United States
Protect! on Agency
Solid Waste and
Emergency Response
 PB2000-10T 887
  February 2000
     RCRA, Superfund & EPCRA
         Hotline Training Module
      Introduction to:
                   Drip Pads
           (40 CFR Parts 264/265f Subpart W)
             Updated October 1999


This document was developed by Booz-AIlen& Hamilton Inc. under contract 68-W 0-0039 to EPA.  It is intended to
be used as a training tool for Hotline specialists and does notrepresenta 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 too Ion Hotline calls.
The Hotline revises and updates this document as regulatory pro gram areas change.

The information in this docume ntmay not necessarily reflect the current position of the Agency. This document is
not intended and cannot be relied upon to create any rights, subs tan tive orprocedural, enforceable by any party in
litigation with the United States.
                          RCRA, Superfund & EPCRA Hotline 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 Hotline is open from 9 am to 6 pm Eastern Time,
                           Monday through Friday, except for federal holidays.

                               DRIP PADS


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
                            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

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.

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.

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

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
 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.

	Drip Pads - 3

storage of excess wood preservative prior to its removal from the unit. 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.  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


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

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 Hotline training purposes.

4 - Drip Pads
                                            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

       Drip Pad
 Must be constructed with a raised berm around
    perimeter to prevent waste run-off into the

 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

 Is subject to regulation as a hazardous waste
  264.573(h), (1)
  265.443(h), (1)

264.573(d), (e), ()
    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

         Dust            Must be used to minimize tracking of waste by
       Controls            personnel and vehicles
* 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 Hotline training purposes.

	     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 Hotline training purposes.

6 - Drip Pads

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.

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 Hotline training purposes.

                                                                      Drip Pads - 7

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/opera tor must also obtain a post-closure permit
addressing specific conditions for groundwater monitoring, corrective action, and post-
closure care.

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

 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.

8 - Drip Pads
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.

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 Hotline training purposes.