United States Environmental Protection Agency
Region 2
Caribbean Environmental Protection Division
City View Plaza ll-Suite 7000, #48 Rd. 165 km 1.2
Guaynabo, Puerto Rico 00968-8069
FACT SHEET
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM
MINILLAS WTP
PERMIT No. PR0026794
This Fact Sheet sets forth the principle facts and technical rationale that serve as the legal basis forthe requirements
of the accompanying draft permit. The draft permit has been prepared in accordance with Clean Water Act (CWA)
section 402 and its implementing regulations at Title 40 of the Code of Federal Regulations (CFR), Parts 122
through 124, and the Water Quality Certificate (WQC) issued by the Puerto Rico Department of Natural and
Environmental Resources (DNER) pursuant to CWA section 401 requirements.
Pursuant to 40 CFR 124.53, the Commonwealth of Puerto Rico must either grant a certification pursuant to CWA
section 401 or waive this certification before the U.S. Environmental Protection Agency (EPA) may issue a final
permit. On November 17, 2022, DNER provided in the Intent to issue a WQC that the allowed discharge will not
cause violations to the applicable water quality standards at the receiving water body if the limitations and monitoring
requirements in the WQC are met. In accordance with CWA section 401, EPA has incorporated the conditions of
the WQC into the draft permit. The WQC conditions are discussed in this Fact Sheet and are no less stringent than
allowed by federal requirements. Additional requirements might apply to comply with other sections of the CWA.
Review and appeals of limitations and conditions attributable to the WQC were made through the applicable
procedures of the Commonwealth of Puerto Rico and not through EPA procedures.
Background
A. Permittee and Facility Description
The Puerto Rico Aqueduct and Sewer Authority (PRASA) (referred to throughout as the Permittee) has applied for
renewal of its National Pollutant Discharge Elimination System (NPDES) permit. The Permittee is discharging
pursuant to existing NPDES Permit No. PR0026794. The Permittee submitted Application Form 1 and Form 2C
dated May 28, 2021 and applied for an NPDES permit to discharge treated wastewater from Minillas WTP, called
the facility. The facility is classified as a minor discharger by EPA in accordance with the EPA rating criteria.
The Permittee owns and operates water treatment plant. Attachment A of this Fact Sheet provides a map of the
area around the facility and a flow schematic of the facility.
The treatment system consists of the following:
The Minillas Water Treatment Plant (WTP) is a filtration plant that treats raw water from the Bayamon River to
provide potable water to the municipality of Aguas Buenas. The treatment consists of coagulation, flocculation,
sedimentation, filtration, and disinfection.
Water is processed through the following units:
> Coagulator / Flocculator Tanks
> 3 Sedimentation Tank
> 3 Filters
> Chlorination
> Sludge Treatment System
> Dechlorination Tanks
> Sludge Drying Beds
NPDES Fact Sheet 1
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Puerto Rico Aqueduct and Sewer Authority NPDES NO. PR0026794
Minillas WTP
A long-term remedial measure to construct a Sludge Treatment System (STS) by 2025 is included in the Consent
Decree Civil Action No 3:15-CV-02283(JAG).
Summary of Permittee and Facility Information
Permittee
Puerto Rico Aqueduct and Sewer Authority (PRASA)
Facility contact, title, phone
Mr. Edgardo Bermudez Valentin, Executive Director
Compliance and Quality Control
(787) 620-2277
Permittee (mailing) address
Puerto Rico Aqueduct and Sewer Authority
P.O. Box 7066
Barrio Obrero Station
Santurce, Puerto Rico 00916-7066
Facility (location) address
State Road 174, Km. 21.6 Interior, Minillas Sector, Mulas Ward, Aguas Buenas, PR 00703
Type of facility
WTP
Pretreatment program
N/A
Facility monthly average flow
0.06284 MGD
Facility design flow
2.0 MGD
Facility classification
minor
B. Discharge Points and Receiving Water Information
Wastewater is discharged from Outfall 001 to an intermittent creek tributary to Bayamon River, a water of the
United States.
The draft permit authorizes the discharge from the following discharge point(s):
Outfall
Effluent description
Outfall latitude
Outfall longitude
Receiving water name and
classification
001
filters backwasher and
sedimentation tanks
drains
18°, 15', 7.6" N
66°, 07', 52.6" W
Intermittent Creek tributary to the
Bayamon River, SD
As indicated in the Puerto Rico Water Quality Standards (PRWQS) Regulations, the designated uses for Class
SD receiving waters include:
> Use as a raw source of public water supply; and
> Propagation and preservation of desirable species, including threatened or endangered species.
C. Mixing Zone/Dilution Allowance - N/A
D. Compliance Orders/Consent Decrees
The Permittee has a Consent Decree with the Agency (civil action Civil Action No 3:15-CV-02283(JAG)) in
which the facility is included. This consent decree does not affect this permit action.
E. Summary of Basis for Effluent Limitations and Permit Conditions - General
The effluent limitations and permit conditions in the permit have been developed to ensure compliance with the
following, as applicable:
NPDES Fact Sheet 2
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Puerto Rico Aqueduct and Sewer Authority NPDES NO. PR0026794
Minillas WTP
> Clean Water Act section 401 certification requirements;
> NPDES regulations (40 CFR Part 122); and
> PRWQS (August, 2022).
PART I. RATIONALE FOR EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS
CWA section 301(b) and 40 CFR 122.44(d) require that permits include limitations more stringent than applicable
technology-based requirements where necessary to achieve applicable water quality standards. In addition,
40 CFR 122.44(d)(1)(i) requires that permits include effluent limitations for all pollutants that are or may be
discharged at levels that cause, have the reasonable potential to cause, or contribute to an exceedance of a
water quality criterion, including a narrative criterion. The process for determining reasonable potential and
calculating water quality-based effluent limits (WQBELs) is intended to protect the designated uses of the
receiving water, and achieve applicable water quality criteria. Where reasonable potential has been established
for a pollutant, but there is no numeric criterion for the pollutant, WQBELs must be established using (1) EPA
criteria guidance under CWA section 304(a), supplemented where necessary by other relevant information; (2) an
indicator parameter for the pollutant of concern; or (3) a calculated numeric water quality criterion, such as a
proposed state criterion or policy interpreting the state's narrative criterion, supplemented with other relevant
information, as provided in 40 CFR 122.44(d)(1)(vi).
The effluent limitations and permit conditions in the permit have been developed to ensure compliance with all
federal and state regulations, including PRWQS. The basis for each limitation or condition is discussed below.
A. Effluent Limitations
The permit establishes WQBELs for several pollutants and the basis for these limitations are
discussed below.
1. Flow: An effluent limitation for flow has been established in the permit. Monitoring conditions are applied
pursuant to 40 CFR 122.21 (j)(4)(ii) and DNER's Water Quality Certificate.
2. Color: The effluent limitation is based on the water quality criterion for Class SD waters as specified in Rule
1303.2.C.2.e of PRWQS, and the WQC.
3. pH: The effluent limitation is based on the water quality standards as specified in Rule 1303.2.C.2.d of
PRWQS, and the WQC.
4. Temperature: The effluent limitation for temperature is based on the water quality criterion for Class SD
waters as specified in Rule 1303.1.D.1 of PRWQS, and the WQC.
5. Dissolved Oxygen (DO): The effluent limitation is based on the water quality criterion for Class SD waters as
specified in Rule 1303.2.C.2.a. of PRWQS, and the WQC
6. Turbidity: The effluent limitation is based on the water quality criterion for Class SD waters as specified in
Rule 1303.2.C.2.f. of PRWQS, and the WQC.
7. Taste and Odor Producing Substances: The effluent limitation is based on the water quality criterion for
Class SD waters as specified in Rule 1303.2.D.2.h of PRWQS, and the WQC.
8. Suspended, Colloidal or Settleable Solids: The effluent limitation is based on the water quality standards
as specified in Rule 1303.1 .E of PRWQS, and the WQC.
9. Solids and Other Matter: The effluent limitation is based on the water quality standards as specified in Rule
1303.1 .A of PRWQS, and the WQC.
10. Copper, Lead, Residual Chlorine, and Zinc: The effluent limitation is based on the water quality standards
as specified in Rule 1303.1.J.1 of PRWQS, and the WQC.
11. Total Ammonia Nitrogen (TAN): The effluent limitation is based on the water quality criterion for Class SD
waters as specified in Rule 1303.2 C.2.I of PRWQS, and the WQC.
12. Total Phosphorus: The effluent limitation is based on the water quality criterion for Class SD waters as
specified in Rule 1303.2 C.2.n of PRWQS, and the WQC.
NPDES Fact Sheet 3
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Puerto Rico Aqueduct and Sewer Authority NPDES NO. PR0026794
Minillas WTP
B. Effluent Limitations Summary Table
1. Outfall Number 001
Parameter
Units
Effluent limitations
Averaging
period
Highest
Reported Value
(1)
Existing
limits
Final
limits
Basis
Notes
BOD5
mg/L
Daily maximum
-
5.0
5.0
WQBEL
(1)
Color
Pt-Co
Daily maximum
15
15
15
WQBEL
(1)
Copper
Mg/i
Daily maximum
543
8.4
7.7
WQBEL
(1)
Cyanide
Mg/i
Daily maximum
-
-
-
WQBEL
(1)
Dissolved Oxygen
mg/L
Daily Minimum
3.02
No less than
5.0
No less than
5.0
WQBEL
(1)
Flow
MGD
Daily maximum
0.60
0.150
0.150
WQBEL
(1)
Lead
Mg/L
Daily maximum
74.80
2.7
2.4
WQBEL
(1)
Mercury
Mg/L
Daily maximum
-
-
-
WQBEL
(1)
pH
su
Daily min/maxim
6.21 - 8.09
6.0-9.0
6.0-9.0
WQBEL
(1)
Residual Chlorine
Mg/L
Daily maximum
1,260
11
11
WQBEL
(1)
Suspended, Colloidal or
Setteable Solids
ml/L
Daily maximum
800
Monitor
Monitor
WQBEL
(1)
Temperature
"C
Daily maximum
28.9
32.2 °C max
30 °C max
WQBEL
(1)
Total Ammonia Nitrogen
(TAN)
mg/L
Daily maximum
263
Monitor
Monitor
WQBEL
(1)
Total Dissolved Solids
mg/L
Daily maximum
-
-
500
WQBEL
(1)
Total Phosphorus
Mg/L
Daily maximum
12830
160
160
WQBEL
(1)
Turbidity
NTU
Daily maximum
4300
50
50
WQBEL
(1)
Zinc
Mg/L
Daily maximum
197
107.53
99.34
WQBEL
(1)
Note: Dashes (-) indicate there are no effluent data, no limitations, or no monitoring requirements for this parameter.
(1) Wastewater data from DMRs dated September 30, 2020 to August 31, 2022.
NPDES Fact Sheet 4
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Puerto Rico Aqueduct and Sewer Authority NPDES NO. PR0026794
Minillas WTP
2. Outfall 001 Narrative Limitations
a. The waters of Puerto Rico must not contain any substance, attributable to the discharge at such
concentration which, either alone or as result of synergistic effects with other substances, is toxic or
produces undesirable physiological responses in humans, fish, or other fauna or flora.
b. The discharge must not cause the presence of oil sheen in the receiving water body.
c. The waters of Puerto Rico must not contain floating debris, scum, or other floating materials attributable
to discharges in amounts sufficient to be unsightly or deleterious to the existing or designated uses of the
water body.
d. Solids from wastewater sources must not cause deposition in or be deleterious to the existing or
designated uses of the waters.
e. Taste and odor-producing substances must not be present in amounts that will interfere with primary
contact recreation, or will render any undesirable taste or odor to edible aquatic life.
f. Except by natural causes, no heat may be added to the waters of Puerto Rico, which would cause the
temperature of any site to exceed 86°F (30°C).
C. Monitoring Requirements
NPDES regulations at 40 CFR 122.48 require that all permits specify requirements for recording and reporting
monitoring results. The Part III of the Permit establishes monitoring and reporting requirements to implement
federal and state requirements. The following provides the rationale for the monitoring and reporting requirements
for this facility.
1. Effluent Monitoring Requirements
Effluent monitoring frequency and sample type have been established in accordance with the
requirements of 40 CFR 122.44(i) and recommendations in EPA's TSD. Consistent with 40 CFR Part 136
monitoring data for toxic metals must be expressed as total recoverable metal. Effluent monitoring and
analyses shall be conducted in accordance with EPA test procedures approved under 40 CFR Part 136,
Guidelines Establishing Test Procedures for the Analysis of Pollutants Under the Clean Water Act, as
amended. For situations where there may be interference, refer to Solutions to Analytical Chemistry
Problems with Clean Water Act Methods (EPA 821-R-07-002). A licensed chemist authorized to practice
the profession in Puerto Rico shall certify all chemical analyses. All bacteriological tests shall be certified
by a microbiologist or licensed medical technologist authorized to practice the profession in Puerto Rico.
The sampling point for Outfall 001 shall be located immediately after the primary flow measuring device
of the effluent of the treatment system.
D. Compliance with Federal Anti-Backsliding Requirements and Puerto Rico's Anti-Degradation Policy
Federal regulations at 40 CFR 131.12 require that state water quality standards include an anti-degradation policy
consistent with the federal policy. The discharge is consistent with the anti-degradation provision of 40 CFR
131.12, 72 Federal Register 238 (December 12, 2007, pages 70517-70526) and DNER's Anti-Degradation Policy
Implementation Procedure in Attachment A of PRWQSR. In addition, CWA sections 402(o)(2) and 303(d)(4) and
federal regulations at 40 CFR 122.44(1) prohibit backsliding in NPDES permits. Further, the Region 2
Antibacksliding Policy provides guidance regarding relaxation of effluent limitations based on water quality for
Puerto Rico NPDES permits. These anti-backsliding provisions require effluent limitations in a reissued permit to
be as stringent as those in the previous permit with some exceptions where limitations may be relaxed.
• The water quality-based effluent limitation from the previous permit for Lead, BODs, Copper,
Temperature, and Zinc have been replaced with a more stringent water quality-based limitation in
the Intent to Issue a WQC issued by the DNER. Pursuant to Section 401 (d) of the Act and 40 C.F.R.
122.44 (d) and 124.55, all State certified limitations and requirements contained in a Section 401
certification must be incorporated into a NPDES permit issued by EPA. The water quality-based
effluent limitations referenced in this paragraph have been included in the draft NPDES permit, based
on DNER's Intent to Issue a Water Quality Certificate.
NPDES Fact Sheet 5
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Puerto Rico Aqueduct and Sewer Authority NPDES NO. PR0026794
Minillas WTP
PART II. RATIONALE FOR STANDARD AND SPECIAL CONDITIONS
A. Standard Conditions
In accordance with 40 CFR 122.41, standard conditions that apply to all NPDES permits have been incorporated
by reference in Part IV.A.1 of the permit and expressly in Attachment B of the permit. The Permittee must comply
with all standard conditions and with those additional conditions that are applicable to specified categories of
permits under 40 CFR 122.42 and specified in Part IV.A.2 of the Permit.
B. Special Conditions
In accordance with 40 CFR 122.42 and other regulations cited below, special conditions have been incorporated
into the permit. This section addresses the justification for special studies, additional monitoring requirements,
Best Management Practices, Compliance Schedules, and/or special provisions for POTWs as needed. The
special conditions for this facility are as follows:
1. Special Conditions from the Water Quality Certificate
In accordance with 40 CFR 124.55, EPA has established Special Conditions from the WQC in the permit
that DNER determined were necessary to meet PRWQSR. The Special Conditions established in this
section are only those conditions from the WQC that have not been established in other parts of the
permit.
2. Best Management Practices (BMP) Plan
In accordance with 40 CFR 122.2 and 122.44(k), BMPs are schedules of activities, prohibitions of
practices, maintenance procedures, and other management practices to prevent or reduce the pollution to
waters of the United States. The Permittee is required to develop a BMP Plan in Part IV.B.3.a of the
permit to control or abate the discharge of pollutants.
3. Compliance Schedules
A compliance schedule has not been authorized for any pollutant or parameter in the permit on
the basis of 40 CFR 122.47.
PART III. COMPLIANCE WITH APPLICABLE PROVISIONS OF OTHER FEDERAL LAWS OR
EXECUTIVE ORDERS
A. Coastal Zone Management Act
Under 40 CFR 122.49(d), and in accordance with the Coastal Zone Management Act of 1972, as amended,
16 United States Code (U.S.C.) 1451 etseq. section 307(c) of the act and its implementing regulations (15 CFR
Part 930), EPA may not issue an NPDES permit that affects land or water use in the coastal zone until the
Permittee certifies that the proposed activity complies with the Coastal Zone Management Program in Puerto
Rico, and that the discharge is certified by the Commonwealth of Puerto Rico to be consistent with the
Commonwealth's Coastal Zone Management Program. The Permittee has indicated the outfall is not in a
coastal area managed by the Commonwealth's Coastal Zone Management Program and, although nearby,
EPA has determined it will not affect the coastal area. Therefore, the requirements of 40 CFR 122.49(d) do
not apply to this discharge.
B. Endangered Species Act
Under 40 CFR 122.49(c), EPA is required pursuant to section 7 of the Endangered Species Act (ESA), 16 U.S.C.
1531 etseq. and its implementing regulations (50 CFR Part 402) to ensure, in consultation with the National
Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (USFWS) that the discharge authorized by
the permit is not likely to jeopardize the continued existence of any endangered or threatened species or
adversely affect its critical habitat. On April 16, 2009, EPA designated PRASA (a non-Federal representative) to
conduct informal consultations or prepare a biological assessment for Section 7 Consultations, according to 50
CFR 402.8. In the past, no federally listed endangered or threatened species, or critical habitat, are in the vicinity
of the discharge. Therefore, it has been determined that the discharge is not likely to affect species or habitat
listed under the ESA.
NPDES Fact Sheet 6
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Puerto Rico Aqueduct and Sewer Authority NPDES NO. PR0026794
Minillas WTP
C. Environmental Justice - Not Applicable
D. Coral Reef Protection - Not Applicable
E. Climate Change
EPA has considered climate change when developing the conditions of the permit. This is in accordance with the
draft National Water Program 2012 Strategy: Response to Climate Change that identifies ways to address climate
change impacts by NPDES permitting authorities (77 Federal Register 63, April 2, 2012, 19661-19662). Climate
change is expected to affect surface waters in several ways, affecting both human health and ecological
endpoints. As outlined in the draft National Water Program 2012 Strategy, EPA is committed to protecting surface
water, drinking water, and ground water quality, and diminishing the risks of climate change to human health and
the environment, through a variety of adaptation and mitigation strategies. These strategies include encouraging
communities and NPDES permitting authorities to incorporate climate change strategies into their water quality
planning, encouraging green infrastructure and recommending that water quality authorities consider climate
change impacts when developing water load and load allocations for new TMDLs, identifying and protecting
designated uses at risk from climate change impacts. The 2010 NPDES Permit Writers' Manual also identifies
climate change considerations for establishing low-flow conditions that account for possible climatic changes to
stream flow. The conditions established in the permit are consistent with the draft National Water Program 2012
Strategy.
F. National Historic Preservation Act
Under 40 CFR 122.49(b), EPA is required to assess the impact of the discharge authorized by the permit on any
properties listed or eligible for listing in the National Register of Historic Places (NRHP) and mitigate any adverse
effects when necessary in accordance with the National Historic Preservation Act, 16 U.S.C. 470 et seq. EPA's
analysis indicates that no soil disturbing or construction-related activities are being authorized by approval of this
permit; accordingly, adverse effects to resources on or eligible for inclusion in the NHRP are not anticipated as
part of this permitted action.
G. Magnuson-Stevens Fishery Conservation and Management Act - NOT APPLICABLE
PART IV. PUBLIC PARTICIPATION
The procedures for reaching a final decision on the draft permit are set forth in 40 CFR Part 124 and are
described in the public notice for the draft permit, which is published which is published on EPA's website at
https://www.epa.gov/npdes-permits/puerto-rico-npdes-permits. Included in the public notice are requirements for
the submission of comments by a specified date, procedures for requesting a hearing and the nature of the
hearing, and other procedures for participation in the final agency decision. EPA will consider and respond in
writing to all significant comments received during the public comment period in reaching a final decision on the
draft permit. Requests for information or questions regarding the draft permit should be directed to
Hector Ortiz
EPA Region 2, Caribbean Environmental Protection Division
Permit Writer Phone: 787-977-5883
Permit Writer Email: ortiz.hector@epa.gov
NPDES Fact Sheet
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Puerto Rico Aqueduct and Sewer Authority NPDES NO. PR0026794
Minillas WTP
ATTACHMENT A — FACILITY MAP AND FLOW SCHEMATIC
The facility map and flow schematic are attached as provided by the discharger in the application.
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