Design Requirements

DOE-STD-1020-2002

4.3.2 Design Requirements

Design criteria (i.e., for allowable stress or strength design, load factors, and load

combinations) for loads on exterior walls or roofs due to rain, snow, and ice accumulation should

follow applicable regulations. The design criteria are to be used in conjunction with flood loads

and effects derived from the SSCs DBFL (see Tables 4-1 and 4-2).

4.3.2.1 Performance Categories 1 and 2

Facilities that are subject to flood loads should be designed according to provisions in

applicable regulations. Design loads and load combinations are determined from the DBFL.

Load factors specified in applicable regulations shall be used.

4.3.2.2 Performance Categories 3 and 4

The exterior wall of buildings and related structures that are directly impacted by flood

hazards should be constructed of reinforced concrete and designed according to current versions

of ACI 349 (Ref. 4-13). Design loads and load combinations are determined from the DBFL.

Load factors specified in applicable regulations shall be used.

4.3.3 Site Drainage and Roof Design

For new construction the stormwater-management system (i.e., street drainage, storm

sewers, open channels, roof drainage) can be designed according to applicable procedures and

design criteria specified applicable regulations. Applicable local regulations must be considered

in the design of the site stormwater management system. The minimum design level for the

stormwater management system is the 25-year, 6-hour storm.

Once the site and facility drainage design has been developed, it should be evaluated for

the DBFL precipitation for each SSC. The evaluation should consider the site-drainage area,

natural and man-made watercourses, roof drainage, etc. The analysis shall determine the level of

flooding that could occur at each SSC. The analyst may choose to evaluate the site stormwater

management system for the highest category DBFL (as a limiting case). If the results of this

analysis demonstrate that flooding does not compromise the site SSCs, then it may be concluded

that the site stormwater management system is adequate. Note, that local flooding in streets,

parking lots, etc. may occur due to the DBFL precipitation. This is acceptable if the effect of

local flooding does not exceed the requirements of the performance goals. If however, flooding

does have an unacceptable impact, increased drainage capacity and/or flood protection will be

required.

Building roof design should provide adequate drainage in accordance with applicable

regulations. Secondary drainage (overflow) should be provided at a higher level and have a

capacity at least that of the primary drain. Limitations of water depth on a roof are specified by

Ref. 4-15 or other applicable local regulations. The roof should be designed to consider the

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