANTA HOLDINGS, INC.
                           QUANTA XXXI ACQUISITION, INC.
                           QUANTA LI ACQUISITION, INC.
                           QUANTA LIV ACQUISITION, INC.
                           QUANTA LVII ACQUISITION, INC.
                           QUANTA LVIII ACQUISITION, INC.
                           QUANTA LIX ACQUISITION, INC.
                           QUANTA LX ACQUISITION, INC.
                           QUANTA LXI ACQUISITION, INC.

                        NINTH AMENDMENT TO THIRD AMENDED
                          AND RESTATED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

                           QUANTA LXII ACQUISITION, INC.
                           QUANTA LXIII ACQUISITION, INC.
                           QUANTA LXIV ACQUISITION, INC.
                           QUANTA LXV ACQUISITION, INC.
                           QUANTA LXVI ACQUISITION, INC.
                           QUANTA LXVII ACQUISITION, INC.
                           QUANTA LXVIII ACQUISITION, INC.
                           QUANTA LXIX ACQUISITION, INC.
                           QUANTA LXX ACQUISITION, INC.
                           QUANTA LXXI ACQUISITION, INC.
                           QUANTA LXXII ACQUISITION, INC.
                           QUANTA LXXIII ACQUISITION, INC.
                           QUANTA UTILITY INSTALLATION CO., INC,
                           R. A. WAFFENSMITH & CO., INC.
                           RANGER FIELD SERVICES, INC.
                           SOUTHEAST PIPELINE CONSTRUCTION, INC.
                           SOUTHWESTERN COMMUNICATIONS, INC.
                           SOUTHWEST TRENCHING COMPANY, INC.
                           SPALJ CONSTRUCTION COMPANY
                           SPECIALTY DRILLING TECHNOLOGY, INC.
                           SUMTER UTILITIES, INC.
                           THE RYAN COMPANY, INC.
                           TOM ALLEN CONSTRUCTION COMPANY
                           TRANS TECH ACQUISITION, INC.
                           TRAWICK CONSTRUCTION COMPANY, INC.
                           TTGP, INC.
                           TTLP, INC.
                           TTM, INC.
                           TXLP, INC.
                           UNDERGROUND CONSTRUCTION CO., INC.

                        NINTH AMENDMENT TO THIRD AMENDED
                          AND RESTATED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

                           UTILCO, INC.
                           VCI TELCOM, INC.

                           W.C. COMMUNICATIONS, INC.
                           W.H.O.M. CORPORATION

                           By: /s/Dana Gordon
                               -------------------------------------------------
                               Dana Gordon, President or Vice President
                               of each Guarantor

                           QDE LLC
                           QUANTA DELAWARE, INC.
                           QUANTA ASSET MANAGEMENT LLC

                           By: /s/Linda Bubaoz
                               -------------------------------------------------
                               Linda Bubaoz, President

                           BROWN ENGINEERING, LLC

                           By: Ranger Field Services, Inc., Its Member

                               By: /s/Dana Gordon
                                   ---------------------------------------------
                                   Dana Gordon, Vice President

                           COAST TO COAST, LLC

                           By: Environmental Professional Associates, Limited,
                               a California corporation, Its Member

                               By: /s/Dana Gordon
                                   ---------------------------------------------
                                   Dana Gordon, Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                          AND RESTATED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

                           DOT 05, LLC
                           TJADER, L.L.C.
                           OKAY CONSTRUCTION COMPANY, LLC

                           By: Spalj Construction Company, Its Member

                               By: /s/Dana Gordon
                                   -----------------------------------
                                   Dana Gordon, Vice President

                           LAKE NORMAN PIPELINE, LLC

                           By: Bradford Brothers, Inc., Its Member

                               By: /s/Dana Gordon
                                   ------------------------------------
                                   Dana Gordon, Vice President

                           MEARS/CPG, LLC
                           MEARS ENGINEERING, LLC
                           MEARS/HDD, LLC
                           MEARS SERVICES, LLC

                           By: Mears Group, Inc., The Sole Member of
                               each of the foregoing limited liability companies

                               By: /s/Dana Gordon
                                   ------------------------------------
                                   Dana Gordon, Vice President

                           S.K.S. PIPELINERS, LLC

                           By: Arby Construction, Inc., Its Member

                               By: /s/Dana Gordon
                                   -----------------------------------
                                   Dana Gordon, Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                          AND RESTATED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

                           TNS-VA, LLC

                           By: Professional Teleconcepts, Inc. (NY), Its Member

                               By: /s/Dana Gordon
                                   -------------------------------------
                                   Dana Gordon, Vice President

                           LINECO LEASING, LLC

                           By: Mustang Line Contractors, Inc., Its Sole Member

                               By: /s/Dana Gordon
                                   -------------------------------------
                                   Dana Gordon, Vice President

                           AIRLAN TELECOM SERVICES, L.P.
                           NORTH HOUSTON POLE LINE, L.P.
                           LINDSEY ELECTRIC, L.P.
                           DIGCO UTILITY CONSTRUCTION, L.P.

                           By: Mejia Personnel Services, Inc., Its General
                               Partner

                               By: /s/Dana Gordon
                                   ---------------------------------------
                                   Dana Gordon, Vice President

                           QUANTA SERVICES MANAGEMENT PARTNERSHIP, L.P.
                           QUANTA ASSOCIATES, L.P.

                           By: QSI, Inc., Its General Partner

                               By: /s/Dana Gordon
                                   ---------------------------------------
                                   Dana Gordon, Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                          AND RESTATED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

                           TRANS TECH ELECTRIC, L.P.

                           By: TTGP, Inc., Its General Partner

                               By: /s/Dana Gordon
                                   --------------------------------------
                                   Dana Gordon, Vice President

                           PWR NETWORK, LLC

                           By: PWR Financial Company, Its Sole Member

                               By: /s/Dana Gordon
                                   --------------------------------------
                                   Dana Gordon, Vice President

                           Q RESOURCES, LLC

                           By: Quanta Holdings, Inc.

                               By: /s/Dana Gordon
                                   --------------------------------------
                                   Dana Gordon, Vice President

                           QUANTA RECEIVABLES, L.P.

                           By: PWR Network, LLC, Its General Partner

                               By: PWR Financial Company, Its Sole Member

                                   By: /s/Dana Gordon
                                       -----------------------------------
                                       Dana Gordon, Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                          AND RESTATED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

                           TOTAL QUALITY MANAGEMENT SERVICES, LLC

                           By: Environmental Professional Associates, Ltd., Its
                               Sole Member

                               By: /s/Dana Gordon
                                   --------------------------------------
                                   Dana Gordon, Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                      AND RESTATED SECURED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                    Bank of America, N.A

                                    By: /s/John K. Barrett
                                        -------------------------------------
                                    Name:  John K. Barrett
                                    Title: Principal

                        SCHEDULE 1 TO NINTH AMENDMENT TO
               THIRD AMENDED AND RESTATED SECURED CREDIT AGREEMENT

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                    BANK ONE. N.A., as a Bank

                                    By: /s/Dennls Warren
                                        -------------------------------------
                                    Name:  Dennls Warren
                                    Title: First Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                      AND RESTATED SECURED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                    Comerica Bank

                                           /s/William S. Rogers
                                           ----------------------------------
                                    Name:  William S. Rogers
                                    Title: Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                      AND RESTATED SECURED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                    CREDIT LYONNAIS NEW YORK BRANCH

                                    By: /s/Attala Koc
                                        -------------------------------------
                                    Name:  Attala Koc
                                    Title: Senior Vice President

                        SCHEDULE 1 TO NINTH AMENDMENT TO
               THIRD AMENDED AND RESTATED SECURED CREDIT AGREEMENT

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                           Fleet National Bank

                                    By: /s/G. Christopher Miller
                                        -------------------------------------
                                    Name:  G. Christopher Miller
                                    Title: Vice President

                        SCHEDULE 1 TO NINTH AMENDMENT TO
               THIRD AMENDED AND RESTATED SECURED CREDIT AGREEMENT

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                           JPMorgan Chase Bank

                                    BY: /s/Robert L. Mendoza
                                        -------------------------------------
                                    Name:  Robert L. Mendoza
                                    Title: Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                      AND RESTATED SECURED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                           LaSalle Bank National Association

                                    BY: /s/David L. Saverman
                                        -------------------------------------
                                    Name:  David L. Saverman
                                    Title: Senior Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                      AND RESTATED SECURED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                    National City Bank

                                    By: /s/Michael J. Durbin
                                        -------------------------------------
                                    Name:  Michael J. Durbin
                                    Title: Senior Vice President

                        NINTH AMENDMENT TO THIRD AMENDED
                      AND RESTATED SECURED CREDIT AGREEMENT
                                 SIGNATURE PAGE

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002, by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                   [ILLEGIBLE]
                                    --------------------------------------------

                                    By: The Bank of Nova Scotia_________________
                                    Name:  Mark Sparrow_________________________
                                    Title: Director_____________________________

<PAGE>

         Lender signature page to that certain Ninth Amendment to Third Amended
and Restated Secured Credit Agreement dated to be effective as of December 20,
2002. by and among Quanta Services, Inc., the Lenders party thereto, and Bank of
America, N.A., as Agent for the Lenders.

                                    Guaranty Bank

                                    By: /s/Scott Brewer
                                        -------------------------------------
                                    Name:  Scott Brewer
                                    Title: VP

                        SCHEDULE 1 TO NINTH AMENDMENT TO
               THIRD AMENDED AND RESTATED SECURED CREDIT AGREEMENT

<PAGE>

                               AMENDED EXHIBIT 6.6

                             COMPLIANCE CERTIFICATE

         Quanta Services, Inc. (the "BORROWER"), the various financial
institutions from time to time parties thereto (the "LENDERS"), and Bank of
America, N.A., as Agent for the Lenders (in such capacity, the "AGENT"),
executed and delivered that certain Third Amended and Restated Secured Credit
Agreement dated as of June 14, 1999 (as amended, supplemented and restated from
time to time, the "CREDIT AGREEMENT"). Any term used but not defined in this
Compliance Certificate shall have the meaning given to it in the Credit
Agreement.

         The undersigned, solely in his or her capacity as__________ of the
Borrower hereby certifies to the Agent and the Lenders that:

         A.       This Compliance Certificate and the attached financial
statements are delivered on this ______day of________,_________.

         B.       The attached financial statements are (check one)[ ] monthly
financial statements dated_________________, [ ] quarterly financial statements
dated__________________, [ ] annual financial statements dated_________________,
and fairly present on a consolidated or consolidating basis, as the case may
be and as applicable, the balance sheet [,] [and] statements of income [ADD THE
FOLLOWING FOR QUARTERLY AND ANNUAL FINANCIAL STATEMENTS:, retained earnings and
cash flows] of the Borrower and its Subsidiaries covered thereby as of the date
thereof and for the period covered thereby, subject to normal year-end audit
adjustments and the omission of any footnotes as permitted by the SEC for any
such financial statements that are monthly or quarterly financial statements,
[ADD THE FOLLOWING FOR QUARTERLY REPORTING:, together with a summary of asset
dispositions during such period and in the aggregate to date under SECTION
6.16(c), (d) and (e) of the Credit Agreement] [ADD THE FOLLOWING FOR MONTHLY
REPORTING:, together with an accounts receivable aging summary, a status report
on (i) the contractual obligations of the Borrower as disclosed to the Agent
described in CLAUSE(c)(ii) of the definition of "PERMITTED CHARGES", and (ii)
the top 20 accounts receivable of the Borrower, and the three month cash flow
projections required under SECTION 6.6(c)].

         C.       As of the date of the attached and with respect to the
Borrower and its Subsidiaries on a consolidated basis, the following (calculated
in accordance with the Credit Agreement):

                                  EXHIBIT 6.6

<PAGE>

<TABLE>
<S>      <C>                                                                                           <C>
1.       CONSOLIDATED NET WORTH

         a.       CONSOLIDATED NET WORTH                                                               $______________

         b.       Starting Consolidated Net Worth (90% of Consolidated Net Worth
                  as of June 30, 2002 and determined without giving effect to
                  any adjustments made in accordance with SFAS 142 and SFAS 144)                       $______________

         c.       75% of positive Consolidated Net Income for Current fiscal
                  quarter commencing July 1, 2002                                                      $______________

         d.       100% of any equity issuances                                                         $______________

         e.       Subchapter S distributions                                                           $______________

         f.       Permitted Charges (clauses (a) and (b))                                              $______________

         g.       SFAS 142 and SFAS 144 charges (when taken together with all
                  other charges previously taken in connection with SFAS 142 and
                  SFAS 144, shall not, in the aggregate, exceed $850,000,000)                          $______________

         h.       MINIMUM CONSOLIDATED NET WORTH (SUM OF b, c AND d MINUS e, f
                  AND g)

                  (Increases in Consolidated Net Worth required after June 30,
                  2002 shall be appropriately adjusted to eliminate any adverse
                  effects on the Consolidated Net Worth of the Borrower
                  occasioned by the expensing of Make-Whole Amounts (as defined
                  in the Note Purchase Agreement) paid pursuant to Section 8.8
                  of the Note Purchase Agreement. The calculation of
                  Consolidated Net Worth shall not take into consideration the
                  non-cash charges related to the Borrower's stock option
                  program or stock compensation plan as required to be taken
                  pursuant to GAAP.)                                                                   $______________

2.       MINIMUM INTEREST COVERAGE RATIO

         a.       EBIT                                                                                 $______________

         b.       Consolidated Interest Expense (excluding any make-whole
                  payments made in connection with asset sales which result in a
                  mandatory prepayment on the Senior Notes)                                            $______________

         c.       INTEREST COVERAGE RATIO (RATIO OF a TO b)                                            _____to 1.00
</TABLE>

                                  EXHIBIT 6.6

                                       2

<PAGE>

<TABLE>
<S>      <C>                                                                                           <C>

         d.       MINIMUM INTEREST COVERAGE RATIO FOR SUCH PERIOD                                      _____to 1.00

3.       FUNDED DEBT TO EBITDA RATIO

         a.       FUNDED DEBT (SUM OF i, ii, AND iii BELOW)                                            $___________

                  i.       Indebtedness for borrowed money                                             $___________

                  ii.      Reimbursement Obligations                                                   $___________

                  iii.     Capitalized lease Obligations                                               $___________

         b.       EBITDA                                                                               $___________

         c.       FUNDED DEBT TO EBITDA RATIO (RATIO OF a TO b)                                        _____to 1.00

         d.       MAXIMUM FUNDED DEBT TO EBITDA RATIO FOR SUCH PERIOD                                  _____to 1.00

4.       SENIOR DEBT TO EBITDA RATIO

         a.       Senior Debt                                                                          $___________

         b.       EBITDA                                                                               $___________

         c.       RATIO (RATIO OF a TO b)                                                              _____to 1.00

         d.       MAXIMUM SENIOR DEBT TO EBITDA RATIO FOR SUCH PERIOD                                  _____to 1.00

5.        MINIMUM ASSET COVERAGE RATIO(1)

         a.       Consolidated Net Accounts                                                            $___________

         b.       Consolidated Net PP&E                                                                $___________

         c.       CONSOLIDATED NET ASSETS (SUM OF a PLUS b)                                            $___________

         d.       Senior Debt                                                                          $___________
</TABLE>

-------------------------------------
(1) Minimum Asset Coverage Ratio is tested monthly. All other financial
covenants are tested quarterly, or annually in the case of Capital Expenditures.

                                  EXHIBIT 6.6

                                       3

<PAGE>

<TABLE>
<S>      <C>                                                                                           <C>

         d.       ASSET COVERAGE RATIO (RATIO OF c TO d)                                               _____to 1.00

         d.       MINIMUM ASSET COVERAGE RATIO FOR SUCH PERIOD                                         _____to 1.00

6.       CAPITAL EXPENDITURES

         a.       Capital Expenditures for such period                                                 $___________

         b.       Capital Expenditures fiscal year to date                                             $___________

         c.       Portion of Capital Expenditures fiscal year to date, if any,
                  in connection with outsourcing utility contract equal to or
                  greater than $30,000,000 and confirmed by the Agent (subset of
                  b)                                                                                   $______________

         d.       Line b minus line c.                                                                 $______________

         e.       MAXIMUM AMOUNT FOR LINE.                                                             $30,000,000

         f.       MAXIMUM AMOUNT FOR LINE d ((i) $60,000,000 FOR 2002 AND 2003
                  AND (ii) $50,000,000 FOR 2004 AND THEREAFTER)                                        $______________
</TABLE>

         D.       Attached hereto is back-up documentation (in form reasonably
acceptable to the Agent) showing information on a Subsidiary by Subsidiary basis
supporting the calculations of the financial covenants contained herein.

         [FOR QUARTERLY AND ANNUAL COMPLIANCE CERTIFICATE INSERT THE FOLLOWING
SECTIONS E AND F:]

         E.       To the best of my knowledge after due inquiry, all of the
representations and warranties contained in the Credit Agreement are true and
correct on the date hereof as if made on the date hereof except, (i) to the
extent such representation and warranty relates solely to an earlier date in
which case it shall have been true and correct as of such earlier date, (ii) as
a result of the transactions expressly permitted under the Credit Agreement,
(iii) as previously disclosed to the Lenders or (iv) as to the following
matters: [Describe or attach a schedule of all such representations and
warranties that are no longer true or correct and, if applicable, what action
the Borrower has taken or proposes to take].

                         _____________________________
                         _____________________________
                         _____________________________

                                   EXHIBIT 6.6

                                       4

<PAGE>

         F.       (Check EITHER 1 or 2) to the best of my knowledge after due
inquiry:

         [_]      1.       As of the date hereof, no Default or Event of Default
                  has occurred and is continuing.

         [_]      2.       As of the date hereof, no Default or Event of Default
                  has occurred and is continuing except the following matters:
                  [Describe all such Defaults or Events of Default, specifying
                  the nature, duration and status thereof and what action the
                  Borrower has taken or proposes to take with respect thereto].

Date:______________,______.

                                    QUANTA SERVICES, INC.
                                    By:_________________________________
                                    Name:_______________________________
                                    Title:______________________________

                                  EXHIBIT 6.6

                                       5

