4130 ARTICLE 17.

mission, and shall be immediately assessed at the rate of assessment deter-
mined upon by said Commission for agricultural land; provided, further,
that State, County and Municipal buildings or property or public parks
or playgrounds owned by a municipality, and any building owned by a
regularly organized volunteer fire department while so used, shall be ex-
empt from said front foot benefit charge, and from the service and water
consumption charge for water used exclusively for public or fire depart-
ment purposes.

Future front foot benefit charges for water supply and sewer construc-
tion shall be uniform for each class of property throughout the Sanitary
District for any one year, except, however, Gaithersburg and Washington
Grove, against which a benefit charge approximating the cost of the sys-
tems therein shall be levied; provided, however, that whenever the Com-
mission acquires an existing system, other than a municipal system, the
construction cost of which has been added in whole or in part to the pur-
chase of land or lots abutting upon said system and which contribution
the Commission has determined to be a factor in the cost to the Commis-
sion of such system, the Commission may, in its discretion, levy a front
foot assessment less than the uniform front foot assessment levied in the
remainder of said Sanitary District. The amount of the charge per front
foot for each class of property for both water main and sewer shall be

determined from time to time by the Commission as costs and conditions
require, but no benefit charge once levied by said Commission shall be in-
creased.

Said benefit charge shall be paid annually beginning from the time of

the levy thereof by all properties located as above specified, for a period

of years co-extensive with the period of maturity of the bonds out of the
proceeds of which such construction was done; provided, however, that any
property owner may, at his option, within one year from time said front
foot benefit charge is levied, extinguish the same by the payment in cash,
in one sum, of the proportion of the estimated cost of the project, con-
sidered as a part of the whole system of which the construction abutting
upon his property is a part, represented by the number of front feet which
he is assessed, with interest at the rate of six per centum per annum from
the date of said levy, less any annual payment that may have been made
thereon. The Commission, however, in estimating said cost for the pur-
pose of extinguishment may add thereto a reasonable margin to protect
itself against possible changes in the cost of construction and loss of inter-
est. All sums received under such plan of extinguishment shall be pre-
served intact by said Commission less the payment of the proportion of
interest and sinking fund properly chargeable to the amount so received
and used for future construction, and provided, further, that any property

owner, whose property is classified under business or industrial, or sub-
division, may, at his option, at any time during the life of said benefit

charge, extinguish the same by payment in cash of an amount which, if
put at interest at three and a half per cent., compounded annually, would
yield an annuity equal to the annual assessment at the base rate and dis-