Prospectus excerpt:  We are distributing, at no charge, to the holders of our common units representing limited partner interests as of 5:00 p.m., New York City time, on September 27, 2011 (the “Record Date”), transferable subscription rights (the “Rights”) to subscribe for Series A Preferred Units representing limited partner interests in our partnership. Our common unitholders will receive 0.5412 Rights for each common unit held of record as of the Record Date. As of the Record Date, we had 21,890,224 common units issued and outstanding. Accordingly, we are distributing Rights exercisable for up to 11,846,990 Series A Preferred Units. We expect the total purchase price for all of the Series A Preferred Units offered in this rights offering to be approximately $77.0 million, assuming full participation. The Series A Preferred Units are convertible in whole or in part into common units at the holder’s election as set forth in this prospectus supplement. In addition, under certain circumstances, we can convert all of the Series A Preferred Units into common units. See “Questions and Answers Related to the Rights Offering.”

Each whole Right entitles the holder (including holders of Rights acquired during the subscription period) to purchase for $6.50 in cash one Series A Preferred Unit, which we refer to as the Basic Subscription Right. In addition, holders of Rights will be entitled, subject to limitations, to subscribe (the “Over-Subscription Right”) for additional Series A Preferred Units that remain unsubscribed as a result of any unexercised Basic Subscription Rights (which we collectively refer to as the “Excess Preferred Units”) at the subscription price of $6.50 per unit.

The Rights will expire if they are not exercised by 5:00 p.m., New York City time, on October 31, 2011 (the “Expiration Date”), unless we extend the offering period. Any Rights not exercised by the Expiration Date will expire worthless without any payment to the holders of those unexercised Rights. There is no minimum subscription amount required for consummation of this rights offering.