not been noticeably turbid at some time.

A general idea of the quantity of mud contained in the river water,
the quantity excluded by closing the gates at Great Falls, and that
removed by sedimentation and filtration, may be gained from Table 2,
which is, of course, only a rough approximation.

Table 2 also shows that the gates were closed 10.50% of the time,
thereby excluding 40.06% of the total suspended matter which
otherwise would have entered the system.

The turbidities, bacterial counts, and chemical analyses of numerous
samples of water are shown in Tables 3, 4, 5, and 6. The amount of
work done in the pumping station, average consumption of water,
death rate from typhoid fever, and filter runs are shown in Tables
7, 8, 9, and 10.

_Raking._--At the time the filters were first put in service, the
sand bins had not been completed, and, consequently, the work of
cleaning the filters was carried on in the old-fashioned way of
scraping by hand and wheeling out the sand in barrows. This method
of cleaning was used from October, 1905, to April, 1906; then the
regular sand-handling system was commenced.

At times, during the first two summers the filters were in
operation, considerable difficulty was experienced in keeping them
cleaned as fast as was necessary to provide an ample supply of
filtered water. For a short period in each summer it was found
necessary to organize night shifts, and keep the work of cleaning
in progress for from 16 to 24 hours per day.

[Illustration: ~Figure 2--General Plan of Washington Filtration Plant
Showing Finished Surfaces.~]

~Table 2--Tons of Suspended Matter Entering System, Etc.~

Columns:
A - Amount that would have entered the system if the gates
had been left continuously open.
B - Number of hours gates were closed.
C - Amount shut out.
D - Amount deposited in Dalecarlia Reservoir.
E - Amount deposited in Georgetown Reservoir.
F - Amount deposited in McMillan Park Reservoir.
G - Amount entering filtration plant.
=========+=======+=======+=======+=======+=====+=====+=====+========
Month. | A | B | C | D | E | F | G | Total.
---------+-------+-------+-------+-------+-----+-----+-----+--------
1909.
---------+-------+-------+-------+-------+-----+-----+-----+--------
July | 318 | 32.0 | 3 | 0 | 125 | 74 | 116 | 318
August | 146