UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) TO THE ISSUER
OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY
CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME
AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY
AND ANY PAYMENT IS MADE TO CEDE & CO., ANY TRANSFER, PLEDGE OR OTHER USE
HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE THE
REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

REGISTERED                                                     PRINCIPAL AMOUNT
NO. FLR-__                                                        $

CUSIP:

                           QUESTAR PIPELINE COMPANY
                               MEDIUM-TERM NOTE
                                (Floating Rate)

Original Issue Date:                         Minimum Rate:

Stated Maturity:                             Maximum Rate:

Interest Payment Date(s):                    Interest Reset Dates:

Regular Record Date(s):                      Interest Reset Period:

Base Rate(s):                                Interest Determination Date:

Index Maturity:                              Redemption Percentage:

Initial Interest Rate:                       Annual Redemption Percentage:

Spread:                                      Redemption Commencement Date:

Spread Multiplier:                           Sinking Fund/Repayment Provision:

Calculation Agent:                           Optional Repayment Date:

Other Provisions:

                  The Redemption Price (if applicable) shall initially be the
Redemption Percentage of the principal amount of this Note to be redeemed and
shall decline (but not below par) at each anniversary of the Redemption
Commencement Date by the Annual Redemption Percentage of the principal amount
to be redeemed until the Redemption Price is 100% of such principal amount.
"N/A" as used herein means "Not Applicable". "A/S" as used herein means "As
stated in this Note".



                  QUESTAR PIPELINE COMPANY, a corporation duly organized and 
existing under the laws of the State of Utah (herein called the "Company",
which term includes any successor corporation under the Indenture hereinafter
referred to), for value received, hereby promises to pay to

, or registered assigns, the principal sum of

                                                                     DOLLARS

at Stated Maturity as specified above (except to the extent redeemed or repaid
prior to the Stated Maturity), and to pay interest thereon from the Original
Issue Date specified above or from the most recent Interest Payment Date
(subject to the provisions below) to which interest has been paid or duly
provided for, periodically on each Interest Payment Date, commencing with the
first such Interest Payment Date next succeeding the Original Issue Date
specified above, and at Stated Maturity (the date on each such Stated
Maturity, Redemption Date, and Optional Repayment Date and the date on which
principal or an installment of principal is due and payable by declaration of
acceleration pursuant to the Indenture being referred to hereinafter as a
"Maturity" with respect to principal payable on such date), at the Interest to
be determined in accordance with the provisions below, depending on the Base
Rate(s) shown above (the "Floating Interest Rate"), until the principal hereof
is paid or made available for payment; provided, that if such Original Issue
Date is after a Regular Record Date and before the Interest Payment Date
immediately following such Regular Record Date, interest payments will
commence on the second Interest Payment Date following the Original Issue
Date. The interest so payable, and punctually paid or duly provided for, on
any Interest Payment Date (except at Maturity) will, as provided in the
Indenture, be paid to the Person in whose name this Note (or one or more Notes
which are Predecessor Securities) is registered at the close of business on
the Regular Record Date next preceding such Interest Payment Date. Any such
interest which is payable, but not so punctually paid or duly provided for on
any Interest Payment Date, will forthwith cease to be payable to the Holder on
such Regular Record Date and may either be paid to the Person in whose name
this Note (or one or more Notes which are Predecessor Securities) is
registered at the close of 

                                      2



business on a Special Record Date for the payment of such Defaulted Interest
to be fixed by the Trustee, notice whereof shall be given to the Holder of
this Note not less than 10 days prior to such Special Record Date, or be paid
at any time in any other lawful manner not inconsistent with the requirements
of any securities exchange on which the Notes of this series may be listed,
upon such notice as may be required by such exchange, all as more fully
provided in the Indenture. Reference herein to "this Note", "hereof", "herein"
and comparable terms shall include an Addendum hereto if an Addendum is
specified above.

                  Any provision contained herein with respect to the
calculation of the rate of interest applicable to this Note, its payment dates
or any other matter relating hereto may be modified as specified in an
Addendum relating hereto if so specified above.

                  This Note is one of a duly authorized series of Securities
of the Company (herein called the "Securities", and the series thereof to
which this Note belongs being herein called the "Notes"), issued and to be
issued under an Indenture, dated as of August [ ], 1998, (herein called the
"Indenture") between the Company and First Security Bank, N.A. (herein called
the "Trustee", which term includes any successor trustee under the Indenture),
to which Indenture and all indentures supplemental thereto reference is hereby
made for a statement of the respective rights, limitations of rights, duties
and immunities thereunder of the Company, the Trustee and the Holders of Notes
and of the terms upon which the Notes are, and are to be, authenticated and
delivered. This Note is one of the series of Securities designated as
"Medium-Term Notes". The Notes may be issued from time to time at varying
maturities, interest rates and other terms and in an aggregate principal
amount up to $175,000,000, which amount may be increased if duly authorized by
the Company.

                  If this Note is a Definitive Note, payments of the principal
of, premium, if any, and interest on this Note will be made in immediately
available funds at the Corporate Trust Office of the Trustee in Salt Lake
City, Utah or at such other place as the Company may designate, provided that
this Note is presented to the Trustee in time for the Trustee to make such
payments in such funds 

                                      3



in accordance with its normal procedures. Interest (other than interest
payable at Maturity) will be paid by check mailed to the address of the Person
entitled thereto as it appears in the Security Register as of the Regular
Record Date or, at the option of the Company, by wire transfer to an account
maintained by such Person with a bank located within the United States;
provided, however, that the Holder of this Note may be entitled to receive
payments of principal, premium, if any, and interest by wire transfer to an
account maintained by such Holder with a bank located in the United States if
an appropriate written request has been received by the Trustee prior to the
Regular Record Date in respect of any interest payment, or the date which is
fifteen days before the Stated Maturity of the Note, as the case may be.

                  If this Note is a Global Security representing Book-Entry
Notes, payments of the principal of, premium, if any, and interest on the Note
will be made by check or by wire transfer to an account maintained by the
Depositary for such purpose.

                  This Note is not subject to redemption prior to the Stated
Maturity unless a Redemption Commencement Date and Redemption Percentage are
specified on the first page of this Note. If so specified, this Note is
subject to redemption upon not more than 60 days' nor less than 30 days'
notice by mail, at any time on or after the Redemption Commencement Date
specified on the first page hereof, as a whole or in part, at the election of
the Company, at the Redemption Prices set forth on the first page hereof,
together, in the case of any such redemption, with accrued interest to the
Redemption Date, but interest installments whose Stated Maturity is on or
prior to such Redemption Date will be payable to the Holder of this Note (or
one or more Notes which are Predecessor Securities) at the close of business
on the relevant Record Dates referred to on the first page hereof, all as
provided in the Indenture.

                  In the event of redemption of this Note in part only, a new
Note for the unredeemed portion hereof will be issued in the name of the
Holder hereof upon the surrender hereof.

                                      4



                  If so provided on the first page hereof, this Note will be
subject to repayment at the option of the Holder hereof on the Optional
Repayment Date, if any, indicated on the first page hereof. If no Optional
Repayment Date is set forth on the first page hereof, this Note will not be
repayable at the option of the Holder prior to Stated Maturity. On any
Optional Repayment Date, this Note will be repayable in whole or in part in
increments of $1,000 at the option of the Holder hereof at a price equal to
100% of the principal amount to be repaid, together with interest thereon
payable to the Optional Repayment Date, on notice in the form entitled "Option
to Elect Repayment" below, duly completed, given together with this Note by
such Holder to the Company not more than 60 nor less than 30 days prior to the
Optional Repayment Date. In the event of repayment of this Note in part only,
a new Note for the portion hereof not repaid will be issued in the name of the
Holder hereof upon the surrender hereof. Exercise of such repayment option by
the Holder shall be irrevocable.

                  The "Floating Interest Rate" on this Note will be calculated
by reference to the Base Rate(s), as specified on the first page hereof, (a)
plus or minus the Spread, if any, and/or (b) multiplied by the Spread
Multiplier, if any. The Base Rate may be one or more of: (a) the Commercial
Paper Rate, (b) the Federal Funds Rate, (c) LIBOR, (d) the Prime Rate, (e) the
Treasury Rate or (f) such other interest rate formula as is set forth on the
first page hereof. The "Index Maturity" is the period to maturity of the
instrument or obligation with respect to which the related Base Rate or Rates
are calculated. Except as otherwise provided herein, all percentages resulting
from any calculation will be rounded out to the nearest one hundred-thousandth
of a percentage point (with five one-millionths of a percentage point rounded
upward), and all dollar amounts used in or resulting from such calculation
will be rounded to the nearest cent (with one-half cent being rounded upward).

                  Notwithstanding the foregoing, if this Note is designated
above as having an Addendum attached, the Note shall bear interest in
accordance with the terms described in such Addendum.

                  Unless otherwise specified on the first page hereof, the
"Regular Record Date" with respect to this 

                                      5



Note shall be the fifteenth calendar day immediately preceding the related
Interest Payment Date or Dates, whether or not such date shall be a Business
Day, and interest will be payable, in the case of Notes which reset daily,
each Business Day, in the case of Notes which reset weekly, on Wednesday of
each week (with the exception of weekly reset Floating Rate Notes as to which
the Treasury Rate is an applicable Base Rate, which will reset Tuesday of each
week, except as described below), in the case of Notes which reset monthly, on
the third Wednesday of each month, in the case of Notes which reset quarterly,
on the third Wednesday of [March, June, September and December] of each year,
in the case of Notes which reset semi-annually, on the third Wednesday of the
two months of each year specified on the first page hereof, and in the case of
Notes which reset annually, on the third Wednesday of the month specified on
the first page hereof (each an "Interest Payment Date"); and, in each case, at
Maturity.

                  Payments of Interest with respect to any Interest Payment
Date will include interest accrued to but excluding such Interest Payment
Date. Accrued interest is calculated by multiplying the face amount of this
Note by an accrued interest factor. Such accrued interest factor is computed
by adding the interest factor calculated for each day from the later of the
Original Issue Date, or from the last date to which interest has been paid or
duly provided for, to the date for which accrued interest is being calculated.
The interest factor (expressed as a decimal rounded to the nearest one
hundred-thousandth of a percentage point) for each such day is computed by
dividing the interest rate (expressed as a decimal rounded to the nearest
one-hundred-thousandth of a percentage point) applicable to such day by 360,
in the case of Commercial Paper Rate Notes, Federal Funds Rate Notes, LIBOR
Notes, or Prime Rate Notes or by the actual number of days in the year, in the
case of Treasury Rate Notes. The interest factor for Floating Rate Notes for
which the interest rate is calculated with reference to two or more Base Rates
will be calculated in each period in the same manner as if only the lowest of
the applicable Base Rates applied. If any Interest Payment Date for this Note
falls on a day that is not a Business Day with respect to this Note, such
Interest Payment Date for this Note will be the following day that is a
Business Day for this Note, except that, in the case of a LIBOR Note (or a

                                      6



Note for which LIBOR is the applicable Base Rate), if such Business Day is in
the next succeeding calendar month, such Interest Payment Date will be the
immediately preceding day that is a Business Day for this Note. If the
Maturity of this Note falls on a day that is not a Business Day with respect
to this Note, the payment of principal, premium, if any, and interest will be
made on the next succeeding Business Day, and no interest on such payment
shall accrue for the period from and after Maturity. Unless otherwise
specified on the first page hereof or in an Addendum hereto, "Business Day"
means any day that is not a Saturday or Sunday, and that in The City of New
York is not a day on which banking institutions are generally authorized or
obligated by law or executive order to close, and, with respect to any LIBOR
Note, is a London Business Day. "London Business Day" means any day on which
dealings in deposits in United States dollars are transacted in the London
interbank market.

                  Except as provided on the first page hereof, the rate of
interest on this Note will be reset daily, weekly, monthly, quarterly,
semi-annually or annually (each an "Interest Reset Date"), as specified on the
first page hereof. Except as provided on the first page hereof, if this Note
resets daily, the Interest Reset Date will be each Business Day, if this Note
resets weekly, the Interest Reset Date will be on Wednesday of each week (with
the exception of weekly reset Floating Rate Notes as to which the Treasury
Rate is an applicable Base Rate, which will reset on Tuesday of each week,
except as described below), if this Note resets monthly, the Interest Reset
Date will be the third Wednesday of each month, if this Note resets quarterly,
the Interest Reset Date will be the third Wednesday of each [March, June,
September and December] of each year, if this Note resets semi-annually the
Interest Reset Date will be the third Wednesday of each of the two months of
each year specified on the first page hereof, and if this Note resets
annually, the Interest Reset Date will be the third Wednesday of the month of
each year as specified on the first page hereof, provided, however, that (a)
the interest rate in effect from the Original Issue Date to the first Interest
Reset Date will be the Initial Interest Rate (as set forth on the first page
hereof), and (b) the interest rate in effect for the ten calendar days
immediately prior to Maturity will be the interest rate 

                                      7



in effect on the tenth calendar day preceding such Maturity. If any Interest
Reset Date would otherwise be a day that is not a Business Day, such Interest
Reset Date shall be the next succeeding Business Day (or, in the case of a
LIBOR Note or a Note for which LIBOR is an applicable Base Rate, if such
Business Day falls in the next calendar month, such Interest Reset Date shall
be the last Business Day in the preceding month).

                  The interest rate applicable to each Interest Reset Period
commencing on the Interest Reset Date or Dates with respect to such Interest
Reset Period will be the rate determined as of the applicable "Interest
Determination Date." The Interest Determination Date with respect to the
Commercial Paper Rate, the Federal Funds Rate and the Prime Rate will be the
second Business Day preceding each Interest Reset Date. The Interest
Determination Date with respect to LIBOR will be the second London Business
Day preceding each Interest Reset Date. With respect to the Treasury Rate, the
Interest Determination Date will be the day in the week in which the Interest
Reset Date falls on which day Treasury Bills are normally auctioned (Treasury
Bills are normally sold at auction on Monday of each week, unless that day is
a legal holiday, in which case the auction is normally held on the following
Tuesday, except that such auction may be held on the preceding Friday);
provided, however, that if, as a result of a legal holiday, an auction is held
on the Friday of the week preceding the Interest Reset Date, the related
Interest Determination Date shall be such preceding Friday; and provided,
further, that if an auction shall fall on any Interest Reset Date, then the
related Interest Reset Date shall instead be the first Business Day
immediately following such auction. If the interest rate of this Note is
determined with reference to two or more Base Rates, the Interest
Determination Date will be the first Business Day which is at least two
Business Days prior to such Interest Reset Date on which each Base Rate shall
be determinable. Each Base Rate shall be determined and compared on such date,
and the applicable interest rate shall take effect on the related Interest
Reset Date.

                  The Calculation Agent (which shall be the Trustee unless
otherwise specified on the first page hereof and which may be changed by the
Company from time to time) shall calculate the Floating Interest Rate on 

                                      8



this Note on or before each Calculation Date and, upon request, provide to
holders the Floating Interest Rate then in effect and, if different, the
interest rate which will become effective as a result of a determination made
for the next succeeding Interest Reset Date with respect to this Note. The
Calculation Agent's determination of any Floating Interest Rate will be final
and binding in the absence of manifest error. Unless otherwise specified on
the first page hereof or in an Addendum hereto, the "Calculation Date", where
applicable, pertaining to any Interest Determination Date will be the earlier
of (i) the tenth calendar day after such Interest Determination Date, or if
any such day is not a Business Day, the next succeeding Business Day or (ii)
the Business Day immediately preceding the applicable Interest Payment Date or
Maturity, as the case may be.

                  Notwithstanding the other provisions herein, the Floating
Interest Rate hereon which may accrue during any interest period shall not be
greater than the Maximum Interest Rate, if any, or less than the Minimum
Interest Rate, if any, shown on the first page hereof and, in addition, the
Floating Interest Rate shall in no event be higher than the maximum rate
permitted by New York law, as the same may be modified by United States law of
general application.

Determination of Commercial Paper Rate.

                  The "Commercial Paper Rate" will be determined by the
Calculation Agent in accordance with the following provisions:

                  "Commercial Paper Rate" means, with respect to any Interest
Determination Date relating to a Commercial Paper Rate Note or to any Note for
which the Commercial Paper Rate is one of the Base Rates (a "Commercial Paper
Rate Interest Determination Date"), the Money Market Yield (as defined below)
on such date of the rate for commercial paper having the Index Maturity
specified on the first page hereof as published by the Board of Governors of
the Federal Reserve System in "Statistical Release H.15(519), Selected
Interest Rates" or any successor publication ("H.15 (519)") under the heading
"Commercial Paper--Nonfinancial" or, if unavailable, under such other heading
representing commercial paper issued by non-financial entities whose bond
rating is "AA", or the 

                                      9



equivalent, from a nationally recognized statistical rating organization. In
the event that such rate is not published by 3:00 P.M., New York City time, on
the Calculation Date pertaining to such Commercial Paper Rate Interest
Determination Date, then the Commercial Paper Rate shall be the Money Market
Yield on such Commercial Paper Rate Interest Determination Date of the rate
for commercial paper having the Index Maturity specified on the first page
hereof as published by the Federal Reserve Bank of New York in its daily
statistical release "Composite 3:30 P.M. Quotations for U.S. Governmental
Securities" or any successor publication ("Composite Quotations") under the
heading "Commercial Paper" (with an Index Maturity of one month or three
months being deemed to be equivalent to an Index Maturity of thirty days or
ninety days, respectively). If such rate is not published in either H.15 (519)
or Composite Quotations by 3:00 P.M., New York City time, on such Calculation
Date, then the Commercial Paper Rate will be calculated by the Calculation
Agent and will be the Money Market Yield of the arithmetic mean of the offered
rates, as of approximately 11:00 A.M., New York City time, on such Commercial
Paper Rate Interest Determination Date, of three leading dealers of commercial
paper in The City of New York (which may include one or more of the Agents or
their affiliates) selected by the Calculation Agent (after consultation with
the Company) for commercial paper having the specified Index Maturity placed
for a nonfinancial issuer whose bond rating is "AA," or the equivalent, from a
nationally recognized statistical rating agency; provided, however, that if
the dealers selected as aforesaid by the Calculation Agent are not quoting as
mentioned in this sentence, the Commercial Paper Rate determined as of such
Commercial Paper Interest Determination Date will be the Commercial Paper Rate
in effect on such Commercial Paper Rate Interest Determination Date.

                  "Money Market Yield" shall be a yield (expressed as a
percentage) calculated in accordance with the following formula:

                                   D x 360
         Money Market Yield = [----------------] x 100
                                 360 - (DxM)

                                      10



where "D" refers to the applicable per annum rate for commercial paper quoted
on a bank discount basis and expressed as a decimal and "M" refers to the
actual number of days in the interest period for which interest is being
calculated.

Determination of Federal Funds Rate.

                  The "Federal Funds Rate" will be determined by the
Calculation Agent in accordance with the following provisions:

                  "Federal Funds Rate" means, with respect to any Interest
Determination Date relating to a Federal Funds Rate Note or a Floating Rate
Note for which the interest rate is determined with reference to the Federal
Funds Rate (a "Federal Funds Rate Interest Determination Date"), the rate on
such date for United States dollar federal funds as published in H.15(519)
under the heading "Federal Funds (Effective)" or, if not published by 3:00
P.M., New York City time, on the related Calculation Date, the rate on such
Federal Funds Rate Interest Determination Date as published in Composite
Quotations under the heading "Federal Funds/Effective Rate." If such rate is
not published in either H.15(519) or Composite Quotations by 3:00 P.M., New
York City time, on the related Calculation Date, then the Federal Funds Rate
on such Federal Funds Rate Interest Determination Date will be calculated by
the Calculation Agent and will be the arithmetic mean of the rates for the
last transaction in overnight Untied States dollar federal funds arranged by
three leading brokers of federal funds transactions in The City of New York
(which may include the Agents or their affiliates) selected by the Calculation
Agent prior to 9:00 A.M., New York City time, on such Federal Funds Rate
Interest Determination Date; provided, however, that if the brokers so
selected by the Calculation Agent are not quoting as mentioned in this
sentence, the Federal Funds Rate determined as of such Federal Funds Rate
Interest Determination Date will be the Federal Funds Rate in effect on such
Federal Funds Rate Interest Determination Date.

Determination of LIBOR.

                  "LIBOR" will be determined by the Calculation Agent in 
accordance with the following provisions:

                                      11


                  (i) With respect to an Interest Determination Date relating
to a LIBOR Note or any Floating Rate Note for which LIBOR is an applicable
Base Rate (a "LIBOR Interest Determination Date"), either, as specified on the
first page hereof: (a) the arithmetic mean of the offered rates for deposits
in U.S. dollars for the period of the Index Maturity specified on the first
page hereof, commencing on the second London Business Day immediately
following such LIBOR Interest Determination Date, which appear on the Reuters
Screen LIBOR Page as of 11:00 A.M., London time, on the LIBOR Interest
Determination Date, if at least two such offered rates appear on the Reuters
Screen LIBO Page ("LIBOR Reuters"), or (b) the rate for deposits in U.S.
dollars having the Index Maturity designated on the first page hereof,
commencing on the second London Business Day immediately following that LIBOR
Interest Determination Date, that appears on the Telerate Page 3750 as of
11:00 A.M., London time, on that LIBOR Interest Determination Date ("LIBOR
Telerate"). Unless otherwise indicated on the first page hereof, "Reuters
Screen LIBO Page" means the display designated as Page "LIBO" on the Reuters
Monitor Money Rate Service (or such other page as may replace the LIBO page on
that service for the purpose of displaying London interbank offered rates of
major banks). "Telerate Page 3750" means the display designated as page "3750"
on the Telerate Service (or such other page as may replace the 3750 page on
that service or such other service or services as may be nominated by the
British Bankers' Association for the purpose of displaying London interbank
offered rates for U.S. dollar deposits). If neither LIBOR Reuters nor LIBOR
Telerate is specified on the first page hereof, LIBOR will be determined as if
LIBOR Telerate had been specified. If fewer than two offered rates appear on
the Reuters Screen LIBO Page, or if no rate appears on the Telerate Page 3750,
as applicable, LIBOR in respect of that LIBOR Interest Determination Date will
be determined as if the parties had specified the rate described in (ii)
below.

                  (ii) With respect to a LIBOR Interest Determination Date on
which fewer than two offered rates appear on the Reuters Screen LIBO Page, as
described in (i)(a) above, or on which no rate appears on the Telerate Page
3750, as specified in (i)(b) above, as applicable, LIBOR will be determined on
the basis of the rates at which deposits in U.S. dollars having the Index
Maturity desig-

                                      12



nated on the first page hereof are offered at approximately 11:00 A.M., London
time, on such LIBOR Interest Determination Date by four major banks
("Reference Banks") in the London interbank market selected by the Calculation
Agent (after consultation with the Company) to prime banks in the London
interbank market commencing on the second London Business Day immediately
following such LIBOR Interest Determination Date and in a principal amount of
not less than U.S. $1,000,000 that is representative for a single transaction
in such market at such time. The Calculation Agent will request the principal
London office of each of the Reference Banks to provide a quotation of its
rate. If at least two such quotations are provided, LIBOR for such LIBOR
Interest Determination Date will be the arithmetic mean of such quotations. If
fewer than two quotations are provided, LIBOR for such LIBOR Interest
Determination Date will be the arithmetic mean of the rates quoted at
approximately 11:00 a.m., New York City time, on such LIBOR Interest
Determination Date by three major banks (which may include the Agents or their
affiliates) in The City of New York selected by the Calculation Agent (after
consultation with the Company) for loans in U.S. dollars to leading European
banks having the specified Index Maturity designated on the first page hereof
commencing on the second London Business Day immediately following such LIBOR
Interest Determination Date and in a principal amount equal to an amount of
not less than U.S. $1,000,000 that is representative for a single transaction
in such market at such time; provided, however, that if the banks selected as
aforesaid by the Calculation Agent are not quoting as mentioned in this
sentence, LIBOR determined as of such LIBOR Determination Date will be LIBOR
then in effect on such LIBOR Interest Determination Date.

Determination of Prime Rate.

                  The "Prime Rate" will be determined by the Calculation Agent
in accordance with the following provisions:

                  "Prime Rate" means, with respect to any Interest
Determination Date relating to a Prime Rate Note or a Floating Rate Note for
which the interest rate is determined with reference to the Prime Rate (a
"Prime Rate Interest Determination Date"), the rate on such date as such rate
is published in H.15(519) under the heading 

                                      13




"Bank Prime Loan." If such rate is not published prior to 3:00 P.M., New York
City time, on the related Calculation Date, then the Prime Rate shall be the
arithmetic mean of the rates of interest publicly announced by each bank that
appears on the Reuters Screen USPRIME1 Page (as hereinafter defined) as such
bank's prime rate or base lending rate as in effect for such Prime Rate
Interest Determination Date. If fewer than four such rates appear on the
Reuters Screen USPRIME1 Page for such Prime Rate Interest Determination Date,
then the Prime Rate shall be the arithmetic mean of the prime rates or base
lending rates quoted on the basis of the actual number of days in the year
divided by a 360-day year as of the close of business on such Prime Rate
Interest Determination Date by four major money center banks (which may
include affiliates of the Agents) in The City of New York selected by the
Calculation Agent. If fewer than four such quotations are so provided, then
the Prime Rate shall be the arithmetic mean of four prime rates quoted on the
basis of the actual number of days in the year divided by a 360-day year as of
the close of business on such Prime Rate Interest Determination Date as
furnished in The City of New York by the major money center banks, if any,
that have provided such quotations and by a reasonable number of substitute
banks or trust companies (which may include affiliates of the Agents) to
obtain four such prime rate quotations, provided such substitute banks or
trust companies are organized and doing business under the laws of the United
States, or any State thereof, each having total equity capital of at least
$500 million and being subject to supervision or examination by Federal or
State authority.

         "Reuters Screen USPRIME1 Page" means the display on the Reuter
Monitor Money Rates Service (or any successor service) on the "USPRIME1" page
(or such other page as may replace the USPRIME1 page on such service) for the
purpose of displaying prime rates or base lending rates of major United States
banks.

Determination of Treasury Rate.

                  The "Treasury Rate" will be determined by the Calculation
Agent in accordance with the following provisions:

                                      14



                  "Treasury Rate" means, with respect to any Interest
Determination Date relating to a Treasury Rate Note or any Note for which the
interest rate is determined by reference to the Treasury Rate (a "Treasury
Rate Interest Determination Date"), the rate applicable to the most recent
auction of direct obligations of the United States ("Treasury Bills") having
the Index Maturity specified on the first page hereof, as such rate is
published in H.15(519) under the heading "Treasury Bills -- auction average
(investment)" or, if not published by 3:00 P.M., New York City time, on the
Calculation Date pertaining to such Treasury Rate Interest Determination Date,
the auction average rate (expressed as a bond equivalent on the basis of a
year of 365 or 366 days, as applicable, and applied on a daily basis) as
otherwise announced by the United States Department of the Treasury. In the
event that the results of the auction of Treasury Bills having the specified
Index Maturity are not reported as provided by 3:00 P.M., New York City time,
on such Calculation Date, or if no such auction is held in a particular week,
then the Treasury Rate shall be calculated by the Calculation Agent and shall
be a yield to maturity (expressed as a bond equivalent on the basis of a year
of 365 days or 366 days, as applicable, and applied on a daily basis) of the
arithmetic mean of the secondary market bid rates, as of approximately 3:30
P.M., New York City time on such Treasury Rate Interest Determination Date, of
three leading primary United States government securities dealers (which may
include one or more of the Agents or their affiliates) selected by the
Calculation Agent (after consultation with the Company), for the issue of
Treasury Bills with a remaining maturity closest to the specified Index
Maturity; provided, however, that if the dealers selected as aforesaid by the
Calculation Agent are not quoting as mentioned in this sentence, the Treasury
Rate determined as of such Treasury Rate Interest Determination Date will be
the Treasury Rate in effect on such Treasury Rate Interest Determination Date.

                  If an Event of Default with respect to the Notes shall occur
and be continuing, the principal of all of the Notes may be declared due and
payable in the manner and with the effect provided in the Indenture.





                  The Notes are subject to satisfaction, discharge and
defeasance as provided in Section 403 of the Indenture.

                  The Indenture permits, with certain exceptions as therein
provided, the amendment thereof and the modification of the rights and
obligations of the Company and the rights of the Holders of the Securities of
each series to be affected under the Indenture at any time by the Company and
the Trustee with the consent of the Holders of a majority in principal amount
of the Securities at the time Outstanding or, in the case less than all of the
several series of Securities are affected, the holders of a majority in
aggregate principal amount of the Securities at the time Outstanding of each
series to be affected. The Indenture also contains provisions permitting the
Holders of specified percentages in aggregate principal amount of the
Securities of each series at the time Outstanding, on behalf of the Holders of
all Securities of such series, to waive compliance by the Company with certain
provisions of the Indenture and certain past defaults under the Indenture and
their consequences. Any such consent or waiver by the Holder of this Note
shall be conclusive and binding upon such Holder and upon such future Holders
of this Note and of any Note issued upon the registration of transfer hereof
or in exchange herefor or in lieu hereof, whether or not notation of such
consent or waiver is made upon this Note.

                  No reference herein to the Indenture and no provision of
this Note or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of,
premium, if any, and interest on this Note at the times, place and rate, and
in the coin or currency, herein prescribed.

                  As provided in the Indenture and subject to certain
limitations therein set forth, the transfer of this Note is registrable in the
Security Register, upon surrender of this Note for registration of transfer at
the office or agency of the Company in Salt Lake City, Utah, or at such other
place as the Company may designate from time to time, duly endorsed by, or
accompanied by a written instrument of transfer in form satisfactory to the
Company and the Security Register duly executed by, the Holder hereof or his
attorney duly authorized in writing, and thereupon one or more new Notes, of
autho-

                                      16



rized denominations and for the same aggregate principal amount, will be
issued to the designated transferee or transferees.

                  The Notes are issuable in registered form without coupons in
minimum denominations of $1,000 or any amount in excess thereof that is an
integral multiple of $1,000. As provided in the Indenture and subject to
certain limitations therein set forth, Notes are exchangeable for a like
aggregate principal amount of Notes of different authorized denominations, as
requested by the Holder surrendering the same.

                  No service charge shall be made for any such registration of
transfer or exchange, but the Company may require payment of a sum sufficient
to cover any tax or other governmental charge payable in connection therewith.

                  Prior to due presentment of this Note for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name this Note is registered as the owner hereof
for all purposes, whether or not this Note be overdue, and neither the
Company, the Trustee nor any such agent shall be affected by notice to the
contrary.

                  All terms used in this Note which are defined in the
Indenture shall have the meaning assigned to them in the Indenture.

                  THE INDENTURE AND THE NOTES, INCLUDING THIS NOTE, SHALL BE
GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK
APPLICABLE TO AGREEMENTS MADE AND TO BE PERFORMED IN SUCH STATE.

                  Unless the certificate of authentication hereon has been
executed by First Security Bank, N.A., the Trustee under the Indenture, or its
successor thereunder, by the manual signature of one of its authorized
officers, this Note shall not be entitled to any benefit under the Indenture
or be valid or obligatory for any purpose.

                                      17


                           ------------------------

                  The following abbreviations when used in the inscription on
this Note, shall be construed as though they were written out in full
according to applicable laws or regulations:

TEN COM - as tenants in common    UNIF GIFT MIN ACT - ______ Custodian_________
TEN ENT - as tenants by the                           (Cust)            (Minor)
          entireties                            Under Uniform Gifts to Minor
 JT TEN - as joint tenants with         Act_________________________
          right of survivorship                      (State)
          and not as tenants
          in common

   Additional abbreviations may also be used though not in the above list.

                           ------------------------

 FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers unto

PLEASE INSERT SOCIAL SECURITY OR OTHER
  IDENTIFYING NUMBER OF ASSIGNEE

- --------------------------------------

- --------------------------------------


- --------------------------------------------------------------------------------
(Please print or typewrite name and address including postal zip code of
assignee) 

- --------------------------------------------------------------------------------
the within Note of Questar Pipeline Company and does hereby irrevocably 
constitute and appoint

___________________________________________________________________Attorney to
transfer said Note on the books of said Company, with full power of
substitution in the premises.

Dated:____________________      ______________________________________________

         NOTICE: The signature of the Holder to this assignment must
correspond with the name as it appears upon the face of the within Note in
every particular, without alteration or enlargement or any change whatsoever,
and be guaranteed by an acceptable bank or broker.




                           OPTION TO ELECT REPAYMENT

               The undersigned hereby irrevocably requests and instructs the
Company to repay the within Note (or portion hereof specified below) pursuant
to its terms at a price equal to 100% of the principal amount hereof, together
with interest thereon payable to the Optional Repayment Date, to the
undersigned at _______________________________________________________________
         (Please Print or Typewrite Name and Address of the Undersigned)

               For this Note to be repaid, the trustee must receive this
"Option to Elect Repayment" form, duly completed, together with this Note not
more than 60 nor less than 30 days prior to an Optional Repayment Date shown
on the face of this Note at its Corporate Trust Office, or at such other place
or places designated by the Company and notified by it to the Holder of this
Note.

               If less than the entire principal amount of the within Note is
to be repaid, specify the portion thereof which the Holder elects to have
repaid _________________________________________________; and specify the
denomination or denominations (which shall be authorized denominations) of the
Notes to be issued to the Holder for the portion of the within Note not being
repaid (in the absence of any specification, one such Note will be issued for
the portion not being repaid) _______________.

Date:___________________


                                    ________________________________
                                    Note: The signature on this Option to
                                    Elect Repayment must correspond with the
                                    name as written in this Note in every
                                    particular without alteration or
                                    enlargement or any change whatsoever.