GREEN INFRASTRUCTURE PERMITTING AND ENFORCEMENT SERIES: FACTSMEET 3
Depending on the causes of sanitary sewer overflows
fora particular system, green infrastructure
approaches may be used in conjunction with "
measures to help eliminate overflows.
United States
Environmental Protection
Agency
EPA832F12014
Sanitary Sewer Overflows
This factsheet is the third in a series of six on integrating green
infrastructure concepts into permitting, enforcement, and
water quality standards actions.
Introduction
CMOM or Remedial Measures
Plan Components
Consent Decree Components
-------
Integrating Green Infrastructure Concepts into
Permitting, Enforcement, and Water Quality
Standards Actions
This factsheet is the third in a series
of six factsheets in the U.S. EPA Green
Infrastructure Permitting and Enforcement
Series (http://water.epa.gov/infrastructure/
greeninfrastructure/gi_regulatory.
cfm#permittingseriesA This series
describes how EPA and state permitting and
enforcement professionals can incorporate
green infrastructure practices and approaches
into National Pollutant Discharge Elimination
System (NPDES) wet weather programs,
including stormwater permits, Total
Maximum Daily Loads (TMDLs), combined
sewer overflow (CSO) long-term control
plans (LTCPs), and enforcement actions.
This series builds upon EPA's continued
investment in green infrastructure and low
impact development. Existing EPA authority,
guidance, and agreements enable EPA
Regions and state agencies to work with
permittees to include green infrastructure
measures as part of control programs.
For additional resources on green infrastructure,
go to the EPA Green Infrastructure Web
page: http://water.epa.gov/infrastructure/
greeninfrastructure/index.cfm.
Key green infrastructure guidance issued
to date can be found at: http://water.epa.
gov/infrastructu re/green infrastructure/
gLpolicy.cfm.
Introduction
Properly designed, operated, and maintained sanitary
sewer systems are meant to collect and transport all of the
sewage that flows into them to a publicly owned treatment
works (POTW). However, in some communities under some
circumstances discharges of raw sewage from municipal
sanitary sewers may occur. These types of discharges
are called sanitary sewer overflows (SSOs). SSOs may
be attributable to blockages in the system or mechanical
failure such as a lift station power outage. In addition,
SSOs often occur because of excessive "l&l" - infiltration
of water into collection systems and inflow. In the context
of SSOs, infiltration means stormwater or groundwater
that seeps into the sewer system through cracks and
other vulnerable locations in the pipes and joints. Inflow
is the introduction of stormwater into the sanitary sewer
system via specific storm connections, either deliberate or
inadvertent. Common sources of inflow are the connection
of roof downspouts or discharges from sump pumps to the
sanitary sewer system.
Where there is excessive l&l of rainwater and/or
groundwater into the sanitary sewer system, the system
may become overloaded and overflow. All flows in sanitary
sewer systems need to be transported to treatment
plants and treated in accordance with NPDES permit
requirements. EPA guidance on SSOs can be found here:
PERMITTING: http://cfpub.epa.gov/npdes/home.
cfm?program_id=4
ENFORCEMENT: http://cfpub.epa.gov/compliance/
resources/policies/civil/cwa/
Grey infrastructure improvements/expansions and
implementation of a capacity, management, operations and
maintenance (CMOM) or remedial measures program are
among the traditional approaches used to bring separate
sanitary systems into compliance with the Clean Water
Act. Depending on the causes of SSOs for a particular
system, green infrastructure approaches may be used
in conjunction with grey infrastructure improvements
and CMOM to help eliminate SSOs. Green infrastructure
may help by keeping some wet weather flows out of the
separate sewer system.
-------
GREEN INFRASTRUCTURE PERMITTING AND ENFORCEMENT SERIES: FACTSMEET 3
Green infrastructure approaches may be ideal solutions
for inflow problems. They are preventive measures rather
than treatment measures, and eliminate or reduce the
need to create additional capacity in the sewer system by
keeping water out of the system. Disconnecting sources
of stormwater to sanitary sewer systems should be a high
priority for any SSO abatement program. Downspouts
and other stormwater conveyances should not simply
be rerouted to storm sewer systems as that is simply a
transfer of the water quality problems from one system to
another. Instead these sources should be routed to rain
barrels, cisterns, rain gardens, swales or other measures
where the stormwater can recharge groundwater, irrigate
landscapes, or serve other non-potable water needs.
A number of communities have successfully instigated
downspout disconnection programs to keep water out of
sewer systems (sanitary, combined and storm). In these
situations rainwater is typically directed to vegetated areas
where stormwater can be infiltrated and evapotranspired,
or directed to water harvesting devices.
For examples of municipal downspout
disconnection programs see:
http://water.epa.gov/infrastructure/
greeninfrastructure/gi_what.cfm#downspout
When infiltration of water into the sanitary sewer system is
the primary problem, the most effective solution is typically
sanitary sewer rehabilitation. In the interim, reducing the
amount of groundwater and stormwater near the laterals
and joints that may be allowing water into the pipes may
be a goal. In this particular situation green infrastructure
approaches are still valuable, but there are important
considerations: 1) Practices that encourage infiltration of
stormwater into the ground should be located away from
laterals where 'leaky' systems are identified or suspected;
and 2) placement of trees relative to pipes, especially older
or 'leaky' pipes, should be carefully considered in order to
avoid root growth into joints.
CMOM or Remedial Measures Plan Components
As noted, a CMOM program may bean important tool for
preventing SSOs and bringing sanitary sewer systems
into compliance with the Clean Water Act. The following
sections discuss how CMOM plans can be adapted to
accommodate green as well as grey infrastructure.
Capacity Estimates: Green infrastructure may reduce the
capacity improvements required to prevent SSOs. The
process of estimating the capacity improvements required
for plans that include green infrastructure may be divided
into two steps. The first step is to estimate the volume
of water that can be kept out of the system, based on
estimates of the collective capacities of distributed green
technologies. The second step consists of fairly standard
hydraulic modeling of the system. This step is required
•X
regardless of the type of technologies in use, in orderto
determine discharge reductions at respective outfalls or
overflow points.
In general, estimating the impact of distributed controls
located throughout a sewershed on accumulated flow at a
discharge point can be more complicated than estimating
the impact of a single control atone location (e.g., as with
CSOs, where one central tunnel or basin may be used to
enhance capacity). However, in the case of SSOs, modeling
green technologies may not differ very much from modeling
more traditional technologies since reducing inflow is
traditionally accomplished through the removal of many
individual sources to the system.
CMOM or Remedial Measures Plan Components
• Capacity estimates
• Legal authority
• Maintenance
• Monitoring
• Mapping/tracking
-------
Legal Authority: Reduction of inflow through the use of
green infrastructure may present novel legal issues when
these controls are located on privately owned land. Where
bioinfiltration cells or other structures are installed on
private property, maintenance agreements, local ordinance
or other enforceable mechanisms will be required to
allocate legal responsibility for proper operation and
maintenance of the control measures.
Maintenance: As discussed above, green infrastructure
controls may be located on private property. For these
practices, legal mechanisms and institutional arrangements
typically need to be in place to ensure proper maintenance.
The community may want to establish education programs
or simple guidance materials for maintenance of green
infrastructure practices that will be maintained by private
property owners or operators.
When practices are located on public lands or within
public rights-of-way, the municipal operator should
establish standard operating procedures for maintenance
that include schedules, and procedures for maintenance,
reporting and tracking.
Monitoring: Monitoring provisions for green and grey
infrastructure solutions should be very similar. Documenting
performance of individual control measures typically is
not necessary as part of a monitoring program; a solid
maintenance program will ensure long-term function. Since
the goal of the SSO abatement program is to reduce flows
into the system and overflows out of the system, variables
that address those objectives (e.g., in-pipe flow monitoring
or tracking of volume and frequency of overflows) maybe
appropriate metrics. In cases where green infrastructure to
reduce inflow is a major part of the overall SSO reduction
strategy, monitoring similar to that recommended in the CSO
context would also be appropriate.
Mapping/Tracking: As relevant, mapping or otherwise
identifying the locations of control measures (whether grey
or green) is important for when maintenance is required
and performed. See case study below.
CMOM guidance is provided in this document:
http://www.epa.gov/npdes/pubs/cmom_guide_
for_collection_systems.pdf
SANITARY SEWER OVERFLOWS: Or.O1.'2012 - 05-31.2012
State of California Case Study
As an example, the State of California has
established procedures concerning monitoring
and mapping. All collections systems in California
must report their sanitary sewer overflows in
accordance with State Water Resources Control
Board, Order No. 2006-0003-DWQ, Monitoring and
Reporting Program, Statewide General Waste
Discharge Requirements for Sanitary Sewer
Systems, issued May 6,2006, and amended by
State Water Resources Control Board Order No.
WQ 2008-0002-EXEC on February 20, 2008. Each
collection system must enroll for coverage under
this Order and register with the online reporting
database. Enrollees must report the details of
each spill to the database, providing information
which includes: date of SSO, whether it reached
surface water, total volume, total volume
recovered, total volume reaching surface water,
location of the spill, time the agency was notified,
time the operator arrived, time the spill ended, actions taken to stop the SSO and perform clean-up activities, and planned future
actions for that site. The database is publicly accessible, and users can search for and view reported SSOs statewide by Street
Address, County, Responsible Agency, Spill Start & End Dates, Water Board Region, and Spill Category. The State Board has
launched a web-based GIS mapping tool using Google Earth base maps for plotting all SSOs and private lateral spills in the State.
Links to the California order, database and mapping tool, fact sheets, and other information are at: http://www.waterboards.
ca.gov/water_issues/programs/sso/index.shtml#general
-------
GREEN INFRASTRUCTURE PERMITTING AND ENFORCEMENT SERIES: FACTSMEET 3
Consent Decree Components
Green infrastructure approaches may be a useful
component of judicial consent decrees entered in Clean
Water Act enforcement actions to resolve SSO violations.
An SSO decree providing for green infrastructure may
include the following concepts:
The Collection System and Waste Water Treatment Plant
(WWTP) Remedial Measures Plan should identify all
measures necessary to achieve adequate capacity. If
green infrastructure is proposed as a solution to reduce
system capacity demands, it should be identified in this
Plan. The Plan shall include specific metrics that can be
measured and quantified on a continuous basis. If green
infrastructure is used, the operator shall demonstrate
appropriate legal authority to ensure adequate operations
and maintenance.
The reporting provisions of a consent decree or
administrative order contain numerous specific provisions.
Green infrastructure approaches may be a useful
component of judicial consent decrees entered in
Clean Water Act enforcement actions to resolve
SSO violations.
As with other reporting requirements, a summary that
quantifies the effectiveness of all measures, including
green infrastructure measures, should be included.
Should evaluation of metrics indicate that green
infrastructure measures are not providing the anticipated
flow volume reductions to the sanitary sewer system, the
Plan should identify additional actions consistent with
meeting the SSO abatement objectives.
-------
By disconnecting downspouts and routing stormwater flows to swales,
rain gardens, or other green infrastructure measures, the need to create
additional capacity in the sewer system can be significantly reduced.
Green Infrastructure Permitting and Enforcement Series
This series on integrating green infrastructure concepts into
permitting, enforcement, and water quality standards actions
contains six factsheets plus four supplemental materials
that can be found at http://water.epa.gov/infrastructure/
greeninfrastructure/gi_regulatory.cfm#permittingseries.
Factsheets
1. Potential Challenges and Accountability Considerations
2. Combined Sewer Overflows
3. Sanitary Sewer Overflows
4. Stormwater
5. Total Maximum Daily Loads
6. Water Quality Standards
Supplemental Materials
1. Consent Decrees that Include Green Infrastructure Provisions
2. Consent Decree Language Addressing Green for Grey
Substitutions
3. Green Infrastructure Models and Calculators
4. Green Infrastructure in Total Maximum Daily Loads (TMDLs)
United States
Environmental Protection
Agency
For additional resources on green infrastructure,
goto the EPA Green Infrastructure Web page:
http://www.epa.gov/greeninfrastructure/.
------- |