(8) *Intermittent sand filters*. The installation has

depth of 12 feet (3.7 meters). The water surface area can then

indicated that the facility need not be fully

be calculated as follows:

operational for 7 days after a major washing

operation that takes about 2 days (54 hours).

The designer chooses two filters, which will

allow one filter to operate while the other one

Using the method described for sizing the equalization basin

is allowed to rest. A loading rate of 8 inches

and assuming a square basin gives the average basin size at the

(20.3 centimeters) per filter dose will be used.

midpoint of water depth is 301 feet by 301 feet (92 meters by

The filter dose frequency is every 8 hours. The

92 meters). With the side slopes of I to 3.5, the dimensions of

designer calculates the area required for the

the basin at the top of the water level would be 336 feet by 336

sand filters:

feet (102.4 meters by 102.4 meters). With the 3 feet (0.9

meters) of freeboard added, the overall top dimension of the

basin will be 357 feet by 357 feet (109 meters by 109 meters).

The bottom of the basin would be 252 feet by 252 feet (77

meters by 77 meters).

(11)

Thus, each filter should be 0.47 acres or 20473 sf(1904 SM).

revealed that, if wells are drilled as the

primary source of makeup water for the

(9) *Dosing base. *The designer has performed an

CVWF, the return on investment will be 37

economic study which showed that a dosing

years. Since the design life of the facility is

basin would be cost-effective when compared

only 20 to 25 years; the installation chooses

with installing larger pumps. Water can flow

to use the existing potable water supply as a

by gravity to the sand filter. Small pumps can

source of makeup water since the supply is

take water from the equalization basin to the

dependable. The existing 10-in (25.4-cm)

dosing basin. With a dosing basin, the de--

water line running adjacent to Range Road

signer is able to use smaller pumps for

can be tapped. Makeup water will be added

charging the dosing basin over a long period of

to the water supply basin at night when

time. The basin is sized to hold the volume of

demand on the potable water supply is

water to charge one filter. The volume is

lowest.

calculated as follows:

(12)

sewer connection is approximately 0.75 mi

(1.2 km). The designer decides to provide a

sewer from the water supply basin to the

existing sanitary sewer line to handle

emergency overflows. This will prevent

(10)

overflows from otherwise being discharged

the size of the water supply basin to be the

to the environment.

larger of Vmax (724522 cf or 20287 CM); or

Vave for a S day wash period.

(13)

the expected water volume in the

equalization basin at any given time during

the washing activities. This graph confirms

that at no time during a major wash will the

Since Vmax is larger than five times Vave, the designer uses a

equalization basin volume of 5.5 mg be

safety factor of 1.25 times Vmax to size the water supply basin or

exceeded during the peak water usage

905653 cf (25358 CM). Because of the large water volume

period. The projected volume for the water

required, the designer chooses an effective depth of 10 feet (3.0

supply basin is also plotted (fig A-12). This

meters) with 2.0 feet (0.6 meters) of dead storage for a total

graph shows that 5.5 Mg is sufficient to

ensure that an adequate supply of wash

water is available at all times.

Integrated Publishing, Inc. |