Cambridge, Massachusetts

• Preventing exposure to airborne asbestos for on-site workers, nearby public and
  offsite residents,
• Providing data to confirm successful asbestos abatement or to evaluate the need to
  initiate actions to mitigate airborne asbestos generation and/or migration of airborne
  asbestos on and off the site, and
• Monitoring and documenting airborne particulate and asbestos levels at perimeter and
  downwind locations at the sire.

Excavations less than 100 square feet in size will not require the use of the airborne asbestos
management and monitoring plan.

Throughout the excavation activities, generation of airborne asbestos will be managed at the
work location, and airborne particulate monitoring will be conducted at the perimeter of the
excavation and/or at the perimeter of the site to evaluate the effectiveness of the airborne
asbestos management plan. If monitoring indicates the airborne asbestos management
techniques being used are ineffective to control airborne particulate generation, more
aggressive techniques will be employed, as outlined in this plan. If monitoring indicates less
exposure potential, the controls will be relaxed.

SOIL CHARACTERIZATION

Prior to the beginning of excavation activities, further soil characterization for the asbestos
content will be completed in areas where visually detectable amounts of asbestos (Trace or
percent levels) have been detected by Grace, the COC and ASG through prior investigations.
The purpose of the additional characterization is to define the size of the portion of the site
that will be subject to dust management protocols. Soil sampling will be conducted in a
manner similar to prior programs. Samples will be analyzed using the EPA Protocol for
Screening Soil and Sediment Samples for Asbestos Content (EPA Protocol), plus EPA
Method 600/R-93-116, Polarized Light Microscopy (PLM).

Management techniques, such as paving or treatment with bitumen and sand on frequently
used access roads, maintaining vegetation cover, spraying exposed soil with water combined
with additives, and slurry cover sprays will be considered for use at the site in addition to the
techniques discussed in the following sections if deemed appropriate considering site
activities. For example, to prevent airborne asbestos generation on frequently-used dirt
access roads leading to the excavation, the road could either be paved, covered with clean,
off-site soil, bituminous material, or a non-toxic, non-reactive and non-volatile particulate
suppression wetting agent or soil stabilizer could be applied to the access road to prevent
particulate generation and erosion.

To minimize the potential for tracking mud off-site, site workers will park personal vehicles
in a designated parking area constructed of gravel, asphalt or other suitable material. For
vehicles in contact with asbestos-containing soil, temporary wheel-wash stations will be used
to prevent mud and dirt on vehicles from leaving the sire.

During load-in, load-out or maintenance activities of stockpiled soil, either water or a wetting
agent will be used to maintain the moisture content of the stockpiled soil. If a stockpile of
asbestos-containing soil will be undisturbed for a length of time, the inactive stockpile will be
sprayed with a soil stabilizer and covered with anchored plastic tarps. Soil stored on-site or
leaving the site in roll-offs or haul trucks will be securely covered.

The airborne asbestos management plan is broken down into three levels of aggressiveness,
beginning with Level 1, which will be used in areas where currently available data indicates
No Visible Asbestos is present in the soil. Level 2 will be employed when excavations are
planned in areas where data obtained by Grace indicates asbestos is present in the soil in
concentrations ranging from trace levels to less than or equal to 3 percent. Level 3 will be
used when excavations are planned in areas where Grace data indicates asbestos is present in

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Page 3

the soil in concentrations equal to or greater than 4 percent.

Management Level 1

Level 1 management techniques will be used at excavations completed in areas where
previously collected data indicates No Visible Asbestos is present in the soil. Level 1 will
include the following management technique:

Water sprays will be used to suppress the creation of airborne asbestos at the excavation.
Water will be provided from municipal mains or stored in either tanks, tank trucks, or other
devices capable of providing a regulated flow and a positive shut-off. Water will be sprayed
on soil exposed in and around the excavation and on soil during loading and unloading,
throughout excavation activities at timed intervals, or as needed based on soil moisture
conditions .

Level 2 management techniques will be used for excavations completed in areas where data
indicates asbestos has been detected at concentrations ranging from Trace to 3 percent are
present in the soil. Level 2 will include the following management techniques:

Wind screens will be used to decrease wind velocity and soil moisture loss at exposed
surfaces caused by excavation activities. Construction fencing will be erected around the
excavation and wind screening, constructed of durable fabric mesh, will be attached to the
construction fencing.

See above discussion.

Management Level 3

Level 3 management techniques will be used for excavations completed in areas where data
indicates asbestos has been detected at concentrations equal to or above 4 percent are present
in the soil. Level 3 will include the following management techniques:

See above discussion.

W.R. Grace & Co.-Conn.
Airborne Asbestos Management and Monitoring Plan
22 April 1999
Page 4

See above discussion.

Additives include polymers, adhesives and surfactants, that when combined with water and
sprayed on soil extend the waters' airborne particulate suppression effectiveness. Surfactants
reduce water tension allowing for more effective coating of particles, and are the most
effective agent to add to water while excavating because they do not create crusts on the soil
surface like polymers, or bind and weigh the soil down like adhesives. Water-additive
mixtures would be sprayed on soil exposed in and around the excavation and on soil during
loading and unloading, throughout excavation activities at timed intervals, or as needed based
on soil moisture conditions.

Airborne asbestos management requirements will be reduced or suspended once sufficient
cover materials are in place to control potential exposure to asbestos containing soil. These
materials would include clean off-site soil cover, foundation units and floor slabs.

AIRBORNE PARTICULATE MONITORING

Air monitoring will be conducted at the Grace site to evaluate airborne particulate
concentrations in air during soil disturbance activities. Particulate concentrations will be
monitored at the location of construction activities and at the site perimeter, depending on the
size of the excavation. Monitoring will be implemented in addition to airborne asbestos
management to confirm the effectiveness of the management techniques and provide criteria
for increasing or decreasing management efforts as required or allowed by data.

Monitoring Locations

A construction monitoring technician will wear a particulate aerosol monitor during
construction activities while monitoring at or in the excavation or work site. The data
collected from the particulate aerosol monitor will quantify the levels of airborne particulate
being generated in the work area such that recommendations can be made regarding the level
of management to implement. The site representative will also wear personal air sampling
equipment capable of collecting air samples for analytical testing for asbestos.

Air monitoring stations will be established around the perimeter of the excavation, and
depending on the size of the excavation, at locations along the perimeter of the site. Up to

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Airborne Asbestos Management and Monitoring Plan
22 April 1999
Page 5

two meteorological stations will be established based on excavation or work site size and/or
location to evaluate prevailing wind directions. Meteorological information will be used to
establish the positioning of the site representative with monitoring and sampling equipment
and the placement of air monitoring stations.

Monitoring stations will consist of a particulate aerosol monitor and a separate sampling
pump fitted with filter cassettes and filter media to collect air samples for asbestos analytical
testing. The equipped monitoring stations will be inspected and manually read a minimum of
four times daily to record and assess total particulate levels. On a daily basis up to three
stations will be equipped with particulate monitoring devices that continuously record
particulate levels based on prevailing wind direction.

Monitoring Methods and Analytical Testing

• Total Airborne Particulates: Real-time particulate aerosol monitoring for total
  airborne particulates in the work area and at a selected number of down-wind and up-
  wind monitoring stations at the site perimeter will be conducted. Portable, real-time
  particulate aerosol monitors have the capability of measuring mass concentrations of
  airborne particulates, aerosols, and mists while providing real-time readouts.
  Particulate aerosol monitors do not identify the composition of the particles detected.
  
  The data obtained from real-time monitoring for total airborne particulates will be
  compared the National Primary Ambient Air Quality Standard, or a value less than
  the standard, to indicate if a higher level of management is needed to adequately
  suppress airborne particulates at the excavation or work site.
• Asbestos: Since real-time monitoring instruments that identify asbestos fibers in air
  are not currently available, a testing program will be implemented to evaluate the
  concentration of asbestos in air. The OSHA permissible exposure limit (PEL) for
  asbestos is an 8-hour time weighted average concentration of O. 1 fiber (longer than 5
  micrometers and having a length to diameter ratio of at least 3 to 1) per cubic
  centimeter of air (0. 1 fiber/cm'). Asbestos filter media from personal air monitors
  and monitoring station sampling pumps will be analyzed daily using phase contrast
  microscopy (PCM) to count fibers present on the filter media. This method does not
  differentiate between asbestos and non-asbestos fibers. If the PEL for asbestos is
  exceeded using this method, the daily sample will be submitted for supplemental
  testing by transmission electron microscopy (TEM), which identifies whether the
  fibers are asbestos or not. If action levels described herein are exceeded in a
  particular area, those areas will be controlled by increasing the level of management,
  or implementing more aggressive techniques if necessary.

At a minimum, management Level I will be employed during excavation activities, however,
management levels will be decreased from Levels 2 and 3 if monitoring indicates no airborne

particulates, low levels of airborne particulates, or low levels of airborne asbestos, are
sustained for a period of time.