CIVIL DEFENSES SIRENS
March 10, 1983
To: Mr. Craig, City Manager
From: Gordon Anderson
Subject: Bid - Civil Defense Sirens
Bids were opened at 10:00 A.M., Thursday, March 3, 1983 for two Civil Defense
funded sirens. Bids were received as follows:
BIDDER
TYPE
TOTAL COST
Tommy's Firehouse
Federal Thunderbolt 1000AT $17,865.00
Electric Service Co. ACA Allerter
19,980.00
16,800.00
*Ridgedale Electric Sentry 10v2T
* does not meet minlmum speclfications.
Bids were requested for rotating horn, non-electronic, two signal, two tone,
sirens with an output of at least 125 db ratlng at 100'. The sirens bid by
Tommy's Firehouse and Electric Service Company meet those specifications.
Each are rated at 127 db. 125 db output would have an anticipated calculated
range of 4500 feet, the design used for the warning plan as approved. 127db
would have a range of about 5200 feet.
The siren bid by Rldgedale Electric was for a non-rotating, two tone, two
signal siren. The output of the siren bid is rated at 123 db. A 123 db
output siren would have a range of about 4200 feet, below that of the range
needed to cover the city as shown on the warning plan.
To insure the reliabillty of the Sentry siren in freezing weather, eight 200
watt heaters are installed in the siren. These are operated thermostatically,
being turned on when the temperature goes down to 300F. With about 110 days of
average high temperature below 320F, over 4000 kilowatt hours wlll be used durlng
a year at a cost of about $220 per siren. To this will be added a standard meter
monthly charge of $425 each for a total estimated operating cost of $542 per year
for the two sirens.
Northern States Power Company charges $4.00 per month per Slren for those sirens
that have no other electrlcal use other than the siren itself. The $96 annual
charges for two such sirens is estimated at $446 per year less than the two sirens
with heaters and metered electriclty.
The low bid of Tommy's Firehouse for two Federal Thunderbolt 1000AT sirens meets
the specificatlons and is recommended for approval.
February 18, 1983
e
To:
Mr. Craig
From: Gordon Anderson
Subject: Bid - Civil Defense Sirens
The City received notice by letter dated September 28, 1982, that two project
applications for civil defense warning sirens had been funded and approved f@r
purchase. Subsequently, bids were received and presented to the City Council
on November 2, 1982. Bids were requested on two-tone, two-signal rotating
sirens with an output of at least 125 db at 100'. Bids were rejected by the
City Council.
Bids are now again being s01icited for sirens. Bids are to be received on
March 3, 1983. There has been quite a bit of discussion and communciations re-
garding which sirens are acceptable for Federal funding and which are not. The
confusl-on arises between the terms of IItwo-tonell and IItwo signalll. A two signal
siren has the capability of producing a straight or even tone or a warbling or
intermittent tone. This is a requirement to receive matching funds. A two tone
siren produces two tones simultaneously in either of the two signals. This two-
tone signal better covers the hearing spectrum (see bulletin No. 12 attached).
The following is an excerpt from 1I0utdoor Warning Systems Guide, FEMA, March 1,
1980, (emphasis added).
IIHearing - Whether the amount of sound available to warn people will indeed
be sufficient to do the job depends upon several factors. First, the warn-
ing sound must be audible above the ambient or background noises. These
ambient noises change constantly in loudness and pitch, depending upon ,
noise-producing activities in the vicinity of the listener. Second, the
warning sound must get the attention of the listener away from what he is
doing. Normally, people IIclose outll of their minds distracting sounds
that are not pertinent to what they are doing. A warning sound must pene-
trate this mental barrier. Tests have shown that to attract a listener's
attention away from what he is doing, a warning sound must be about 9 db(C)
greater than would be sufficient to make it audible to someone who was con-
centrating on listening for it, and not doing anything else.1I
There are several types of sirens of the size needed that are on the market, as
foll ows:
Non-rotating electronic
Oscillating electronic (3600 oscillation)
Non-rotating mechanical (single or dual tone)
Rotating mechanical (single or dual tone)
Presently most of the Civil Defense Warning Sirens in the metropolitan area are
of the two-tone rotating type. This type of siren is distinctive and different
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Mr. Craig
Civil Defense Sirens
Page 2
in tone and propagation method. By producing a growling type of signal, its
distinctive tone is recognized by the public as to the type of warning in con-
trast to all of the other single tone sirens that are heard in the area. By
rotating the siren, the signal is concentrated in one direction, increasing
the chance that it will be heard.
SpecificatiQns have been written to include these two important items. The size
of the sirens were selected to cover the area as shown on the approved City of
Hopkins Warning Plan. Bidders will be informed that bids for sirens that do not
meet these specifications will not be acceptable.
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