Evening star., 1942-08-11
Piney Branch
Sewer 0dors
Bring Study
Diversion Tunnel Not
Designed to Garry
Maximum Rains

Obnoxious odors in Piney Branch
Valley between Sixteenth street and
Rock Greek following periods of
heavy rainfall, despite completion of
the $500 900 diversion tunnel that
empties into the Potomac. caused
engineers of the District government
today to make a survey to deter
mine what was wrong
They declared their confidence in
the efficiency of the planning of the
District public works program for
freeing Rock Creek of pollution, but
explained that the Piney Branch
connection had not been designd to
eliminate all sanitary draining
through the branch at times of
maximum rains. They said the
maximum plan had not been adopted
because Of the great cost.
However, complaints of continued
pollution of the atmosphere along
the Piney Branch valley brought to
light that studies are being made to
determine whether the bed of the
normally nearly dry branch should
be smoothed to cleanse it further of
repeated pollution.
Manhole Cover Blown.
The studies are being stimulated
by the fact that twice during recent
rains the cast iron top on the great
manhole over the Piney Branch end
OF the diversion tunnel on the east
side OF Rock Creek, had been blown
of, apparently either by high water
pressure or by air pressure. Geysers
of water spurted from the manhole
and washed sod and dirt down the
steep hillside.
The principal difiiculty involved
in the public works program was
that q wide area in and near the
Piney Branch valley east of Six
teenth street and north toward Ia
koma Park is a combined" sewer
system, that is. both sanitary sew
age and storm water are carried in
the same mains. Engineers say the
result is that in times of heavy
rains there is an overflow. with
storm water carrying some sanitary
sewage with it.
1t would cost millions" to change
this combined system into A dual
system, engineers say, so the Dis
trict and the Public Works Admins
tration, in plans to free the Rock
Greek OF pollution, did not order
system for Piney Branch which
would meet the rare" and maxi
mum" conditions. Aside from the
cost of changing the sewer system
IN the upper reaches of the District,
they say there would have been a
cost OF several times greater than
what vas spent on building the big
diverslonstunnel.
Large Diversion Structure"
Near Sixteenth street there now is
large diversion structure" which
operates automatically to limit to
about 1900 cubic feet a second the
flow into the new diversion sewer
that pipes into the tunnel near the
Park Road Bridge. II the flow at the
diversion structure" is more than
this, gates open and the excess runs
down Piney Branch and into Rock
Creek. Engineers agree that this
means some sanitary sewage at
times goes into the branch. but they
had no immediate answer as to why
the dig manhole cap should have
blown OH.
The tunnel at the Piney Branch
end has a 9-foot diameter and at the
Potomac River end it is considerably
larger. The new Piney Branch sewer
the Sixteenth street di-
version structure with the head of
the tunnel is 10 feet by feet. En-
gineers say it was intended that the
diversion tunnel should operate un-
der pressure of the weight of the
water pouring into the mains above.
They said that by this means tun-
mel could carry a heavier cubic foot
age per second. obviating a larger
and more costlier tunnel which
would operate without pressure.