HomeMy Public PortalAboutLetter from EPA clarifying Design Criteria for CSO Control Measures for RDP Storage Tunnels (Non-Material Modification B) (3/9/15):goo ary.
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UNITED STATES ENVIRONMENTAL PROTECTION AGE
11201 Renner Boulevard
REGION 7 -�--- EIV
Lenexa, Kansas 66219 MAR r 1 20
CERTIFIED MAIL
RETURN RECEIPT REQUESTED
Article No.: 7006 2760 0000 8649 7673
Mr. Brian Hoelscher
Metropolitan St. Louis Sewer District
2350 Market Street
St. Louis, Missouri 63103-2555
09 MAR
RE: Clarification of Combined Sewer Overflow control measures associated with the tunnels
required by Consent Decree no.4:07-CV-1120
Dear Mr. Hoelscher:
The U.S. Environmental Protection Agency has received the Proposed Non -Material Modification of
CSO control measures submitted by the Metropolitan St. Louis Sewer District (MSD) on February 4,
2015. The MSD requested clarification of the Design Criteria for the CSO control measures associated
with the Upper River Des Peres Storage Tunnel, River Des Peres Tributary Storage Tunnel, and the
Lower & Middle River Des Peres Storage Tunnel. In the approved Long Term Control Plan, the MSD
describes various control technologies that will be implemented to achieve the required Performance
Criteria (i.e. no more than four overflows per year), Appendix D of Consent Decree No.4:07-CV-1120
requires the construction of three storage tunnel systems to address CSOs along the River Des Peres in
addition to other control measures. The MSD is concerned that the language of Appendix D could be
interpreted to mean that every one of the CSO outfalls set forth in the Appendix must be physically
connected to the storage tunnel. MSD proposes to modify the Consent Decree to "allow MSD to use
other design methods, so long as they reflect good engineering practice, in order to satisfy the specified
Performance Criteria and Critical Milestones."
The EPA believes that when reading the Description, Design Criteria and Performance Criteria of
Appendix D together, it is clear that the Storage Tunnel CSO control measures required by the Consent
Decree are tunnel systems that include the tunnel structure near -surface facilities, pump stations, sewer
separation and consolidated sewers. The description of the control measures set forth in Appendix D
associated with the tunnel systems includes "deep storage tunnel, near -surface facilities, pump stations,
sewer separation and consolidated sewers." The design criteria does not require the physical connection
of the listed CSO outfall to the tunnel. The design criteria requires the construction of a tunnel system
that captures at least the described volume to reduce the number of overflows from the listed CSOs to no
more than four per typical year. For the reasons state above, the EPA does not believe that the Decree
needs to be modified to clarify that the MSD may utilize one of the control measures that have already
been identified in Appendix D. If the MSD is proposing to utilize control measures that are not
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identified in the description of the control measure set forth in Appendix D, then the EPA views that
request as a major modification to the Consent Decree.
Paragraph 51 of the Decree states that the MSD shall construct and implement the CSO Control
Measures in accordance with the description, design and performance criteria, and critical milestones set
forth in Appendix D. Paragraph 61 of the Decree only addresses proposed modifications to the design
criteria (e.g., storage capacity, diameter of tunnel) of the CSO Control Measures, and not to the actual
CSO Control Measures employed. The goal of Paragraph 61 was to provide a definition — in this case
less than 20% revision of design criteria — for such modifications to the design criteria to be considered
non -material. A request to change a technique or CSO Control Measure from what is described in
Appendix D will be treated as a major modification under Paragraph 136, and will be subject to the
analysis and criteria that went into the development and preparation of the LTCP.
If you have any questions or would like to discuss this further, please contact Jodi Bruno of my staff at
913-551-7810 or email at bruna jodi@epa.gov.
Karen A. Floumoy
Director
Water, Wetlands and Pesticides Division
cc:
U.S. Department of Justice, Chief, Environmental Enforcement Section
State of Missouri Office of Attorney General, Chief Counsel, Agriculture and Environment Division
Missouri Dept. of Natural Resources, Chief, Water Pollution Compliance and Enforcement Section
Missouri Department of Natural Resources, Director, St. Louis Regional Office
Heather Navarro, Director, Missouri Coalition for the Environment
Maxine Lipeles, Elizabeth Hubertz, Interdisciplinary Envt'l Clinic, Washington Univ. School of Law
etropolitan St. Louis Sewer District, General Counsel
Metropolitan St. Louis Sewer District, Director of Engineering
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