MIL-HDBK-1005/9A
At smaller Naval installations, where LETs of less than
15,000 gallons (56,781 liters) are required, circular steel LET
may be more cost-effective than a rectangular concrete LET.
Based on the quantity of material required and local availability
and cost of materials, the circular tank could be less expensive
to fabricate. The circular tank design also may allow more
efficient use of available ground for system layouts on smaller
parcels of land.
Secondary containment such as berm may be required to
capture 100 percent of the capacity of the largest tank plus the
maximum 24-hour rainfall in the last 25 years within its
boundary. Premanufactured tanks should conform to Underwriters
Laboratories Inc. (UL) 142, Steel Aboveground Tanks for Flammable
and Combustible Liquids, specifications. Refer to local
regulations for complete list of tank system requirements.
Where facility topography will permit, LETs should be
located out of ground to facilitate gravity flow to downstream
processes or the discharge point.
Example Calculations 1 and 2 give further guidance on
LET sizing.
a) Example Calculation 1 - LET sizing (calculation is
given first in English units and then in metric (SI) units):
Given:
Daily Discharge from Pierside
Collection System, Qdaily = 70,000 gpd [264,970 L/d]
Required:
LET to receive for 7 days.
LET Volume = (70,000 gpd)(7 days) = 490,000 gal
[(264,970 L/d)(7 days)= 1,854,852 L]
(490,000 gal)(1 ft3/7.48 gal)= 65,508 ft3
[(1,854,852 L)(1 m3/1000 L)= 1,855 m3
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