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HEALTH IMPACT ASSESSMENT (2014-2016) OF PROPOSED CODE CHANGES REGARDING
INDIVIDUAL SEWERAGE SYSTEMS IN SUFFOLK COUNTY, NEW YORK
About HIAs
A health impact assessment (HIA) is a systematic process
that uses data, analytical methods, and input from
stakeholders to determine the potential effects of a
proposed policy, plan, program, or project on the health
of a population. The HIA examines who will be impacted
and provides recommendations for monitoring and
managing those effects.
About the Suffolk County HIA
The U.S. Environmental Protection Agency (EPA)
conducted an HIA of proposed code changes regarding
individual sewerage systems in Suffolk County, New York.
Individual sewerage systems can contribute nutrients,
such as nitrogen, to ground and surface waters. The
Suffolk County Government was considering changes to
Table 1. Decision Scenarios Assessed
Scenario
Details
Baseline
(No code
change)
More than 70% of single-family residences in Suffolk County utilize individual sewerage systems1 [i.e., onsite sewerage system
(OSDS)2 or conventional onsite wastewater treatment systems (C-OWTS)3], and of those, over half are assumed to be served by
cesspools alone (i.e., have no septic tank) because they were built prior to 1973.
Alternative I
All existing OSDS serving single-family residences must conform to current County Sanitary Code and standards (in place as of
September 2016). All existing cesspools must be upgraded to the County-defined C-OWTS.
Alternative II
All existing OSDS serving single-family residences in high priority areas4 must conform to current County Sanitary Code and
standards (in place as of September 2016). All existing cesspools must be upgraded to the County-defined C-OWTS in lots
located in those areas.
Alternative III
All individual sewage systems (OSDS or C-OWTS) serving single-family residences in high priority areas must be upgraded to
County-approved innovative/alternative onsite wastewater treatment systems (l/A OWTS).5
1	Individual sewerage system describes the overall category of individual (onsite) systems used to treat and/or dispose of wastewater from single-family
residences in Suffolk County.
2	Onsite sewage disposal system (OSDS) describes the pre-1973 type of individual sewerage system that includes a disposal unit alone (i.e., a cesspool)
serving single-family residences in Suffolk County.
3	"Conventional" onsite wastewater treatment system (C-OWTS) describes the post-1973 type of individual sewerage system that includes a septic tank
and disposal unit (leaching pool) serving single-family residences in Suffolk County.
4	At the time of the HIA, Suffolk County designated "high priority areas" as areas in the 0-50-year groundwater contributing zone to public drinking water
wells fields, areas in the 0-25-year groundwater contributing zone to surface waters, areas located in Sea, Lake, and Overland Surges from Hurricanes
(SLOSH) zones, and areas located where groundwater is less than 10 feet below grade. Priority area designations have since been revised and can be
found in the Subwatersheds Wastewater Plan released by the County (https://reclaimourwater.info/TheSubwatershedsWastewaterPlan,aspx).
5	Innovative/alternative onsite wastewater treatment system (l/A OWTS) describes the innovative (pending approval) type of individual sewerage system
designed for nitrogen reduction/control, used as an alternative to the C-OWTS serving single-family residences in Suffolk County.
the County Sanitary Code for single-family residential
individual sewerage systems as one of several efforts to
address the growing environmental issues related to
nitrogen pollution impacting local waters.
The goal of the HIA was to help inform the County's
decision regarding the proposed sanitary code changes by
evaluating the potential for the proposed changes to
impact individual and community health. The HIA would
also be able to provide evidence-based recommendations
for the County to utilize in its decision-making process.
The HIA evaluated four decision scenarios - the baseline
(should no alternative be implemented) and three
alternatives under consideration by the County at the
time of the assessment (Table 1).
1
U.S. Environmental Protection Agency
Office of Research and Development

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Community and Household Economics. There
are considerable costs associated with all three
Alternatives, which could reduce the amount of
expendable household income available for nutrition
and essential health-related goods and services if
funding assistance is not provided. However, upgrades
could also result in new employment opportunities, and
improvements in water quality from Alternative
could result in increased property values and
bolster revenue and employment from water-
related industries.
Water Quality. Alternatives I and II (C-OWTS) would provide no nitrogen
reduction and limited reduction in pathogens. The l/A OWTS in Alternative
III would provide a considerable reduction in nitrogen and may also reduce
pathogens, especially when treatment/disinfection options are included. Water
quality improvements in groundwater could influence the quality of surface,
recreational, and coastal waters, all of which are essential to public health, the
economy, and the desirability of living in Suffolk County.

( Resiliency to Natural Disasters.
Nitrogen loading can contribute to the
loss of native eelgrass and the wetlands that
protect the shoreline from storm and tidal
surges, flooding, and erosion, especially during
lower intensity storms and coastal flooding. While
the reduction in nitrogen loading from implementing
Alternative III should help increase wetlands and eelgrass,
the degree of improvement in shoreline protection is
unknown, as there are other factors contributing to the
loss of eelgrass and wetlands (e.g., legacy nitrogen loading,
accelerated sea level rise, etc.). Storm and tidal surges and
coastal flooding can lead to property and infrastructure
damage, evacuations, and human injury and death.
The proposed
decision has the
potential to affect the
risk of water-related
illness, vector-borne
disease, injury, and
premature death;
stress; and overall
health and
well-being.
Individual Sewerage System Performance and Failure.
All three alternatives would reduce the risk of system failures
and likely improve system performance through upgrades to
existing systems, many of which are at the end of their useful lives
(i.e., 25+ years old). Upgrades would also likely lead to reduced
risk of injury due to structural failure (as long as original system
components are no longer present or, if present, are filled with
soil or gravel) and reduced risk of illness from exposure to
untreated wastewater in cases of hydraulic failure (i.e., backup into
the home or surfacing above ground), provided the systems are
properly designed, sited, and maintained.
Vector Control. Upgrades to individual sewerage systems would reduce
the number of old, failing systems and reduce potential mosquito
breeding habitats and mosquito populations near residential areas, if systems
are maintained. Alternative III would lead to a further reduction in mosquito
populations by reducing nitrogen-enriched waters. Reductions in mosquito
habitat would reduce the spread of mosquito-borne diseases and the need for
pesticide application for mosquito control.
Figure 1. The Five Health Pathways Used to Evaluate the Proposed Co
The HIA Process
Based on input from stakeholders, including community
members, scientific experts, and decision-makers, the
HIA Project Team identified pathways through which the
proposed code changes could potentially impact health.
Five pathways were prioritized for assessment in the HIA
(Figure 1).
The HIA assessed each of the five pathways by answering
the following questions:
•	What are the current conditions?
•	How will each decision alternative impact the
current conditions?
•	What is the connection to health?
•	How might health be impacted by each decision
alternative?
The HIA Project Team used various methods to conduct
the assessment, including different types of data,
mapping or geographic information system (GIS)
methods, statistical and graphical analysis, and scientific
literature review.
Main HIA Findings and Recommendations
The HIA found several connections between the proposed
code changes and health (Figure 1). The HIA demonstrated
that the proposed sanitary code changes could have both
a positive and negative effect on health, but only
VS U.S. Environmental Protection Agency
H3 Office of Research and Development
Changes and Associated Health Impacts
Alternative III (l/A OWTS) would result in a net positive
public health impact. The HIA's recommendations not only
support the selection of Alternative III, but they also
identify ways to maximize potential positive health
impacts, minimize or avoid potential negative health
impacts, and offer health supportive measures.
The Impact of the HIA
This HIA brought together the community, stakeholders,
and decision makers at the local, state, regional, and
federal levels to promote health, equity, and
sustainability. Since reporting the preliminary HIA findings
and recommendations to the decision makers and
stakeholders in the fall of 2016, the County undertook a
number of activities to address nitrogen pollution. Some
of those activities were also recommendations from this
HIA. The County acknowledges that implementation of
code changes that require individual property owners to
upgrade to l/A OWTS would require a stable recurring
revenue source to reduce financial impacts to individual
households.
Where to Learn More
The HIA Report (EPA/600/R-21/186F) is located at
www.epa.gov/healthresearch/health-impact-assessments.
CONTACT: Rabi Kieber, EPA Region 4, kieber.rabiPepa.gov
Shannon Griffin, EPA Office of Research and Development,
griffin.shannon (5)epa.gov
July 2021

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