oEPA

Research SUMMARY

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Summary of EPA Region 1 and ORD Merrimack River Projects - July 2021

This project summary provides an overview of the
work EPA Region 1 and the EPA Office of
Research and Development (ORD) have done for
the Merrimack River in the Lawrence, MA area
from 2015 to 2019. EPA produced several
deliverables during this time and collected data sets
for research use. Below is a discussion about the
project history and data sets that EPA collected.

Background of EPA Work on the Merrimack
River

The Merrimack River is the source of drinking
water for approximately 600,000 people in New
Hampshire and Massachusetts. The river begins in
Northern New Hampshire and flows into the
Atlantic Ocean in Newburyport, Massachusetts.
EPA has been involved in projects on the
Merrimack River for several decades.

In 2015, EPA began working directly with the City
of Lawrence, Massachusetts, and other partners as
part of the regional "Making a Visible Difference
in Communities" project. Lawrence is the farthest
downstream of five Massachusetts communities
along the Merrimack River which use the river as
their only source of drinking water. The other
Massachusetts communities using the Merrimack
River for drinking water are Methuen, Andover,
Tewksbury, and Lowell.

The Merrimack River is a critical, but threatened
resource. In addition to providing drinking water, it
also receives the discharge of wastewater treatment
effluent, combined sewer overflow, and stormwater
discharges, many of which are from communities
upstream of Lawrence. EPA learned more about
the community's priorities by hosting stakeholder
meetings from 2015 -2017 with City of Lawrence
officials, citizens, planning agencies, non-profit
organizations, and state agencies.

Abe Bashara River Boat House on the Merrimack
River in Lawrence, Massachusetts

Priorities included addressing water quality
concerns and improving the resiliency of the
drinking water treatment plant.

In 2015, staff from ORD, based in Cincinnati,
visited Lawrence to see and learn about some of
the city's water quality and flooding issues. As part
of EPA Region l's "Making a Visible Difference"
project in Lawrence, EPA ORD staff were able to
offer technical assistance to the City of Lawrence.
One outcome of ORD's visit was to assist the
community in developing a "comprehensive water
strategy" for the river. This included conducting
research to assess the issues and possible solutions.

EPA worked closely with Lawrence water officials,
Groundwork Lawrence, the Merrimack River
Watershed Council, and the U.S. Army Corps of
Engineers as a research plan was developed. EPA's
research focused on three objectives:

•	Flooding Vulnerability

•	Water Quality

•	Environmental Justice

Office of Research and Development

Center for Environmental Solutions and Emergency Response

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Lawrence's drinking water treatment plant is
vulnerable to flooding, as it is situated in the
100-year flood zone. One component of the water
strategy was to develop a climate and flooding
vulnerability assessment of the Lawrence drinking
water treatment plant, situated along the
Merrimack River. The water strategy also included
mapping and analyzing water quality data to
advance the community's priorities. EPA captured
local community knowledge of sensitive sites and
locations where Lawrence residents go boating,
swimming, and fishing to identify potential
exposure locations.

Collaborating with the stakeholders, EPA gathered
historical water quality data and information on
point source discharges (e.g., sewer overflows) to
map against social vulnerability metrics and
identified exposure points. EPA mapped and
analyzed flood zones, using an updated analysis of
precipitation data. EPA developed a mapping tool
for the watershed, bringing together interactive
data to visualize the watersheds greatest challenges
and attributes. The Merrimack River mapping tool
is in the mapping section of the EPA Merrimack
River webpage (www.epa.gov/merrimackriver).
This tool also allows users to add their own data,
enabling those who do not have access to GIS tools
to create maps to analyze multiple data layers.

To support these efforts, EPA gathered additional
water quality data from two monitoring stations in
the river. The stations were funded by ORD
(https://www.epa.gov/merrimackriver/basic-
information-about-lower-merrimack-river-
monitoring-station) and operated by the EPA
Regional Laboratory. Water quality monitoring
data were used to characterize the variability of
river conditions and to develop predictive models
of contamination levels impacting its use. EPA
collected real-time water chemistry measurements
as well as grab samples for microbial analysis
during wet and dry weather. These data allowed
ORD to evaluate the potential for nowcasting water

quality using real-time monitoring, observed
meteorological information, and river flow data.
Nowcasting is a short time forecasting of water
quality.

Data Collected

During the environmental monitoring and research,
EPA both produced original data sets and gathered
data from other sources to complete their analyses.

EPA deployed two real-time monitors that
collected data every 15 minutes, from December
2016 to 2019. The preliminary data were displayed
in near real-time on EPA's public website
(https://www.epa.gov/merrimackriver).

Measurements are available on EPA's website and
included the following:

•	Temperature

•	Dissolved oxygen

•	Specific conductance (conductivity)

. pH

•	Turbidity

•	Chlorophyll

•	Phycocyanin

Additional water quality parameters were collected
every 15 minutes at each station. These parameters
were not transmitted to EPA's web page because
these data are considered preliminary due to the
experimental nature of operating this equipment in
the field. EPA scientists and water quality
managers used data from these two stations to
assess and understand water quality conditions.
The experimental research data that were collected
included:

•	Total organic carbon (TOC)

•	Fluorescent dissolved organic matter
(FDOM)

•	Nitrate

•	Phosphate

The above datasets have not been published or
QA/QC reviewed.

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Lastly, from 2016-2018, EPA conducted
seventeen grab sampling events in the Lawrence
area to examine bacteria levels. EPA tested for
presence of Escherichia coli and nutrients at six
sites during dry and wet weather conditions. These
data have gone through EPA's internal review and
clearance process, and are available upon request.

EPA also gathered additional secondary datasets to
use in their analyses:

•	Merrimack River water level data for the USGS
stations

•	Precipitation datasets for Lawrence and Lowell,
MA

•	Lowell CSO event dates and discharge volumes
Analyses Conducted

•	Flooding Analysis: A detailed flooding
analysis was conducted for Lawrence. The
results pertain to the probability of flood levels
overtopping the protective berm of the
Lawrence drinking water plant located at the
northern side of the river. Also, the flooding
risk in Spicket River was analyzed to determine
the potential impact on Lawrence water supply
and wastewater collection systems. The results
and datasets include:

o Hydraulic profiles related to the river and

water treatment plant
o River flow and stage modeling
o Areal precipitation and river stage

variations in hydrological modeling
o Flooding recurrence interval and design

river stages in hydrological analysis
o Datasets for both Lawrence and Lowell
o Reconstruction of the historical 2006

flooding map for Lawrence
o Flooding risk and water stages for Spicket
River developed for small-probability
floods

• Indicators of Pathogen Levels: River water
quality nowcasting (models) and analyses were
conducted based on datasets from the sensor
monitoring data, river flow data, CSO
discharge data, and other hydrological datasets.
The results are in a summary presentation that
is available upon request. Datasets from the
nowcasting analysis include:

o Nowcasting equations and methods for
estimating E. coli in the river water based
on real-time sensor monitoring results, CSO
data in Lowell, and area precipitation
o River water turbidity nowcasting using
river flow and water turbidity variations,
and their correlations
o Datasets for identifying flow-contaminant
events using coupled sensor stations, and
river stage data

Through modeling and preliminary engineering
analysis, EPA found that the changes in
precipitation, watershed hydrology, and aged water
infrastructure are the major factors affecting water
quality and water supply resilience. EPA presented
its research to the City of Lawrence in 2017 to help
the city understand risks to their water supply in
the event of extreme flooding or power loss.

Future Areas of Research

This work could lead to further investigation by
Merrimack River stakeholders. Below are potential
research questions and technical support needs that
could be further explored.

Nowcasting models of fecal indicator bacteria
could be used to develop a real-time notification
system for recreational activities on the Merrimack
River. Such a system would color-code water
quality conditions via a web app or flagging system
to inform the public about anticipated
contamination levels that exceed acceptable
thresholds.

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These thresholds could be based directly on
recreational water quality criteria for E. coli, or on
pathogen infection risks predicted using
quantitative microbial risk assessment (QMRA).
QMRA would: use the fecal indicator
concentrations to model likely pathogen levels
based on their respective densities in wastewater (a
worst-case assumption) and the fate and transport
of each; combine these with reported water
ingestion rates to estimate exposure doses during
various recreational activities; and then use
pathogen-specific dose-response relationships to
quantify associated infection risks for comparison
against defined acceptable rates.

While this modeling introduces additional
uncertainty through its assumptions, it has the
benefit of relating contamination events to explicit
risk-based conclusions. In doing so, the different
levels of risk associated with swimming or non-
contact recreation (e.g., boating or fishing) could
be differentiated, informing which types of
activities are suitable under current water quality
conditions. However, because water quality sensors
used to develop the nowcasting model are no
longer in place, and if they cannot be replaced, new
correlations using readily accessible data sources
(e.g., precipitation levels and CSO reporting)
would need to be developed in order to implement
the notification system.

Additional monitoring would be needed to support
future research involving modeling water quality
conditions. Monitoring could be conducted to
support model development or validation. A
monitoring plan would be developed as part of the
research needs.

Contacts:

Modeling

Jeff Yang, Office of Research and Development,
Water Quality Modeling, vang.ieff@epa.gov

Michael Jahne, Office of Research and
Development, Microbial Risk Modeling,
Jahne.michael@epa.gov

Dan Murray, Office of Research and Development,
CSO Infrastructure Technical Support,
murrav. dan@epa. gov

Monitoring

Tom Faber, Region 1, Laboratory Services and
Applied Science, faber.tom@epa. gov

Drinking Water Program

Kira Jacobs, Region 1, Water Division, Source
Water Protection, iacobs.kira@epa.gov

Disclaimer

The views expressed in this document are those of
the authors and do not necessarily represent the
views or the policies of the U.S. Environmental
Protection Agency. This document has been
reviewed in accordance with U.S. Environmental
Protection Agency policy and approved for release.

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