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Municipal Sewerline Upgrades Improved North Susupe's Water Quality
Waterbody Improved T'ie Nort'1 SusuPe watershed (Segment CN1SA) is on the island
of Saipan within the Commonwealth of the Northern Mariana
Islands (CNMI) in the western Pacific Ocean. The watershed was first listed as impaired on the
2004 Clean Water Act (CWA) section 303(d) list for exceeding bacteria (Enterococci). The primary
source of bacteria was identified as stormwater/urban runoff through the Commonwealth Utility
Corporation's (CUC) municipal sewer system. Repair work of the sewer system began in 2009. CUC
has now completed the needed municipal sewer system upgrades in the North Susupe watershed.
The results showed a marked reduction in bacteria in the surface water over the past 5 years,
leading to the removal of 2.4 coastal miles from the 303(d) list as impaired for Enterococci in 2020.
Problem
Saipan is the most highly developed and densely
populated island in the CNMI archipelago. Susupe's
watershed on Saipan's west coast has the largest
wetland area in the CNMI and the only lake on Saipan,
Susupe Lake (2020 CNMI Integrated Report). Susupe
is a developed urban area with several large resorts,
public beaches, recreational areas, two farmers
markets, restaurants, stores and gas stations. The
CUC's municipal sewer system runs adjacent to Saipan
Lagoon along the watershed length (Figure 1). Susupe
is divided into north and south subwatersheds.
North Susupe watershed extends from Chalan Laulau
Beach to Saipan Community School; it Includes 2.4
coastai miies with six beach monitoring sites. It
contains half the largest wetiand area in the CNMI,
with several ephemera! streams in the upper water-
shed. Like the surrounding watersheds, the entire
North Susupe watershed's coastline is more developed
than the middle and upper portions of the watershed,
except areas immediately adjacent to roads where
homes are located. These homes rely on onsite
wastewater treatment (septic) systems due to a lack of
lateral lines to the municipal sewer system.
In 2004, the North Susupe watershed (Segment
CN18A) was listed under CWA section 303(d) for
exceeding the CNMI water quality standard (WQS)
for Enterococci bacteria, which also meant that it was
not attaining its recreation designated use. The WQS
is violated when a single water sample result exceeds
the Enterococci statistical threshold value of 130 most
Figure 1. North Susupe watershed is on the island of Saipan,
probabie number per 100 milliliters (MPN/100 mL) or
the geometric mean is calculated over 30 days and
the single sample result is >35 MPN/100 mL. A single
exceedance in WQS for bacteria triggers a public beach
advisory. A waterbody moves to an impaired status for
Enterococci when at least one monitoring site has over
10% beach advisories annually. In 2002-2003, these
sites exceeded the CNMI WQS 15% of the time on
average, triggering the 2004 impairment listing.
The CNMI Bureau of Environmental arid Coastal
Quality (BECQ) identified this watershed as a
priority area for sewer system upgrades and com-
municated this recommendation to CUC and the U.S.
Environmental Protection Agency (EPA). BECQ identi-
fied the contamination source as storrnwater/urban
runoff into the CUC municipal sewer system through

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maintenance hole covers during periods of inunda-
tion from storm events, especially during the rainy
season (July-October). The inundation caused sewage
overflows into the adjacent Saipan Lagoon. In 2009,
the CNMI Superior Court stipulated that CUC reha-
bilitate the entire municipal system, which was done
through a cooperative agreement by CNMI and EPA. A
2018 total maximum daily load (TMDL) was developed
to address bacteria in Saipan's coastal waters. The
TMDL recommendations were narrative rather than
numeric. North Susupe's recommendations directed
local agencies to determine the types of wastewater
infrastructure improvements and methods of mainte-
nance that were needed and to continue funding the
utility infrastructure upgrades to meet demands.
Story Highlights
CUC has been working on system upgrades for Saipan
on a priority basis. CUC completed significant improve-
ments in the North Susupe watershed in 2017. The
upgrades cost over $1.6 million and included rehabili-
tating Lift Stations A-7 and W-5, installing a new gravity
main between the two, installing a new sewer force
main, and eliminating the old W-4 lift station. These
sewer Infrastructure improvements occurred between
the San Jose and Civic Center beaches, resulting in
fewer sewer overflows during heavy rain events.
Results
Since 2014, all water quality monitoring sites have
met the CNMI WQS for Enterococci 90% of the time
or better (Figure 2). This successful collaboration
between CUC and BECQ led to 2.4 coastal miles of the
North Susupe watershed being delisted for Enterococci
in the 2020 CNMI Integrated Report. The water now
supports its recreation designated use (Figure 3).
Partners and Funding
Multiple agencies work collaboratively to identify
sources of contamination, strategize best management
practices (BMPs) to address pollution sources, and
prioritize plans and funding to restore water quality.
CUC is responsible for prioritizing and conducting
upgrades to rehabilitate the CNMI municipal sewer
system. Over 5 years, CUC used over $1.6 million in
CWSRF funds for five sewer system upgrade projects
in the watershed. BECQ is responsible for permitting,
Percent Exceedance at
North Susupe Watershed Stations
20
2004 2005 2006 2007 2008 2009	2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
¦	WB 24 Chalan Laulau	BWB 25 San Jose
¦	WB 26 Civic Center	¦ WB 27 Saipan World Resort
¦	WB 28 Kanoa Resort	¦ WB 29 Community School
Figure 2. North Susupe bacteria data (2004-2019).
Figure 3. Coastal waters once again support
recreational uses such as this outrigger canoe trip.
regulating, and monitoring CNMI coastal, surface,
and groundwater quality. Over 5 years, BECQ's Water
Quality Surveillance/Nonpoirit Source (NPS) branch
used an estimated $101,556 in CWA 106 funding and
$21,317 of CWA 406 (BEACF1 Act) funding to monitor
coastal waters in the watershed and to develop the
2018 bacteria TMDL. BECQ's NPS branch used $10,127
of CWA 319 funding to investigate and monitor NPS
pollution issues in the watershed.
BECQ's Wastewater, Earthmoving and Erosion Control
(WEEC) branch has reciprocity to permit and regulate
the CUC municipal sewer system and onsite waste-
water treatment systems. BECQ's WEEC works closely
with the BECQ NPS branch to determine causes and
sources of impairments. WEEC also conducts sanitary
surveys to determine the location of illicit discharges
and sewer system failures. Over 5 years, WEEC used an
estimated $86,335 of CWA '106 funding to permit and
regulate sewerline construction and maintenance in
the watershed. WEEC also used an estimated $20,253
of CWA 319 funding to investigate stormwater pol-
lution sources, conduct sanitary surveys, and review
construction-related BMPs.
&
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-21-001K
August 2021
For additional information contact:
Kathy Yuknavage
Sphere Management
670-287-8347 • kathyjuk@gmail.com
Larry Maurin
CNMI Bureau of Environmental and Coastal Quality
670-664-8521 • larry.maurin@becq.gov.mp
Larry Manacop
Commonwealth Utilities Corporation
670-664-4282 • larry.manacop@cucgov.org

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