Fact Sheet on the Puerto Rico 2020 Impaired Waters List
December 2020

Section 303(d) of the Clean Water Act requires states, territories and authorized tribes to develop lists of
impaired waters. Impaired waters are waters that are too polluted or otherwise degraded to meet the state
water quality standards. Federal law requires that these jurisdictions establish priority rankings for
waters on the lists and develop total maximum daily loads for impaired waters. A total maximum daily
load, or TMDL, is a calculation of the maximum amount of a pollutant that a waterbody can receive and
still safely meet water quality standards. The EPA has approved the Puerto Rico 2020 list of impaired
waters requiring a TMDL. The Puerto Rico 2020 impaired waters list presents information on impaired
waters, pollutants causing the impairment and pollutant sources.

How States Report on the Quality of their Waters

The Clean Water Act requires states (Section 502 of the Act defines "state" to include Puerto Rico) to
assess the quality of their waterbodies and to report their findings every two years to the EPA. States
adopt specific water quality standards that serve as the foundation for water quality management. Water
quality standards identify the designated uses for each body of water (such as swimming, drinking,
shellfish harvesting, etc.) and set criteria to protect those uses. During the assessment process, states
compare the collected data to the established water quality standards.

In addition to reporting on the overall quality of all waters, the Clean Water Act directs states to identify
and list specific waterbodies where water quality is impaired by pollutants. A waterbody is considered
impaired if it does not meet water quality standards. The requirement to prepare the impaired waters list
is found in section 303(d) of the Clean Water Act, and the list is often called the 303(d) list.

Each impairment reflected on the 303(d) list requires a calculation of the maximum amount of the
impairing pollutant that a waterbody can receive and still meet water quality standards. TMDLs include
reductions for pollution sources impacting the waterbody that, when achieved, will result in the
attainment of water quality standards in the waterbody.

In certain cases, impaired waterbodies may not appear on a state's 303(d) list. If a TMDL has already
been developed for the waterbody, another required control measure is expected to result in the
attainment of water quality standards within a reasonable amount of time, or the impairment is the result
of pollution not caused by a pollutant (e.g., hydrologic or habitat alteration), then the waterbody may not
be included.

Water quality monitoring data and other information must be considered by states in assessment and
reporting efforts. Monitoring may be carried out by national, state, local and tribal authorities,
universities, dischargers, volunteers and others. It can include measurements of physical and chemical
parameters (temperature, dissolved oxygen, suspended sediment, nutrients, metals, oils, and/or
pesticides, for example), examinations of stream flow, water color, condition of stream banks and lake
shores, observations of communities of aquatic wildlife, and sampling of fish tissue or sediment. Land
use data, predictive models and land surveys may also be used.

Summary of 2020 Findings

The Puerto Rico 2020 303(d) list includes 856 instances where a pollutant is causing a designated use
impairment. The indicators/causes of impairments are:

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•	turbidity (118),

•	dissolved oxygen (96),

•	enterococcus (91),

•	copper (87),

•	temperature (65),

•	phosphorus (61),

•	pH (58),

•	hexavalent chromium (51),

•	nitrogen (45),

•	lead (32),

•	mercury (28),

•	thallium (28),

•	surfactants (20),

•	nickel (18),

•	pesticides (16),

•	arsenic (13),

•	oil and grease (10),

•	ammonia (8),

•	zinc (5),

•	fecal coliform (3),

•	cadmium (1),

•	selenium (1), and

•	silver (1).

Pollutant sources include:

•	confined animal feeding operations (point source),

•	sanitary sewer overflows (collection system failures),

•	on-site treatment systems (septic systems and similar decentralized systems),

•	urban runoff/storm sewers,

•	agriculture,

•	industrial point source discharge,

•	municipal point source discharges,

•	dam or impoundment,

•	upstream impoundments,

•	landfills,

•	marinas and recreational boating,

•	package plant or other permitted small flows discharges,

•	sand/gravel/rock mining or quarries,

•	industrial thermal discharges, and

•	historic bottom deposits (not sediment).

Note:	a pollutant may come from more than one source.

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Puerto Rico added 280 new waterbody/pollutant combinations to the 2020 303(d) list. The number of
waters listed for a new pollutant are summarized below:

temperature (52),
hexavalent chromium (51),
thallium (27),
copper (26),
pH (24),
lead (19),
mercury (19),
nitrogen (18),
nickel (10),
turbidity (9),
arsenic (7),
phosphorus (5),
zinc (4),
ammonia (3),
surfactants (3),
dissolved oxygen (2), and
enterococcus (1).

The 2020 303(d) list also reflects waterbody/pollutant combinations that no longer require listing.
Removal of a waterbody/pollutant combination from the 303(d) list, called delisting, may indicate that
the water is restored, a TMDL was developed, the water is receiving management attention that is
expected to result in the attainment of water quality standards, or other factors (including errors). Puerto
Rico delisted 90 waterbody/pollutant combinations for the 2020 cycle, including:

• 78 waterbody/pollutant combinations where water quality standards are now met, based on new
water quality data, including:

o	34 waterbody/pollutant combinations for dissolved oxygen,

o	14 waterbody/pollutant combinations for pH,

o	7 waterbody/pollutant combinations for copper,

o	7 waterbody/pollutant combinations for turbidity,

o	4 waterbody/pollutant combinations for temperature,

o	3 waterbody/pollutant combinations for lead,

o	3 waterbody/pollutant combinations for nitrogen,

o	3 waterbody/pollutant combinations for phosphorus,

o	1 waterbody/pollutant combination for enterococcus,

o	1 waterbody/pollutant combination for mercury, and

o	1 waterbody/pollutant combination for surfactants.

• 12 waterbody/pollutant combinations listed as impaired for free cyanide where there is no longer an
applicable water quality standard for free cyanide for these waters.

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How the Water Quality Sampling and Reporting Process Works

There are 358 assessment units in Puerto Rico. The Puerto Rico Department of Natural and
Environmental Resources' monitoring activities for this reporting cycle (October 1, 2017 to September
30, 2019) included routine ambient water quality sampling at the various networks, special water quality
studies performed in the waterbodies of concern, and existing or secondary data requested. Where
available, effluent quality data from the discharge monitoring reports submitted by permitted point
sources are used as those point sources may be contributing sources impacting the use support potential
of the waterbodies. The PRDNER may perform special sampling when necessary to investigate fish
kills, hydrocarbons leaks and spills, and illegal discharges to storm sewers and waterbodies.

The PRDNER generates data from five routine monitoring networks that provide physical, chemical and
biological water quality data from the different waterbodies:

•	Surface Water Monitoring Network: Operated by the U.S. Geological Survey under a cooperative
agreement with Puerto Rico, this network includes water quality sampling stations in 49 assessment
units.

•	Clean Lakes Monitoring Network: Operated by the PRDNER, this network monitors water quality in
18 major lakes (reservoirs) that are mostly used as raw sources of public water supply, propagation
and preservation of desirable species, and primary and secondary contact recreation.

•	Groundwater Monitoring Network: This network is composed of 53 wells, that are drinking water
supply wells operated by the Puerto Rico Aqueduct and Sewer Authority. The wells are sampled at
least annually.

•	Coastal Monitoring Network: Operated by the PRDNER, this network includes 104 monitoring
stations around the coastal perimeter of Puerto Rico. This network covers a total of 419.01 coastal
miles of Puerto Rico's main island, out of a total 546.63 shore miles.

•	Beach Monitoring and Public Notification Program: Operated by the PRDNER and implemented in
the 35 beaches included in the Beach Monitoring and Public Notification Program, all stations are
sampled biweekly for enterococcus, pH and temperature.

Puerto Rico uses the data collected through its monitoring program to determine the health of its waters
by comparing the data to its water quality standards. Impaired waters are those waters that do not meet
water quality standards even after limits based on treatment technology are applied, such as technology
requirements at publicly-owned wastewater treatment facilities. For the waters listed as impaired, Puerto
Rico must develop loading limits to restore the waterbody. The list must include a priority ranking for
each segment and Puerto Rico must document its decisions on which waterbodies to include and not
include on the list. The documentation includes a description of the methodology used to develop the
list. The availability of the Puerto Rico 2020 draft 303(d) list was publicized by posting notices in the
newspapers Primera Hora and El Nuevo Dia on September 11, 2020. The public comment period for the
2020 303(d) list concluded 30 days after the notices were published. During the public comment period,
those requesting information were emailed copies of the draft list and methodology in English and
Spanish.

How to Get Involved

Recognizing that stakeholders throughout Puerto Rico collect valuable water quality data, the PRDNER
has established a process that allows groups and individuals to submit information for Puerto Rico to use
in its assessment. Submissions must be sent to the PRDNER by September 30 of odd-numbered years.
The Department requests that where possible, all data be submitted in electronic format (Word, Excel,

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and/or delimited text file formats); however, data may also be submitted in hard copy (paper format if
the electronic format is not available) to Department of Natural and Environmental Resources, Plan and
Special Projects Division, Water Quality Area, San Jose Industrial Park, 1375 Ave Ponce de Leon, San
Juan, PR 00926. You may also submit the information by email to the following address:
waterqualitv@i ca.pr. gov. If you have questions or would like to speak directly with a PRDNER
representative from the Plan and Special Projects Division of the Water Quality Area, call (787) 767-
8181. The PRDNER provides the opportunity for formal public comment on draft 303(d) lists during a
public hearing and/or its 30-day comment period.

The EPA Contact for Puerto Rico's 303(d) List

If you have questions or concerns, contact Jacqueline Rios by phone at (212) 637-3859 or by email at

rios.iacqiieline@epa.gov.

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