Section 6.
LININGS FOR RESERVOIRS AND POLLUTION CONTROL FACILITIES
1. PURPOSE. Linings are used to reduce water loss, to minimize seepage
which can cause instability in embankments, and to keep pollutants from
migrating to groundwater sources as in holding ponds at sewage treatment and
chemical facilities, and in sanitary landfills. For further guidance see
Reference 4 and Reference 11, Wastewater Stabilization Pond Linings, by the
Cold Regions Research and Engineering Laboratory.
2. TYPES. Table 2 lists types of linings appropriate where wave forces are
insignificant. Where erosive forces are present, combine lining with slope
protection procedure. See Chapter 7, Section 6.
3. SUBDRAINAGE. If the water level in the reservoir may fall below the
surrounding groundwater level, a permanent subdrainage system should be
provided below the lining.
4. INVESTIGATION FOR LINING. Check any potential lining for reaction to
pollutants (e.g., synthetic rubber is subject to attack by hydrocarbons),
potential for insect attack (e.g., certain synthetic fabrics may be subject
to termite attack), and the potential for borrowing animals breaching the
lining.
Section 7.
EROSION CONTROL
1. GENERAL. The design of erosion controls must consider the volume of
runoff from precipitation, the runoff velocity, and the amount of soil loss.
a. Volume of Runoff. The volume of runoff depends on the amount of
precipitation, ground cover, and topography. For guidance on evaluating the
volume of runoff see DM-5.3 or Reference 12, Urban Hydrology for Small
Watersheds, by the Soil Conservation Service.
b. Amount of Soil Loss. Soil losses can be estimated using the
Universal Soil Loss Equation developed by the Soil Conservation Service:
A = EI [multiplied by] KLS
where
A
= computed soil loss per acre, in tons
EI
= rainfall erosion index
K
= soil erodibility factor
L
= slope length factor
S
= slope gradient factor
7.1-286
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