United States

Environmental Protection

Agency

Solid Waste and

Emergency Response

(5305W)

RCRA, Superfund & EPCRA

Call Center Training Module

Introduction to:

Drip Pads

(40 CFR Parts 264/265, Subpart W)

Updated October 2001

EPA530-K-02-008I

October 2001
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.
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

Drip Pads - 1

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.

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.
2 - Drip Pads

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.

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 unitspecific 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, freedraining 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.
Drip Pads - 3

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.

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
4 - Drip Pads

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.

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)(1)

§265.443(a)(1)

§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), (l)

§§265.443(h), (l)

§§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)(1)

§265.443(b)(1)

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.
Drip Pads - 5

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.

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).
6 - Drip Pads

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.

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).
Drip Pads - 7

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.

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)(1)(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)(1)(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-
8 - Drip Pads

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.

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.