&EPA
         United States
         Environmental Protection
         Agency
Model NPDES Permit for
Discharges Resulting From
The Cleanup of Gasoline
Released From
Underground Storage Tanks

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                          PART I

INSTRUCTIONS FOR MODEL NPDES PERMIT PACKAGE FOR DISCHARGES
     RESULTING  FROM THE CLEANUP OF GASOLINE RELEASED
              FROM UNDERGROUND STORAGE TANKS

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                               TABLE OP CONTENTS



                                                                     Page

1.0  INSTRUCTIONS FOR MODEL NPDES PERMIT PACKAGE	      1-1

1.1  NPDES PERMITTING AUTHORITY	      1-2

     1.1.1  NPDES Permit Application Requirements	      1-3

1.2  MODEL NPDES PERMIT	      1-3

     1.2.1  Authorization to Discharge	      1-4
     1.2.2  Effluent Limitations and Monitoring Requirements...      1-4
     1.2.3  Standard Conditions	      1-5
     1.2.4  Special Conditions	      1-5

1.3  FACT SHEET	      1-6

1.4  DECISION TOOL FOR DEVELOPING WATER QUALITY-BASED
     EFFLUENT LIMITATIONS	      1-6

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                1.0  INSTRUCTIONS FOR MODEL NPDES  PERMIT PACKAGE

      This package was developed to assist U.S.  Environmental  Protection Agency
 (EPA) Regional and State permitting authorities in writing National  Pollutant
 Discharge Elimination System (NPDES) permits for  direct discharges to  surface
 waters resulting from the cleanup of gasoline from leaking underground storage
 tank (UST) sites.

      The UST program originally was mandated under Subtitle I of  the Resource
 Conservation and Recovery Act of 1976 (RCRA) to regulate  the  installation,
 operation, and closure of USTs.   The Hazardous  and Solid  Vaste Amendments of
 1984 (HSWA) strengthened the existing RCRA provisions  to  provide  for a com-
 prehensive regulatory program to address  USTs and releases of regulated sub-
 stances (primarily petroleum products) into the environment.  Like other RCRA
 programs,  States may be authorized by EPA to implement their own  UST programs.

      When  a release is detected,  the enforcement  agency (either EPA  or its
 delegated  State) has the authority to require the owner/operator  to  conduct a
 release response and corrective  action to cleanup the release.  Depending on
 the  situation,  the EPA or delegated State may choose to conduct the  release
 response or corrective action.   Any discharge to  surface  waters occurring
 during a release response or corrective action  would be subject to regulation
 under an NPDES  permit.

      This  Model Permit  package is  only intended for use at facilities  where
 gasoline has  been released and the cleanup  (or  corrective action) involves a
 release  or discharge of waters and wastewaters  to  surface waters.  It  is not
 intended for  use at  sites where  nongasoline  products are  the primary source of
 contamination (e.g.,  jet  fuels,  fuel  oil, diesel  fuel,  etc.).   This package
 consists of  four documents.   Part  I,  Instructions  for Model NPDES Permit
Package, briefly describes NPDES permit requirements.  The remaining three
documents  are briefly described  below:
                                      1-1

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      •  Part II - Model NPOES Permit For Discharges Resulting From The Cleanup
         Of Gasoline Released From Underground  Storage Tanks
      •  Part III - Fact Sheet For Model  NPDES  Permit For Discharges Resulting
         From The Cleanup Of Gasoline Released  From Underground Storage Tanks
      •  Part IV - Decision Tool For Developing Water Quality-Based Effluent
         Limitations.

      The UST Model Permit Package is available on diskette in WordPerfect*
version  4.2.   In addition,  the Model Permit  Package can be made available in
IBM®  Document Control Architecture revisable-format-text (DCA RFT) or ASCII
formats  for use on IBM PC (or compatibles) or  for Apple Macintosh® computers.

1.1   NPDES PERMITTING AUTHORITY
      This Model Permit is intended for use in  developing individual, site-
specific NPDES permits.   NPDES permit application requirements (discussed in
Section  1.1.1 below)  may vary depending  upon the NPDES permitting authority.
Under the NPDES Program,  a  total  of 57 jurisdictions are regulated including
the 50 States plus the District of Columbia, Puerto Rico, the Virgin Islands,
American Samoa,  Guam,  West  Marinaras, and U.S. Trust Territories.  Thirty-nine
of these jurisdictions have the authority to conduct their own NPDES program.
In the remaining 18 jurisdictions,  EPA is responsible for implementing the
NPDES program.

      According to 40  CFR §122.28,  States can apply for the authority to issue
general  NPDES permits.   General permits apply  the same set of limitations to a
group of dischargers  that discharge the same types of vastes, require the same
effluent  limitations  or  operating conditions,  and require similar monitoring.
The information  provided  in this  Model Permit  Package may also be used as the
basis  for  developing  a general  permit.  Thirteen NPDES-approved States have
the authority to issue general  permits.  EPA can issue general permits in all
of the 18  jurisdictions where EPA is the permitting authority.  Currently,
general  permits  cannot be issued  in 26 jurisdictions.
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 1.1.1  NPDES Permit Application Requirements
      Dischargers must submit an NPDES permit application before an individual
 NPDES permit can be issued.  The information provided in the permit applica-
 tion serves as one source of data for developing NPDES permit requirements.
 States may have their ovn permit application forms and requirements but must
 request from the applicant as a minimum,  the information required by the
 Federal NPDES regulations.

      Some of the major constituents of gasoline can be detected by analytical
 methods for volatile organlcs.   Analytical methods are specified at 40 CFR
 Part 136.  Certain other chemicals (e.g.,  xylene)  should be  tested for if  the
 applicant believes that other substances  are present in the  discharge,  for
 which there are no approved analytical methods.   For these other substances,
 the applicant is required to use another  suitable  analytical method.   One  such
 method that is particularly suitable for  potential gasoline  constituents is
 EPA Method 8240.   This method is an approved RCRA  method for the analysis  of
 volatile organic compounds such as xylene.

      The data provided in the NPDES permit  application should be carefully
 reviewed by the permit writer.   Specifically, information such as discharge
 flow rates and the presence of  toxic pollutants  should be carefully evaluated.
 For example,  the effluent limits in the Model Permit  may be  modified  to
 account  for the presence of additional pollutants.   Similarly,  the monitoring
 requirements  may need  to be modified based  upon  unique discharge characteris-
 tics  (e.g.,  batch discharges).

 1.2   MODEL NPDES  PERMIT
      This  Model  Permit  is based  on the approach  taken,  in part,  by several
 States and EPA Regional Offices.   Vhile a Model  Permit  may not  be applicable
 in  every  situation,  the information contained in this  Model  Permit  Package
 should serve  as a framework for  the permit writer  and  expedite  the NPDES
 permit issuance process.   Key elements of the Model Permit include chemical-
 specific effluent  limitations, standard conditions, and  special  conditions
 including  Best Management  Practices  (BMPs) and biomonitoring  requirements.
These elements are recommended for  inclusion  in all NPDES permits  for
discharges  from the cleanup  of gasoline-related UST sites.
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      This Model Permit was-, based principally on  guidance  provided  by  the NPDES
 regulations and the Training Manual For NPDES Permit Writers, EPA  Office of
 Water and Permits,  May 1987.  However,  the Model Permit should  be  modified to
 conform with State  regulations and policies,  air and ground-water  protection
 strategies or requirements,  or site-specific conditions.  This  Model  Permit
 differs from most NPDES permits in that gasoline cleanups typically last for
 one  or two years while most  NPDES permits  are issued for  a  five year  period.
 Due  to this shorter time span, biomonitoring requirements may need to be
 altered or deleted  in some cases.   The  following subsections highlight  four
 major components of the Model Permit.

 1.2.1  Authorization to Discharge
      The "Authorization to Discharge" section of the Model  Permit  must  be
 completed by the permit writer.   In order  to fill in this section  the
 following information must be provided:

      •  Name and Address of  Facility
      •  Outfall Designations
      •  Receiving Water Name and Present/Future  Water Quality Standard
         Classification of Receiving Water
      •  Effective Date of Permit
      •  Expiration  Date of Permit.

 1.2.2   Effluent Limitations  and  Monitoring Requirements
      Part  I of  the  Model Permit  provides technology-based effluent limitations
 and monitoring  requirements  for  surface water discharges  from corrective
 actions  at  gasoline underground  storage  tank  sites.  Specifically, effluent
 limitations have been developed  for benzene and  the aggregate parameter 8ETX
 (benzene,  ethylbenzene,  toluene,  and the xylenes).  The technology basis used
 to develop these limits is free  product recovery, followed  by air  stripping.
These  effluent  limits are based  on  the  characterization of  constituents
 commonly  found  in gasoline as  described in the Fact Sheet (listed  in  Tables
3-1, 5-1,  and 5-2 of the Fact  Sheet).  Additional site-specific constituents,
such as gasoline additives,  may  be  reported in the sampling data required as
                                      1-4

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 part of the NPDES permit application.   Should  this  occur,  the  permit  writer

 may need to develop additional effluent limitations.


      NOTE:   An optional set of effluent limitations has also been developed
      based  upon consideration of the potential impacts of  treatment costs,
      particularly on smaller firms  that ovn  retail  motor fuel  outlets.  These
      optional effluent  limitations,  based  upon a  reduction in  air stripping
      efficiency,  could  be used by permit writers  if a firm could not  afford
      the cost of  compliance with the more  stringent effluent limitations.
      However, if  these  optional effluent limitations, as with  all technology-
      based  limitations,   would result  in the exceedance of water quality
      standards and/or endanger aquatic life, human  health,  or  the environment,
      then water-quality based limitations  should  be established.


      Weekly flow  and chemical-specific monitoring is recommended based on EPA
 guidelines.   In addition,  chronic toxicity testing  requirements are recom-
 mended  and  provided in  the permit.   Alternative approaches to  establishing

 biomonitoring requirements,  such as  the whole  effluent toxicity screening

 approach, are provided  in the Fact Sheet.


 1.2.3   Standard Conditions

     The  standard conditions established in  Part  II of the Model NPDES Permit

 are  based on  those required  in 40 CFR  §122.41.  Standard conditions may vary
 from State  to State.  Therefore,  the permit  writer  is free to  substitute State
 requirements  for  the Standard Conditions in  this  Model Permit  as appropriate.


 1.2.4   Special  Conditions

     Part III  of  the Model Permit requires the  permittee to develop a Best

Management  Practices (BMP) plan.  In addition,  biomonitoring is recommended

for  inclusion  in  each gasoline UST cleanup NPDES  permit.   The  Fact Sheet

provides additional guidance for  developing  and implementing biomonitoring

requirements.   Additional  special conditions may  be required to address

site-specific problems. The  conditions  presented  in this Model Permit are

severable, which  means if  one condition  is proven to be invalid the other

conditions still  hold.  Regions and  States may  choose to incorporate addi-

tional  requirements  in accordance with  their own  policies  on BMPs and bio-

monitoring requirements.
                                      1-5

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 1.3   FACT SHEET
      The NPDES regulations [40 CFR §124.8(a)]  require  the preparation of a
 Fact  Sheet for every major NPDES permit  to document the facts, methodology,
 and basis used to develop the permit.  For purposes of this Model Permit it is
 assumed  that  the discharge from an UST cleanup may constitute a major point
 source discharge.   Therefore,  a Fact Sheet has been prepared as part of this
 package  that  provides a rationale for the effluent limitations, monitoring
 requirements,  and special conditions set forth in the Model Permit.  This Fact
 Sheet should  be reviewed carefully by the permit writer before using the Model
 Permit.   The  rationale given  in the Fact Sheet may need to be modified to
 account  for site-specific considerations.

 1.4   DECISION TOOL FOR DEVELOPING WATER QUALITY-BASED EFFLUENT LIMITATIONS
      Both the Clean Water Act  and NPDES regulations require all NPDES permits
 to include effluent limitations to achieve applicable State water quality
 standards.  Since  State standards are typically specified on a site-specific
 basis, water  quality-based effluent limitations have not been developed for
 this  Model Permit.   However, a Decision Tool for addressing site-specific
water quality  criteria is presented for use by State and EPA Regional permit
writers.   This  Decision Tool  includes EPA's ambient water quality criteria for
 the protection  of  aquatic life and human health for benzene, ethylbenzene,
 toluene,  xylene, and  naphthalene,  the only constituents of gasoline for which
water quality  criteria have been  established.
                                      1-6

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             MODEL NPDES PERMIT FOR DISCHARGES RESULTING FROM THE
          CLEANUP OF GASOLINE RELEASED FROM UNDERGROUND STORAGE TANKS
                      AUTHORIZATION TO DISCHARGE  UNDER THE
                NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM

 In compliance with the provisions of the Federal Water  Pollution  Control Act,
 as amended (33 U.S.C. Section 1251 et seq.,  hereinafter the  "Clean Water Act"
 or "Act"), and attendant  regulations incorporated by the U.S.  Environmental
 Protection Agency under Title 40 of the Code of  Federal Regulations,
                (Name of Discharger)  (hereinafter "Permittee")

 is  authorized  to  discharge  from  (description of  facility), located at

                    (insert Address)	

 to  the  receiving  waters named  (identify)	 in  accordance with
 effluent  limitations, monitoring  requirements, and other conditions set forth
 in  Parts  I, II, and  III herein.   The permit consists of this cover sheet, Part
 I - 1 page, Part  II  - 13 pages, and Part III - 3 pages.

All references to Title 40 of  the Code of Federal Regulations  are to regula-
 tions that are in effect on  the effective date of this permit.  Unless other-
vise specified herein, all terms  are defined as provided in the applicable
 regulations in Title 40 of the Code of Federal Regulations.

This permit shall become effective on (insert date).  This permit and the
authorization to  discharge shall  expire at midnight (insert date)	.
     Date                                               Director
                                            (or Other Authorized Official)

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                                                                     Page 1-1
                                                         Permit No.
 PART  I
      EFFLUENT  LIMITATIONS AND  MONITORING REQUIREMENTS;  Outfall 001 -
      discharge resulting from  gasoline underground storage tank corrective
      actions.

      During  the period  beginning on  the effective date of the permit and
      lasting through  the term  of this permit, the permittee is authorized to
      discharge treated  vater and vastevater that has been contaminated by
      gasoline.

      Such discharges  shall be  limited and monitored by the Permittee as
      specified  below:
Effluent Characteristic
Flow, MGD

Benzene

Total BETX*
Discharge Limitations
Hicrograms per Liter
Daily Avg.  Daily Max.

Report      Report

   5           5

 100         100
Monitoring Requirements


Measurement
 Frequency   Sample Type

1 per week  'Continuous

1 per week   Grab

1 per veek   Grab
    The pR shall neither be less than 6.0 standard units nor greater than 9.0
    standard units and shall be monitored once per veek by grab sample.

    There shall be no discharge of floating solids or visible foam in other
    than trace amounts.

    Samples taken in compliance vith the monitoring requirements specified
    above shall be taken at the following location(s):   nearest accessible
    point after final treatment but prior to actual discharge or nixing vith
    the receiving vaters.

  * BETX shall be measured as the sum of benzene,  ethylbenzene, toluene, and
    xylenes.  EPA methods 602,  624, or 1624 shall  be used for the measurement
    of benzene, ethylbenzene, and toluene.   EPA method  8240,  or an equivalent
    method, shall be used for the measurement of xylenes including ortho-,
    meta-,  and para-xylene.  (Note:  Depending on  Regional/State policy, EPA
    Method  8240 may be used as  a substitute or equivalent for the CUA methods
    602,  624,  or 1624 required  under the CWA in 40 CFR  Part 136.)

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                                                             Optional Page 1-1
                                                         Permit No. 	

             OPTIONAL EFFLUENT  LIMITATIONS FOR DISCHARGES RESULTING
     FROM THE  CLEANUP OF GASOLINE RELEASED FROM UNDERGROUND STORAGE TANKS
PART  I

A.
EFFLUENT LIMITATIONS AND MONITORING REQUIREMENTS!   Outfall 001 -
discharge resulting from gasoline underground storage tank corrective
actions.

During the period beginning on the effective date  of the permit and
lasting through the term of this permit, the permittee is authorized to
discharge treated water and vastevater that has been contaminated by
gasoline.

Such discharges shall be limited and monitored by  the Permittee as
specified below:
Effluent Characteristic
Flow, MGD

Benzene

Total BETX*
                         Discharge Limitations
                         Micrograms per Liter
                         Daily Avg.   Daily Max.

                         Report      Report

                            50          50

                           750         750
Monitoring Requirements


Measurement
 Frequency   Sample Type

1 per week   Continuous

1 per week   Grab

1 per week   Grab
    The pH shall neither be less than 6.0 standard units nor greater than 9.0
    standard units and shall be monitored once per week by grab sample.

    There shall be no discharge of floating solids or visible foam in other
    than trace amounts.

    Samples taken in compliance with the monitoring requirements specified
    above shall be taken at the following location(s):  nearest accessible
    point after final treatment but prior to actual discharge or mixing with
    the receiving waters.

  * BETX shall be measured as the sum of benzene, ethylbenzene, toluene, and
    xylenes.   EPA methods 602, 624, or 1624 shall be used for the measurement
    of benzene, ethylbenzene, and toluene.  EPA method 8240, or an equivalent
    method, shall be used for the measurement of xylenes including ortho-,
    meta-,  and para-xylene.  (Note:  Depending on Regional/State policy, EPA
    Method  8240 may be used as a substitute or equivalent for the CVA methods
    602, 624,  or 1624 required under the CVA in 40 CFR Part 136.)

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                PART II

   MODEL NPDES PERMIT POR DISCHARGES
 RESULTING  FROM THE CLEANUP OF GASOLINE
RELEASED FROM UNDERGROUND STORAGE TANKS

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                                                                     Page  II-l
                                                          Permit No.
 PART II

 STANDARD CONDITIONS


 SECTION A.   GENERAL CONDITIONS

 1.   Duty to Comply

 The Permittee must comply with all conditions  of  this permit.  Any permit
 noncompliance constitutes a violation  of  the Clean Vater Act and is grounds
 for enforcement action,  for permit termination, permit revocation and permit
 reissuance, or modification,  or for denial  of  a permit renewal application.

 2.   Toxic Pollutants

 The Permittee shall comply with effluent  standards or prohibitions established
 under Section 307(a) of  the Clean  Vater Act for toxic pollutants within  the
 time provided in the regulations that  establish those standards or pro-
 hibitions,  even if the permit has  not  yet been modified to incorporate the
 requirement.

 3.   Penalties for Violations  of Permit Conditions

 Any person  vho violates  a permit condition  is subject to a civil penalty not
 to  exceed $10,000 per day for each violation.  Any person who willfully or
 negligently violates permit conditions is subject to a fine of not less than
 $2,500 nor  more than $25,000  per day for  each violation, or by imprisonment
 for not  more than 1 year,  or  both.

 4.   Duty to Reapply

 (a)   If  the Permittee wishes  to continue an activity regulated by this permit
 after the expiration date of  this  permit, the Permittee must apply for and
 obtain a renewal  permit.   The Permittee shall submit a new application at
 least 180 days before the expiration date of this permit, unless permission
 for  a later date  has been granted  by the Director.

 (b)   Where  EPA is the Permit  Issuing Authority for the renewal permit, the
 terms and conditions of  this  permit  continue in force under 5 U.S.C. Section
 558(c) until  the  effective date of  the new permit (or permit denial) only if
 the  Permittee  has submitted a timely and complete application under 40 CFR
 Section  122.21  for a renewal  permit  and the Permit Issuing Authority, through
 no  fault  of the Permittee,  does not  issue a new permit (or deny the permit)
 before the  expiration date of this  permit.  The permit continued under
 5 U.S.C.  Section  558(c)  remains fully  effective and enforceable, including
 subject  to  the actions set  forth in  40 CFR §122.6(c).

 5.  Duty  to Mitigate

The Permittee  shall  take  all  reasonable steps to minimize or prevent any
 discharge in violation of  this  permit  that has a reasonable likelihood of
 adversely affecting  human  health or  the environment.

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                                                                    Page II-2
                                                         Permit No. 	
 6.   Permit Actions (Modification,  Revocation  and Reissuance, or Termination)

 (a)   This  permit  may be modified,  revoked  and reissued, or terminated for
 causes  (as described in 40 CFR Sections  122.62, 122.63, and 122.64),
 including, but not limited to:  violation  of  any terms or conditions of this
 permit;  obtaining this permit by misrepresentation or failure to disclose
 fully all  relevant facts;  or a change  in any  condition that requires either a
 temporary  or permanent reduction or  elimination of the permitted discharge.
 The  filing of a request by the Permittee for  a permit modification, revocation
 and  reissuance, or termination,  or a notification of planned changes or
 anticipated noncompliance, does  not  stay any  permit condition.

 (b)   Notwithstanding Paragraph II-A-6(a) above, if a toxic effluent standard
 or prohibition (including  any schedule of  compliance specified in such
 effluent standard or prohibition)  is established under Section 307(a) of the
 Clean Water Act for a toxic pollutant  that  is present in the discharge and
 such standard or  prohibition is  more stringent than any limitation for such
 pollutant  in this permit,  this permit  may  be  modified or revoked and reissued
 to conform to the toxic effluent standard  or  prohibition.

 (c)   Nothwithstanding Paragraph  II-A-6(a)  above, this permit may be modified,
 or alternatively  revoked and reissued, to  comply with any applicable effluent
 standard or limitation issued or approved  under Sections 301(b)(2)(A), (C),
 (D),  (E),  and (F),  or 304(b)(2)  of the Clean  Water Act, if the effluent
 standards  or limitation so issued  or approved contains different conditions or
 is otherwise more stringent than any effluent limitation in this permit; or
 controls any pollutant not limited in  this  permit.

 7.   Effect of Permit/Other Lavs

 (a)   Issuance of  this permit does  not  convey  any property rights of any sort,
 or any exclusive  privileges,  nor does  it authorize any injury to persons or
 property,  or invasion of other private rights, or any infringement of Federal,
 State, or  local laws or regulations.

 (b)   Nothing in this permit shall  be construed to preclude the institution of
 any  legal  action  or relieve the  Permittee  from any responsibilities,
 liabilities,  or penalties  established  pursuant to any applicable State lav or
 regulation under  authority preserved by  Section 510 of the Clean Water Act.

 (c)   Nothing in this permit shall  be construed to preclude the institution of
any  legal  action  or relieve the  Permittee  from any responsibilities,
liabilities,  or penalties  to which the Permittee is or may be subject to under
Section  311  of the  Act.

 (d)   Except  as provided in permit  conditions  on "Upsets," Paragraph II-B-4
below, and pH Excursions,  Paragraph  II-C-7(c)  below, nothing in this permit
shall be construed  to relieve the  Permittee from civil or criminal penalties
 for noncompliance with a permit  condition.

 (e)   Pursuant  to  Section 509(b)(l)(F)  of the  Clean Water Act, a challenge to
the validity of permit conditions, including  the effluent limitations in Part
I-A of this  permit,  shall  not be a defense  to an enforcement action under
Section  309  or 505  of the  Clean  Water  Act.  Each and every violation of a
permit condition  is subject to an  enforcement  action.

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                                                                     Page II-3
                                                          Permit  No.
 (f) 'Compliance with the terms of this permit does not  constitute a defense to
 any action brought under Section 504 of the Clean Water Act,  or any other lav
 governing protection of public health or welfare, for any imminent and
 substantial endangerment to public health or welfare.

 8.    Onshore or Offshore Construction

 This permit does not authorize or approve the construction of any onshore or
 offshore physical structures or facilities or the undertaking of any work in
 any waters of the United States.

 9.    Inspection and Entry

 The Permittee shall allow the Director,  or an authorized representative,  upon
 the presentation of credentials and other documents as  may be required by law,
 to:

      a.   Enter upon the Permittee's premises where a regulated facility or
          activity is located or conducted,  or where records must be kept  under
          the conditions of this permit;

      b.   Have access to and copy,  at reasonable  times,  any records that must
          be kept under  the conditions  of  this permit;

      c.   Inspect at reasonable times any  facilities, equipment (including
          monitoring and control equipment),  practices,  or  operations' regulated
          or required under this permit; and

     d.   Sample or monitor at  reasonable  times,  for the purposes of ensuring
          permit compliance or  as  otherwise authorized by the  Clean Water  Act,
          any substances or parameters  at  any location.

 10.  Severability

The  provisions of this  permit  are  severable,  and  if any provision  of  this
permit,  or  the application of  any  provision  of this permit  to  any
circumstance,  is held invalid,  the application of  such  provision to other
circumstances,  and the  remainder of  this  permit,  shall  not be  affected
thereby.

SECTION  B.   OPERATION AND  MAINTENANCE  OF  POLLUTION CONTROLS

1.  Proper  Operation and Maintenance

The Permittee  shall at  all  times properly operate  and maintain all  facilities
and systems  of  treatment and control (and related  appurtenances)  that are
installed or used  by the Permittee  to  achieve compliance with  the  conditions
of this  permit.   Proper operation and  maintenance  also  includes  adequate
laboratory  controls and appropriate quality assurance procedures.  This
provision requires  the operation of back-up or auxiliary facilities or  similar
systems  that are  installed  by a Permittee only when  the operation  is necessary
to achieve  compliance with  the conditions of  the permit.

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                                                                    Page II-4
                                                         Permit No. 	
2.  Need to Halt or Reduce not a Defense

It shall not be a defense for a Permittee in an enforcement action that it
would have been necessary to halt or reduce the permitted activity in order to
maintain compliance with the conditions of this permit.

3.  Bypass of Treatment Facilities

     a.  Definitions

    (1) "Bypass" means the intentional diversion of waste streams from any
        portion of a treatment facility, which is not a designed or
        established operating mode for the facility.

    (2) "Severe property damage" means substantial physical damage to
        property, damage to the treatment facilities that renders them
        inoperable, or substantial and permanent loss of natural resources
        that can reasonably be expected to occur in the absence of a bypass.
        Severe property damage does not mean economic loss caused by delays in
        production.

    b.  Bypass Not Exceeding Limitations

        The Permittee may allow any bypass to occur that does not cause
        effluent limitations to be exceeded, but only if it also is for
        essential maintenance to ensure efficient operation.  These bypasses
        are not subject to the provisions of Paragraphs c. and d. of this
        section.

    c.  Notice

    (1) Anticipated bypass.  If the Permittee knows in advance of the need for
        a bypass, it shall submit prior notice, if possible at least ten days
        before the date of the bypass; including an evaluation of the
        anticipated quality and effect of the bypass.

    (2) Unanticipated bypass.  The Permittee shall submit notice of an
        unanticipated bypass as required in Paragraph II-D-6 (24-hour notice).

    d.  Prohibition of Bypass

    (1) Bypass is prohibited and the Permit Issuing Authority may take
        enforcement action against a Permittee for bypass, unless:

        (a) Bypass was unavoidable to prevent loss of life, personal injury,
            or severe and extensive property damage;

        (b) There were no feasible alternatives to the bypass, such as mainte-
            nance of sufficient reserve holding capacity, the use of auxiliary
            treatment facilities, retention of untreated wastes, waste haul-
            ing, or maintenance during normal periods of equipment downtime.
            This condition is not satisfied if adequate back-up equipment

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                                                                     Page  II-5
                                                          Permit No.
             should have been installed  in the  exercise  of  reasonable  engi-
             neering judgment to prevent a bypass  that occurred during normal
             periods of equipment downtime or preventive maintenance;  and

         (c) The Permittee submitted notices as required under Paragraph b. of
             this section.

     (2)  The Permit Issuing Authority may,  within  its authority, approve an
         anticipated bypass,  after considering  its adverse  effects,  if the
         Permit  Issuing Authority determines that  it will meet the  three
         conditions listed above in Paragraph d.(l) of this section.

 4.   Upsets

     "Upset" means an exceptional incident  in which there is unintentional and
     temporary noncompliance with technology-based permit effluent  limitations
     because of  factors beyond  the control  of the  Permittee.  An upset does not
     include noncompliance to the extent caused by operational error,  improp-
     erly designed treatment  facilities,  inadequate treatment facilities, lack
     of preventive maintenance,  or careless or  improper  operation.  An upset
     constitutes an affirmative  defense  to  an action brought for noncompliance
     with such technology-based  permit limitations if the requirements of 40
     CFR  Section 122.Al(n)(3) are met.   (Note that this  provision does not
     apply to water quality requirements).

 5.   A Schedule  of Maintenance

     Any  maintenance of facilities,  which might necessitate unavoidable
     interruption of operation and degradation  of effluent  quality, shall be
     scheduled during noncritical water  quality periods  and carried out in a
     manner approved by the Permitting Authority.

 6.   Removed Substances

     This permit  does not  authorize  discharge of solids, sludge, filter back-
     wash,  or other pollutants removed in the course of  treatment or control of
     wastewaters  to waters of the United  States  unless specifically limited in
     Part  I.

 SECTION  C.   MONITORING AND RECORDS

 1.   Representative Sampling

 Samples  and measurements  taken  as required herein shall be representative of
 the  volume  and nature  of  the monitored  discharge.  All  samples shall  be taken
at the monitoring  points  specified  in this permit and,  unless otherwise
specified,  before  the  effluent  joins or  is diluted by any other wastestream,
body of  water, or  substance.  Monitoring points shall not be changed without
notification to  and  the approval  of  the  Permit Issuing Authority.

2.   Sampling Points

All  samples  shall  be  taken at the monitoring points specified in this permit
and, unless  otherwise  specified,  before  the effluent joins or is diluted by

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                                                                     Page II-6
                                                          Permit  No.
 any other vastestream, body of vater, or substance.   Monitoring points  shall
 not be changed vithout notification to and the approval of  the  Permitting
 Authority.

 3.   Flov Measurements

     Appropriate flow measurement devices and methods  consistent with  accepted
 scientific practices shall be selected and used to ensure  the accuracy  and
 reliability of measurements of the volume of monitored  discharges.  The
 devices shall be installed, calibrated,  and maintained  to ensure that the
 accuracy of the measurements is consistent with the accepted capability of
 that type of device.  Devices selected shall be capable of  measuring  flows
 with a maximum deviation of less than ± 10 percent from the true discharge
 rates throughout the range of expected discharge volumes.   Guidance in
 selection, installation, calibration, and operation of  acceptable flow
 measurement devices can be obtained from the following  references:

     (1) "A Guide of Methods and Standards for the Measurement of Vater  Flow,"
         U.S. Department of Commerce,  National Bureau  of Standards, NBS  Special
         Publication 421, May 1975, 97 pp.   (Available from  the  U.S. Government
         Printing Office, Washington,  DC  20402.   Order  by SD Catalog  No.
         C13.10:421).

     (2) "Vater Measurement Manual," U.S.  Department of  Interior,  Bureau of Re-
         clamation,  Second Edition, Revised Reprint, 1974, 327 pp.  (Available
         from the U.S.  Government Printing Office,  Washington, DC  20402.
         Order by Catalog No.  127.19/2.-V29/2,  Stock No.  S/N  24003-0027).

     (3) "Flow Measurement in Open Channels and Closed Conduits,"  U.S.
         Department  of  Commerce,  National  Bureau of Standards, NBS Special
         Publication 484, October 1977,  982 pp.   (Available  in paper copy or
         microfiche  from National Technical Information  Service  (NTIS),
         Springfield, VA  22151.   Order by NTIS No. PB-273 535/5ST).

     (4) "NPDES Compliance Flow Measurement Manual," U.S. Environmental
         Protection  Agency,  Office of  Vater Enforcement,  Publication MCD-77,
         September 1981,  135 pp.   (Available from the  General Services
         Administration (8BRC),  Centralized Mailing Lists Services, Building
         41,  Denver  Federal  Center,  Denver,  CO  80225).

4.   Monitoring Procedures

Monitoring must  be  conducted  according to  test  procedures approved under 40
CFR  Part  136,  unless other  test  procedures have  been  specified  in  this
permit.

5.   Calibration

The  Permittee  shall periodically calibrate and  perform  maintenance on all
monitoring and analytical equipment used  to monitor the  pollutants discharged
under  this permit,  at  intervals  that  will  ensure the  accuracy of  measurements.

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                                                                     Page II-7
                                                          Permit  No.
 6.   Testing Variability Not a Defense

 If  the Permittee believes or has reason to believe  that  monitoring  or  sampling
 results reflect an analytical variability so as  to  render  the  results
 inaccurate, he may monitor or sample more frequently  than  required  by  this
 permit.  The validity of the testing results,  whether or not the  Permittee  has
 monitored or sampled more frequently,  shall not  be  a  defense to an  enforcement
 action under Sections 309 or 505 of  the Clean Water Act.

 7.   pH Effluent Limitations Under Continuous Monitoring

 Notwithstanding Part I of this permit,  where the Permittee continuously
 measures the pH of water and wastewater discharges  pursuant to a  requirement
 or  option in this permit, excursions from the  range provided in Part I are
 permitted,  provided:

     (a)  The pH limitation in Part I of this permit is based upon a
          requirement imposed under 40 CFR Part 401, Subpart N.

     (b)  The total time during which the pH values  are outside the  required
          range of pH values shall not  exceed 446 minutes in any calendar
          month.

     (c)  No individual excursions from the range of pH values  shall exceed 60
          minutes.

     (d)  For purposes  of this section,  an "excursion" is an unintentional and
          temporary incident in which the pH value of  the discharge  exceeds the
          range set forth in Part  I of  this permit.  The  number of individual
          excursions  exceeding 60  minutes and the total accumulated  excursion
          time in  minutes occurring in  any calendar  month shall be reported in
          accordance  with Paragraph II-D-4 of this permit.

8.   Penalties for Tampering

The  Clean Water Act  provides  that any  person who falsifies, tampers with, or
knowingly renders  inaccurate,  any monitoring device or method  required to be
maintained  under  this  permit  shall,  upon conviction, be punished  by a fine of
not  more  than $10,000  per violation, or  by imprisonment for not more than 2
years per violation, or  by both.

9.   Retention of Records

The  Permittee shall  retain records of all  monitoring information,  including
all  calibration and  maintenance records  and  all  original strip chart
recordings  for continuous  monitoring instrumentation,  copies of all reports
required  by  this permit,  and  records of  all  data  used to complete the
application  for this permit,  for a period  of at  least three years from the
date of the  sample, measurement, report  or application.  This  period may be
extended  by  the Permitting  Authority at  any  time.

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                                                                    Page II-B
                                                         Permit No. 	

10.  Monitoring  Records

Records of monitoring  information  shall  include:

     a.  The  date,  exact  place, and  time of sampling or measurements;
     b.  The  individual(s)  who performed the sampling or measurements;
     c.  The  date(s) analyses were performed;
     d.  The  individual(s)  who performed the analyses;
     e.  The  analytical  techniques or methods used; and
     f.  The  results of  such analyses.

11.  Additional  Monitoring  by the  Permittee

If  the Permittee monitors any pollutant  more frequently than required by this
permit, using test  procedures approved under 40 CFR Part 136 or as specified
in  this permit,  the results of this  monitoring shall be included in the
calculation and  reporting of the data submitted in the Discharge Monitoring
Report (DMR).  Such increased frequency  shall also be indicated.

12.  Averaging of Measurements

Calculations  for limitations that  require averaging of measurements shall
utilize an arithmetic  mean  unless  otherwise specified by the Permitting
Authority in  the permit.

SECTION D.  REPORTING  REQUIRHENTS

1.  Change in Discharge

The Permittee shall give  notice to the Permitting Authority as soon as
possible of any  planned  physical alterations or additions to the permitted
facility.  Notice is required only when:

    a.  The alteration or addition to a  permitted facility may meet one of the
        criteria for determining whether a facility is a new source; or

    b.  The alteration or addition could significantly change the nature or
        increase the quantity of pollutants discharged.  This notification
        applies  to  pollutants that are subject neither to effluent limitations
        in the permit, nor  to notification requirements under Section D,
        Paragraph 10(a).

2.  Anticipated  Noncompliance

The Permittee  shall give  advance notice  to the Permitting Authority of any
planned change in the  permitted facility or activity that may result in
noncompliance with  permit requirements.  Any maintenance of facilities, which
might necessitate unavoidable interruption of operation and degradation of
effluent quality, shall be  scheduled during noncritical water quality periods
and carried out  in  a manner approved by  the Permitting Authority.

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                                                                     Page II-9
                                                          Permit  No.
 3.   Transfer of Ownership -or Control

 A permit may be automatically transferred to another party if:

     a.   The Permittee notifies the Permitting Authority  of the  proposed
         transfer at least 30 days in advance of the proposed  transfer  date;

     b.   The notice includes a written agreement between  the existing and  new
         Permittees containing a specific date for transfer of permit
         responsibility,  coverage, and liability between  them; and

     c.   The Permitting Authority does not notify the existing Permittee of  its
         intent to modify or revoke and reissue the permit.  If  this  notice  is
         not received, the transfer is effective on the date specified  in  the
         agreement mentioned in Paragraph b,  above.

 4.   Reporting of Monitoring Results

 Monitoring results obtained during the previous calendar quarter shall be
 summarized for each month (each quarter if monitoring frequency is quarterly)
 and  must be reported on  a Discharge Monitoring Report Form (EPA No.  3320-1),
 postmarked no later than the day of the month following  the completed  calendar
 quarter.   Duplicate signed copies of these,  and all other  reports required  by
 Section D of Part II, Reporting Requirements,  shall be submitted to  the
 Permitting Authority at  the following addresses:

     U.S.  EPA Regional Office;                State Office;

     (insert address)	               (insert  address)	
5.  Compliance  Schedules

Reports of  compliance  or noncompliance with, or any progress reports on,
interim and final  requirements  contained  in any compliance schedule of  this
permit shall be submitted no later  than 14 days following each schedule date.
Any reports of  noncompliance shall  include the cause of noncompliance, any
remedial actions taken, and the probability of meeting the next scheduled
requirement.

6.  Twenty-Four Hour Reporting

The Permittee shall orally report any noncompliance that may endanger health
or the environment within 24 hours  from the time the Permittee becomes aware
of the circumstances.  A written submission shall also be provided within five
days of the time the Permittee  becomes aware of the circumstances.  The
written submission shall contain a  description of the noncompliance, its
cause, and  the  period  of noncompliance, including exact dates and times.  If
the noncompliance has  not been  corrected, the written submission shall also
include the anticipated time it is  expected to continue, and steps taken or
planned to  reduce, eliminate, and prevent reoccurrence of the noncompliance.
The Permitting  Authority may verbally waive the written report, on a
case-by-case basis, when the oral report  is made.

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                                                                    Page 11-10
                                                         Permit No. 	

The  following  violations  shall  be  included in  the 24-hour report vhen they
might endanger health  or  the  environment:

     a.  An unanticipated  bypass that exceeds any effluent limitation in the
        permit.

     b.  Any upset  that exceeds  any effluent limitation in the permit.

7.   Other Noncompliance

The  Permittee  shall  report, in  narrative form, all instances of noncompliance
not  previously reported under Section D, Paragraphs 2, 4, 7, and 8, at the
time monitoring reports are submitted.  The reports shall contain the
information listed in  Paragraph 8.

8.   Other Information

Where the Permittee  becomes aware  that it failed to submit any relevant facts
in a permit application,  or submitted incorrect information in a permit
application or in any  report  to the Permitting Authority, it shall promptly
submit such facts or information.

9.   Changes in Discharges of  Toxic Substances

The  Permittee  shall  notify the  Permit Issuing Authority as soon as it knows or
has  reason to  believe:

     a.  That any activity has occurred or will occur that would result in the
        discharge, on  a routine or frequent basis,  of any toxic substance(s)
        (listed  at  40 CFR Part  122, Appendix D, Tables II and III) that is
        not limited  in the permit, if that discharge will exceed the highest
        of the  following  "notification levels":

        (1)  One hundred micrograms per liter (100 ug/1);

        (2)  Two hundred micrograms per liter (200 ug/1) for acrolein and
             acrylonitrile; five hundred micrograms per liter (500 ug/1) for
             2,4-dinitrophenol  and for 2-methyl-4,6-dinitrophenol; and one
             milligram per liter (1 mg/1) for antimony; or

        (3)  Five (5)  times the maximum concentration value reported for that
             pollutant(s) in  the permit application.

    b.   That any activity has occurred or will occur that would result in any
        discharge, on  a nonroutine or infrequent basis, of a toxic pollutant
        (listed at 40  CFR Part  122, Appendix D, Tables II and III) that is not
        limited in the permit,  if that discharge will exceed the highest of
        the following  "notification levels:"

        (1)  Five hundred micrograms per liter (500 ug/1);

        (2)  One milligram per  liter (1 mg/1) for antimony;  or

        (3)  Ten (10)  times the maximum concentration value reported for that
             pollutant(s) in  the permit application.

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                                                                    Page 11-11
                                                         Permit No.
10.  Duty  to Provide Information
The Permittee shall furnish to the Permitting Authority, vithin a reasonable
time, any information that the Director may request to determine whether cause
exists for modifying, revoking and reissuing, or terminating this permit, or
to determine compliance with this permit.  The Permittee also shall furnish to
the Permitting Authority, upon request, copies of records required to be kept
by this permit.

11. Signatory Requirements

All applications, reports, or information submitted to the Permit Issuing
Authority shall be signed and certified.

    a.  All permit applications shall be signed as follows:

        (1)  For a corporation:  by a responsible corporate officer.   For the
             purpose of this Section, a responsible corporate officer means:
             (1) a president,  secretary, treasurer or vice president  of the
             corporation in charge of a principal business function,  or any
             other person who performs similar policy or decisionmaking
             functions for the corporation; or (2) the manager of one or more
             manufacturing, production, or operating facilities employing more
             than 250 persons  or having gross annual sales or expenditures
             exceeding $25 million (in second-quarter 1980 dollars),  if
             authority to sign documents has been assigned or delegated to the
             manager in accordance with corporate procedures.

        (2)   For a partnership or sole proprietorship:  by a general  partner
             or the proprietor,  respectively;  or

        (3)   For a municipality,  State, Federal,  other political subdivision,
             public agency/agents thereof:   by either a principal executive
             officer or ranking elected official.

    b.  All  reports required by the permit  and other information requested by
        the  Permitting Authority shall be signed by a person described above
       or  by a duly authorized representative of  that person.   A person is a
       duly authorized  representative only if:

       (1)   The authorization is made in writing  by a person described above;

       (2)   The authorization specifies either  an  individual or a position
             having responsibility for the  overall  operation of the regulated
             facility  or activity,  such as  the position of plant manager,
             operator  of a veil  or a  well field, superintendent, position  of
             equivalent  responsibility,  or  an  individual or position  having
             overall responsibility  for environmental  matters for the company
             (A duly authorized  representative thus may be either a named
             individual  or any  individual occupying a  named position.);  and

       (3)   The written authorization is submitted to the Permit Issuing
             Authority.

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                                                                     Page 11-12
                                                          Permit No.  	

     c.   Certification.   Any person signing a  document under  Paragraphs  (a) or
         (b)  of this section shall make the following certification:

              "I certify under penalty of lav  that  this document and
              all attachments were prepared under my direction or
              supervision in accordance with a system designed to
              assure that qualified personnel  properly gather and
              evaluate the information submitted.   Based on my inquiry
              of the person or persons who manage the system, or those
              persons directly responsible for gathering the  informa-
              tion,  the  information submitted  is, to the best of my
              knowledge  and belief,  true,  accurate, and complete.  I  am
              aware  that there are significant penalties for  submitting
              false  information,  including the possibility of fine and
              imprisonment for knowing violations."

 12.  Availability of Reports

 Except  for data determined to be confidential under 40 CFR Part 2, all  reports
 prepared in  accordance  with the  terms of  this permit shall be available for
 public  inspection at the offices of the Permitting Authority.  As required by
 the  Act,  permit applications and permit and effluent data shall not  be
 considered confidential.

 13.  Penalties for Falsification  of Reports

The  Clean Water Act provides that any person  who knowingly makes any false
statement, representative,  or certification in any record or other document
submitted or required to be maintained under  this permit, including  monitoring
reports  or reports  of compliance or noncompliance, shall, upon conviction, be
punished  by  a fine  of not more than $10,000 per violation, or by imprisonment
for  not  more than 2 years per violation,  or by both.

SECTION  E.   DEFINITIONS

1.   Permit Issuing  Authority

The  Regional Administrator or his designee, unless at some time in the future
the  State receives  the  authority to administer the NPDES program and assumes
jurisdiction over the permit,  at which time the Director of  the State program
receiving authorization becomes  the issuing authority.

2.   Act

"Act" means  the Clean Water Act  (formerly  referred to as the Federal Water
Pollution Control Act)  Public Law 92-500,  as  amended by Public Law 95-217,
Public Law 95-576 and Public Law 100-4, 33  U.S.C. 1251 et seq.

3.   Concentration Measurements

    a.  The  "average monthly concentration" is the sum of the concentrations
        of all  daily discharges  sampled and/or measured during a calendar
        month on  which  daily discharges are sampled and measured, divided by
        the  number  of daily discharges  sampled and/or measured during such

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                                                                     Page 11-13
                                                          Permit No.  	

         month (arithmetic ..mean of the daily concentration values).   The daily
         concentration value is equal to the concentration of a composite
         sample or, in the case of grab samples,  is the arithmetic mean
         (weighted by flow value) of all the samples collected during the
         calendar day.

     b.   The "maximum daily concentration" is the concentration of a  pollutant
         discharge during a calendar day.   It is  identified as "Daily Maximum"
         in Part I of the permit and the highest  such value recorded  during the
         reporting period is reported under the "Maximum"  column under
         "Quality" on the DMR.

 4.   Other Measurements

     a.   The effluent flow, expressed as MGD, is  the 24-hour average  flow
         averaged monthly.   It  is the arithmetic  mean of the total daily flows
         recorded during the calendar month.   Where monitoring requirements for
         flow are specified in  Part I of the permit,  the flow rate values are
         reported in the "Average" column under "Quantity" on the DMR.

     b.   An "instantaneous  flow measurement"  is a measure  of flow taken at the
         time of sampling,  when both the sample and flow will be representative
         of the total discharge.

     c.   Where monitoring requirements for pH or  dissolved oxygen are specified
         in Part I of the permit,  the values  are  generally reported in the
         "Quality or Concentration" column on the DMR.

 5.   Types  of Samples

     a.   Grab Sample:   A "grab  sample" is  a single influent  or effluent portion
         that is not a composite  sample.   The sample(s)  shall be collected at
         the period(s) most representative of the total  discharge.

 6.   Calendar Day

 A calendar day is defined  as the  period from midnight of  one day until mid-
 night of the next day.   However,  for purposes of this permit,  any consecutive
 24-hour  period that reasonably represents the calendar  day  may be used for
 sampling.

 7.   Hazardous  Substance

 A hazardous  substance means any substance designated under  40 CFR Part 116
 pursuant to  Section 311  of the Clean Water Act.

 8.   Toxic  Pollutant

A toxic  or  "priority"  pollutant is one of 126 substances  listed  as toxic under
 Section  307(a)(l)  of  the Clean Water Act.

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                                                                    Page III-l
                                                           Permit No.
 PART III

 A.  SPECIAL CONDITIONS


 1.  Best Management Practices Requirements

 A Best Management Practices (BMP) plan shall be developed vithin one month
 after the effective date of the permit and shall be implemented as soon as
 practicable but no later than two months from the effective date of the
 permit.   The plan must address the following BMPs:

      a.   Prevention of run-on/interception of runoff:   Technologies that are
          designed to prevent or reduce run-on include  dikes,  diversion
          channels, flood walls, terraces,  grading,  and revegetation.
          Temporary diversion dikes,  diversion channels,  and terraces are con-
          structed upslope of a site  to direct run-on from offsite to a collec-
          tion system or away from the site.   Terraces  are used  in combination
          with dikes or ditches to channel  water stopped by the  terraces away
          from the site.

      b.   Prevention of infiltration:   The  primary method for  preventing infil-
          tration of onsite surface water is  capping.   Grading also helps to
          minimize infiltration by maximizing the amount  of water that  will run
          off without causing significant erosion.   Revegetation can either
          promote or minimize infiltration.

      c.   Collection and transfer of water:   Several technologies can be used
          to collect diverted water for discharge or transfer  to a storage or
          treatment system.   Chutes (or flumes)  and  downpipes  are designed to
          transfer water away from diversion  structures such as  dikes  or
          terraces to stabilized channels or  outlets.   Vaterways can be used  to
          intercept or divert water as well as to collect and  transfer  water
          diverted elsewhere.

      d.   Storage and discharge of water:  Technologies for this purpose
          include seepage basins and ditches,  sedimentation basins,  and storage
          ponds.   Their function depends  on the  level of  contamination  of the
          water  they receive.   Seepage basins  and ditches are  used to discharge
          uncontaminated or  treated water down and away from the site.   Sedi-
          mentation basins are  used to control suspended  solid particles in
          surface-water flow.

2.  Reopener  Clause

This  permit shall be modified,  or alternatively  revoked  and reissued,  to
comply with any  applicable  effluent standard  or  limitation  issued  or approved
under Sections 301(b)(2)(C)  and  (D),  304(b)(2),  and 307(a)(2) of  the Clean
Vater Act, if the effluent  standard or limitation so issued or  approved:

     a.  Contains  different  conditions or is  otherwise more stringent  than any
         condition  in  the permit;  or

     b.  Controls any  pollutant not limited in  the permit.

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                                                                   Page III-2
                                                          Permit No.	

3.  Chronic Toxicity Testing Requirements for Characterizing Effluent Toxicity

The Permittee shall perform toxicity testing, as described below, on the
discharge from Outfall 001.

     a.  The Permittee shall initiate the following series of tests as soon as
         practicable, but within 30 days of the effective date of this permit
         to evaluate toxicity of the discharge.  Such testing will determine
         if an appropriately dilute effluent sample affects the survival,
         growth, or reproduction of the test species.  All tests will be
         conducted on 24-hour composite samples.  A minimum of four replicates
         will be used in each of the following tests.  The Student's t test
         shall be used to determine whether differences in control and
         effluent data are significant.

         (1) The Permittee shall conduct a seven-day Ceriodaphnia survival and
             reproduction toxicity test on the final effluent diluted by
             appropriate control water.  Toxicity will be demonstrated if
             there is a statistically significant difference at the 95-percent
             confidence level in survival or reproduction between Ceriodaphnia
             exposed to an appropriate control water and the final effluent.
             All test solutions shall be renewed using an approved renewal
             schedule.   If, in any control,  more than 20 percent of the test
             organisms die, that test shall be repeated.

         (2) The Permittee shall conduct a seven-day fathead minnow survival
             and growth toxicity test on the final effluent diluted by
             appropriate control water.  Toxicity will be demonstrated if
             there is a statistically significant difference at the 95-percent
             confidence level in survival or growth between fathead minnows
             exposed to an appropriate control water and the final effluent.
             All test solutions shall be renewed using an approved renewal
             schedule.   If, in any control,  more than 20 percent of the test
             organisms  die, that test shall  be repeated.

     b.   The toxicity tests specified in Paragraph (a) above,  shall be con-
         ducted  once per month for a period  of one year following initiation
         of  the  tests and once every six months thereafter for the duration of
         the permit.  Results shall be reported according to EPA/600/4-85/014,
         Section 10 Report Preparation,  and  shall be submitted to EPA with the
         monthly Discharge Monitoring Report.   If any one test indicates the
         effluent is toxic, another confirmatory chronic toxicity test using
         the same species and the same methodology shall be conducted within
         one week.

     c.   All test species,  procedures,  and quality assurance criteria used
         shall be in accordance with Short Term Methods for Estimating the
         Chronic Toxicity of Effluents and Receiving Waters to Freshwater
         Organisms,  Section 13;  Ceriodaphnia Survival and Reproduction Test
         Method  1002.0;  Section 11; Fathead  Minnow (Pimephales promelas);
         Larval  Survival and Growth Test Method 1000.0,  EPA 600/4-85/04.   The
         selection of an appropriate control water for all toxicity tests
         shall be submitted to EPA for review and approval prior to use.

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                                                                   Page III-3
                                                          Permit No.
4.  Modification of Honito.ring Requirements

     a.  After three months of weekly flov and chemical-specific monitoring,
         the Permittee may submit a written request for reduced frequency of
         monitoring requirements.  The Permitting Authority may grant or
         refuse the request based on site-specific conditions, as appropriate.

     b.  After three months of monthly toxicity testing as required in
         Paragraph III-A-3, the Permittee may submit a written request for
         cessation or reduction of biomonitoring requirements.  The Permitting
         Authority may grant or refuse the request based on site-specific
         conditions, as appropriate.

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                     PART III

      FACT SHEET FOR MODEL NPDES PERMIT FOR
DISCHARGES RESULTING FROM THE CLEANUP OF GASOLINE
     RELEASED FROM UNDERGROUND STORAGE TANKS

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                               TABLE OF CONTENTS


                                                                          Page
 1.0   FACT  SHEET  FOR  MODEL NPDES  PERMIT  FOR DISCHARGES RESULTING FROM
      THE CLEANUP OF  GASOLINE  RELEASED FROM UNDERGROUND STORAGE TANKS  	 1-1


 2.0   SCOPE OF THE PROBLEM 	 2-1


 3.0   DISCHARGE CHARACTERIZATION  	 3-1

      3.1   VOLUME OF  DISCHARGE 	 3-1

      3.2   CONSTITUENTS OF GASOLINE  	 3-1

      3.3   POTENTIAL  SOURCES OF DISCHARGE 	 3-4


4.0  TREATMENT TECHNOLOGIES	 4-1

     4.1   FREE PRODUCT RECOVERY  	 4-1

     4.2   TREATMENT  OF CONTAMINATED WATER AND WASTEWATERS 	'	 4-1

           4.2.1  Air Stripping 	 4-2
           4.2.2  Carbon Absorption  	 4-2


5.0  TECHNOLOGY-BASED EFFLUENT LIMITATIONS 	 5-1

     5.1   SELECTION OF POLLUTANTS TO BE REGULATED 	 5-1

          5.1.1  Solubility of Gasoline Constituents 	 5-1
          5.1.2  Henry's Law Constants of Gasoline Constituents 	 5-4
          5.1.3  Indicator Pollutants Recommended for Limitation 	 5-4

     5.2  CALCULATION OF TECHNOLOGY-BASED EFFLUENT LIMITATIONS 	 5-8

          5.2.1  Optional Effluent Limitations 	 5-9
          5.2.2  Additional Effluent Limitations 	5-10

     5.3  TREATMENT COSTS 	5-10

          5.3.1  Costs of Selected Treatment  Technologies 	5-10
          5.3.2  Air Emissions Control 	5-12
          5.3.3  Costs of Alternative Treatment Technologies 	5-12

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                               TABLE OF CONTENTS
                                  (Continued)

                                                                          Page

6.0  BEST MANAGEMENT PRACTICES	  6-1


7.0  MONITORING  	  7-1

     7.1  FLOW MONITORING  	  7-1

     7.2  CHEMICAL-SPECIFIC MONITORING 	  7-1

     7.3  BIOMONITORING 	  7-2


8.0  REFERENCES  	  8-1
                                     ii

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                                LIST OF TABLES


TABLE                                                                     Page

 3-1   CONSTITUENTS OF GASOLINE 	 3-2

 5-1   SOLUBILITY OF CONSTITUENTS OF GASOLINE 	 5-2

 5-2   HENRY'S LAV CONSTANTS FOR CONSTITUENTS OF GASOLINE 	 5-5

 5-3   PURCHASE AND RENTAL COSTS FOR PRE-ENGINEERED PACKED COLUMN
       AIR STRIPPER UNITS 	5-11

 5-4   RELATIVE COST FACTORS FOR TREATMENT OF GROUND WATER	5-14

 7-1   RECOMMENDATIONS FOR WHOLE-EFFLUENT TOXICITY SCREENING 	 7-4
                                     iii

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                   1.0  FACT SHEET FOR MODEL NPDES  PERMIT  FOR
               DISCHARGES RESULTING FROM THE CLEANUP OF GASOLINE
                    RELEASED FROM UNDERGROUND STORAGE TANKS

      Pursuant to the Clean Water Act  (CWA),  the  U.S.  Environmental  Protection
 Agency (EPA), or an EPA-approved State,  is  authorized to  issue  a National
 Pollutant  Discharge Elimination System (NPDES) permits for  the  discharge of
 "pollutants"  from any "point source"  into "waters  of  the  United States."   CWA
 301(b) requires  all point  sources that discharge directly to  the waters of the
 U.S.  to meet  technology-based effluent limitations and State  water  quality
 standards  for the discharge of pollutants.  EPA has determined technology-based
 effluent limitations through the development of  National  effluent limitations
 guidelines for many specific categories  of  industries.  However, national
 effluent guidelines have not been promulgated for  wastewater  discharges
 resulting  from gasoline underground storage tank (UST)  cleanups.  Conse-
 quently, this technology-based permit  has been developed  on a best  profes-
 sional judgment  (BPJ)  basis in accordance with 40  CFR 125.3.  BPJ is used  to
 develop technology-based effluent  limits in those  cases where an effluent
 guideline  has not  been promulgated for the  industry and water quality
 standards  do  not  dictate limits  more  stringent than technology-based limits.

     Water quality-based limitations  should be used in a  permit when
 technology-based  effluent  limits are not stringent enough to  protect the
 "designated use"  of the receiving waters (as determined by the  State).  Water
 quality-based permits  involve  a  site-specific evaluation of the discharge, the
 State's  water quality  standards,  the designated use of the receiving water,
 and published EPA water quality  criteria.  Therefore,  the Model Permit and
 this Fact  Sheet only address  technology-based effluent limitations.  Guidance
 for addressing water quality considerations is included in Part IV - Decision
Tool for Developing Water Quality-Based Effluent Limitations.
                                     1-1

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                           .2.0  SCOPE OF THE PROBLEM

      It is estimated that 1.7 million underground storage tanks exist in the
 United States.   Based on data collected by EPA's Office of Underground Storage
 Tanks (OUST) (Ref.  No.  1)*,  15 percent of these tanks are currently leaking.
 Gasoline leaks, have been cited in more than 70 percent of the  reported release
 incidents (Ref. No. 14).  The OUST estimates that over the next 5  years,
 approximately 200,000 cleanups will be conducted to mitigate releases of
 petroleum-related products into the environment.   Assuming that 70 percent  of
 all  underground tank releases involve gasoline,  then as many as 140,000
 gasoline-related UST cleanups could occur over the next 5 years.

      Any discharges to  surface waters resulting from gasoline  UST  cleanups
 fall under the  auspices of the NPDES program.   These discharges could include
 treated ground  water, storm  water,  and tank cleaning wastewaters.   The
 treatment  technologies  commonly employed  for gasoline UST cleanups are
 discussed  in greater detailed in  Section  4.0.
^Reference numbers correspond to the number assigned to each reference listed
in Section 8.0 of this Fact Sheet.
                                     2-1

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                        3.0  DISCHARGE CHARACTERIZATION

        The volume and nature of discharges resulting from gasoline UST
 cleanups is expected to be highly variable.   Based  on available  data,  the
 following sections briefly describe the  volume and  nature of  the discharges
 that  would be .expected from gasoline UST cleanups.

 3.1   VOLUME OF DISCHARGE
      The volume of discharges generated  from gasoline UST cleanups varies.
 Such  variation is due to site-specific factors such as the size  of the
 release,  depth to ground water,  etc.  However,  OUST estimates  the typical flow
 rate  of treated water and wastewater discharges resulting from gasoline
 cleanups falls in the range of three to  20 gallons  per minute, or about 4,000
 to 30,000 gallons per day (Ref.  No.  2).

 3.2   CONSTITUENTS OF GASOLINE
      Available data that  enumerate  the constituents of gasoline  was -reviewed,
 based on  the assumption that  the same compounds identified in  gasoline would
 likely  be found in treated water and  wastewater resulting from gasoline clean-
 ups.  Those constituents  are  shown  in Table  3-1.  The chemical properties of
 these constituents,  such  as  solubility (in water) and volatility,  have been
 used  to characterize the  treatability of  discharges resulting  from gasoline
 UST cleanups (see Section 5.0).   It  should be  noted that  lead  is  used  as  an
 anti-knocking compound  in gasoline.   However,  lead  is present  in  gasoline as a
 component  of the  organic  compound tetraethyllead.

      The  characterization of gasoline shown  in  Table  3-1  is based  on an
 analysis  of constituents  commonly found  in gasoline.   However, little  to  no
data  are  available  regarding  the concentration  of pollutants in  treated water
and wastewater  discharges from UST cleanups  of  gasoline.   Similarly,
additional  site-specific  constituents, such  as  gasoline additives, may be
present.  Some  of  these are proprietary additives for  which little or  no  data
exist (Ref.  No. 6).
                                      3-1

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                     TABLE- 3-1.   CONSTITUENTS OP GASOLINE
Gasoline Constituent                             Reference
Isobutane                                           3,4,5
n-Butane                                            3,4,5
Isopentane                                          3,4,5
n-Pentane                                           3,4,5
n-Octane                                              3
Benzene                                             3,4,5
Toluene                                             3,4,5
o-Xylene                                              5
m-Xylene                                              5
p-Xylene                                              5
n-Hexane                                            3,4,5
2-Methylpentane                                     3,4,5
3-Methylpentane                                     4,5
2,2-Dimethylhexane                                    5
2,4-Dimethylhexane                                    3
Ethylbenzene                                        3,4,5
2,2,4-Trimethylhexane                                 3
2,2,5,5-Tetramethylhexane                             3
1-Hexene                                              3
1,3,5-Tritnethylbenzene                                3
2,2-Dimethylpropane                                   4
2,2-Dimethylbutane                                    4
1,2,4-Trimethylbenzene                                4
2,3-Dimethylbutane                                    5
2-Methylhexane                                        5
3-Methylhexane                                        5
2,3-Dimethylpentane                                   5
2,4-Dimethylpentane                                   5
2,2,4-Trimethylpentane                                5
2,3,4-Trimethylpentane                                5
2,3,3-Trimethylpentane                                5
2,2,3-Trimethylpentane                                5
2-Methyloctane                                        5
3-Methyloctane                                        5
4-Methyloctane                                        5
Cyclopentane                                          5
Methylcyclopentane                                    5
Methylcyclohexane                                     5
l,cis,3-Dimethylcyclopentane                          5
Cyclohexane                                           5
n-Heptane                                             5
                                     3-2

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               TABLE 3-1. - CONSTITUENTS OF GASOLINE (Continued)
Gasoline Constituent                                Reference
l,cis,3-Dimethyl-cyclopentane                         5
1,trans,3-Dimethyl-cyclopentane                       5
Propylene                                             5
trans Butene-2                                        5
cis Butene-2                                          5
1-Pentene                                             5
trans Pentene-2                                       5
cis Pentene-2                                         5
2-Methylpentene-l                                     5
2-Methylpentene-2                                     5
1-Methyl, 3-Ethylbenzene                              5
1-Methyl, 4-Ethylbenzene                              5
1,2,4-Trimethylbenzene                                5
Tetraethyllead                                        6
Naphthalene                                           5
                                     3-3

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3.3  POTENTIAL SOURCES OF DISCHARGE
     Discharges  from gasoline UST cleanups can originate from one or more of
several sources.  Examples of these sources include:

     •  Contaminated ground water that has been extracted and treated
     •  Contaminated storm water that has been collected and treated
     •  Wastewaters that are generated from tank cleaning operations
     •  Contaminated water that results from product recovery operations.

As discussed in  Section 1.1, any direct discharge to waters of the U.S. would
be subject to regulation under a NPDES permit.
                                     3-4

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                          4.0  TREATMENT TECHNOLOGIES

      The cleanup or "corrective action" for releases from gasoline USTs
 usually involves two phases.   The first phase includes actions  designed to
 immediately contain and control a release.   The second phase  involves
 assessing and .developing long-term measures designed to rectify and mitigate
 contamination to a level that  will protect  human health and  the environment.

 4.1.   FREE PRODUCT RECOVERY
      Where site conditions  permit,  an UST cleanup typically begins with
 recovery of gasoline (known as free product) floating on the  water table.
 Prompt removal of free product can minimize the extent of soil  and ground
 water that may potentially  be  contaminated  by an UST release.

      Free product is often  removed by digging a trench to intercept the flow
 of  floating gasoline or by  pumping ground water to  create a cone of depression
 in  the water table.   In either case,  the free product  flows toward the
 collection point where it is removed  by pumping.  The  ongoing process of free
 product removal often requires the pumping  or collection of substantial
 amounts of ground water which  may contain dissolved  gasoline  constituents.
 This  water may require treatment  prior to discharge.   This Fact  Sheet
 describes two technologies  commonly used to treat such water.  These
 technologies are air stripping and  carbon adsorption.

 4.2   TREATMENT OF CONTAMINATED WATER  AND WASTEWATERS
      As product recovery continues, a variety of aqueous  wastestreams and
 contaminated waters  may require additional  treatment  (see section  3.3). There
 are many  treatment technologies and methods  available  that could remove
 gasoline  constituents  from  these  aqueous wastestreams  and contaminated  waters
 including air stripping, carbon adsorption,  biorestoration, reverse osmosis,
 steam  stripping,  ozonation, etc.  Use of any  one of  these treatment
 technologies  will depend upon  the site-specific  factors  involved in an  UST
 corrective  action.   For  example,  due  to equipment and  utility requirements,the
use of  steam  stripping  is not  practicable for  emergency  field use  unless the
contaminated  ground  water can  be  transported  form the  site to a  steam
                                      4-1

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 stripping facility (Ref. No. 7).  However,  air stripping and  carbon adsorption
 are the most cost-effective and widely used treatment  technologies  available.
 In fact, these two technologies are used in over 95  percent of  ground-water
 cleanups and are applicable to most cases where gasoline has  contaminated  the
 groundwater (Ref. No. 6).  Therefore,  both  air stripping and  carbon adsorption
 are described below.

 4.2.1  Air Stripping
      Due to the high volatility of many of  the soluble  constituents of
 gasoline that remain in contaminated water  and wastewater, air  stripping is  an
 efficient and cost effective wastewater treatment  technology.   Air  stripping
 is a proven,  effective means to remove volatile organic compounds (VOCs) from
 ground  water.   Less volatile compounds (e.g.,  compounds with  low Henry's Law
 Constants) are not as easily removed via air stripping.   There  are  several
 methods of air stripping including diffused aeration,  tray aerators, spray
 basins,  and packed towers.   Regardless of the  configuration used, all air
 stripping units provide contact between air and water  to allow  the  volatile
 substances to diffuse from  the liquid  to the gaseous phase (Ref. No. 6).

      Air stripping transfers the pollutants removed  from the  contaminated
 water into the air.   In some cases,  volatilized pollutants may  require
 additional treatment  (e.g.,  vapor phase carbon adsorption) to control
 pollutant  discharges  to air.

 4.2.2  Carbon  Adsorption
      Activated carbon is widely used in the treatment of wastewater contami-
 nated with gasoline  (Ref. No.  6).  This treatment may be  used either separately
 or  in combination with air  stripping to address air quality concerns that may
 arise from volatilizing the  constituents of gasoline.  The process  of
 absorption onto activated carbon requires the  wastewater to come into contact
with  the  carbon,  which selectively adsorbs  organic constituents by  a surface
attraction phenomenon (due  to  chemical or physical properties).  The organic
molecules  are  attracted to  the internal pores  of the carbon granules.
Adsorption depends on the strength of  the molecular attraction  between
                                      4-2

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adsorbent and adsorbate, molecular weight, type and characteristic of
adsorbent, electrokinetic charge, pH, and adsorbent surface area.

     Most waste treatment applications use granular activated carbon (GAC)
adsorption units.  These units are generally used in a downflow fixed bed
series mode where the waste stream flows through a series of packed bed
reactors.  Eventually the carbon surfaces become saturated with organic
molecules, and reach the "breakthrough" point.  The carbon must be replaced
and disposed of or regenerated for treatment to continue.

     Use of GAC may be limited by site-specific conditions and cost
considerations.  For example, treatment of ground water with naturally high
iron and manganese levels can clog the carbon filters.  In addition,
requirements for disposing of the spent carbon may add significantly to
treatment costs (see section 5.3.3).
                                     4-3

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                   5.0  TECHNOLOGY-BASED EFFLUENT LIMITATIONS

      After a gasoline UST release has occurred,  free product  floats  on  the
 surface or ground water near the site where it  is skimmed  or  recovered  using a
 product recovery system.  While many gasoline constituents remain  as part  of a
 free floating gasoline layer (as opposed to dissolving  into the  water),  the
 more soluble fractions of the gasoline can dissolve  into the  surface or ground
 water.   Dissolved gasoline constituents typically remain in oil/water
 separator effluent at a concentration of 15 ppm  (Ref. No.  6).

      The technology-based effluent limitations developed in the  Model Permit
 were based on the use of an air stripping unit.   Air stripping units have  been
 demonstrated to be effective in removing the same or similar  pollutants  that
 are  found in gasoline.   In addition,  air stripping units are  widely  used and
 readily available,  and are generally  less expensive  than other available
 treatment technologies.   It is important to note that EPA  does not intend  to
 specify the actual treatment that  must be used at  gasoline UST cleanup  sites.
 Other treatment technologies,  such as carbon adsorption and biorestoration,
 have also been  used to treat contaminated water  and  wastewater resulting from
 gasoline UST cleanups.   Air stripping units are  only used  as  the technology-
 basis for justifying BPJ effluent  limitations that are achievable with an
 existing treatment  technology.

 5.1   SELECTION  OF POLLUTANTS TO BE REGULATED
      As  discussed in Section 3.0,  the chemical properties  of gasoline
 constituents  determine  the treatability of  these  constituents.  Constituent
 treatability  forms  the  primary  basis  for selecting pollutants for which
 effluent  limitations  should  be  developed.

 5.1.1  Solubility of  Gasoline Constituents
     Gasoline constituent  solubilities  in water are  shown  in Table 5-1.
Generally,  the  higher  the  solubility  of  a constituent in water, the  more
difficult  it is  to  remove  the constituent from water using  an air stripper.
                                      5-1

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               TABLE 5-1. -SOLUBILITY OP CONSTITUENTS OF GASOLINE
 Gasoline Constituent
Solubility in Water
     (mg/1)
 Isobutane
 n-Butane
 Isopentane
 n-Pentane
 n-Octane
 Benzene
 Toluene
 o-Xylene
 m-Xylene
 p-Xylene
 n-Hexane
 2-Methylpentane
 3-Methylpentane
 2,2-Dimethylhexane
 2,4-Dimethylhexane
 Ethylbenzene
 2,2,4-Trimethylhexane
 2,2,5,5-Tetramethylhexane
 1-Hexene
 1,3,5-Trimethylbenzene
 2,2-Dimethylpropane
 2,2-Dimethylbutane
 1,2,4-Trimethylbenzene
 2,3-Dimethylbutane
 2-Methylhexane
 3-Methylhexane
 2,3-Dimethylpentane
 2,4-Dimethylpentane
 2,2,4-Trimethylpentane
 2,3,4-Trimethylpentane
 2,3,3-Trimethylpentane
 2,2,3-Triraethylpentane
 2-Methyloctane
 3-Methyloctane
 4-Methyloctane
Cyclopentane
Methylcyclopentane
Me thylcyclohexane
Cyclohexane
n-Heptane
       48.9
       61.4
       47.8
       38.5
        6.57x10
    1,780.0
      515.0
      175.0
      162.0
      198.0
        9.5
       13.8
       12.8
        -i
          24
          28
      152.0
        0.87
        0.33
       59.
       69.
       33.
       18.
  .5
  ,1
  .2
  .4
57.0
       22
        2
        2
        5
        4
        1
        1
        2
        2
        1.42
        1.42
        0.01
     160.0
       61.1
       14.0
       55.6
        2.96
   5
   54
   64
   25
   06
   14
   36
   59
   59
                                     5-2

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        TABLE 5-1.  SOLUBILITY OF CONSTITUENTS OF GASOLINE (Continued)
Gasoline Constituent                              Solubility in Water
                                                        (mg/1)


l,cis,3-Dimethyl-                                         7.07
  cyclopentane
1,trans,3-Dimethyl-                                       7.07
  cyclopentane
Propylene                                              2006.0
trans Butene-2                                          430.0
cis Butene-2                                            430.0
1-Pentene                                               148.0
trans Pentene-2                                         203.0
cis Pentene-2                                           203.0
2-Methylpentene-l                                        78.0
2-Methylpentene-2                                        84.2
1-Methyl, 3-Ethylbenzene                                 40.0
1-Methyl, 4-Ethylbenzene                                 40.0
1,2,4-Trimethylbenzene                                   57.0
Tetraethyllead                                            0.80
Naphthalene                                           3,400.0


Source:   Reference No. 8
                                     5-3

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The  three  compounds  of gasoline  with  the  highest solubilities are naphthalene
(3,400  mg/1),  propylene (2,006 mg/1)  and  benzene (1,780 mg/1).  Propylene,
however, accounts  for  only 0.03  percent of gasoline  (Ref. No. 5) and would not
be likely  to dissolve  into ground  water in significant amounts.  Naphthalene
is also a  minor  constituent of gasoline.  Therefore, effluent limitations for
naphthalene and  propylene  were not  included  in  this  Model Permit.  Benzene was
selected as the  main pollutant of  concern since it is a more significant
constituent of gasoline than naphthalene  or  propylene.

5.1.2   Henry's Law Constants of  Gasoline  Constituents
     The Henry's Law Constant for  each of the constituents of gasoline is
shown in Table 5-2 (Ref. No.  8).   As  discussed  in Section 4.2, the Henry's Law
Constant describes the ease with which specific compounds can be removed by
air  stripping.   Compounds  with lower  Henry's Law Constants are more difficult
to remove  by air stripping than  compounds with higher Henry's Law Constants.
Where multiple volatile organic  compounds are present, the compound with the
lowest  Henry's Law Constant will generally be the limiting compound {Ref. No.
6).  As shown  in Table 5-2,  benzene,  ethylbenzene, toluene, the xylenes,
1,3,5-trimethylbenzene,  and naphthalene have the lowest Henry's Law Constants.
While these compounds  are  the least strippable constituents of gasoline, all
of the  gasoline  constituents are within the  range where air stripping is
considered to  be effective (Ref. No.  6).

5.1.3   Indicator Pollutants Recommended for  Limitation
     Based on  the  chemical properties of  gasoline constituents (i.e.,
solubility and Henry's  Law Constants), there are several primary pollutants of
concern for discharges  from UST  cleanups:

     •  Benzene
     •  Propylene
     •  Ethylbenzene
     •  Xylene
                                      5-4

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        TABLE 5-2.  HENRY'S LAV CONSTANTS FOR CONSTITUENTS OF GASOLINE
Gasoline Constituent
Henry's Law Constant (20°C)
       (atm-m /mole)
Isobutane
n-Butane
Isopentane
n-Pentane
n-Octane
Benzene
Toluene
o-Xylene
m-Xylene
p-Xylene
n-Hexane
2-Methylpentane
3-Methylpentane
2 , 2-Dimethylhexane
2 , 4-Dimethylhexane
Ethylbenzene
2,2, 4-Trimethylhexane
2,2,5, 5-Te t rame thylhexane
1-Hexene
1 , 3 , 5-Tr ime thylbenzene
2 , 2-Dimethylpropane
2,2-Dimethylbutane
1,2,4-Trimethylbenzene
2 , 3-Dimethylbutane
2-Methylhexane
3-Me thylhexane
2 , 3-Dimethylpentane
2 , 4-Dimethylpentane
2,2, 4-Trimethylpentane
2,3, 4-Trimethylpentane
2,3, 3-Trimethylpentane
2,2, 3-Trimethylpentane
2-Methyloctane
3-Methyloctane
4-Methyloctane
Cyclopentane
Methylcyclopentane
Hethylcyclohexane
Cyclohexane
n-Heptane
0.9 to 1.0(1)
0.859
1.31
1.26
3.20
5.47x10
6. 65x10" 3
5. 20x10" 3
5.27xlO"3
5. 27x10" 3
1.86
1.53
1.07
2.28
3.55
8.74x10"
3.03
5.94
0.346
5. 70x10" 3
1.25
1.27
3.02xlO"2
0.993
1.73
1.42
1.81
1.61
2.34
1.24
1.28
1.52
2.56
2.48
2.64
0.144
0.250
0.374
0.194
2.04
                                     5-5

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        TABLE  5-2.   HENRY'5  LAW CONSTANTS FOR CONSTITUENTS OF GASOLINE
                                  (Continued)
Gasoline  Constituent
Henry's Law Constant (20°C)
       (atm-m /mole)
l,cis,3-Dimethyl-
  cyclopentane
1,trans,3-Dimethyl-
  cyclopentane
Propylene
trans Butene-2
cis Butene-2
1-Pentene
trans Pentene-2
cis Pentene-2
2-Methylpentene-l
2-Methylpentene-2
1-Hethyl, 3-Ethylbenzene
1-Methyl, 4-Ethylbenzene
Tetraethyllead
Naphthalene
      0.468

      0.47 to 0.50(2)

      0.230
      0.193
      0.172
      0.294
      0.229
      0.224
      0.271
      0.211
      2.63x10
      0.027 to .030(3)
      3 x 10"2(4)
      5.47 x 10
-2
(1)A1though no Henry's Law Constant was found for this compound,  the number
   shown was estimated based on the values for n-Butane and Isopentane.

(2)Although no Henry's Law Constant was found for this compound,  the number
   shown was estimated based on the value for l,cis,3-Dimethyl-cyclopentane.

(3)Although no Henry's Law Constant was found for this compound,  the number
   shown was estimated based on the value for 1-Methyl,3-Ethylbenzene.

(4)Reference No. 6

Source:  Reference No. 8
                                     5-6

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      •  Toluene
      •  1,3,5 - Trimethylbenzene
      •  Naphthalene

 The Model Permit includes effluent limitations for the  aggregate  parameter of
 benzene,  ethylbenzene,  toluene,  and the xylenes (BETX).   In  addition,  a
 limitation for benzene  has been  developed for use as  an indicator parameter
 for the removal of propylene,  1,3,5-trimethylbenzene, and naphthalene.   As an
 indicator,  it is assumed that  if benzene is  removed,  then the  other  compounds
 with similar treatability characteristics will also be  removed.   The primary
 advantage of using an indicator  parameter is the  reduction of  monitoring
 required  to ensure compliance.   In addition,  an indicator can  be  used  for
 constituents for which  no EPA  approved  analytical methods are  available for
 monitoring.

      A traditional approach to limiting effluent  contaminated  with gasoline or
 other fuel  oils has been to limit  BETX.   This  approach  stems from petroleum
 industry  practices for  determining the  quality of fuels  by measuring BETX.
 Monitoring  and limitation of BETX  in discharges from gasoline  UST corrective
 actions is  prudent for  several reasons.   First, the composition of gasoline is
 highly variable and for some gasoline products any  one  of the  four BETX
 constituents can be the predominant constituent.   Second, EPA  has promulgated
 or  proposed  water quality criteria for  benzene, ethylbenzene,  toluene,  and  the
 xylenes.  Except  for  naphthalene,  criteria have not been  proposed for  the
 other  constituents of gasoline.  Finally, as shown  in Table 5-2,  benzene,
 ethylbenzene,  toluene,  and  the xylenes  are gasoline constituents  with  low
Henry's Law  Constants.   Therefore, limitation  of  the aggregate parameter,
BETX,  is  provided  in  this Model  Permit.   On a  site-specific basis, however, it
may be more  appropriate  to  individually  limit  ethylbenzene, toluene, and
xylenes in addition to  benzene.

      In  addition  to  BETX,  the Henry's Law Constants for  1,3,5-
trimethylbenzene and  naphthalene are relatively low, as compared  to  other
constituents contained  in gasoline.  The Merck Index (Ref. No.  19) states  that
1,3,5-trimethylbenzene  is "practically insoluble  in water..."  but may be
                                     5-7

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 soluble in benzene.   Furthermore,  naphthalene is  insoluble  in  water,  but
 soluble in both benzene and toluene.   Therefore,  benzene  is considered  an
 appropriate indicator parameter for 1,3,5-trimethylbenzene  and naphthalene.
 That is,  if benzene  is sufficiently treated  or removed, then 1,3,5-
 trimethylbenzene and naphthalene should also be removed.  In addition,
 naphthalene is. considered to be a minor constituent  in gasoline, accounting
 for less  than 1 percent of the total  gasoline product (Refs. No. 3 and  5).

      The  removal of  benzene is also an indicator  of  the removal of propylene.
 As  discussed in Section 5.1.1, propylene is  slightly more soluble in  water
 than benzene.  However, propylene  has a much higher  Henry's Law Constant.
 Consequently, propylene is more amenable to  treatment, by air  stripping, than
 benzene.   Therefore,  removal of benzene is assumed to be indicative of  the
 removal of propylene.   As such, benzene is limited in this  Model Permit.

 5.2  CALCULATION OF  TECHNOLOGY-BASED  EFFLUENT LIMITATIONS
      A recent EPA publication (Ref. No.  6) on UST cleanup technologies
 estimates  that 15 ppm (or 15 mg/1) of dissolved product remains in ground
 water following free product recovery,  under optimal operating conditions.
 Case studies have documented dissolved hydrocarbon levels of 2 to 10  mg/1
 after free product recovery was completed (Refs.  No. 6, 18,  and 20).  These
 values have been used  to estimate  that the potential influent  levels  of total
 BETX into  an air stripper (or other wastewater treatment system) varies from 2
 to  15 mg/1.   Vendors  report that the  potential removal efficiency of  BETX
 using a commercially available air stripper  unit  is  99.5 percent.  If air
 stripping  is applied  to influent BETX  levels of  15  mg/1, the  stripped
 effluent would contain 0.075 mg/1  (or 75 ug/1)  total BETX.   One case  study
 reported air stripper  performance  capable of reducing hydrocarbon influent
 levels  of  4  to 6 mg/1  to less than 100 ug/1  after initial startup and
 shakedown  testing was  completed (Ref.  No. 18).  However, product recovery and
 air  stripping technologies may not always occur under optimal  conditions.
Therefore,  the total BETX discharge limit is 0.1  mg/1 (or 100  ug/1).  This is
 in keeping with total  BETX effluent limitations currently required by EPA
Region  1 (Ref.  No. 20)  and the State  of  Louisiana (Ref. No.  22).
                                      5-8

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      Influent concentrations of benzene,  which have rarely exceeded 1 mg/1 in
 the State of Maryland, would be stripped  to 0.005 mg/1 (or 5 ug/1)  at 99.5
 percent efficiency (Ref. No. 21).   Therefore,  the limit  of 5 ug/1 was chosen
 for benzene. Further, EPA Region 1 (Ref.  No.  20)  and the States  of  Maryland
 (Ref.  No. 21) and Nebraska (Ref. No.  23)  have all indicated that dischargers
 in their jurisdictions have been able to  meet  the 5 ug/1 limit  for  benzene.

 5.2.1   Optional Effluent Limitations
      Permit limitations based on BPJ  must be  achievable  with existing
 technology at a reasonable cost.  Based on data contained in the Regulatory
 Impact Analysis of Technical Standards for Underground Storage Tanks  (Ref.  No.
 1),  over 75 percent of retail motor fuel  outlets  (which  accounts for  the
 majority of gasoline USTs) in the  U.S.  are either owned  or operated by
 businesses meeting the Small Business Administrations's  definition  for small
 businesses.   Almost one-half of these own a single outlet with assets totaling
 over $400,000.   Therefore, many of the smaller firms may be severely  affected
 by  the cost of  compliance with the effluent limitations  established in Section
 5.2.   Therefore,  optional technology-based effluent  limitations  have  been
 developed for discharges from gasoline UST cleanups  where these  costs will
 severely hinder a firm's ability to perform the remedial cleanup activities.

     The same treatment  technologies  (i.e., free  product recovery followed  by
 air  stripping)  were used to establish the optional effluent  limitations.
 However,  the optional limitations  are based on a  95  percent  removal efficiency
 for  both benzene  and  BETX.   Using  the same influent  concentrations  described
 in Section 5.2,  the resultant  effluent  limitations will  be  50 ug/1  for benzene
 and  750  ug/1 for  BETX.   This  relaxed  removal efficiency  for  benzene and BETX
 reduces  the  capital and  operating  costs for air stripping.  This  cost  savings
 could  be realized  through a reduction in  the tower height and packing depth,
or a reduction  in  power  requirements  because a lower air-water ratio  can be
used,  or  both.  For example, assuming the  benzene  influent  concentration and
all other  operating conditions  (e.g.,   loading  rate, air-water ratio)  remain
 the same,  the depth of packing  could  be reduced by about  7  feet  if  the desired
removal  efficiency  requirements  were  reduced from  99.5 percent removal  to 95
percent  removal.
                                     5-9

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5.2.2   Additional  Effluent. Limitations
     The  Daily  Discharge  limits  set  forth in Part I of the Model Permit
restrict  benzene and  total  BETX. In  addition, pH is limited to the widely-
accepted  range  of  6-9 standard units established for most industrial point
source  categories.

     Some NPDES permit writers may be concerned about the potential presence
of lead in gasoline at UST  sites.  In gasoline, however, lead is present as
tetraethyllead  (TEL)  a component of  an organic compound and thus not amenable
to traditional  metals removal technologies such as pH adjustment, flocculation
and sedimentation.  Based on the Henry's Law Constant for TEL, it would likely
be removed by air  stripping.  TEL is also amenable to treatment by GAC, as
discussed earlier  in  Section 4.2 (Ref. No. 6).  Permit writers may consider
applying  monitoring requirements for lead, if lead is expected to be present
in gasoline contaminated  ground water in concentrations or quantities of
concern.

5.3  TREATMENT  COSTS
     The  following subsections briefly describes the cost of implementing
product recovery, air stripping and  carbon adsorption technologies.

5.3.1   Costs of Selected  Treatment Technologies
     According  to Cleanup of Releases from Petroleum USTs;  Selected
Technologies (Ref. No. 6) the costs  for free product recovery equipment will
vary according  to  the methods chosen for remediation (e.g., surface vs.
subsurface).  Generally,  the purchase costs will range from $6,000 to $10,000
for product recovery  equipment.

     Numerous literature  sources report capital and operating and maintenance
(O&M) costs for air stripping treatment systems.  However, the literature
reports costs for permanent structures rather than more flexible equipment.
Because flexible equipment  is more appropriate for use over the relatively
short duration  of many UST  corrective actions, cost data has been collected
for this  Model  Permit  from  vendors for pre-engineered, sled-mounted air
stripping units (Ref.  No. 10).  Table 5-3 presents a summary of these costs,
including total purchase  costs and estimated annual operation and maintenance
                                     5-10

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                           TABLE 5-3.   PIKBASB AND RENTAL COSTS PCR PRE-OGDHHED PtOfD OOUIK AIR SHOPPER WETS
Ul
 i
Air Stripper
Design Flow
(gallons/minute)
3-20
3-20
30
30
15-60
15-60
150
150
Tower
Height/Diameter
(feet)
18.5/1
28.5/1
16/1
19/1
12.5/2
22.5/2
11/3
19/3
Packing Height
(feet)
D
21
11
14
8
16
5.5
13.5
Total Purchase
Cost (S)1
6,000
8,595
5,150
5,400
8,450
11,700
7,900
12,900
Estimated Annual
Monthly Rental Operations and
Cost ($)2 Maintenance Costs ($)
1,160
NA
1,400
1,400
1,699
NA
1,800
1,800
1,200
1,700
1,030
1,080
1,690
2,340
1,580
2,580
      NA - Not Available


      1 Does not include delivery, installation,  engineering, and contingency costs.   These costs are estimated to be about 30-50 percent

        of purchase cost.


      2 Rental costs will vary according to the length of rental time.  At least a 6 month rental period was assured.


      3 Operational and maintenance costs are highly variable; assumed to be 20 percent of total purchase cost based on vendor estimates.

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 costs.   In  addition,  if  the  corrective action is anticipated to be a
 relatively  short  term cleanup,  the  owner/operator or cleanup contractor may
 consider renting  an air  stripping treatment system.  Therefore Table 5-3 also
 presents monthly  rental  costs.

     Effluent  limitations  for pH are established as 6.0 (minimum) and 9.0
 (maximum) standard units based  on available pH adjustment technologies.  These
 technologies include  acid  and/or base addition, the costs of which are inci-
 dental  to the  overall costs  of  treating water and wastewater prior to
 discharge.

 5.3.2   Air  Emissions  Control
     Emissions of volatile organ!cs from wastewater treatment systems may
 impact  local air  quality.  Carbon adsorption can be used to treat vapors
 containing  volatile organics that are emitted from air strippers in those
 areas of the Nation where  such  controls are necessary (Ref. No. 7).  Based on
 the procedures outlined  in Underground Storage Tank Corrective Action
 Technologies (Ref. No. 7), costs for control of air emissions are estimated
 below for three daily discharge flows:
Discharge Flow
<50,000 gpd
500
150,000 gpd
5,000
750,000 gpd
8,000
Airflow rate, cfm

Capital Cost                  $40,000         $75,000       $100,000
Annual Operating and
  Maintenance Cost             $6,000         $60,000       $100,000

5.3.3  Costs of Alternative Treatment Technologies
     Free product recovery followed by air stripping is the treatment tech-
nology used as a basis for the development of effluent limitations in the
Model Permit.  Carbon adsorption and biological treatment technologies are
also reported, in the literature, as examples of appropriate treatment
                                     5-12

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technologies for discharges resulting from gasoline underground storage tank
cleanups.

     The use of GAC may substantially increase treatment costs.  Capital costs
may be twice to four times those capital costs generally needed for use of air
stripping treatment units.  Operation and maintenance (O&M) costs incurred
when using GAC may increase to up to eight times the O&M cost of air
stripping.  This eight-fold increase in O&M costs is due to the need to renew
the GAC carbon and dispose of spent carbon.  These relative costs are shown in
greater detail in Table 5-4.
                                    5-13

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        TABLE 5-4.  RELATIVE COST FACTORS FOR TREATMENT OF GROUND WATER
Technique
Air stripping
Air stripping &
vapor-phase GAC
Air stripping &
liquid-phase GAC
Air stripping &
Relative Cost
Capital
1*
2.0
3.0
4.0
Factors
O&M2
1*
3.0
3.0
5.0
O&M
(RCRA)
1
4.0
4.5
7.5
liquid-phase  &
vapor-phase GAC

Liquid GAC only              1.5                 4.0                     8.0


*Assigned

 Cost factors indicated are  relative to air stripping.

 O&M costs for GAC include costs for carbon replacement/regeneration.

 Indicates cost if spent carbon must be treated as a hazardous waste under
RCRA.

Source:  Reference No. 6
                                     5-14

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                        6.0  BEST MANAGEMENT PRACTICES

     The Model Permit requires the permittee to develop a Best Management
Practices (BMP) plan to minimize potential for release of pollutants from
corrective action activities.  BMPs are designed to minimize contamination of
surface waters, as a result of cleanup operations.  In addition, BMPs such as
diversion and collection of runoff, prevent offsite transport of surface
waters that may have become contaminated.  The BMPs set forth in Part III,
Section A.I, of the Model Permit are based on recommendations provided in the
OUST document entitled Underground Storage Tank Corrective Action Technologies
(Ref. No. 7).
                                     6-1

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                                7.0  MONITORING

      Monitoring is the primary means of ensuring that  the  permit  limitations
 are met.   It is also the basis for enforcement  actions against  permittees who
 are in violation of their permit  limits.   State and  EPA Regional  offices
 usually recommend monitoring frequencies  based  on the  design  capacity  of the
 treatment facility (Ref. No.  12).

      The  permittee may request reduced frequency of  monitoring  requirements
 (or elimination of toxicity monitoring requirements) after 3  months of the
 effective date of the permit.   Part  IV,  Section A.4  of the Model  Permit allows
 the permittee to collect data  sufficient  to  demonstrate that  the  treatment
 system is performing well.   After  a  review of discharge data  collected over a
 3 month period,  the Permitting Authority  may reduce  the frequency of,  or
 eliminate monitoring requirements.

 7.1  FLOW MONITORING
      Weekly  flow monitoring is recommended for  discharges less  than 100,000
 gallons per  day  (Ref.  No.  12).  Since  discharges from  gasoline  UST cleanups
 are expected to  be approximately 30,000 gallons per day (see  Section 3.1), the
 Model Permit requires  weekly flow  monitoring.

 7.2  CHEMICAL-SPECIFIC MONITORING
      Chemical-specific monitoring  is recommended on a  quarterly basis  for
 flows  less than  100,000 gallons per day (Ref. No.  12).   However, high
 concentrations of  hydrocarbons are expected  to  be  present in  water and
wastewater resulting from UST  site corrective actions.   Therefore weekly
 chemical-specific  monitoring is recommended.

      Chemical-specific monitoring  is required for  benzene, ethylbenzene,
 toluene,  and the xylenes.   Analytical  methods 602, 624,  and 1624 are approved
under authority of  the CWA  for analyses of benzene, ethylbenzene, and  toluene.
 EPA Method  8240 is  an approved RCRA method  for  the analysis  of ortho-, meta-,
and para-xylene which  are reported as  "total xylenes"  or "xylene."  EPA Method
8240 should  be used  to test "xylenes"  unless State or  EPA Regional policies
specify alternative  analytical methods.   EPA Method 8240 can  also be used to
                                      7-1

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 analyze for benzene, ethyliienzene, and toluene.   Depending upon EPA Regional
 or State policy, the permit writer may opt to substitute Method 8240,  when
 using the Model Permit for the CWA methods generally required  under the  NPDES
 program.  Hence the permittee would not be required  to perform two  tests to
 report the required data for benzene,  ethylbenzene,  toluene, and total
 xylenes.  Method 8240 is described in  Test Methods for Evaluating Solid  Waste
 Volume IA;  Laboratory Manual Physical/Chemical  Methods (Ref.  No. 15).

      Grab sample collection is required based on procedures recommended  in the
 EPA Handbook for Sampling and Sample Preservation of Water and Wastewater
 (Ref.  No.  13).

 7.3  BIOMONITORING
      In the absence of information on  the toxicity of a specific discharge the
 EPA recommends  biological monitoring requirements (Ref.  No. 11).  There  are
 three  principal reasons for generating biomonitoring data:

      1)  to ascertain whether a permittee exceeds the narrative no toxics water
         quality standard and thus  needs water quality-based permit  limits for
         toxicants
     2)  to identify a sensitive test species  for toxicity  monitoring purposes
     3)  to generate data on the variability of effluent  toxicity.

     Permits  can be and are routinely  issued  with data generation requirements
described  in  Part III,  Special Conditions, of the permit  to augment  the  limits
imposed  on other parameters.   These testing procedures  require permittees to
generate data on their  effluent so that the permit writer  can  determine
whether  additional permit limits or controls  will be  necessary to meet other
statutory  requirements,  such as water  quality standards.

     This  data  generation mechanism should result in  subsequent  modification
of  the NPDES  permit  if  the data generated  show unacceptable toxicity.  Should
toxicity be demonstrated,  the permit writer should consider developing site-
specific water  quality-based limits (see Part IV - Decision Tool  for
Developing Vater Quality-Based Limitations).
                                      7-2

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     The  biomonitoring  requirements set  forth in Part III(A)(3) of  the Model
Permit were adapted  from  EPA guidance on developing water-quality based

permits (Ref. No.  11).  Specifically, chronic aquatic life toxicity testing is

required  to characterize  effluent  toxicity.  As an alternative, the permit
writer could use  the whole-effluent toxicity screening procedure that is
recommended in.  the EPA  Technical Support Document for Water Quality-Based

Toxics Control  (Ref. No.  24).  This approach, provided in Table 7-1, allows
for decisions to  be made  regarding toxic impact early in the testing process.

Effluents with  low potential for instrearn toxicity can be eliminated as a

priority  or given a low priority for further analysis.


     States may also have their own toxicity testing requirements that can be
substituted as appropriate.  One such approach has been successfully used in
the State of North Carolina and has been included for consideration as an

alternative for gasoline UST cleanups.  The State of North Carolina developed

a standard approach to  whole-effluent toxicity testing that is based on the
instream waste concentration (IWC) resulting from a discharge.  The IWC, which

is expressed as a percentage, is calculated by dividing the effluent flow or
discharge flow by the sum of the receiving water low flow (defined as 7Q10 low

flow) plus the effluent flow.  Depending upon the IWC, one of three types of

toxicity tests are generally required (Ref.  No.  16):


     •  If the IWC exceeds 1 percent,  then the permittee is required to
        perform the Ceriodaphnia Pass/Fail chronic toxicity test.   This static
        renewal test is conducted at the IWC and runs for 7 days.   Passing the
        Pass/Fail chronic test means there is no observable inhibition of
        reproduction or significant mortality at the  IWC.

     •  If the IWC is between 0.25 and 1 percent,  then the permittee is
        required to perform a static,  nonrenewal,  48  hour acute toxicity test.
        This test is conducted over a range  of effluent concentrations using
        either Ceriodaphnia dubia or Daphnia pulex.   To pass,  the 48 hour
        concentration of effluent lethal to  50 percent of the organisms (LC50)
        must be greater than or equal  to the IWC (expressed as a
        concentration).

     •  If the IWC is less than 0.25 percent,  then a  short term Pass/Fail
        acute toxicity test must be performed by the  permittee.  This static
        nonrenewal test  uses either the fathead  minnow (Pimephales promelas),
        Daphnia pulex,  or Ceriodaphnia dubia,  and  runs for 24 hours; typically
        at 90 percent of the effluent  concentration.   This test is failed if
        it is determined that mortality in the effluent treatment  is
        significantly different than the control population (measured using
        the Student's test and a 99 percent  confidence interval).
                                     7-3

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TABLE 7-1.  RECOMMENDATIONS FOR WHOLE-EFFLUENT TOXICITY SCREENING
  Individual Dischargers - Compare receiving water flow rate (in terms
  of whatever water quality-based design low flow is  specified by the
  State) to average effluent flow rate.

  -  If dilution exceeds 10,000 to 1,  and there is a  reasonably rapid
     mix of the effluent outside of the  rapid initial dilution area in
     the receiving water, then the effluent  should be given a low
     priority for any further attention.

  -  If dilution is less than 10,000 to  1, or mixing  is not rapid and
     toxicity within a plume is of concern,  then toxicity screening
     tests should be performed.

  -  If dilution is between 1,000 to 1 and 10,000 to  1,  or a poorly
     mixed effluent plume in a large receiving water  (>10,000 to 1
     dilution) is of concern, conduct  acute  toxicity  screens as follows:

     1.  Collect four to six effluent samples on one day (grab or short
        term composite), quarterly.  Conduct screening tests (24-hour)
        in 100% effluent, using a daphnid and a fish,  on each sample.

     2.  If 50% mortality or greater is observed in three samples,  the
        potential for toxicity is assumed and further testing is
        required.

     3.  If 50% mortality or greater is observed for two or fewer
        samples,  the discharge should  be  given a low  priority for
        further analysis.

  -  If dilution is less than 1,000 to 1, conduct chronic  toxicity
     screens (short term chronic tests are recommended)  as follows:

     1.  Collect four to six effluent samples (24-hour composite) on four
        to six successive days.  Conduct  static screening tests (seven-
        day) in 100% effluent,  using a cladoceran and a fish,  on each
        sample.

     2.  If a 50% or greater effect is  observed between controls and test
        organisms,  the potential for toxicity is assumed and further
        testing is  required.

     3.  If less than 50% effect is observed,  the discharge should be
        given a low priority for further  analysis

 Acute  tests can be used in these dilution  situations,  but it should be
 noted  that there  will be cases where no acute toxicity is measured but
  the effluent is chronically toxic.
                               7-4

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        TABLE 7-1.  RECOMMENDATIONS  FOR WHOLE-EFFLUENT TOXICITT  SCREENING
                    (Continued)
        -  Where  dilution  is  less  than  100  to  1,  the use of a  toxicity-
           testing-based screening  procedure is not recommended.  Screening
           has already  been accomplished  through  dilution analysis.  Even  in
           discharge  situations where no  toxicity is observed  in screening
           tests,  the narrow  margin between effect concentration and available
           dilution suggests  more complete effluent toxicity characterization
           is mandatory.   If  uncertainty  factors  are applied in a 100  to 1
           discharge  situation, dilution  alone would mandate further testing.
           Where  very limited dilution  is available, it is recommended that
           toxicity-testing screening be  skipped  and the discharger be
           required to  begin  DEFINITIVE DATA GENERATION procedures (see Ref.
           No 24).

        Ambient Toxicity Analysis - Use ambient toxicity analysis to identify
        areas of  instream  toxicity  associated with specific dischargers.   This
        analysis  may  be most  useful when  conducted by the regulatory agency,
        but dischargers may be required to conduct the tests in conjunction
        with effluent tests.  A systematic plan for identifying problem areas
        is recommended.  This procedure is useful for multiple source
        discharge  situations.  The  analysis should be conducted concurrently
        with discharge-specific screening and must be done at low flow
        conditions.   A procedure is described in Appendix C (contained in  Ref.
        No. 24).
Source:  Reference No. 24.
                                     7-5

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                           8.0  REFERENCES
 1.   Regulatory Impact Analysis of Technical  Standards  for  Underground
     Storage Tanks.   Prepared for the EPA Office  of  Underground  Storage
     Tanks by ICF,  Inc.   August 24,  1988.

 2.   Based on SAIC  conversations with EPA staff members,  Office  of  Under-
     ground Storage Tanks.

 3.   Based on draft  data submitted to EPA,  Office of Underground Storage
     Tanks by Camp,  Dresser and McKee,  Inc. (1987).

 4.   Guard,  H.E.  James,  N.G.,  Roy B.  Laughlin, Jr.   Characterization  of
     Gasolines,  Diesel Fuels and Their  Water  Soluble Fractions.   Naval
     Biosciences Laboratory, Naval Supply  Center,  Oakland,  CA.   September
     1983.

 5.   Fate  and Transport  of  Substances Leaking from USTs;  COM Draft  Report
     January,  1986.

 6.   Cleanup of  Releases From Petroleum USTs:  Selected Technologies.  EPA
     Office  of Underground  Storage Tanks,  (EPA/530/UST-88/001) April  1988.

 7.   Underground  Storage Tank Corrective Action Technologies.  Hazardous
     Waste Engineering Research Laboratory, ORD/Office of Underground
     Storage Tanks/OSWER (EPA/625/6-87-015) January  1987.

 8.   Quantitative Structure Activity  Relationship  System  (QSARS)  Data
     Base. Environmental Research  Lab,  EPA Office  of Research and
     Development, Duluth, MN.

 9.   Quality Criteria  For Water 1986.   EPA Office  of Water Regulations and
     Standards  (EPA  440/5-86-001)  May 1, 1987.

 10.  Delta Cooling Towers,  Inc.; Ground Water Technology, Inc.

 11.  Permit  Writer's Guide  to Water Quality-Based  Permitting for Toxic
     Pollutants.  EPA  Office of  Water (EPA 440/4-87-005) July 1987.

 12. Training Manual for  NPDES  Permit Writers.  EPA Office of Water
    Enforcement  and Permits.   May 1987.

 13. Handbook for Sampling  and  Sample Preservation of Water and Waste-
    water.  U.S. Environmental  Protection Agency  (EPA-600/4-82-029)
    September 1982.

14. Summary of State Reports on Releases from Underground Storage Tanks.
    EPA Office of Underground  Storage Tanks (EPA/600-M-86/020) August
    1986.

15. Test Methods for Evaluating Solid Waste Volume IA:   Laboratory Manual
    Physical/Chemical Methods.  EPA Office of Solid Waste and Emergency
    Response (SW-846) November  1986.
                                8-1

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 16. North  Carolina Whole Effluent Toxicity  Program.  North Carolina
    Division  of  Environmental  Management, Biological Services Unit,
    (Undated).

 17. Kirk-Othmer  Encyclopedia of  Chemical Technology, Third Edition,
    Volume 11.   John  Wiley  & Sons,  1980.

 18. Oil  Spill Conference Proceedings,  sponsored by USEPA, U.S. Coast
    Guard;  American Petroleum  Institute held  in Los Angeles, CA, February
    25-28,  1985.

 19. The  Merck Index,  Tenth  Edition.  Merck  and Company, Inc. 1983.

 20. Science Applications International Corporation.  Based on memos and
    telephone conversations with EPA Region I, Industrial Permits
    Section.

 21. Science Applications International Corporation.  Based on memos and
    telephone conversations with the Maryland Department of  the
    Environment.

 22. Science Applications International Corporation.  Based on memo
    submitted by  the  Louisiana Department of  Environmental Quality,
    Office of Water Resources, Permits Section.

 23. Science Applications International Corporation.  Based on memos and
    telephone conversations with the Nebraska Department of  Environmental
    Control,  Water Quality  Division.

 24. Technical Support Document for  Water Quality-Based Toxics Control.
    EPA  Office of  Water,  September  1985.

'25. Lange's Handbook  of  Chemistry,  Thirteenth Edition McGraw-Hill Book
    Company,  1985.
                                 8-2

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              PART IV

DECISION TOOL FOR DEVELOPING WATER
QUALITY-BASED EFFLUENT LIMITATIONS

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                              TABLE OF CONTENTS


                                                                  Page
1.0  DECISION TOOL FOR DEVELOPING WATER QUALITY-BASED EFFLUENT
     LIMITATIONS	    1-1

1.1  BACKGROUND	    1-1

1.2  METHODOLOGY	    1-4

1.3  DISCHARGES FROM GASOLINE UNDERGROUND STORAGE TANK CLEANUPS.    1-7

1.4  DISCUSSION	    1-9

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                                LIST OF TABLES
Table                                                             Page

1-1         WATER QUALITY CRITERIA FOR POLLUTANTS IN DISCHARGES
            FROM GASOLINE UST CLEANUPS	   1-8

1-2         RECEIVING STREAM FLOW REQUIRED TO ACHIEVE WATER
            QUALITY CRITERION FOR BENZENE	  1-10
                                     ii

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                    1.0  DECISION TOOL FOR DEVELOPING WATER
                       QUALITY-BASED EFFLUENT LIMITATIONS

      This document defines a procedure for deciding whether  water quality-
 based effluent limitations should be required in a NPDES permit for discharges
 resulting from the cleanup of gasoline from leaking underground storage tank
 (UST) sites.

      The development  of one-hour maximum and four-day  average water quality-
 based effluent limitations according to  guidance set forth in the EPA
 Technical Support Document for Water Quality-Based Toxics Control (September
 1985),  or TSD, requires site-specific information.   Certain  assumptions have
 been made to  simplify the  application of this Decision Tool  to a wide variety
 of  site-specific conditions and circumstances in a manner consistent  with  the
 way the majority of the States now develop water quality-based effluent
 limitations.   The site-specific information  required for this simplified
 approach is limited to effluent flow,  effluent  concentration,  and receiving
 water flow.   Where the simplifying assumptions  are not  applicable,  the
 procedure developed here for use as a Decision  Tool should be modified
 accordingly.   The simplifying assumptions  and the limits they place on the
 application of the Decision Tool are summarized following the discussion of
 the methodology and its  application to leaking  UST cleanups.

 1.1  BACKGROUND
      Both the  Clean Water  Act  and  promulgated Federal  regulations  require  that
 all NPDES permits include  limitations  to achieve  all applicable  State  water
 quality  standards.  Further, NPDES  permits must  include  limitations that
 reflect  any total maximum  daily loads or wasteload  allocations set  by  EPA  or
 States  to  achieve applicable water  quality standards.

     EPA's policy and  legal  basis regarding  the use of State  water  quality
 standards  to set  NPDES permit  limits on  toxicants  is provided  by  the Office of
Water's  Policy  for  the Development  of Water  Quality-Based  Permit Limits  for
                                      1-1

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Toxic  Pollutants,  49 FR 9016,  March  9,  1984.   In  part,  this  policy  states

that:


           Where  violations  of  water  quality standards are  identified
           or  projected,  the State  will  be  expected  to develop water
           quality-based effluent limits for inclusion in any issued
           permit.   Where necessary,  EPA will develop these limits in
           consultation with the State.   Where  there is  a significant
           likelihood of toxic  effects to biota in the receiving
           water, EPA and the States  may impose permit limits on
           effluent toxicity and may  require an NPDES permittee to
           conduct  a toxicity reduction  evaluation (TRE).  Where
           toxic  effects are present  but there  is  a significant like-
           lihood that compliance with technology-based  requirements
           will sufficiently mitigate the effects, EPA and  the States
           may require chemical and toxicity testing after  instal-
           lation of treatment  and  may reopen the  permit to incorpo-
           rate additional limitations if needed to meet water
           quality  standards.   [Toxicity data,  which are considered
           "new information" in accordance  with 40 CFR 122.62(a)(2),
           could  constitute  cause for permit modification where
           necessary].


     Two forms of  State water  quality standards for toxicants can be used  to

set NPDES  permit limits:  numerical  standards  and narrative  standards.

Numerical  standards for some individual toxicants are contained in  virtually

all State  water  quality standards.   They are usually expressed as an instream

"not-to-be-exceeded"  concentration of a toxicant  (e.g., 0.019 mg/1  for total

residual chlorine).


     All States  also  have narrative  standards  for pollutants.  The  most common
form of the narrative standard contains  language  establishing that  the waters

are free from substances  in amounts  that will:


     1.  Settle  to  form objectionable deposits;

     2.  Float as debris, scum, oil, or  other  matter to form nuisances;

     3.  Produce objectionable color, odor, taste, or turbidity;

     4.  Injure, be toxic to, or produce adverse  physiological responses in
         humans, animals, or plants; and

     5.  Produce undesirable or nuisance aquatic  life.
                                      1-2

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 States must also include a procedure for translating this "free from" language
 into numerical "water quality criteria," from which can be derived water
 quality-based effluent limitations.  In addition,  a State's water quality
 standards rule is not considered administratively  complete unless it contains
 an antidegradation provision to protect existing water quality,  where it is
 better than the minimum required to support at least fishing and swimming.
 Degradation only can be allowed when certain tests of social or economic
 benefit are met.  Those tests are set forth in Section 302(b) of the Clean
 Water Act and the regulations developed to implement that section.

      The standard under (4)  above pertains to toxic effects and  is  an
 important element in any effective toxics control  strategy.   This standard
 should be used by States and EPA Regions to limit  both individual toxicants
 (where a toxic effect can be traced to a specific  chemical for which no
 standards or criteria exist) and whole effluent  toxicity  (where  it  is not
 obvious which chemicals are  causing toxicity or  where the limitation of
 generic effluent toxicity is more appropriate to that particular discharge
 situation).

      Clean Water Act Section 303(d)(l)(C) mandates  that water-quality based
 effluent  limits more stringent  than those required  by Best  Available
 Technology (BAT)  regulations be imposed on a site-specific  basis to  assure  the
 protection of receiving water quality with an ample margin  of safety.  Such
 limits, developed by the States,  are  to be based on the capacity of  receiving
 waters  to assimilate a particular toxic substance entering  the system from  all
 well-characterized  sources.   The  assimilative capacity of  the receiving  water
 for a particular  pollutant is defined in terms of  the rate  at which  that
 pollutant is  degraded at  a concentration equal to  the water quality  standard
 or the  existing concentration,  whichever is  lower under design low flow
 conditions.   That rate in pounds  or kilograms  per day is specified as  the
Total Maximum Daily Load  (TMDL).

     The  maximum  load  attributable  to nonpoint sources (load  allocation) is
 then subtracted  from the  TMDL,  and  the  difference is  apportioned  among point
sources according to an allocation rule.  This is the  point source waste load
allocation (WLA)  for the  particular substance and receiving water.  TMDL/WLA-
                                      1-3

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 based  toxic substance effluent limits  are  then  incorporated into all affected
 point  source discharge permits.

     NPDES permits  must be developed and issued in accordance with current
 permit issuance policies,  including current Agency operating guidance, permit
 issuance  strategies,  and State-specific agreements and workplans.  Applicable
 water  quality standards and site-specific  water quality data, as well as
 effluent  composition  data,  should  be assessed during the permit issuance
 process to determine  whether water quality-based permit requirements for
 toxics are necessary  for a particular  discharge.

     This  is particularly  important for waterbodies that have been identified
 as not achieving water quality standards pursuant to Section 304(1) of the
 Clean  Water Act.  For each stream  segment  or waterbody identified, Section
 304(1) requires that  individual control strategies be developed to reduce the
 discharge  of toxic  pollutants from point source discharges to the stream
 segment or waterbody.   In  addition, NPDES  permits incorporating all necessary
 and appropriate elements should be developed for all point sources identified.

     However,  the requirement to-develop water  quality-based effluent limita-
 tions  as necessary  to achieve applicable water  quality standards in the
 receiving  water is  not limited to  304(1) waterbodies.  The requirements of
 Section 303(d)(l)(C)  of the Clean  Water Act apply to all U.S. waterbodies
whose  water quality is protected under the Clean Water Act.

 1.2  METHODOLOGY
     The technology-based  effluent limitations  set forth in the Model Permit
are based  on removal  efficiencies  of product recovery and air stripping
 treatment  systems.  While  use of such  technologies may significantly reduce
 the contaminant  levels of  the pollutants of concern, technology-based effluent
limitations  may  not adequately address water quality concerns of affected
receiving  waters.

     To guide NPDES permit  writers in  implementing the requirements of CWA
Section 303(d)(l)(C),  EPA's Office of Water published the TSD.  This guidance
                                      1-4

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 describes  approved approaches  for  measuring  or  calculating  the  dimensions  of
 and  dilution afforded by zones of  initial  dilution  (ZIDs) and mixing  zones.
 This guidance also provides  procedures  for the  calculation  of chemical-
 specific and whole effluent  toxicity-based 1-hour maximum or 4-day average
 effluent limitations,  taking into  account  dilution  within the ZID or  mixing
 zone,  the  applicable  acute or  chronic water  quality criterion,  effluent
 composition  variability,  the receiving  water flow,  and  the  statistical
 confidence level  equivalent  to an  acceptable frequency  of recurrence  of
 effluent limitation exceedance.

      To quantify  the  relationship  between  the chemical-specific pollutant
 loading rate from a single discharge, or from multiple  discharges, and the
 downstream receiving  water quality at any  point outside of  the mixing zone,
 the  permit writer has  several  options.  For  toxic pollutant discharges to
 rivers and run-of-river  reservoirs, a simple mass balance equation can be
 used.  This  equation  is  based  on the assumption that the flow and pollutant
 concentration  of  the  effluent  are  fixed at their average values [i.e.,
 constant average  loading  rate); the flow of  the receiving water is treated as
a constant (generally  the once-in-ten-year,  7-day (7Q10) drought flow is
applied for  the chronic scenario and the once-in-three-year, 1-day low flow
 (1Q3) is applied  for  the acute scenario); and the rates of pollutant
production,  destruction, and storage within  the system are assumed to be zero.

     The simple mass balance equation as it applies to a single discharge  and
assuming complete mixing is as follows:
                                   Q. + Q
                                         e
     where:  C  - downstream concentration of pollutant
             C  = upstream concentration of pollutant
             Qs = upstream design flow of receiving water
             Ce = effluent pollutant-specific concentration limit
             Qe = effluent design flow.
                                     1-5

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      In situations where only a fraction of the  receiving water  flow  is
 allocated for mixing to ensure that the mixing zone  does not  inhibit  the  free
 passage of fish,  then a factor "f"  is used.  This  factor accounts  for the
 fraction of the upstream receiving  water flow that constitutes the allocated
 mixing zone.   To ensure that applicable water quality  criteria are achieved
 downstream of the effluent discharge, C is  defined such that:

                                 C = f-VQC

      where:   WQC » the pollutant-specific water  quality criteria to be
                    achieved in the  receiving water

 Rearranging and solving for the effluent concentration:

                           [f-VQC-(Qe  + Qs)] - Cs-Qs
     According  to  the TSD,  the final  effluent  limitations should be derived
taking  into  account  effluent  variability.  The more restrictive of the aquatic
acute,  aquatic  chronic or long-term human health-based 1-hour maximum and
4-day average limitations are then used as the basis for the final effluent
limitations.  If the permit writer chooses not to address effluent varia-
bility,  then acute aquatic and chronic aquatic or human health-based effluent
limitations  should be treated as  "not to exceed" levels.  As most States use
the "not  to  exceed"  approach,  that approach will be followed here.

     The  above  mass  dilution  equation is used  to calculate 4-day average "not
to exceed" effluent  limitations from  the more  protective of chronic aquatic
criteria  or  human  health  criteria, using the appropriate flow of the receiving
water and "f" is taken to be  the  fraction of the receiving water flow with
which the effluent mixes  in the mixing zone.

     The mass dilution equation can also be used to calculate 1-day maximum
effluent  limitations.   For  this purpose, the upstream concentration is usually
assumed to be zero,  the VQC becomes the acute  aquatic criterion, and "f" is
taken to be  the fraction  of the flow of the receiving water with which the
                                      1-6

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 effluent mixes in the ZID.-  In the absence of a ZID and  mixing zone,  however,
 water quality criteria must be met at the end-of-pipe.

      Where specific numerical criteria for a chemical or biological  parameters
 (such as toxicity) are absent or where exposure to  multiple  pollutants  is
 occurring via a complex effluent,  compliance with the standards must  be based
 on the general narrative criteria and on  protection of the designated use  of
 the receiving water.   This standard is implemented  via whole effluent toxicity
 testing using short-term tests (e.g.,  %8  to 96 hour) to  protect from  acute
 lethal effects at the edge of the ZID and long-term tests to protect  from
 chronic sub-lethal effects at the edge of the mixing zone.   In  both circum-
 stances the testing includes  exposure to  effluent diluted with  upstream
 receiving water to the extent dictated by mixing within  the  ZID or within  the
 mixing zone under drought  flow conditions.

 1.3  DISCHARGES FROM  GASOLINE UNDERGROUND STORAGE TANK CLEANUPS
      For the pollutants known to be present  in gasoline  UST  discharges  (see
 Part  III - Fact Sheet),  Federal  water  quality criteria have  been developed
 only  for benzene,  ethylbenzene,  toluene and  naphthalene.  The water criteria
 for each of these pollutants  are shown in Table  1-1, as  reported in Quality
 Criteria for Water 1986 (EPA  440/5-86-001).   The  air stripping  effluent
 concentrations  are reported in the  Fact Sheet.

      A  comparison of  water quality  criteria  to achievable undiluted air
 stripping effluent concentrations  (i.e.,  the  technology-based effluent
 limitations included  in  the Model Permit)  reveals that only  the water and  fish
 ingestion criteria for  protection of human health would  be exceeded for
 benzene.   A relationship for  the downstream concentration of benzene  is
established  below.  First, the assumptions explained in  the legend below are
made, and  the corresponding values  are substituted  in the mass  balance
equation.

             Cs   = assumed zero
             WQC = human health criterion for benzene (water and fish
                   ingestion) assuming an acceptable increased  lifetime cancer
                   risk at 10
                                     1-7

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                 TABLE 1-1.  UffTER QUttJTY CRTEERIA FDR PttLUEANTS FWSENT IN DESOBABGES FRCH GASQLDE 1ST CLEANUPS
                                                      (Cbnoaitrations in
Aquatic Life Protection

Benzene
Ethylbenzene
Toluene
Xylene
Naphthalene
Priority
Pollutant
Yes,
Tes
Yes
No
Yes
Carcinogen
Yes
No
No
No •
No
r^sisri
Acute
Criteria
5.30*
32*
17.5*

2.3*
Marine
Acute
Criteria
5.10*
0.430*
6.30*

.620*
Marine
Chronic
Criteria
0.70*

5.0*

2.35*
Hunan Health Protection
Water and
Fish
Ingestion
0.00066**
1.4
14.3


Fish
Consumption
Only
0.040**
3.28
424


.  * Means the data were insufficient to develop criteria;  the value presented is the lowest observed effect level (L.O.E.L.).
** Human health criteria for carcinogens are generally reported for three risk levels; the value presented is for the 10-  risk level.

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              C   = technology-based effluent  concentration for  benzene
              f   = assumed 1.0 (i.e.,  the entire  upstream receiving  water  flow
                    is allocated for mixing).
      C = f-VQC =
                    CsQs
                     (0.005 mg/1)  Q
      0.00066 mg/1 = 	 or  Qe  =  (0.152)QS
      For  the optional effluent  limitations:
                    (0.05  mg/1)  Qe
      0.00066  mg/1  = 	— or  Q  =  (0.013)QS
                        Q.  +  Q.
                             *s
     The  relationship  between  the  effluent  flow and  the receiving stream  flow
calculated above  can also  be expressed  in tabular form.  Table 1-2 shows  the
receiving stream  flow  required to  provide sufficient dilution to achieve  the
water quality  criterion  for benzene.

     It should be noted  that while the  benzene water quality criterion to
protect human  health is  lower  than that  to  protect aquatic life, the potential
need for  a whole  effluent  toxicity-based effluent limitation is not removed.
This is because of  the potential complex composition of UST-contaminated
ground water even after  treatment  has been  carried out utilizing the
equivalent of  the best available technology.  Whereas benzene, singly, is not
expected  to be acutely or  chronically toxic to aquatic life at effluent
concentrations necessary to protect human health, this situation may not
necessarily hold  for other constituents  that may be present.  In the absence
of water  quality  criteria  for  all  the potential contaminants present in the
effluent  or in anticipation of a potentially additive or synergistic toxic
effect from the complex mixture, it is appropriate to also include a whole
effluent  toxicity monitoring requirement in the permit.
                                      1-9

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             TABLE  1-2.  RECEIVING STREAM FLOW REQUIRED TO ACHIEVE
                         WATER QUALITY CRITERION FOR BENZENE
       Effluent Flow
(Gallons per
  minute)
(Gallons per
     day)
                            Receiving  Stream Flow
(Gallons per
   minute)
(Cubic feet
 per second)
Air stripping effluent = 0.005 mg/1
     1
     5
    10
    20
    50
   100
    1,440
    7,200
   14,400
   23,800
   72,000
  144,000
       7
      33
      66
     132
     329
     658
    0.015
    0.07
    0.15
    0.29
    0.73
    1.47
Air stripping effluent = 0.05 mg/1 (optional effluent limitations)
     r
     5
    10
    20
    50
   100
    1,440
    7,200
   14,400
   28,800
   72,000
  144,000
      77
     334
     769
   1,538
   3,846
   7,692
    C.17
    0.83
    1.7
    3.4
    8.6
   17.1
                                     1-10

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 1.4  DISCUSSION       .   :
      The use of the simple mass balance equation for calculating water
                                                   it
 quality-based effluent limitations presupposes  that  the  volumes  of  the ZID and
 mixing zone have been defined and that  the dilutions afforded  by mixing within
 those volumes have been accurately quantified.   In many  States no provisions
 are made for ZIDs (acute limitations are met  at  the  end-of-pipe) and  the
 mixing zone is defined as a function of the cross-sectional area of the
 receiving water under 7Q10  conditions (e.g.,  1/4 to  1/2).  The length  of the
 mixing zone is often chosen based on a  maximum allowable distance (e.g.,  1000
 meters).   Complete mixing with the 7Q10 flow  of  the  receiving  water is assumed
 to  occur within the mixing  zone.

      For fast-flowing or highly turbulent  rivers, the complete mix assumption
 may be valid.   But under 7Q10 conditions many rivers are slow  moving and
 relatively quiescent.   Under these conditions, mixing can be slow.  More'so
 than for rivers and run-of-river  estuaries, the  assumption of  uncomplies.ted,
 rapid  mixing with receiving water flow  to  achieve a  chemical-specific  or
 narrative standard at  the edge of the ZID  or  edge of the mixing  zone is likely
 to  be  inapplicable for lakes and  Impoundments, or for estuaries  and near-shore
 ocean  discharges.                                                       :

     For  complex mixing  situations,  permit  writers should refer  to the various
 hydrodynamic mixing models,  referenced  in  the TSD.   Such situations include
 submerged,  low velocity  discharges,  particularly those with significant
 temperature and or salinity differences  than  the surrounding water.  The
 application of the simple mass  balance  equation  is inappropriate  for these
 situations.  This  is also true  of  surface discharges with the  same properties.
 In  these  circumstances it is  necessary  to conduct site-specific mixing  studies
 under  conditions  that  represent a  worst-case  (e.g.,   maximum temperature and
density differences; lowest near-shore  flow,  tidal or wave action).  The
general approach  for performing appropriate mixing studies and reference  to
more detailed  guidance are  contained  in  the TSD.
                                     1-11

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