U.S. ARMY ENGINEER DIVISION, PACIFIC OCEAN
CORPS
PROJECT TITLE
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LOCATION
DRAWING (S) NO.
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Wales
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DATE
DESIGN ANALYSIS
SKIMMING WELL AT RUNIT
The estimate of recharge piven on pape 50, ref b, hepinning on line 8 of
It fails to follow even
third paragraph is significantly overoptimistic.
Lipht rains falling on
report.
same
the
the puidelines given on page 10 of
uptake and soil mois,
plant
evaporation
to
dry soil may be completely lost
ture uptake." In addition rain falling within 100 feet of the shoreline
It is noted
generally contributes little or no fresh water to the lens.
A more
shore.
lagoon
the
that the 100m radius centered at Y~-3 intersects
conservative estimate of recharge estimate is as follows:
Consider the maximum circle whose perimeter does not extend closer than 100
feet to the shoreline:
ie, a 500 ft diameter circle whose center is about
350 feet from either shore, and about 22 north of centerline of air strip:
500" diam circle = 196,350 et? area
annual recharge = 25% x 57.88 inches + 12 x 196,350 =
236,764 cp
ft x 7.48
1.77 x 10 gal/yr
+ 365
4,850 pal/dav
Required Capacity = 3,900 gal/day
The ground water level at center may he expected to be only about 0,2 feet
above lapoon level at mean tide, The tidal efficiency may he expected to
be about 9.10,
that is the tidal range of the ground water may be expected
to be about 0.4 feet.
The well will consist of a 12" diam corrupated metal pipe ahout 12 feet
long, securely sealed at the bottom with a 1/4" plate welded watertipht.
The collector pipes will be 5-60 feet long, 2 inch diam corrugated polyethylene drainace tuhing. This tubing is Commercial Standard CS 228-61 is
available from several sources including Hancor Inc., PO Box 1047, Findlay,
Ohio 45840, and Advanced Drainape System, Inc., TO Box 489, Pomona, CA
91769. The 2-inch collector tubes will radiate equally spaced at about 72°.
The collector tubes must be precisely placed at the level of 1.0 ft belov
the mean fround water elevation.
The latter criterion is extremely important hecause of the very thin brackish waterlines.
The pump will he 1/2 hp 230 volt single-phase submersible pump rated at 10
ppm. This pump is available from Sears and other sources. It is verv
important to avoid using an oversized pump,
in order to prevent excessive
drawdown. A windmill] can be substituted:
27' tower, 8' diam fan, 2-3/4" x
12"
x 24" pump cylinder rated at 6,000 ppd @ 15‘ lift: Aeromotor or equal.
POD Form 115
1 Jul 70
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