Evening star., 1900-07-25
DREDGING uOWERPOTOMAC
LEDGE ROCK FOUND On MATrAWo-
MAN sHOAL.
An Expense Of 100000 Above Original
Estimate Will Probably
he Eutailed.

In his annual report to the chief OF en-
gineers Colonel Allen, the engineer officer
in charge Of the Improvement OF the Poto-
mac, says in regard to the commerce of
Washington that no new lines of transp0r-
tation were established during the past MS
cal year, but there was an increase Of ton
mage over 1S.iS OF about IL per cent or TO-
600 tons.
In chapter in regard to the improve
ment of the Potomac below Washington.
Colonel Allen says that dredging was be-
gun at the lower end OF Mattawoman shoal
March 26 last. and has progressed salts
factorily ever since, although delayed some
what by winds, by firing at the naval prov
ing grounds at Indian Head by repairs to
old and the installation Of new machinery,
and the finding Of unexpected beds Of hard
material. The loss OF time due to the fir-
ing tests at Indian Head amounted to TWEEN
ty hours and twenty-five minutes by the
end of the fiscal year. During the progress
OF dredging operations at Malta woman
shoal considerable quantities Of what is
supposed to be partly disintegrated ledge
rock We're encountered in the channel to
be dredged. This was altogether unexpect-
ed, as the report of 1871 showed that six
borings were taken at various places with
out indicating such conditions.
IL appears from recent Investigations
says Colonel Allen. that the Lodges referred
to run diagonally across the channel at
material Probably owing to the small pro-
portion of the area which they occupy the
original borings in 1891 missed them The
hard material is roughly estimated at CO.
900 cubic yards. Ledge rock is not required
to be removed under the terms of the pres
ent contract
At the close OF the fiscal year. 22l 647
cubic yards had been dredged from Malta
woman shoal, resulting in a channel twen-
ty-four feet deep and 200 feet wide for a
length of about 1000 feet, and of about
The same depth. and 1Go feet wide for
about 2.5to feet additional. Colonel Allen
says that this is the shoalest of the OBJ
structions to navigation below the city of
washington, and as the dredge has not as
yet traversed the length OF the shoal the
maximum draught that can be carried over
1t Is 193 feet at mean low water The
presence of the ledge rock in the shoal will
probably entail an expense in the dredging
OF about $4,000 in excess of the original
estimate. Colonel Allen says that If the
same amount Of ledge rock should be en-
countered in the other shoals farther down
the river it will be necessary to increase
the original estimate by about SSpao
The estimate of 1891 for the Improvement
of the Potomac below Washington was
sloS.4oO. Subtracting from this estimate
the sum of SIS 600. which is obtained by
the appropriation of March 3. 1891. to the
$4,000 appropriated by the sundry civil act
OF June 6, 1900, for completing the work.
there remains the sum of $50 100 which
may be regarded as the sum remaining TO
be appropriated in order to complete the
work, though 1t is hoped, says Colonel A.
ien that all of that amount may not be
needed for work under the existing project
1t is on the side of safety, however. to pre-
sent that sum the amount that should
be available for the completion of the work
The contract for dredging the lower Po-
tomac is held by Rittenhouse Moore and
| requires the dredging of not less than So
600 cubic yards in each month. The total
estimated amount of dredging required is
960, 900 cubic yards.