United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5305W)
EPA530-K-02-008I
October 2001
&EPA
RCRA, Superfund & EPCRA
Call Center Training Module
Introduction to:
Drip Pads
(40 CFR Parts 264/265, Subpart W)
Updated October 2001
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DISCLAIMER
This document was developed by Booz Allen Hamilton Inc. under contract 68-W-01-020 to EPA.
It is intended to be used as a training tool for Call Center 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 Call Center training and
is not used as a reference tool on Call Center calls. The Call Center 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 Call Center Phone Numbers:
National toll-free (outside of DC area) (800) 424-9346
Local number (within DC area) (703) 412-9810
National toll-free for the hearing impaired (TDD) (800) 553-7672
The Call Center is open from 9 am to 5 pm Eastern Time,
Monday through Friday, except for federal holidays.
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DRIP PADS
CONTENTS
1. Introduction 1
2. Regulatory Summary 2
2.1 Background 2
2.2 Design Standards 3
2.3 Operating Standards 6
2.4 Inspections 6
2.5 Closure 7
2.6 Drip Pads Used for Temporary Accumulation 7
2.7 Applicability to Storage Yard Drippage 8
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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. The majority of these unit-specific
regulations are discussed in other modules.
Since the early 1980s, EPA has continuously expanded RCRA's hazardous waste
program to regulate a broader range of wastes that 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 these newly identified hazardous waste.
This module explains these standards.
After 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 drip pad
• Summarize the design and operating standards for drip pads
• Describe the relationship between generator accumulation provisions and
drip pads.
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 Call Center training purposes.
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2 - Drip Pads
2. REGULATORY SUMMARY
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 that 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 and
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 the new wood-preserving listings were promulgated. 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
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. Regulated
drip pads will be found only at wood preserving facilities.
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 Call Center training purposes.
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Drip Pads - 3
Generally, the performance standards for most hazardous waste management units
vary depending on whether the unit is permitted or interim status. However, the
permitted and interim status standards for drip pads 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 and 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
The design standards for hazardous waste drip pads are codified in §§264.573 and
265.443 (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 and
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
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 and
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 Call Center training purposes.
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4 - Drip Pads
Figure 1
DRIP PAD DESIGN STANDARDS
Design Criteria
Citations
Pad
Must be constructed of non-earthen materials
(e.g., concrete, metal)
Must provide sufficient structural strength to
prevent unit failure
§264.573(a)(l)
§265.443(a)(l)
§264.573(a)(5)
§265.443(a)(5)
Drip Pad
Surface
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*
§264.573(a)(3)
§265.443(a)(3)
§264.573(a)(2)
§265.443(a)(2)
§264.573(a)(4)
§265.443(a)(4)
Liquid
Collection
System
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
§§264.573(h), (1)
§§265.443(h), (1)
§§264.573(d), (e), (f)
§264.190(c)
§265.190(c)
Liner and Leak
Detection System*
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
§264.573(b)(2)
§265.443(b)(2)
§264.573(b)(l)
§265.443(b)(l)
Dust
Controls
Must be used to minimize tracking of waste by
personnel and vehicles
§264.573(j)
§265.443(j)
: The regulations offer drip pad owners and operators a choice between application of surface coatings
and provision of a liner and leak detection system.
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 Call Center training purposes.
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Drip Pads - 5
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 and operator of the unit
must comply with all applicable provisions in Subpart J of Part 264/265.
When the regulations were first promulgated, a new drip pad was required to
conform to the standards for both surface impermeability and liners and leak
detection. Since that time, the Agency revised the drip pad management standards;
now owners and 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 and 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
that 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 (§§264.571/265.441).
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 Call Center training purposes.
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6 - Drip Pads
2.3 OPERATING STANDARDS
All new and existing drip pads must be in compliance with the operating standards
codified in §§264.573/265.443. 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
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 (§§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 §§264.573/265.443.
Finally, all new and existing drip pads must be inspected weekly and after storms to
ensure that the units and their associated liquid collection systems are functioning
properly and to detect any deterioration of or leaks from the units. Upon inspection,
if 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).
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 Call Center training purposes.
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Drip Pads - 7
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 to protect human health and the environment. Closure of a drip
pad involves removal or decontamination of all associated waste residues,
contaminated soils, and contaminated system components (including equipment)
(§§264.575/265.445). 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 Part 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, and 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.
As stated in §262.34(a)(l)(iii), 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
standards and the disposal or decontamination of all equipment, structures, and
soils.
Under §262.34(d), small quantity generators (SQGs) are subject to a reduced set of
requirements when accumulating hazardous wastes in tanks or containers meeting
the interim status unit standards. SQGs who accumulate wood-preserving 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 wood-preserving
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 requirements that apply to large quantity generators for personnel training,
development of a full contingency plan, and biennial reporting. Conditionally-
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 Call Center training purposes.
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8 - Drip Pads
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 and
operator (§§264.570(c)/265.440(c)). 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 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 Call Center training purposes.
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