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I NONPOINT SOURCE SUCCESS STURY
JAfkine,
Septic System Repairs and Manure Storage Practices Reduce Bacteria
Levels in Pottle Brook
Waterbody Improved
High Escherichia coli bacteria from both human and animal
sources caused the Maine Department of Environmental
Protection (DEP) to place Pottle Brook on its 2002 Clean Water Act (CWA) section 305(b)/303(d) list
of impaired waters. Maine DEP partnered with the local government to conduct sanitary surveys
that identified problem areas needing to be addressed. Implementing best management practices
(BMPs), including the repair and replacement of a number of septic systems by property owners and
improvements in manure storage practices by a horse paddock owner, reduced bacteria levels in the
brook to those that are closer to the Maine Class B water quality standard. The downward trends in
bacteria levels and improved water quality are expected to continue.
Problem
Pottle Brook is a small Class B stream in Perry and
Robbinston, Maine, with a length of 2 miles and a
watershed area of 3.1 square miles (Figure 1). The
brook flows easterly and drains into Passamaquoddy
Bay. The sparsely populated watershed is only 1 per-
cent developed; the predominant cover type is forest
(82 percent), with a small amount of agriculture (3.4
percent) consisting primarily of hayfield.
In 2002 Pottle Brook (segment ME0105000203_
508R02) was included in Maine's Integrated Water
Quality Monitoring and Assessment Report (CWA sec-
tion 303[d] report) because monitoring data showed
that E. coli bacteria levels exceeded the Maine Class
B geometric mean water quality standard of 64 most
probable number per 100 milliliters (mpn/100 mL).
DEP suspected the excessive bacteria in the brook
could be due to malfunctioning septic systems, animal
waste, pet waste or other nonpoint sources.
Project Highlights
Maine DEP conducted water quality monitoring at
five locations (Figure 2) from 2007 through 2015 to
better understand the nature of the impairment and to
help identify bacteria sources. Five sampling locations
were distributed throughout the watershed, with two
located on the mainstem and three on tributaries. The
sampling sites included NPT01 (on the mainstem at
U.S. Route 1) and NPTUA05 (on the Lake Road tribu-
tary). in 2009 Maine DEP developed a statewide total
maximum daily load for bacteria, which included an
assessment of Pottle Brook.
To determine the sources and location of bacteria in
the Pottle Brook watershed, Maine DEP and the town
of Perry conducted sanitary surveys in 2010-2011 that
resulted in 19 properties being inspected (Figure 3).
Of the inspected sites, six were identified as having
septic system and/or animal waste problems, several of
which were located adjacent to a tributary of the brook
Pottle Brook Watershed
Robbinston
Figure 1. The Pottle Brook watershed (dark green).
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iNPTUCOlj
Figure 3. DEP employee performs sanitary survey.
mean for the Lake Road tributary was 154 mpn/100
mL. Following septic system repairs, bacteria levels
lowered to less than 44 mpn/100 mL, which attains the
class B standard of 64 mpn/100 mL (Figure 4).
Partners and Funding
Figure 2. Sampling sites in the Pottle Brook watershed.
i Sampling Stations
Robbinston
DEP Sampling Stations
on Pottle Brook
that runs under Lake Road ("Lake Road tributary"). The
town of Perry prompted property owners with identi-
fied issues to address problems and, as a result, home-
owners replaced or repaired malfunctioning septic
systems, and a horse paddock owner In the watershed
adopted better manure management practices for a
paddock containing approximately 15 horses. Six sites
were treated overall, Including four within the Lake
Road tributary subwatershed of Pottle Brook.
Results
Bacteria levels have dropped over time. In 2007 and
2010 the E. eat bacteria geometric mean for water
samples taken from Pottle Brook at sampling site
NPT01 was 84 and 129 mpn/100 mL, respectively,
exceeding the Maine geometric mean standard of 64
mpn/100 mL for class B waters. In 2015 water quality
sampling showed that the E. coli geometric mean for
Pottle Brook lowered to 77 mpn/100 mL. Also in 2015,
five of the six samples were well below the instanta-
neous (single sample) standard of 236 mpn/100 mi.
This improvement in water quality on the mainstem
of Pottle Brook can be partly attributed to reduced
bacteria levels observed in the Lake Road tributary
(at site NPTLJA05), where several malfunctioning
septic systems were repaired. In 2010 the geometric
The town of Perry (including its licensed plumbing
inspector, property owners and a horse paddock
owner) partnered with the Maine DEP's Division of
Environmental Assessment and Division of Water
Quality Management to perform sanitary surveys,
oversee septic system repair/replacement and
improvements in animal waste management. U.S.
Environmental Protection Agency CWA section 319
funds supported DEP staff services and Americorps
volunteer participation.
E. coli Bacteria Levels, Lake Road Tributary to
Pottle Brook (Sample Site NPTUA05)
200
¦ Geometric mean
at sampling site
¦ Class B Standard
geometric mean
64 mpn/100 mL
NPTUA05
NPTUA05
2011
. I
NPTUA05 NPTUA05
2012 2015
Figure 4. Bacteria levels declined after project
implementation.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-16-001FF
November 2016
For additional information contact:
Greg Beane
Maine DEP, Division of Environmental Assessment
207-299-4703 • greg.e.beane@maine,gov
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