United States
Environmental Protection
.Agency
_«--»:.:. J . ,
Solid Waste and '"'""•
Emergency Response
(5305W)
PB96-207 089
EPA530-R-96-027
vvEPA
RCRA, Superfund & EPCRA
Hotline Training Module
Introduction to:
Drip Pads
(40 CFR Parts 264/265, Subpart W)
Updated July 1996
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DISCLAIMER . . ' . ' ,'
This document was developed by Booz-Allen & Hamilton Inc. under contract 68-W6-0016 to EPA. It is intended
to be used as a training tool for Hotline specialists and does not represent a statement of EPA policy.
The information in this document is not by any means a complete representation of EPA's regulations or policies.
This document is used only in the capacity of the Hotline training and is not used as a reference tool on Hotline
calls. The Hotline revises and updates this document as regulatory program areas change.
The information in this document may not necessarily reflect the current position of the Agency. This document
is not intended and cannot be relied upon to create any rights, substantive or procedural, enforceable by any
party in litigation with the United States.
RCRA, Superfund & EPCRA Hotline Phone Numbers:
National toll-free (outside of DC area)
Local number (within DC area)
National toll-free for the hearing impaired (TDD)
(800) 424-9346
(703)412-9810
(800) 553-7672
The Hotline is open from 9 am to 6 pm Eastern Standard Time,
Monday through Friday, except for federal holidays.
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DRIP FADS
CONTENTS
1. Introduction : 1
. 2. Regulatory Summary .'
x2.1 General.
2.2 Design Standards ; ,
2.3 Operating Standards.......................
2.4 Inspections....
•2.5 Closure • :
2.6 Drip Pads Used for Temporary Accumulation.
2.7 Applicability to Storage Yard Drippage
3
3
4
7
7
s:
8
9
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Drip Pads-1
1. INTRODUCTION
The Resource Conservation and Recovery Act (RCRA) regulations governing
hazardous waste management facilities, found in 40 CFR Parts 264 and 265, consist
of general facility standards as well as unit-specific design and operating
requirements for commonly used hazardous waste treatment, storage, and disposal
units, such as tanks, containers, and landfills. .Most of these regulations are
discussed in other modules. -
Since the early 1980s, EPA has continuously modified RCRA's hazardous waste
program to encompass a broader range of waste materials which may pose a threat
to human health and the environment. Some of these newly identified wastes
proved rather difficult to manage in traditional hazardous waste management units
that were established in the original regulations. In 1990, EPA listed wastes from
wood preserving processes as hazardous. Many of these wastes are generated by
allowing preservative to drip from wood onto concrete pads, called drip pads. To
facilitate proper handling of these wastes, the Agency developed design and
operating standards for drip pads used to manage hazardous waste. This module
explains these standards.
When you complete this module, you will be able to explain the regulatory history
and purpose of drip-pads. Specifically, you will be able to:
• Define a drip pad ^
• Summarize1 the design and operating standards for drip pads
• Describe the relationship between generator accumulation provisions and
drip pads. s , '
Use this list of objectives to check your understanding of this topic after you .
complete the training session.
The information in this document is not by any means a complete representation of EPA s regulations or policies,
but is an introduction to the topic used for Hotline training purposes. ,
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2-Drip Pads
The information in this document is not by any means a complete representation ot br A s regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Drip Pads - 3
y. • 2. REGULATORY SUMMARY
* 'r
Drip pads are hazardous waste management units that are unique to the wood
preserving industry. The history of drip pads is closely tied to EPA's decision to list
wood preserving process wastes as hazardous. The wood preserving industry uses a
standard process to produce treated wood products which are resistant to natural
decay. Fresh lumber is treated with a preservative solution and then placed on a
concrete pad where it remains until any excess solution not absorbed by the wood
has stopped dripping. Once the dripping stops, the wood is transferred to a storage
yard and all excess preservative that has dripped onto the drip pad is removed as
waste.
On December 6, 1990, EPA promulgated regulations listing certain wood preserving
process wastes as hazardous (55 FR 50450). The listings specifically include
wastewaters, process residuals, preservative drippage, and spent formulations from
wood preserving operations using chlorophenolic formulations (F032), creosote
formulations (F034), and inorganic preservatives containing arsenic or chromium
(F035). Once EPA listed these wastes as hazardous, the concrete pads typically used
for. collecting the drippage became subject to regulation under RCRA Subtitle C as
hazardous waste management units. Since the drip pads had never been regulated
and did not resemble any of the existing hazardous waste management units (e.g.,
tanks or containers), there were no protective regulations for drip pad
owners/operators to follow. To ensure proper waste management, EPA developed
unit-specific standards for the design, installation, operation, and closure of drip
pads at the same time these new listings were promulgated. Shortly after
promulgation, difficulties' in implementing the new standards within the wood
preserving industry compelled EPA to grant an. administrative stay delaying the
effective date of the drip pad standards, pending further administrative action. This.
module addresses the current standards for drip pads as hazardous waste
management units. . ,
2.1 BACKGROUND
A hazardous waste drip pad is a non-earthen structure consisting of a curbed, free-
draining base that is designed to convey excess preservative drippage, precipitation,
and surface water run-on from treated wood operations to an associated collection
system. Drip, pads, as defined in §260.10, are exclusive to the wood preserving
industry. ... ' " .
Preservative solutions are commonly applied to wood products using a pressure
treating process. Once the preservative solution has been applied to the wood, it is
removed from the process unit and excess solution is allowed.to drip from the wood
onto drip pads. As a result of this process, excess solution dripping from the wood
'becomes a solid waste and, depending on the type of preservative used, a hazardous
The information in this document is not by any means a complete representation or EPA s regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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4 - Drip Pads
waste. A drip pad is used solely for the collection and temporary accumulation or
storage of excess wood preservative prior to its removal from the unit.' Hazardous
wastes generated by other processes would never be placed on a drip pad for
treatment, storage, or disposal; regulated drip pads will be found only at wood
preserving facilities.. ' '
Generally, the performance standards for most hazardous waste management units
vary depending on whether the unit is permitted or interim status. The permitted
and interim status standards for drip pads, however, are virtually identical.
Distinctions are made between new and existing drip pads. A drip pad is considered
"existing" if construction was completed, or a binding construction agreement was
made, prior to December 6, 1990; all other drip pads are considered "new." The
owner/operator of a new drip pad must comply with all codified standards for unit
design, installation, operation, and closure, and the unit is regulated throughout its
operating life. Existing drip pads/however, may need to be modified or otherwise
upgraded to ensure adequate protection of human health and the environment.
Upgrading steps and corresponding deadlines for existing drip pads are addressed in
the regulations and are discussed later in this module. Other specific regulatory
differences between existing and new drip pads are discussed in the context of each
requirement. ,
2.2 DESIGN STANDARDS
-i
The design standards for hazardous waste drip pads are codified in §§264.573 and
265.443, and are summarized in Figure 1. Drip pads must be designed and
constructed of non-earthen materials that have enough structural strength to
prevent failure of the unit under the weight of the waste, preserved wood products,
personnel, and any moving equipment used in wood preserving operations. The
remainder of the drip pad design requirements are specifically intended to control
the liquid and semi-liquid wood preserving wastes that are stored or accumulated
on the drip pad. To prevent wastes from running over the edges of the flat drip pad
surface, the owner/operator must construct a raised curb or berm around the
perimeter of the pad. In order to simplify removal of wastes from the drip pad, the
surface must be sloped toward a collection unit, such as a sump. Unless this
collection unit has enough capacity to hold precipitation run-on and preservative
drippage, or unless the pad is protected from precipitation (e.g., indoors or covered),
a stormwater run-on and run-off control system must be used. All new and existing
drip pads must be in compliance with these design criteria.
Additional drip pad design standards include measures to prevent infiltration of
liquid waste into or through the unit's structure. Impermeable sealers, coatings, or
covers can reduce the quantity of waste absorbed into the unit itself. Infiltration
protection, especially for porous materials like concrete, is important because when
liquid wastes migrate into the structure, the likelihood of an uncontrolled release
into the environment increases. As a result, drip pads will be more susceptible to
The information in this document is not by any means a complete representation of EPA s regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Drip Pads - 5
Pad
Drip Pad
Surface
Liquid
Collection
System
Liner and Leak
Detection System*
Figure 1
DRIP PAD DESIGN STANDARDS
. Design Criteria
Must be constructed of non-earthen materials
(e.g., concrete, metal)
Must provide sufficient structural strength to
prevent unit failure >
•. Must be constructed with a raised berm around
perimeter to prevent waste run-off into the
environment
• Must be sloped toward a liquid collection unit
• Must be treated with impermeable sealers,
coatings, or covers to meet specific
permeability performance standards*
Must allow for removal of waste for proper
RCRA management and to prevent overflow
Must include run-on and run-off controls as
necessary
Is subject to regulation as a hazardous waste
tank
• Is not subject to specific permeability criteria
• Must signal releases from the drip pad at the
earliest practicable.time
• Must be structurally sound and chemically
compatible
Dust
Controls
Must be used to minimize tracking of waste by
personnel and vehicles
Citations
§264.573(a)(l)
§265.443(a)(l)
x
§264:573(a)(5)
§265.443(a)(5)
§264.573(a)(3)
§265.443
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6 - Drip Pads
cracking and deterioration, and removal of all wastes from the unit becomes more
difficult. Because absolute impermeability is not feasible, EPA put a performance
standard for permeability of the surface coating in the regulations. In general, drip
pad owners/operators can achieve the required level of protection using most of the
sealers, coatings, and covers currently available on the market.
Finally, EPA intends the drip pad design standards to prevent migration of waste
from the unit into the surrounding environment. Provision of an underlying
synthetic liner and leak detection system can prevent waste migration into adjacent
subsurface soil, groundwater, or surface water. No specific permeability criteria are
designated for a drip pad liner, but the unit's leak detection system must be able to
signal releases from the pad at the earliest practicable time. For all pads constructed
after December 24,1992, EPA also mandates the installation of a leak collection
system to remove wastes accumulating on the synthetic liner. In addition, any
sumps or other collection devices used in association with a hazardous waste drip
pad are regulated as hazardous waste tanks, and the owner/operator of the unit
must comply with all applicable provisions in Subpart J of Parts 264/265.
f s'
When the regulations were first promulgated, a new drip pad was required to
conform to the standards for bom surface impermeability and liners arid leak
detection. Since that time, the Agency revised the drip pad management standards;
now owners/operators of new drip pads may choose between these two options. "
EPA does not recommend one option over the other, but believes that, over the
long run, installation of a liner and leak detection system will require less
maintenance and be less costly than repeated applications of surface coatings. Prior
to use for hazardous waste management, the owners/operators of new drip pads
must implement one of the design options.
All existing drip pads (i.e., drip pads that were constructed or for which a binding
contract was made prior to December 6,1990) must be sealed, coated, or covered with
an impermeable material .meeting regulatory specifications. An existing drip pad
that already has a surface coating will need no further upgrading to comply with
federal standards. The owner or operator of an existing drip pad may choose to
modify the unit to meet the performance standards for liners and leak detection
systems, but is under no federal obligation or deadline to do so. An existing unit
which is upgraded to include a liner and leak detection system is no longer subject
to the surface coating requirements. Before such an upgrade is completed, however,
the owner or operator must develop and submit a written plan for modifying the
unit to the Regional Administrator. The plan must include a description of all
proposed repairs and upgrades, as well as a schedule by which modifications will be
made. An independent, qualified, registered, professional engineer must certify that
the proposed plan will bring the drip pad into compliance with all applicable liner,
leak detection, and' leak collection standards.
The information in this document is not by any means a complete representation ot hKA s regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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Drip Pads - 7
2.3 OPERATING STANDARDS
All new and existing drip pads must be in compliance with the operating standards
codified in §§264.572/265.442. Generally, a drip pad must be maintained free of
cracks and show no signs of corrosion or other forms of deterioration. Drip pads
must also be cleaned frequently to allow for weekly inspections of the entire drip
pad surface without interference from accumulated wastes and residues. The
manner and frequency of cleaning required is determined on a case-by-case basis.
The facility's operating log must document the date, time, and method of each
cleaning, and all cleaning residues must be managed as hazardous wastes under
RCRA Subtitle C In addition to occasional cleaning, drippage and precipitation
must be emptied into a collection system as often as necessary to. prevent waste from
overflowing the curb around the perimeter of the unit. All collection tanks must be
emptied as soon as possible after storms to ensure that sufficient containment
capacity is available to accommodate continued run-off:
2.4 INSPECTIONS
v..
Three types of inspections are required for drip pads. First, an existing drip pad must
be inspected to ensure that the unit is still protective of human health and the
environment and thus fit for continued use. Until the unit is in full compliance
with the current standards, an independent, qualified, registered, professional
engineer must prepare an annual written assessment of the drip pad's integrity.
Each assessment must document the extent to which the drip pad meets current
design and operating standards and must include a description of past waste
handling practices and chemical formulations used on the pad (§§264.571/265.441).
Second, §§264.574/265.444 require newly installed or upgraded existing drip pads to
be inspected to verify that the unit was properly constructed and that no damage
occurred prior to use. During this inspection, an independent, qualified, registered,
professional engineer must certify that the drip pad achieves all applicable design
standards in §§264.573 and 265.443. Finally, all new and existing drip pads must be
inspected weekly and after storms to ensure that the units and their asspciated liquid
collection systems are functioning properly and to detect any deterioration of or
leaks from the units. If, upon inspection, a drip pad shows any deterioration, the
affected portion of the unit must be removed from service for repairs in accordance
with specified procedures. If hazardous wastes have been released into the
environment, all appropriate cleanup measures must be taken, and the release may
be reportable under the Comprehensive Environmental Response, Compensation,
and Liability Act (CERCLA) and the Emergency Planning and Community Right-to-
Know Act (EPCRA).
'Tne information in this document is not by any means a complete representation of EPA s regulations or policies,
but is an introduction to the topic used for Hotline training purposes.
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8-Drip Pads
2.5 CLOSURE
To ensure that drip pads are properly managed after their useful lives, drip pads
must be closed so as to prevent the future migration of contaminants into the
environment and protect human health and the environment. The owner/
operator must follow all of the general closure provisions in Subparts G and H of
Parts 264/265, as well as those unit-specific standards found in Subpart W. Closure
of a drip pad involves removal or decontamination of all associated waste residues,
contaminated soils, and contaminated system components (including equipment).
If all contaminated soils cannot be removed or decontaminated, the unit will be
considered a landfill for purposes of closure, post-closure, and financial
responsibility, and must be closed according to .the requirements for landfills in Parts
264/265, Subpart N.. In such instances, the drip pad owner/operator must also
obtain a post-closure permit addressing specific conditions for groundwater
monitoring, corrective action, arid post-closure care.
2.6 DRIP PADS USED FOR TEMPORARY ACCUMULATION
Some of the regulations discussed in detail above apply to drip pads used for
hazardous waste storage (e.g., drip pads operated such that wastes remain in the unit
for more than 90 days after generation). The regulations in §262.34(a)(l)(iii) state
that a generator who accumulates hazardous waste on a drip pad for 90 days or less
will not require a RCRA permit for storage, provided that:
•' The unit conforms to the technical standards in Part 265, Subpart W
• Written procedures are developed to ensure that wastes are removed
from the pad and collection system at least once every 90 days
• Records are kept documenting that those procedures are followed.
\ . ' i
As stated in §262.34, drip pads used for temporary accumulation of wastes by a
generator are exempt from all requirements in Part 265, Subparts G and H, except for
those in §§265.111 and 265.114, which relate to the closure performance standard and
disposal or decontamination of all equipment, structures, and soils.
Under in §262.34(d), small quantity generators are subject to a reduced set of
requirements when accumulating hazardous wastes in tanks or containers meeting
the interim status unit standards. Generators who accumulate wastes on drip pads
do not qualify for this partial exemption. Consequently, all generators of more than
100 kilograms of waste per month who manage wastes on drip pads must comply
with the requirements applicable to large quantity generators in §262.34(a). As a
result, the maximum generator accumulation time period on drip pads is 90 days.
Generators using drip pads must also comply with the *
The information in uus document is not by any means a complete representation or bPA s regulations or policies,
but is an introduction to the topic used for Hotline trairung purposes.
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Drip Pads - 9
requirements that apply to large quantity generators for personnel training,
development of a full contingency plan, and biennial reporting. Conditionally,
exempt small quantity generators, however, are not subject to the drip pad
management standards, nor are they subject to the time limit of 90 days.
2.7 APPLICABILITY TO STORAGE YARD DRIPPAGE
Most wood preserving wastes are generated immediately following wood treatment;
when excess solution drips off the treated wood. This drippage and the drip pad
collecting the drippage are fully subject to the Subpart W standards. Some drippage
can also occur, however, after the treated wood has been transferred to a storage yard
to await shipment off-site. Although this drippage remains a hazardous waste, the
yard is not necessarily subject to the drip pad requirements. Under the drip pad
standards, the management of infrequent and incidental storage yard drippage is
exempt from the drip pad regulations if these releases are immediately cleaned up
in compliance with a written contingency plan developed by the facility owner/
operator. The plan must.stipulate how responses are to be conducted, how
responses will be documented, what methods will be used to ensure that records are
retained for three years, and how contaminated media and residues will be managed
in accordance with applicable federal regulations. . , ,
The information in mis document is not by any means a complete represi
but is ah introduction to the topic used for Hotline
iresentation of EPA s regulations or policies,
training purposes.
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