Exhibit 31.1

CERTIFICATION

PURSUANT TO AND IN CONNECTION WITH THE REPORTS

TO BE FILED UNDER SECTION 13 AND 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

I, Kevin L. Foxx, certify that:

1. I have reviewed this quarterly report on Form 10-Q of SemGroup Energy Partners, L.P.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary
to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the
registrant as of, and for, the periods presented in this report;

4. The registrants other certifying officer(s) and I are
responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for
the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and
procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which
this report is being prepared;

b. [Intentionally omitted pursuant to SEC Release No. 34-47986];

c. Evaluated the effectiveness of the registrants disclosure controls and procedures and presented in this report our conclusions
about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. Disclosed in this report any change in the registrants internal control over financial reporting that occurred during the registrants most recent fiscal quarter (the registrants fourth fiscal
quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrants internal control over financial reporting; and

5. The registrants other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial
reporting, to the registrants auditors and the audit committee of registrants board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are
reasonably likely to adversely affect the registrants ability to record, process, summarize and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrants internal control over financial reporting.

Date: August 16, 2007



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|/s/ Kevin L. Foxx                                                                                                                
|Kevin L. Foxx                                                                                                                    
|President and Chief Executive Officer of SemGroup Energy
Partners G.P., L.L.C., general partner of SemGroup Energy Partners, L.P.