vvEPA
               United States
               Environmental Protection
               Agency
            Office of
            Solid Waste and
            Emergency Response
DIRECTIVE NUMBER:
               9483.01(84)
               TITLE: E: Permitting of Hazardous Waste Treatment/Storage
                    ' Tanks " '              ~ "
               APPROVAL DATE:   2-23-84

               EFFECTIVE DATE:   2-23-84

               ORIGINATING OFFICE: E:, off ice of -solid waste

               0 FINAL

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               REFERENCE (btfter documents):
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 PARTS  264 AND  265   SUBPART J - TANKS                          DOC:  9483.01(84)


 Key  Words:     Minimum Shell Thickness, Tank

 Regulations:   RCRA  Subpart J, 40 CFR 264.194(b),  270.14(b)(50)

 Subject:       Permitting of Hazardous Waste Treatment/Storage Tanks

 Addressee:     Regional RCRA Branch Chiefs

 Originator:    John  H. Skinner, Director, Office of Solid Waste

 Source Doc:    #9483.01(84)

 Date:          2-23-84

 Summary:

 Establishing Minimum Shell Thickness

     Subpart J standards require that a minimum shell thickness be specified in
 the  permit for all  regulated hazardous waste storage/treatment tanks, except for
 covered underground tanks that cannot be entered  for  inspection.  The applicant
 must demonstrate to EPA that the tank complies with all applicable standards
 before the decision to permit the tank is made.   The  applicant should obtain
 current thickness data from the pre-permit inspection and include it in the
 Part B application.

     In general, RCRA-related metal tanks should  not  have a shell thickness of
 less than 1/8 inch.  The permit writer can use different methods to determine
 the appropriate thickness for metal tank shells depending on size, shape, and
 age.  S/he can use standard industry codes, but these may not be practical in
 some cases.

     The permit writer can establish minimum shell thickness for fiberglass-
 reinforced polyester (FRP) tanks and concrete tanks,  once the tank is inspected,
 by subtracting a small amount from the actual measured shell thickness  (less
 than O.I inch for FRP tanks and less than 10 percent  for concrete tanks).  The
 applicant should line or coat concrete tanks with a compatible material to
 prevent possible migration of hazardous wastes through its walls.

 Tank Inspections

     The applicant should conduct an initial inspection prior to the issuance of
 a draft permit.  This inspection should include draining the tank, examining the
 tank interior, and measuring shell thickness through  ultrasonic or some other
non-destructive test method.

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Continued from Document 9483.01(84)


     The inspection plan, required by §270.14(b)(5),  must contain detailed
procedures for conducting periodic, comprehensive inspections for each per-
mitted tank, and should specify the procedures for emptying the tank,  methods
for performing the inspection (which should include an inspection of the tank
interior), and a-prescribed methodology for performing shell thickness measure-
ment* if the internal inspection indicates deterioration that would lead to
thinning of the tank wall to less than the minimum thickness prescribed in the
permit.'  The Downer/ opera tor should perform periodic inspections; at least once
every two years, unless s/he can demonstrate that a more lengthy interval is
appropriate.  Tanks storing or treating corrosive wastes, heated and/or pres-
surized tanks, tanks with relatively thin shells, fiberglass tanks, and concrete
tanks should be considered for more frequent inspections.  The frequency of
comprehensive internal inspections should be established on a case-by-case
basis.

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                                                              9483.01 (34)

                                 ^^ o  I f*- Q - -
                                 ^3  198'


 .•:t.: i' .vANnr.'f;

                    nn  f «r:nJ.t.t inrj  of  Hazardous  w«ato»
                   Tanks

 hi!o-i:     John  h.  Skinner,  L-irector
          office of Solid Waste

 TO:  '     Wogional  PCRA  Brancn Chiefs
      This memorandum  provides guidance  to  permit  writers  on  several
 issues  regarding permitting ot" hazardous waste  treatment  and
 storage tanks.  Several of the current  PCRA  Subpart  J  standards,
 particularly the requirements nor minimum  shell thicknesses  and
 farioaic inspections, have boen difficult  to implement and have
 in  some cases been  resolved differently by the  regional offices.
 Several regions have  requested guidance on these  regulatory  re-
 quirements  to provide a more consistent national  approach to
 permitting  RCRA regulated tanks.

      The following  guidance is applicable  only  to tanks permitted
 under the current Subpart J standards.


 bstaolishing Minimum  Shell Thicknesses

      The current Subpart J standards  require that a  minimum  shell
 thickness be specified in the permit  t'or every  regulated  hazardous
waste storage/treatment tank'.  This requirement applies to all
 tanks (except for covered underground tanks  that  cannot be entered
 tor inspection), and  it cannot be waived.

      The current, actual shell thickness of  each  tank  should  be
determined  prior to the issuance of a draft  permit.   It is essential
that  the applicant  demonstrate to KP\ that the  tank  complies with
all applicable standards before the decision is made to permit  the
tank.   Current thickness data should Lie obtained  from  the pre-permit
inspection, and included in the Part B  application (-see dis-
cussion below).

      Sevoral methods  can be used to determine the appropriate
mininun thickness for netal tank shells.   Standard formulas  can
bo used, such as the  formula specified  in  the API Code 650.   This
formula (also presented in the early  "Tommy  Tank" guidance)
should  be used, however, only for very  large (over 50,000 gallon

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capacity)  non-yrossurized metal tanUs.  For smaller rretal tanks,
the  thicknesses prescribed  in  the r;L  142 code can be used, even
tncu'.jh  this cede  is  intended primarily  for tanks storing ignitable
Liquids.   Other cedes  for more specialized tanks, such as the
AhME iSnction VIII cede  fcor  pressure vessels, can also be used
tor  certain types of tanks".  It should  be understood that the
shell  thicKndsses prescribed in industry cedes are ninipium thick-
nesses  to  ensure  structural integrity,  and do not inclur.o allowance
for  corrosion.

      Tho use of standard industry codes nay not be practical for
'many metal tanks, such'  as' irregularly shaped tanks, older tanks
not  built  to standard  codes, and others.  In such cases, permit
writers should specify  a minimum thickness that is sufficient
not  only to contain  the liquid contents, but also to withstand
normal  operational stresses and minor accidents (e.g., being hit
by a forklift), without massive failure.  Discussions with various
industry officials have suggested that  as a general rule, a metal
shell  thickness of 1/8" (0.1J5")  -3 a satisfactory minimum thick-
ness to provide an adequate deqr-.-e of safety against normal oper-
ational contingencies  (this thickness would not be sufficient,
however, for pressurized tanks, or most large tanks of over
50,000 gallons capacity).   Accordingly, it is recommended that
the  minimum shell thickness specified in RCRA permits for metal
tanks  be not less than  1/8".   If a RCRA regulated tank is measured
and  found  to have a  shell thickness of  less than 1/8", the permit
writer  should consider  requesting that  the applicant provide
additional information  (such as-an engineer's certification) to
demonstrate that  the tank is structurally sound and can  withstand
normal  operational streses  and minor  accidents.

      For fiberglass  reinforced polyester  (FRP) tanks, the standard
formulas for determining. shell thickness based on structural
criteria,  such as those used for metal  tanks, are not appropriate.
Structural strength  of  FRP  tanks  is more a  function of how  the
tanks  are  manufactured  (e.g.,  filament  wound, fiber mat, etc.)
and  the specific  bonding resins used, rather  than  the thickness
of the  wall.  In  general, the  primary concerns for  PKP  tanks  are
shell  cracking  (due  to  improper installation  cr other causes)  and
erosion of the  resin layer  of  the interior  tank wall  surface.
Each FRP tank should be inspected internally  prior  to permitting
to determine if the  inner resin layer is  intact, or has  deteriorated
or eroded  such  that  glass fibers  are  exposed.  FR?  tanks which
exhibit deterioration  of the inner  resin  layer, or  other evidence
of wall deterioration,  snould  be  repaired or  taken  out  of service.
For  FRP tanks in  good  condition,  an appropriate  approach to  estab-
lishing minimum shell  thickness  is  simply  to  subtract  a  snail
amount  from the actual  treasured shell thickness,  to allow for
possible construction  irregularities  and/or  sons  limited erosion
of the( inner resin layer.   This  "allowance"  should  usually  be
0.1" or less, since  the inner  resin  layers  c.f rvost  fiberglass
tanks  as manufactured  typically do  not  exceed 0.1".

      Minimum shell thicknesses for  concrete tanks  can be estab-
lished  in  a similar  manner. Once the tank  has  been inspected

                             -2-

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IMUI" C.II t(JMI*.'S3 C«3II Ut: :    Uv 3>JU<_ r. C i_ •_ L I Hj a n< V, I I A. i.ia i.   Xa.«j«r (nw
rore than 1U%) tren the actual measured thickness of the tank
wall.  Existing concrete tanks in good condition can, with few
exceptions, be presumed to have arterjuata "snell thickness",
since concrete tanks are typically designed tor substantially
greater than normal anticipated structural stresses.

     A primary concern with concrete tanks is possible migration
oc Mflsarvicu.i waacod tnrough the walls ot the tan*.  Conctfnta
tanks should be lined or coated with a compatible material
(even it the wastes are compatible with the concrete), unless
the applicant can aenonstrate that migration of wastes through
the tank walls, will not .occur over the. li.fe of. the. tank.


Tank Inspections

     To ensure that regulated tanks are in compliance with
applicable RCRA standards, each tank should be thoroughly  in-
spected by the applicant or another firm hired for the purpose,
prior to issuance of a draft pernit.  This initial inspection
should involve draining the tank and examining the tank interior
tor leaks, cracks, corrosion, liner or coating failure and
other signs of deterioration.  The inspection should also  include
taking shell thickness measurements using ultrasonics or another
non-destructive test method.  Attachment A presents suggested
methodologies for conducting ultrasonic shell thickness testing
for both vertical and horizontal metal tanks.  Ultrasonic  and
radiographic non-destructive testing must be performed by
qualified personnel.  If the applicant proposes to use his own
personnel to perform such testing, he should be required to
demonstrate that those persons are competent in the use of the
test equipment,, through course work or other training or experience

     The inspection plan required by §270 .14(b)(5) must contain
detailed procedures for conducting periodic, comprehensive
inspections for each permitted tank, as required  in §264.194(b).
This periodic inspection should include a thorough  inspection
of the tank interior.   The inspection plan should specify the
procedures that will be used for emptying the tank, and the
methods to be used in performing the inspection.  If  the internal
inspection indicates evidence of significant corrosion, erosion
or other deterioration which would lead to thinning of  the tank
wall to less than the minimum thickness prescribed  in  the  permit,
the inspection plan should specify that the applicant  shall
then perform shell thickness measurements according to  a pre-
scribed methodology.

     The frequency of the comprehensive internal  inspection
should be established taking into account the age and  general
condition of the tank, the material of construction and relative
compatibility with the wastes to be  stored, waste temperature,
and other relevant factors.  It is recommended that  the periodic
inspections be performed at least once every  two  years, unless
the applicant can demonstrate that a more lengthy interval is
appropriate.  More frequent inspections should be considered for

                            -3-

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sone tanks, including:  tanks storing or treating corrosive
wastes, heated and/or pressurized tanks, tanks with relatively
thin shells, fiberglass tanks, concrete tanks.


Tank checklist

     Attachment B is a checklist developed by Region I which can
be. a. useful tool for permitting tanks.   The checklist can be
used by permit applicants as "a format for presenting the required
information for each tank to be permitted.  It should be noted,
however, that some of the data asked for in the checklist are
not required by the regulations, and applicants should thus be
informed that use of the checklist is entirely optional.  The
checklist can be sent to applicants along with other appropriate
guidance documents as part of the Part B call-in letter.  Permit
writers can also use the checklist as a means of organizing the
information for each tank in the Part B application.


Attachments

cc: Regional Permits Section Chiefs
    J. Lehman
    S. Lingle
    T. Grogan
    P. Guerrero
    B. Weddle
    K. Gray
    PAT staff
                            -4-

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