Stonyfield Farm - Executive Summary
Stonyfield Farm is a manufacturer of quality yogurt (dairy) products, |
located in Londonderry, New Hampshire. The facility is located in a modern industrial park
adjacent to the Manchester, New Hampshire airport, and employs approximately 250 persons on
three shifts. Normal operations are five days per week, with infrequent weekend manufacturing
The covered process at this facility is an ammonia-based mechanical refrigeration system which
contains a maximum intended inventory of 18,500 pounds.
The facility has an active Process Safety Management Program. Operation of the ammonia
equipment is restricted to only a select few trained, authorized operating/maintenance personnel.
The majority of the distribution piping which contains ammonia, and connects to air cooling
evaporator units and process equipment, is located above the roof of the processing areas, and
therefore not very susceptable to damage from accidental, inadvertant contact by lift trucks and
Nearly all equipment and associated piping within those spaces is located as high as
possible within the spaces, to minimize accidents. The significant investment associated with
the pre-planning for safety is an example of the commitment of management to identifying
critical safety control points and improving the process accordingly.
In a worst-case scenario, the entire contents of the ammonia refrigeration system would be
expelled in 10 minutes: the release rate would be 1850 pounds per minute, or less. This might
result from the rupture of a 2" high pressure (180 psig) liquid ammonia pipe, which is an unlikely
but nevertheless plausible scenario. In such a case, the distance to toxic endpoint (200 ppm)
under worst-case ambient conditions (still air) is anticipated to be 2.5 miles. Ammonia is an
extremely hazardous and toxic chemical, but the toxicity level is substantial: the offensive,
choking odor of ammonia is readily distinguished and familiar to most humans, who gener
are intolerant of even low (<20 ppm) dosages. The toxicity concentration is 2400 ppm or above.
The more-likely release scenario selected and evaluated, and having the greatest offsite risk, is
the accidental rupture of a ?" low pressure liquid pipe: in that case, the release rate was found to
be 250 pounds per minute, and the vulnerability zone (distance to toxic endpoint) is reduced to
0.30 miles from the facility. It is possible (but unlikely) that such a release could be on-going
for a period of up to one hour before intervening action can be taken by trained personnel. The
location of the facility in the community, together with the topography and consideration for
prevailiing wind direction, helps to minimize the overall risk to human populations.
An OSHA-prescribed Process Safety Management Program has been adopted for this facility.
Under that Program, the major components of the process are inspected frequently. Operating
conditions are constantly monitored by a
computerized system with integral alarms that notify
process operators of an upset. The readily-distinguished odor of ammonia alerts persons in the
constantly-inhabited areas where ammonia-containing piping and equipment is located that even
the slightest release may have occurred. As stated above, the company has located principal
piping and many key shutoff valves on the roof area for easier access in emergency conditions.
Shutoff valves which allow operators to isolate sections of piping/equipment in compressor room
areas are readily accessed. The compressor room area is well vented with high volume fans, and
is readily accessible in case of a release in that area.
As a testimony to the overall safety of the ammonia refrigeration system operation at this facility,
and the diligence of the process operators, no accidents have occurred within the past five years
which have necessitated an off-site evacuation or have had any offsite consequences.
The Londonderry, NH LEPC has incl
uded the Stonyfield Farm facility in the community
emergency plan. The facility's relationship with the LEPC is expected to include frequent
interactive exercises and regular dialogue regarding the process. The Londonderry Fire
Department does not maintain its own HAZMAT squad, but does have a mutual aid agreement in
place with nearby municipalities for the provision of those services in the event of an accidental
release which requries external intervention or assistance. Stonyfield Farm has adopted the
INTEGRATED CONTINGENCY PLAN format preferred by EPA and OSHA for preparing and
implementing its onsite Emergency Action and Response Plan. Under this plan, emergency
training and practice drills will be frequent and will cover a multitude of potential scenarios.
Three key managers will become involved immediately upon the recognition and characterization
of all non-incidental ammonia releases, and their duties will be as follows: (a) coordination of
and direction to onsite and e
xternal emergency responders; (b) notification of agencies and
on-site safety and security; (c) protection and continuation of business operations and employee
welfare; and (d) communication with the public as necessary.
Stonyfield Farm will continue to investigate and implement changes to the ammonia process in
order to improve safety and minimize risks associated with it. In addition to relocating piping
and valves, future plans include the increase of automatic ammonia leak detection systems,
improved access to safety shutoffs, reduction of the amount of ammonia contained within the
system but necessary for system operation, and systems which will rapidly reduce the pressure
within any major part of the piping/equipment system in case of emergency shutdown.