United States
                   Environmental Protection
                   Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
                   Research and Development
EPA/600/SR-95/135    September 1995
vvEPA        Project  Summary
                   Pollution  Prevention Opportunity
                   Assessment  United  States  Naval
                   Base  Norfolk Naval  Air Station
                   Dan Bowman and Jan DeWaters
                     This report summarizes work con-
                   ducted at the U.S. Navy's Naval Base
                   Norfolk, Naval Air Station (NAS) located
                   at Sewells Point in Norfolk, VA under
                   the  U.S. Environmental  Protection
                   Agency's (EPA's) Waste Reduction
                   Evaluations at Federal Sites (WREAFS)
                   Program, with support provided under
                   the Strategic  Environmental Research
                   and  Development (SERDP) Program.
                   SERDP is a cooperative effort between
                   DoD, DOE and EPA to develop environ-
                   mental solutions that enhance mission
                   readiness in Defense operations.
                     Under  the Chesapeake Bay Agree-
                   ment, Naval Base Norfolk  is a member
                   of the Tidewater Interagency Pollution
                   Prevention  Program. At NAS Norfolk,
                   the Navy and EPA have evaluated tech-
                   niques  and technologies to  reduce
                   waste generation from cooling tower
                   operations, cooperating on the Pollu-
                   tion Prevention Opportunity  Assess-
                   ment which identified areas for waste
                   reduction during operation and mainte-
                   nance of the NAS cooling towers. The
                   study followed procedures outlined in
                   EPA's  Facility Pollution Prevention
                   Guide. Opportunities were  identified for
                   reducing the generation of waste from
                   cooling  tower water  treatment opera-
                   tions. The options for changes  in op-
                   erational and treatment processes and
                   procedures were evaluated for their
                   potential to achieve pollution preven-
                   tion objectives, as well as for technical
                   and  economic feasibility.
                     This Project Summary was developed
                   by EPA's National Risk Management
Research Laboratory, Cincinnati, OH,
to announce key findings of the re-
search project that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).

Introduction
  The purposes of the WREAFS Program
are to identify new technologies and tech-
niques for reducing wastes from process
operations and other activities at Federal
sites, and to enhance the implementation
of pollution prevention/waste minimization
through  technology transfer. New tech-
niques and technologies for reducing waste
generation are  identified through waste
minimization opportunity assessments and
may be further evaluated through joint re-
search, development, and demonstration
projects.
  A cooling tower is an enclosed device
designed for the evaporative  cooling  of
water by direct contact with air. Cooling
towers are used in conjunction  with air
conditioning and industrial process equip-
ment, acting  as the heat  sink for these
systems by providing a continuous source
of cool water for process operations. Open-
system  recirculating cooling  towers  are
typically chosen for operation with air con-
ditioning and refrigeration  equipment be-
cause they are relatively inexpensive and
minimize heat rejection costs while con-
serving water.
  All of the cooling towers at the Norfolk
Naval Air Station identified in this PPOA
are of the recirculating, open-system type.
The Navy and EPA are currently evaluat-

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ing techniques and  technologies to  re-
duce wastes generated from cooling tower
operations  within the Norfolk MAS.  Ap-
proximately 28 open-system recirculating
cooling towers are currently operated at
18 buildings within the MAS. These  units
range in size from 5 to 300 tons, and are
all associated with  comfort  cooling sys-
tems  that  operate on  a seasonal basis
(approximately 6 mo/yr).

General Process  Description
  Approximately 598  buildings or struc-
tures  are located at the Norfolk MAS. Of
these, 18 buildings are equipped with air
conditioning systems that operate in con-
junction with evaporative recirculating cool-
ing towers  for a  continuous supply of
process water. The air  conditioning sys-
tems provide comfort cooling during warm
spring and summer  months, largely be-
tween April and October. The MAS  cool-
ing towers  do not operate during the cool
season. Table 1  is a master equipment
                         list of the 28 cooling towers providing pro-
                         cess water for the air conditioners which
                         service these  18 buildings. As described
                         in Table 1, these cooling towers are lo-
                         cated  on  building roofs, adjacent to an
                         exterior wall,  or  in a courtyard outside of
                         the building and range in capacity from 5
                         to  300 tons.  One  cooling tower ton is
                         equivalent to the removal of 15,000  BTU/
                         hr.
                           Table 1 indicates that only 10 of the 28
                         towers  are  currently  receiving chemical
                         treatment for  control of scale, corrosion,
                         and biological  fouling.  The  remaining
                         18 towers are  primarily small units and do
                         not receive chemical treatment during the
                         operating season.
                           The  last column in  Table 1  lists  the
                         system water volume in gallons for the 10
                         towers  receiving  treatment. The  volumes
                         are used to derive some of the alternative
                         treatment costs.  These system volumes,
                         estimated by  Base  personnel, depend to
                         a large extent on unit  size, but  are also
Table 1. Master Equipment List - Cooling Towers at Norfolk Naval Air Station
Equipment #
Building
                                   Location
                 Size (Tons)
            Volume (Gallons)
Cooling Towers Receiving Chemical Treatment*
081275
028197
028198
021087
024341
081218
093171
093172
 SP367
 SP254*
 SP256*
 V53
 V53
 SP29**
 U16**
 SP45
 SP91
 SP91
East outside
Roof
Roof
Roof
Roof
West courtyard
East side
South side
Behind building
Behind building
 75
200
200
150
175
300
300
125
100
 40
  127
  600
1,000
1,200
1,400
3,500
2,500
1,250
1,000
  400
Cooling Towers Not Receiving Treatment*
022189
080394
086933
080385
080386
080387
080388
022188
080389
052754
086998
093369
097454
021751
085676
085677
050597
083286
LP13
LP13
LP13
LP2
LP2
LP3
LP3
LP4
LP4
S33
S33
SP238
SP64
T26
T26
T26
U48
V82
Roof east side
Roof west side
Roof west side
Roof west side
Roof east side
Roof west side
Roof east side
Roof east side
Roof west side
Roof
West side
South end
Outside building
Roof east side
Roof west side
Roof
West side
Roof
25
25
25
25
25
25
25
25
25
20
5
20
20
20
60
60
7.5
45
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
* Refers to status of treatment at the time of report preparation, August 1994.
"Chemical treatment has been instituted at these new units since the site visit in June 1994.
***The cooling towers currently not receiving treatment are designed for chemical treatment.
—These two new units have not yet been issued equipment identification numbers.
influenced by the cooling tower locations
and piping systems.

Cooling Tower Discharge
Practices
  All  cooling towers at the MAS receive
makeup  water  from the  City  of Norfolk
public water supply. Each of the cooling
towers is equipped with a discharge valve
which directed  the  tower  blowdown  into
floor drains  located in the vicinity of the
heat  exchanger  and condensed  water
pump.

Cooling Tower Maintenance
Activities
  Maintenance  and operation of the cool-
ing  towers and  air conditioning units are
performed by the Public Works Command
(PWC),  under contract to the MAS. PWC
personnel do not currently have a system-
atic method  for managing the  MAS cool-
ing  towers.  Ten of the  28 MAS cooling
towers are serviced under a chemical treat-
ment  contract to PWC by one  of two  wa-
ter treatment specialists. Each of these 10
units  is  maintained  by a treatment  repre-
sentative, whose primary responsibility in-
cludes cooling  tower water testing  and
treatment.
  The remaining  towers,  which  are  not
serviced  by a chemical contractor, are the
responsibility of  the PWC mechanics.
These units  receive no  chemical  treat-
ment  during the operating  season  aside
from the occasional addition of biocide to
control excessive fouling.  General  main-
tenance  activities for the  cooling towers
not serviced by  a water treatment special-
ist include  an  annual overhaul  of each
unit, which is performed during the winter
months while the unit is not operating.
  Following  the annual overhaul,  PWC
maintenance personnel apply an algicide
to each  of  the cooling tower units  not
serviced  by a chemical contractor. A 1-gal
container of algicide is fed by continuous
drip to each unit to control biological growth
in the system.  Some of the towers may
occasionally receive additional biocide dur-
ing the operating season to control exces-
sive biological fouling, although application
rates  and schedules vary.

Chemical Addition Program
  At  the Norfolk MAS,  PWC personnel
purchase the chemicals, and a water treat-
ment  contractor tests the tower water, ad-
justs  control  parameters such as  bleed
and makeup water flowrates,  and admin-
isters chemicals as needed.
  Of  the 28 towers  in  operation, 10 are
currently receiving chemical treatment,  and
are serviced under contract by one of two
cooling tower water treatment specialists

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who also service other units on base. Four
of these units are equipped with chemical
pumps and  metering systems but were
not included in a chemical treatment con-
tract at the time of the site visit in June
1994. Chemical treatment programs have
recently been implemented  at these four
units.  In the future, all towers at the MAS
would be included  in a  chemical  addition
program.

General Procedure for
Chemical Procurement
  The procedure for procurement and  ad-
ministration of water treatment chemicals
involves a cooperative effort between  ap-
propriate PWC  personnel and the water
treatment or chemical contractor respon-
sible for the  unit. Each of the cooling tow-
ers under contract to a water treatment
specialist is  inspected sporadically to  en-
sure that the tower is operating  properly
and is receiving adequate chemical treat-
ment. Operating malfunctions are adjusted
and  corrected by  the  contractor. If  the
contractor  determines that  additional
chemicals must be purchased,  PWC is
notified. PWC personnel order the appro-
priate materials for delivery to the specific
building at the specific zone on base. Once
the chemicals arrive on site, the  contrac-
tor returns to administer treatment.
  PWC  personnel  who were interviewed
during the site visit stated that under no
circumstances do PWC maintenance per-
sonnel administer chemicals to the MAS
cooling towers,  regardless of whether or
not the towers are  maintained under con-
tract by a water treatment specialist. How-
ever,  at the time  of the site visit,  two
towers were observed that were  not cur-
rently under contract by a water treatment
specialist,  but that were connected to a
chemical holding  tank  and an  engaged
metering pump.  Thus, the actual chemical
administration procedures as practiced re-
main somewhat uncertain.
  A chemical exchange program exists
within each  zone  on base.  Most chemi-
cals are stored in the mechanical room of
the building in which they are used.  As
more  chemicals are needed by a particu-
lar  building,  PWC  will first check to see
that excess chemicals do not exist in stor-
age at another building  before ordering a
new supply.  This procedure  avoids stock-
piling  of surplus chemicals.

Chemical Descriptions and
Usage Data
  The chemicals used  for cooling tower
water treatment at the  Naval  Air Station
are presented in Table  2 along with their
primary ingredients, type of control, appli-
cation rate, and frequency of use. Typical
application rates for each chemical, shown
in Table 2, have been combined with cost
information to estimate annual usage rates
and  associated costs.  Usage  rates  are
based on  a  6-mo operating season, and
assume that all towers operate  with 4
cycles of concentration  at 100% capacity
for 12 hr/day.  As described above,  the
chemicals applied  to each of the MAS
cooling towers,  which total approximately
814 gal, are ultimately  discharged to the
environment through tower bleed. The to-
tal annual  chemical  costs  for the MAS
cooling towers currently receiving  chemi-
cal treatment are estimated at $13,900.
For water usage, Table 3 provides bleed
rates  and  make  up requirements  with
monthly costs.

Description  of Available
Options

Non-treatment
  Although non-treatment alternatives may
eliminate the application and subsequent
discharge  of cooling tower water treat-
ment chemicals, these may entail excess
water usage rates to control the accumu-
lation of suspended solids  in the system.
In addition, improper treatment  and man-
agement of  cooling tower water may re-
sult in excessive buildup of scale deposits
and biological fouling, ultimately resulting
in system failure.

Option 1. No Treatment
  Eighteen of the MAS cooling towers cur-
rently have no formal chemical treatment
program. One option for pollution preven-
tion is to  extend  this practice to all 28
MAS cooling towers. Under this scenario,
the towers would receive annual mainte-
nance. During  the off-season,  the units
would be externally cleaned with wire or
nylon brushes,  the heat exchanger end
plates would  be removed,  and  the tubes
reddened with a round  wire brush to re-
move scale deposits as needed. Approxi-
mately one gal of algicide would be added
to each unit  by  means of a drip feed.
  Refraining from chemical  treatment
would result in the annual consumption of
approximately 28 gal of algicide at a cost
of approximately $15 each, for a total of
$420.00/yr. This represents a savings of
approximately $13,300 annually in  chemi-
cal costs,  and a substantial reduction in
the discharge of cooling tower water treat-
ment chemicals to the environment. How-
ever, failure to properly maintain  the towers
during the operating season results in the
buildup of scale deposits and  significant
algal growth, often  leading to operational
down-time for necessary repair work and
mid-season  cleaning. This  is costly  in
terms of employee man-hours. In addi-
tion, the operational lifetime of a unit, typi-
cally  in the range of 15  to  20 yr,  is
significantly reduced by improper mainte-
nance and also by failure to provide ad-
equate  corrosion  protection. Systems
clogged by excessive scale deposits often
require acid dosing to clear blocked pas-
sageways; this is an aggressive treatment
procedure and can be harmful to the ma-
terials of construction, especially where
corrosion has  already exposed oxidized
portions of the metallic surface. Thus, while
a no-treatment option appears to be cost
effective in terms  of operating expenses,
ultimately, the expense of new equipment
purchases due  to  system failure  makes
this option less attractive.

Option 2. Continuous Bleed-off or
Blowdown
  The purpose in using recirculating cool-
ing  systems is to conserve makeup water.
Systems using  higher cycles of concen-
tration use less water. Achievable cycles
of concentration depend on  the concen-
tration of ions such as calcium and silica
in the makeup  water, since  these accu-
mulate  throughout evaporative  losses
which take place in the cooling tower. The
risk of severe scale or corrosion problems
increases dramatically with higher cycles
of concentration. Solids and impurities will
continue to accumulate until the system
water is removed through  bleed-off  or
blowdown. Dissolved oxygen increases in
a recirculating system because the water
is reaerated during each passage through
the  cooling tower.  In  normal practice, a
portion of the  recirculating water will be
removed through system blowdown in or-
der to maintain the concentration  of dis-
solved solids and gases at a required
level,  thereby  preventing  scale deposits
and corrosion.
  Maximum concentration factors are rec-
ommended  for  open cooling water sys-
tems  according to the hardness  of the
water and the  type of treatment applied.
Systems receiving makeup water of rela-
tively  low hardness or those  which  re-
ceive  effective  scale-inhibiting treatment
may operate  at high  concentration fac-
tors, maximizing the portion  of recirculat-
ing water and minimizing the makeup water
requirements. Without treatment, concen-
tration values of about 3 to 7 are enough
to cause some  salts to precipitate out as
scale. Various water treatment approaches
and devices have historically avoided scale
formation by  increasing  the bleed  and
makeup water rates  rather  than  control-

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Table 2.  Treatment Chemicals Currently Used in Norfolk NAS Cooling Towers
Trade Name
                 Principal Ingredients
                Type of Control
Application Rate
Usage Rate
Chemicals Used in Cooling Towers for Buildings SP367. SP254. and SP256
Formula 1100*    Poly [oxyethylene- (dimethyliminio) ethylene-
                 (dimethyliminio) ethylene dichloride]

Formula 1109*    Disodium ethylene bisdithiocarbamate
                 sodium dimethyldithiocarbamate
                 ethylene thiourea

Formula 2055     Sodium hydroxide
                 methylene phosphonic acid

Formula 7200     Potassium hydroxide
                 1-hydroxyethylidene-1, 1-disphosphonic acid
                                                            Biocide
                Biocide
                Scale/corrosion
                inhibitor
                Dispersant/
                antifoulant
Chemicals Used in Cooling Towers for Buildings SP45. SP91. V53. SP29and U16

Dicaton           Sodium hydroxide                           Non-Acid descaler
GAX-16*         Poly ethylene- ethylene dichloride
GAX-20*         2,2-dibromo-3 nitrilopropionamide
GAX-26          5-chlor-2 methyl-4-isothiazolin-3-one
                 2-methyl-4-isothiazolin-3-one

GCO-10-LM      Sodium molybdate
                 polyethylene- ethylene dichloride
GCO-10          Poly ethylene- ethylene dichloride
Penetrex         Not Available""
                                                            Biocide
                                                            Biocide
                                                            Biocide
                Scale/corrosion
                inhibitor
                w/biocide

                Scale/corrosion
                inhibitor
                w/biocide

                Dispersant/ antifoulant
2 qt/wk/300 ton
1/2 qt/wk/100 ton

2 qt/wk/300 ton
1/2 qt/wk/100 ton
1 qt/100 ton/day
approximately
30 gal/yr
2.5 gal/1,000 gal system
water

1/4 to 1/2pt/1,000gal
makeup water"

1/4 to 1/2pt/1,000gal
makeup water**

1/2 gal/1,000 gal system
water

1/2 to 1 pt/1,000gal
makeup water"
1/2 to 1 pt/1,000gal
makeup water"
                                                                                  1/2 pt/'1,000 gal
                                                                                  system water
1/wk
1/wk

1/wk
1/wk
                                                               Continuous
At start-up and
shutdown
                                                               At start-up or
                                                               cleanup

                                                               1/every other wk
                                                               1/every other wk
                                                               At start-up and
                                                               shutdown

                                                               Continuous
                                                                                                           Continuous
                          At start-up and
                          shutdown
*  Biocides are generally alternated on a weekly basis, to increase the effectiveness of treatment.
** Dosage varies depending on system load.
*** Principal ingredients are listed as proprietary information and are not available.
ling  calcium carbonate or silicate forma-
tion  by chemical or mechanical means.
  Minimum dissolved solids  and mineral
concentrations could be  maintained  by
operating the cooling tower  with  a con-
tinuous supply of fresh water and a maxi-
mum flow of tower bleed. A once-through
system would avoid the  buildup of solids,
gases and  impurities in the process wa-
ter, thereby limiting the potential for scale
deposits and  corrosion,  and would elimi-
nate the need for administration and dis-
charge  of  chemicals to the environment
through cooling tower blowdown. However,
the high operating costs of large amounts
of makeup water make this a fairly unat-
tractive option. Makeup water requirements
and  associated  costs are  reduced drasti-
cally by operating at higher cycles of con-
centration.
  Although  a continuous bleed will avoid
the buildup of dissolved solids and gases,
the potential still exists for algal and bac-
terial growth. Thus, the system may still
malfunction during the operating season if
the biofouling is  allowed to progress. Each
cooling tower unit  should  still receive an
annual overhaul and application of a 1-gal
biocide drip, which will increase annual
operating costs  accordingly.
       Additional Options and
       Recommendations
          In addition to the two pollution preven-
       tion  options identified  above, the PPOA
       team noted 6 alternative treatment options
       available. Table 4 provides an overview of
       all the  options. A detailed discussion  of
       the treatment  options  is provided in the
       full report. Three  technologies described,
       including  the DIAS-AID Tower Treatment
       XP-300, the KDF process, and the  mag-
       netic treatment application combined with
       integrated technologies, are attractive eco-
       nomically as well  as for pollution preven-
       tion. Recommendations for further research

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Table 3.  Bleed and Makeup Water Requirements and Monthly Costs at Different Cycles of Concentration*
Cycles of Concentration
                                                                                                                     10
                                                                                                                                    16
Evaporation (gpm)
Total bleed rate (gpm)
Makeup water (gpm)
Water cost ($/mo)**
3
3
6
$443.09
3
1.5
4.5
$335.07
3
1
4
$297.84
3
0.75
3.75
$279.22
3
0.4
3.4
$253.16
3
0.33
3.33
$247.95
3
0.2
3.2
$238.27
'Assumes a 100-ton open-system recirculating cooling tower operating at full capacity for 12 hr/day, with a 10°F temperature drop across the tower.
Pump circulation rate is 300 gal/min.

"Costs are based on a combined water and sewer cost of $3.40/1000 gal. Norfolk City water prices are currently $1.34/1000 gal, and sewer prices are
$2.06/1000 gal. Since cooling towers at the Norfolk NAS are generally not provided separate metering systems for drainage, combined rates are
charged for makeup water.  It is obvious from the above table that as the operating cycles of concentration increase, the volume of bleed discharged to
the drain is substantially reduced. Separate metering systems would allow calculation of a credit for makeup water which is not discharged to the drain
(e.g., evaporative losses), and would result in substantial savings.
Table 4.  Summary of Treatment Options: Advantages and Disadvantages
Treatment Option
  Advantages
Disadvantages
1.    No Treatment
2.    Continuous bleed
3.    Conventional
     chemical addition
4.    DIAS-aid tower
     treatment XP-300
5.   pH adjustment
6.    Base exchange and
     ion exchange
     processes

7.    KDF process
8.    Magnetic applications
•Minimal chemical costs
•Minimal discharge of chemicals to environment


•Minimal chemical costs
•Minimal discharge of chemicals to environment

•Fairly reliable method
•Several chemical options available for customized
treatment

•Recently developed product which has demonstrated
effective treatment
•Operates with little or no system bleed
•Cost effective, in terms of chemical and water use

•Minimal chemical costs; sulfuric acid an economical choice
•Minimal discharge of chemical to environment
•Minimal chemical costs
•Minimal discharge of chemical to environment
•Produces soft, non-scaling water

•Minimal chemical costs
•Minimal discharge of chemical to environment
•Waste product consists of recyclable metallic alloy
•System is self-regulating by responding to changes in pH
•Minimal chemical costs
•Minimal discharge of chemical to environment
•Lifetime warranty
•Minimizes maintenance demands
•Effective against scale and corrosion
•High maintenance demands
•Poor system operation
•Reduced operating lifetime of equipment

•Excessive water consumption and associated
 costs

•Treatment can be costly in terms of chemicals
purchased, required testing and maintenance
•Chemicals may be limited in discharges

•Limited operating experience on which to base a
 level of confidence
•Additional intermittent treatment may be needed for
 control of biological growth

•Difficult to maintain adequate control
•Undesirable dissolved solids may still accumulate in
 system

•Softened water may be corrosive
•Generally quite expensive
•Provide scale control only

•Limited operating experience on which to base a
 level of confidence
•Additional filter unit necessary for solids removal
•May cost slightly more than conventional chemical
 treatment
•Operating experience shows inadequate control
 over microbial growth; dosing with biocide or acid
 may be necessary to maintain a clean system

•Limited operating experience on which to base a
 level of confidence
•Additional sidestream treatment usually necessary
 for solids removal
•Additional control may be required for microbial
 growth

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Table 4. (continued)
Treatment Option
  Advantages
Disadvantages
9.    Ozonation, U. V. light
     treatment
10.  Sidestream treatment
•Minimal chemical costs
•Minimal discharge of chemical to environment
•Effective Sterilization Techniques
                          •Effective treatment for solids removal and control of
                           fouling
                          •Minimal chemical costs
                          •Minimal discharge of chemical to environment
                          •Several options are available
•Generally quite expensive
•U. V. limited to small size; ozone limited to larger size
 units
•Not effective against scale or corrosion

•Generally used in conjunction with another treatment
 method to reduce solids and the potential for
 microbial growth; not an effective stand-alone
 treatment methodology
include site visits to facilities which em-
ploy each  of  these three types of treat-
ment technologies,  in  order  to  gather
operating data  and to observe the sys-
tems in  operation. Additional  information
                  gained through site visits would  be used
                  to select an appropriate technology option
                  to be used in a demonstration project de-
                  signed to evaluate the potential for effec-
                  tively treating the MAS cooling tower water.
       The full  report was submitted in fulfill-
     ment of Contract No. 68-D2-0181, Work
     Assignment  No.  1-011 by TRC Environ-
     mental  Corp. under the sponsorship of
     the U.S. Environmental Protection Agency.

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Dan Bowman and Jan DeWaters are with TRC Environmental Corp., Chapel
  Hill, NC 27514.
Kenneth R. Stone is the EPA Project Officer (see below).
The complete report, entitled "Pollution Prevention Opportunity Assessment
    United States Naval Base Norfolk Naval Air Station," (Order No. PB95-
    264040; Cost: $27.00, subject to change)  will be available only from:
       National Technical Information Service
       5285 Port Royal Road
       Springfield, VA 22161
       Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
       National Risk Management Research Laboratory
       U. S. Environmental Protection Agency
       Cincinnati, OH 45268
   United States
   Environmental Protection Agency
   National Risk Management Research Laboratory
   Cincinnati, OH 45268

   Official Business
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   $300
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   PERMIT No. G-35
   EPA/600/SR-95/135

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