Exhibit 99.3

GLOSSARY OF TERMS

The following abbreviations or acronyms used in these pro forma financial statements are defined below:

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INDEX TO PRO FORMA FINANCIAL STATEMENTS

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DOMINION MIDSTREAM PARTNERS, LP

UNAUDITED PRO FORMA CONSOLIDATED FINANCIAL STATEMENTS

The unaudited pro forma Consolidated Financial Statements of Dominion Midstream consist of a Condensed Consolidated Balance Sheet at September 30, 2016 and Consolidated Statements of Income for the nine months ended September 30, 2016 and for the year ended December 31, 2015, which reflect Dominion Midstream’s acquisition of Questar Pipeline from Dominion on December 1, 2016. Dominion acquired Dominion Questar on September 16, 2016. In August 2016, prior to Dominion’s acquisition of Dominion Questar, Questar Pipeline was reorganized and it distributed 100% of the issued and outstanding capital stock of Questar Southern Trails and Questar InfoComm, Inc. to Dominion Questar. On October 31, 2016, Dominion Midstream, following approval by the Conflicts Committee of Dominion Midstream GP, LLC, its general partner, entered into the Contribution Agreement with Dominion, pursuant to which, upon closing on December 1, 2016, Dominion Midstream became the owner of all of the issued and outstanding membership interests of Questar Pipeline. The unaudited pro forma Consolidated Financial Statements included herein have been derived from the following historical financial statements:

Upon closing of the Contribution Agreement, Dominion contributed to Dominion Midstream all of the issued and outstanding membership interests of Questar Pipeline in exchange for consideration consisting of common and convertible preferred units with a combined value of $467.3 million and cash of $822.7 million. As a result of the transaction, Dominion Midstream owns 100% of the membership interests in Questar Pipeline and will therefore consolidate Questar Pipeline in its financial statements. Because the contribution of Questar Pipeline by Dominion to Dominion Midstream is considered a reorganization of entities under common control, Questar Pipeline’s assets and liabilities are recorded in Dominion Midstream’s consolidated financial statements at Dominion’s historical cost. Common control began on September 16, 2016, concurrent with Dominion’s acquisition of Dominion Questar, which was accounted for using the acquisition method of accounting. Accordingly, the consolidated financial statements of Dominion Midstream will reflect Questar Pipeline’s financial results beginning September 16, 2016.

The pro forma adjustments have been prepared as if the acquisition of Questar Pipeline occurred on September 30, 2016 in the case of the unaudited pro forma Condensed Consolidated Balance Sheet and on January 1, 2015 in the case of the unaudited pro forma Consolidated Statements of Income. The unaudited pro forma Consolidated Financial Statements should be read in conjunction with the related notes, which are included herein, the financial statements and notes included in Dominion Midstream’s Annual Report on Form 10-K for the year ended December 31, 2015 and Quarterly Report on Form 10-Q for the nine months ended September 30, 2016, and the financial statements and notes included in Questar Pipeline’s Annual Report on Form 10-K for the year ended December 31, 2015 and the financial statements and notes included in Questar Pipeline’s unaudited interim financial statements for the nine months ended September 30, 2016.

The unaudited pro forma Consolidated Financial Statements do not necessarily reflect what Dominion Midstream’s financial position and results of operations would have been if it had owned Questar Pipeline during the periods presented. In addition, they are not necessarily indicative of its future results of operations or financial condition. The assumptions and adjustments give pro forma effect to events, described below, that are (i) directly attributable to Dominion Midstream’s acquisition of Questar Pipeline from Dominion (which reflect Dominion’s acquisition adjustments to arrive at its historical cost) and Dominion Midstream’s debt and equity financings in connection with the acquisition, (ii) factually supportable, and (iii) with respect to the unaudited pro forma Consolidated Statements of Income, expected to have a continuing impact on Dominion Midstream. The actual adjustments may differ from the pro forma adjustments.

The unaudited pro forma Consolidated Financial Statements give effect to the following transactions, which occurred in connection with the acquisition described above:

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DOMINION MIDSTREAM PARTNERS, LP

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET

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DOMINION MIDSTREAM PARTNERS, LP

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET (CONTINUED)

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DOMINION MIDSTREAM PARTNERS, LP

UNAUDITED PRO FORMA CONSOLIDATED STATEMENT OF INCOME

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DOMINION MIDSTREAM PARTNERS, LP

UNAUDITED PRO FORMA CONSOLIDATED STATEMENT OF INCOME

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DOMINION MIDSTREAM PARTNERS, LP

NOTES TO UNAUDITED PRO FORMA CONSOLIDATED FINANCIAL STATEMENTS

NOTE 1. BASIS OF PRESENTATION

The unaudited pro forma Consolidated Financial Statements included herein have been derived from the following historical financial statements:

Questar Pipeline’s financial statements are comprised of the operations and related assets of Questar Pipeline, which operates interstate natural gas pipelines and storage facilities in the western United States, providing natural gas transportation and underground storage services in Utah, Wyoming and Colorado. As of September 30, 2016, Questar Pipeline’s natural gas system consisted of nearly 2,200 miles of interstate pipeline, and nearly 56 billion cubic feet of working gas storage capacity. Questar Pipeline’s core transportation system is strategically located near large reserves of natural gas in six major Rocky Mountain producing areas. Questar Pipeline transports natural gas from these producing areas to other major pipeline systems, Questar Gas’ distribution system and other utility systems. Questar Pipeline operates and owns 50% of White River Hub in western Colorado, which is accounted for under the equity method. Questar Pipeline also owns gathering lines and processing facilities in Utah, through which it provides gas-processing services.

Upon closing of the Contribution Agreement, Dominion contributed to Dominion Midstream all of the issued and outstanding membership interests of Questar Pipeline in exchange for consideration consisting of common and convertible preferred units with a combined value of $467.3 million and cash of $822.7 million. As a result of the transaction, Dominion Midstream owns 100% of the membership interests in Questar Pipeline and will therefore consolidate Questar Pipeline in its financial statements. Because the contribution of Questar Pipeline by Dominion to Dominion Midstream is considered a reorganization of entities under common control, Questar Pipeline’s assets and liabilities are recorded in Dominion Midstream’s consolidated financial statements at Dominion’s historical cost. Common control began on September 16, 2016, concurrent with Dominion’s acquisition of Dominion Questar, which was accounted for using the acquisition method of accounting. Accordingly, the consolidated financial statements of Dominion Midstream will reflect Questar Pipeline’s financial results beginning September 16, 2016.

The pro forma adjustments have been prepared as if the acquisition of Questar Pipeline occurred on September 30, 2016 in the case of the unaudited pro forma Condensed Consolidated Balance Sheet and on January 1, 2015 in the case of the unaudited pro forma Consolidated Statements of Income for the year ended December 31, 2015 and for the nine months ended September 30, 2016. The adjustments are based on currently available information and certain estimates and assumptions, and therefore the actual effects of these transactions will differ from the pro forma adjustments. However, management believes that the assumptions used provide a reasonable basis for presenting the significant effects of the transaction, and that the pro forma adjustments in the unaudited pro forma Consolidated Financial Statements give appropriate effect to the assumptions. The effects on the unaudited pro forma Consolidated Financial Statements of the transaction described above are more fully described in Note 3.

NOTE 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

The accounting policies followed in preparing the unaudited pro forma Consolidated Financial Statements are those used by Dominion Midstream as set forth in the audited historical financial statements and notes of Dominion Midstream included in its Annual Report on Form 10-K for the year ended December 31, 2015.

NOTE 3. PRO FORMA ADJUSTMENTS AND ASSUMPTIONS

The following transactions are directly attributable to Dominion Midstream’s acquisition of Questar Pipeline from Dominion, a reorganization of entities under common control whereby Dominion Midstream records the assets and liabilities of Questar Pipeline at Dominion’s historical cost. In addition, certain of the following transactions relate to the financing transactions undertaken by Dominion Midstream in connection with the acquisition. As Dominion’s acquisition of Dominion Questar, including Questar Pipeline, occurred on September 16, 2016, the following adjustments include those necessary to arrive at an approximation of Dominion’s historical cost.

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NOTE 4. PRO FORMA NET INCOME PER LIMITED PARTNER UNIT

Net income per limited partner unit applicable to common units, convertible preferred units and subordinated units is computed by dividing the respective limited partners’ interest in net income attributable to Dominion Midstream, after deducting any incentive distributions, by the weighted average number of common, convertible preferred and subordinated units outstanding. Because Dominion Midstream has more than one class of participating securities, the two-class method is used when calculating the net income per limited partner unit. The classes of participating securities include common units, convertible preferred units, subordinated units, and IDRs.

Dominion Midstream’s net income is allocated to the common and subordinated unitholders in accordance with their respective partnership percentages, after giving effect to priority income allocations for incentive distributions, if any, to Dominion, the holder of the IDRs, and preferred distributions on the convertible preferred units pursuant to the partnership agreement. The distributions are declared and paid following the close of each quarter. Earnings in excess of distributions are allocated to the common and subordinated unitholders based on their respective ownership interests. Payments made to Dominion Midstream’s common and subordinated unitholders are determined in relation to actual distributions declared and are not based on the net income allocations used in the calculation of earnings per unit. The convertible preferred units were considered to be dilutive for both the nine months ended September 30, 2016 and the year ended December 31, 2015, and as such, diluted income per limited partner unit was calculated utilizing the if-converted method, assuming that such convertible preferred units had been converted to common units.

Pro forma net income per limited partner unit is determined by dividing the pro forma net income available to the limited partners by the weighted average number of common, convertible preferred and subordinated units outstanding. Because all pro forma changes in common and convertible preferred units associated with the acquisition were assumed to have been outstanding for the entire periods presented, the pro forma basic and diluted average number of common, convertible preferred and subordinated units outstanding equals the average number of common, preferred and subordinated units outstanding for the nine months ended September 30, 2016 or for the year ended December 31, 2015, plus the net effects of the pro forma transactions involving common and convertible preferred units. For the nine months ended September 30, 2016, the average number of common and subordinated units outstanding was 45,722,286 and 31,972,789, respectively, and for the year ended December 31, 2015, the average number of common and subordinated units outstanding was 38,052,303 and 31,972,789, respectively. In connection with the acquisition, 6,656,839 common units and 11,365,628 convertible preferred units were issued to Dominion, 6,656,839 common units were repurchased from Dominion; 15,525,000 common units were issued to the public and 5,990,634 common units and 18,942,714 convertible preferred units were issued to purchasers through private placement. The convertible preferred units are assumed to be converted to 30,308,342 common units, representing a pro forma effect of 51,823,976 additional common units outstanding during the entire period for purposes of diluted average limited partner units outstanding.

The basic pro forma net income per unit calculations assume that an additional $0.6 million and less than $0.1 million of incentive distributions were made to the general partner for the nine months ended September 30, 2016, and for the year ended December 31, 2015, respectively. The diluted pro forma net income per unit calculations assume that an additional $1.4 million and $0.1 million of incentive distributions were made to the general partner for the nine months ended September 30, 2016, and for the year ended December 31, 2015, respectively.

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