TRANSMITTAL LETTER FOR BOARD MEETING OF AUGUST 12, 2010
COMMITTEE ON ENGINEERING
Mr. Richard Lanyon, Executive Director
Title
Report on status of development of new measures to mitigate impacts on MWRD caused by groundwater infiltration/stormwater inflow in local sanitary sewer systems
Body
Dear Sir:
This reports on the status of MWRD’s local sanitary sewer system rehabilitation program and on the ongoing development of new measures to mitigate adverse impacts on the MWRD’s sewage collection and treatment operations caused by groundwater infiltration and stormwater inflow (referred to as I/I, or extraneous flow) in local sanitary sewer systems.
Background
At its meeting of July 9, 2009, the Board was informed of the status of MWRD’s local sanitary sewer system rehabilitation program requirements contained in Article 6-5 “Correction of Existing Deficiencies in Separate Sewered Areas” (adopted 1973; amended 1985) of the MWRD Manual of Procedures for the Administration of the Sewer Permit Ordinance. The Board was also informed of the Engineering Department’s perceived shortcomings of such requirements; of worsening adverse impacts of I/I on MWRD’s operations; and of preliminary alternatives and recommendations the Engineering Department has been considering relative to establishing new I/I removal program requirements.
A subsequent Board study session on this overall subject was held on December 9, 2009.
Compliance status of sanitary sewer agencies
The number of communities which have not yet completed their sewer rehabilitation programs and thus have not reduced I/I to acceptable levels remains at eight (out of a total of 125 sanitary sewer system agencies subject to the MWRD I/I removal requirements).
Although many communities that selected the I/I Corrective Action Program (ICAP) compliance option (made available by the 1985 Sewer Summit Agreement) completed their cost-effectiveness-based sewer rehabilitation work and achieved “technical” compliance, their sanitary sewer systems remained highly defective with very large amounts of residual excessive I/I which can lead to basement sewage backups and sanitary sewer overflows (SSOs) in wet weather.
Earlier this year, one of the eight non-complying ICAP option communities requested and was granted permission to install flowmeters in MWRD interceptors serving the community, reportedly in an effort to specifically address severe local basement sewage backup flooding problems. Several years ago the community’s Sewer System Evaluation Survey (SSES) and related I/I cost-effectiveness analysis were found by MWRD to be unacceptable and they remain uncorrected because the cost analysis is flawed and significantly underestimates the amount of I/I that must be removed from the system. It is unclear whether or how the results of the current flow monitoring will be utilized or integrated into the SSES in order to make it acceptable so that the community can formulate and implement a satisfactory rehabilitation program.
Local sewer long-term operation and maintenance programs (LTOMPS)
All communities that completed their sanitary sewer rehabilitation programs have been required to submit annual reports to the MWRD on their LTOMPs to help ensure continuous sanitary sewer system maintenance in order to keep I/I at or below the approved and attained levels. The 117 such communities continue, by and large, to be cooperative regarding this requirement by submitting annual reports on their sanitary sewer maintenance and repair activities. However, the quality of local sewer management as indicated by the submitted reports varies widely among communities. In many cases it is questionable as to whether the amount of sewer maintenance/management being performed is sufficient to prevent increases in sewer system I/I levels from the originally approved and attained levels.
Where maintenance is clearly indicated to be less than adequate, the MWRD issues advisory letters urging that maintenance be stepped up. In general, periodic flow metering to assess current wet weather flow levels in sanitary sewer systems/subsystems is encouraged by the MWRD but is not mandatory. Most communities achieved program compliance in the 1980s and 1990s; some in the 1970s; and a few in the 2000s. In the absence of updated flow monitoring information, the current performance level of nearly all local sanitary sewer systems relative to I/I is largely unmeasured and unknown.
Local community planning in anticipation of new I/I removal requirements
Earlier this year, officials of the Village of Tinley Park - a community which achieved compliance with Article 6-5 - proactively approached and met with the MWRD in regard to planning a sewer rehabilitation program that would be consistent with new sewer system performance standards the MWRD may establish under a new overall I/I removal program. We informed the Village that MWRD’s new requirements are still in the development stage and that they will most likely depend on NPDES permit conditions imposed upon MWRD by the Illinois Environmental Protection Agency (IEPA) and any action taken by the United States Environmental Protection Agency (USEPA) regarding the possible modification of NPDES regulations as they apply to municipal sanitary sewer collection systems and SSOs. The Village was also advised that its sewer rehabilitation plan should address not only its public sector sanitary sewer system (sewer mains and manholes), but the private sector system as well, including building sewer service laterals and external and internal illegal connections. The Village also asked whether the MWRD would make funding available to communities for local system rehabilitation, and was advised there are no current plans to do so.
Requests for increases in sanitary sewer system discharge capacity
The Engineering Department has received several permit applications or permit revision requests from local communities for sanitary sewer pumping station upgrades which would increase sewage discharge rates. Where such discharge would be made directly to MWRD interceptors, and the revised pumping capacity would be in excess of the capacity needed to accommodate current and future dry weather sewage loading from residences and businesses with some allowance for non-excessive I/I, the MWRD continues to deny such permit requests since the surplus capacity would be used to convey excessive I/I and create sewer overloading and operational problems for owners of downstream receiving sewer systems including the MWRD.
Annual reporting of existing I/I program status to IEPA
On July 9, 2010 the MWRD mailed all separate sewer communities a copy of its latest annual status report on local sewer system I/I removal programs (report entitled “Excessive Infiltration/Inflow Elimination Programs, Annual Status Report, Volume 37”). This report, which is also found on the MWRD’s website, is published pursuant to our meeting the National Pollutant Discharge and Elimination System (NPDES) permits issued by IEPA for our wastewater reclamation plants (WRPs).
One significant revision in this year’s status report which was brought to the attention of all sanitary sewer system owners is the change in MWRD policy concerning local storage of I/I. Local I/I storage will now be allowed only as a temporary measure to mitigate impacts of residual excessive I/I in a local sewer system, and not as a permanent or final solution. Actual removal of excessive residual I/I must be the solution. MWRD considers wet weather flow above 150 gallons per capita per day (gpcpd) to be residual excessive I/I.
USEPA SSO rulemaking
On June 1, 2010, the USEPA published a notice of rulemaking in the Federal Register seeking stakeholder input as to whether it should modify NPDES regulations applying to municipal sanitary sewer systems to address harmful effects of SSOs. A sixty-day public review and comment period began on the same date. The USEPA is considering two possible modifications to existing regulations: 1) establishing standard NPDES permit conditions for publicly owned treatment plants (POTWs) that specifically address sanitary sewer collection systems and SSOs; and 2) clarifying the regulatory framework for applying NPDES permit conditions to municipal satellite sanitary sewer systems.
By letter dated June 25, 2010, the MWRD notified all local sanitary sewer system owners of USEPA’s rulemaking, and encouraged their engagement in the rulemaking process and their participation in a USEPA “listening session” webinar on the subject held on July 14, 2010.
District staff from the Maintenance and Operations, Engineering and Law Departments participated in the aforesaid webinar. Based on telecom polling of treatment plant owners participating in the session, the vast majority of attendees, including the MWRD, agreed that satellite sewer system owners should be issued and subject to their own NPDES permits separate from NPDES permits issued to the regional treatment plant owner.
MWRD is in virtual complete agreement with written “talking points” in this regard submitted to the USEPA by the National Association of Clean Water Agencies (NACWA), of which MWRD is a member agency. The MWRD sent its own written comments to USEPA echoing many of NACWA’s comments and providing additional commentary.
Lemont WRP I/I-related issues and IEPA-required long-term control plan (LTCP)
On July 14, 2010, a conference call was held between the District, the Village of Lemont (Lemont), and the IEPA to present MWRD’s and Lemont’s LTCPs on the subject of combined sewer overflow correction. Lemont owns sanitary sewers that are tributary to its combined sewer system, and excessive I/I entering the sanitary sewer system contributes to the magnitude and frequency of CSOs. The District informed the IEPA that it plans to eventually decommission its Lemont WRP once it constructs a pumping station and force mains to transport all dry weather flows plus "first-flush" flows from the Lemont Basin to an MWRD interceptor served by the Stickney WRP. Flow exceeding dry weather flow will be diverted to a new wet weather flow treatment facility, with outfall to the Chicago Sanitary and Ship Canal (which will provide primary treatment and disinfection for ten times the dry weather flow volume). An equalization reservoir will also be provided to attenuate the peak wet weather flows from Lemont’s separate sewer system.
As part of its own LTCP, Lemont will continue to implement separation of some combined sewers within its combined sewer area in order to disconnect stormwater from the system and route it directly to waterway(s) via storm sewers.
The IEPA agreed in principle with both agencies’ plans and now awaits formal Compliance Commitment Agreements (CCAs) which will provide the details and implementation schedules.
As to its sanitary sewer system, Lemont completed its sewer rehabilitation work and achieved technical compliance with the ICAP option in 1993, but with a very high wet weather flow rate of 838 gpcpd (with residual excessive I/I of 688 gpcpd, calculated as 838 gpcpd minus 150 gpcpd). Since that time, large areas have been annexed to the Village and the extent of its sanitary sewer system has increased commensurately. The MWRD has informed Lemont that it will be subject to the same I/I removal standards, when adopted by MWRD, that will apply to the other sanitary sewer communities. Lemont was also informed that the storage facility MWRD is proposing to construct to accommodate Lemont’s wet weather flow is a remedial measure to stem CSOs/SSOs and must not be considered as being a substitute for I/I removal that Lemont will be required to undertake under a new MWRD I/I removal program.
I/I public outreach workshops
The M&O Department has retained an outside consultant to present three workshops on MWRD related I/I issues to be held in mid to late September of this year. These workshops are intended to make local sanitary sewer system owners aware of the impacts of I/I and the attention the subject of sanitary sewer system wet weather flows and SSOs is receiving not only locally by MWRD and the IEPA, but nationwide by the USEPA, with new I/I removal requirements probably forthcoming. Local communities have been sent invitation notices and have been urged to attend these workshops.
I/I removal program development issues
In December 2009, the MWRD received draft NPDES permits for the Stickney, Calumet and North Side WRPs. All three draft permits require the MWRD to take action against the owners of local sewer systems that have excessive I/I (i.e. wet weather flows exceeding 150 gpcpd) if the I/I is contributing to basement backups or sanitary sewer overflows. The remedial measures are in addition to those required under Article 6.5 or the Sewer Summit Agreement. Following the hearings on the draft permits, IEPA verbally advised the MWRD that the final permits may also impose additional I/I requirements upon the MWRD. While we have not seen the proposed language, it purportedly will impose some type of capacity, management, operation and maintenance (CMOM) obligation upon the owners of local sewer systems and presumably impose a corresponding obligation upon the MWRD to enforce such obligations.
Until such time as the MWRD receives the final NPDES permits and reviews the I/I language, it is premature to adopt extensive revisions to its existing I/I program. The MWRD will want to ensure that any revisions to its existing program are consistent with whatever requirements are eventually contained in the MWRD's final NPDES permits.
The outcome of aforementioned USEPA rulemaking regarding SSOs and peak wet weather flows may also be a factor in the revised I/I program decision-making process.
In response to inquiries from Engineering, the Law Department is currently researching the legality of various measures that the MWRD may wish to consider including in a new I/I program, subject to any requirements imposed in the final NPDES permits, and it is also evaluating any legal obstacles to implementing such measures. Answers to Engineering’s inquiries will be utilized in conjunction with the I/I language in the final NPDES permits to develop a recommended MWRD I/I removal program.
If further clarification is required, please advise the undersigned.
Requested, Kenneth A. Kits, Director of Engineering, WSS:JRR
Respectfully Submitted, Frank Avila, Chairman Committee on Engineering