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 D DRAFT I r> ] ;-£ Ar Pending OMB^ approval J& STATUS [ C ]r i Bf^ Pending" AAf OSWER ^approva [*'Y" C-_\FOT revie'w^/or comment^ [€"*'! J^s5"r\ *^TJ*I~»""'-^ •* \. ^~ w ~ ^ :ff J ^D^. In developmenr or, circulatir REFERENCE (btfter documents): OSWER OSWER OSWER /£ DIRECTIVE DIRECTIVE Di ------- 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. ------- 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. ------- 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 ------- 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- ------- 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- ------- 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- ------- |