Duncan Energy Partners L.P. is a publicly traded partnership that provides midstream energy services, including gathering, transportation, marketing and storage of natural gas, in addition to NGL fractionation, transportation and storage and petrochemical transportation and storage; and refined products storage. Duncan Energy Partners owns interests in assets located primarily in Texas and Louisiana, including interests in approximately 9,400 miles of natural gas pipelines with a transportation capacity aggregating approximately 7.8 billion cubic feet (“Bcf”) per day; approximately 1,770 miles of NGL and petrochemical pipelines featuring access to one of the world’s largest fractionation complexes at Mont Belvieu, Texas; two NGL fractionation facilities located in south Texas; approximately 17 million barrels (“MMBbls”) of leased NGL storage capacity; 8.1 Bcf of leased natural gas storage capacity; and 34 underground salt dome caverns with approximately 100 MMBbls of NGL, petrochemical and refined products storage capacity at Mont Belvieu. Duncan Energy Partners is managed by its general partner, DEP Holdings, LLC, which is an indirect wholly-owned subsidiary of Enterprise Products Partners L.P.INVESTOR NOTICE In connection with the proposed merger with DEP, EPD has filed a registration statement (Registration No. 333-174321), which includes a preliminary prospectus of EPD and a preliminary proxy statement of DEP and other materials, with the Securities and Exchange Commission (“SEC”). INVESTORS AND SECURITY HOLDERS ARE URGED TO CAREFULLY READ THE REGISTRATION STATEMENT AND THE DEFINITIVE PROXY STATEMENT / PROSPECTUS AND ANY OTHER MATERIALS FILED OR TO BE FILED WITH THE SEC REGARDING THE PROPOSED TRANSACTION WHEN THEY BECOME AVAILABLE, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT EPD, DEP AND THE PROPOSED MERGER. A definitive proxy statement / prospectus will be sent to security holders of DEP seeking their approval of the proposed merger after the registration statement is declared effective by the SEC. Investors and security holders may obtain a free copy of the proxy statement / prospectus (when it is available) and other documents containing information about DEP, without charge, at the SEC’s website ( www.sec.gov). EPD, DEP and their respective general partners, and the directors and certain of the executive officers of the respective general partners, may be deemed to be participants in the solicitation of proxies from the unitholders of DEP in connection with the proposed merger. Information about the directors and executive officers of the respective general partners of EPD and DEP is set forth in the preliminary proxy statement / prospectus, each partnership’s Annual Report on Form 10-K for the year ended December 31, 2010, which were each filed with the SEC on March 1, 2011, and subsequent statements of changes in beneficial ownership on file with the SEC. These documents can be obtained free of charge from the source listed above. FORWARD-LOOKING STATEMENTS This press release includes “forward-looking statements” as defined by the Securities and Exchange Commission. All statements, other than statements of historical fact, included herein that address activities, events, developments or transactions that Duncan Energy Partners expects, believes or anticipates will or may occur in the future, including anticipated benefits and other aspects of such activities, events, developments or transactions, are forward-looking statements. These forward-looking statements are subject to risks and uncertainties that may cause actual results to differ materially, including required approvals by regulatory agencies, the possibility that the anticipated benefits from such activities, events, developments or transactions cannot be fully realized, the possibility that costs or difficulties related thereto will be greater than expected, the impact of competition and other risk factors included in the reports filed with the Securities and Exchange Commission by Duncan Energy Partners. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of their dates. Except as required by law, Duncan Energy Partners does not intend to update or revise its forward-looking statements, whether as a result of new information, future events or otherwise.