Water Resources Division Gaging Station Stilling Wells
To: "A - Division Chief and Staff",
"B - Branch Chiefs and Offices",
"FO - State, District, Subdistrict and other Field Offices",
"PO - Project Offices",
"SO - All Safety Officers",
"DC - All District Chiefs"
cc: " WRD Archive File, Reston, VA ",
"Carole Nethaway, Secretary (OA), Reston, VA ",
"William G Shope Jr., Chief, Br. of Oper. Support, Reston, VA ",
"Melvin Lew, Hydrologist, Reston, VA "
Subject: WATER RESOURCES MEMORANDUM NO. 97.32
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Date: Wed, 10 Sep 1997 08:20:11 -0400
From: "Carole Nethaway, Secretary (OA), Reston, VA "
In Reply Refer To:
Mail Stop 405
September 9, 1997
WATER RESOURCES DIVISION MEMORANDUM NO. 97.32
Subject: Water Resources Division Gaging Station Stilling Wells
The purpose of this memorandum is to present updated interim safety
guidelines (see attachment) for safe entry and work in Water
Resources Division (WRD) gaging station stilling wells; request
atmospheric testing and data collection on stilling wells that have
not been tested; and provide a summary of the incomplete WRD
stilling well atmospheric tests. The guidelines presented in
the attachment are based on information provided in WRD Memorandum
No. 94.30, dated April 29, 1994. These guidelines remain in effect
until a WRD policy statement is issued on the safe operation of
gaging station stilling wells.
Pursuant to the issuance of the OSHA 29 CFR 1910.146, "Permit-Required
Confined Spaces," Final Rule, effective April 15, 1993, WRD began an
evaluation to determine if any confined spaces in the workplace meet
the definition of "Permit-Required Confined Spaces." The OSHA Rule
also requires WRD, as the employer, to develop a written program for
all confined space entry that would communicate and document agency
rules and guidelines for safe confined space operations.
WRD Memorandum No. 94.30, "Plan for Insuring Safe Work in Gaging
Station Stilling Wells" was issued to outline the division's plan to
evaluate and eliminate the safety hazards associated with entry into,
and work inside of, stilling wells. The memorandum gives background
information and defines terminology; lists potential health and safety
hazards; provides interim guidelines for the safe entry of, and work
in, stilling wells; and describes the hazard evaluation and
elimination program.
In addition, Memorandum No. 94.30 requested districts to conduct
atmospheric evaluations. The tests were conducted by most districts
in the summer and early fall of 1995. Those measurements provided a
"snapshot" of the air quality in the division's 2,876 then-active
wells that qualified as "confined spaces." Two rounds of tests for
each well had been requested. In the first round, 1,998 wells were
tested. Of those, 66 (3 percent) had hazardous air quality. All but
one of the hazardous wells had low oxygen levels; the exception was a
well with high carbon monoxide concentrations.
In the second round, 879 wells were tested. Of those, 15 (2 percent)
had hazardous air quality. Again, all but one of the hazardous wells
had low oxygen levels; the exception was a well with high carbon
monoxide. The same well tested high in carbon monoxide for both
rounds. Of the subset of wells tested in both rounds, 7 of the same
wells tested low in oxygen, indicating a chronic or seasonal air
quality problem in those locations. No wells tested on either round
had unacceptable levels of hydrogen sulfide or flammable gasses (lower
flammability level or LFL).
Test results showed the overwhelming percentage of wells had acceptable
air quality. Even most of those that had low oxygen levels tested
acceptable after all doors and hatches were opened, and the well was
ventilated for a few minutes. Yet, while the majority of the tests
conducted on approximately two-thirds of the wells indicated no
atmospheric hazards, an insufficient amount of data was collected to
determine air quality in a given stilling well without sampling.
Although no testing has been done for confirmation, it is believed that
the greater potential for a hazardous atmosphere in a stilling well is
related to the work activity in or around the well. For example,
prolonged occupation of a poorly ventilated well has the potential for
exhausting the oxygen supply to dangerously low levels. Operation of
a gasoline engine in the vicinity of a well introduces the potential
for carbon monoxide poisoning. Operation of propane heaters in poorly
vented field structures can create atmospheric conditions that exceed
the LFL, create elevated carbon monoxide levels, and deplete available
oxygen.
If you have any questions about this requirement and other technical
matters, please contact your Regional Safety Officer.
/signed/
Catherine L. Hill
Assistant Chief Hydrologist
for Operations
Attachment
Distribution: A, B, FO, PO, SO, DC (via electronic mail only)
"This memorandum does not supersede any previous WRD Memorandum."
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Attachment
INTERIM SAFETY GUIDELINES FOR SAFE ENTRY AND WORK
IN WRD GAGING STATION STILLING WELLS
The following WRD minimum interim safety guidelines, established in
WRD Memorandum No. 94.30, dated April 29, 1994, remain in effect until
final WRD safety policy and guidance statements for stilling well
operations are issued. One change and three additional statements,
have been incorporated into the following safety guidelines and are
bracketed.
A. Before entry into any stilling well, open all doors; clean
out doors and vents for a minimum of 5 minutes. Doors should
always be secured in the "open" position to prevent inadvertent
entrapment.
B. Do not enter a stilling well if unusual odors are detected,
until the well is thoroughly vented. Immediately exit a well at
any time odors are detected or if you experience any impairment.
C. Two persons (an entrant and an attendant) are required for entry
if the depth of the well is greater than 5 feet below the lowest
exit door when:
1. Entry over 5 minutes is required; or
2. Maintenance is performed; or
3. Power equipment is used; or
4. Welding or cutting-torch work is performed.
In such situations, on-site mechanical ventilation of the
stilling well will be required prior to entry and while the
entrant is working inside the well. The attendant will
remain outside the well and will maintain communication with
the entrant.
D. The stilling well entrant must wear appropriate and properly
fitted personal protection gear or equipment (hard hat, rubber
gloves, eye protection, etc.).
E. No unsecured objects can be stored in the gage house when
there is entry to the well. Items such as nitrogen tanks,
sounding weights, shovels, and other tools must be either
removed from the shelter or secured to prevent inadvertent
dropping into the well.
F. No well can be entered without an attendant [accompanying
co-worker] whenever unauthorized [individuals with unknown
intentions] persons are present.
G. Atmospheric monitoring is not required under these interim
guidelines. However, districts that have previously purchased
the portable gas meters and have personnel certified to use
them are encouraged to monitor the stilling well's atmosphere
whenever the conditions under item C above are satisfied, even
if mechanical ventilation is provided. The entrant must
immediately exit from a stilling well if monitored
concentrations of:
1. oxygen drop below 19.5 percent;
2. the LFL exceeds 10 percent; or
3. carbon monoxide exceeds [35] PPM; or
4. hydrogen sulfide exceeds 10 PPM.
H. Use of ground-fault interrupters (GFI) on all AC circuits in
gage houses is recommended as outlined in USGS Safety and
Environmental Health Handbook (445-I-H, August 1989).
I. Electric power tools to be used in stilling wells shall be
double-insulated or connected to a GFI, and all flexible cords
must be of an approved type as outlined in USGS Occupational
Hazards and Safety Procedures Handbook (445-2-H, December 1993).
Districts are also encouraged to replace inside reference gages
that require entry to the well with alternative systems, such as
electric-tape gages that do not require entry into the well to take
a reading.
Supervisors are reminded that all field facilities, including
gaging station stilling wells, require annual safety inspections
to identify and correct safety hazards. In addition, all field
personnel must be trained and qualified to perform their assigned
tasks in a safe manner, and have up-to-date training in CPR and First
Aid as outlined in USGS Occupational Hazards and Safety Procedures
Handbook (445-2-H, Dec. 1993).
Finally, employees must be aware of their own and their field
colleagues' skills, physical limitations, and sensitivity to
debilitating allergic reactions, and must not put themselves or
their colleagues at risk.
[Gaging Station Stilling Wells Job Hazard Analysis and training are
to incorporate these safety guidelines.]