Construction stormwater practices - temporary stream crossing
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A temporary steam crossing is a structure designed for short-term (typically less than one year) use that is installed across a watercourse to allow construction vehicles to safely cross without damaging the stream bed or channel. They may also be referred to as “temporary access” or “temporary access crossings.” The most common types of temporary stream crossings include bridges, culverts (or “pipe crossings”), and fords (or “drive-through crossings”).
Purpose and function
The primary function of a temporary stream crossing is to prevent construction equipment from damaging the stream bed and banks, impeding stream flow, blocking fish migration, and tracking sediment and other pollutants into the stream.
Applicability
Because of the potential disturbance created by construction of a temporary stream crossing, they should be used only when they are completely necessary for construction purposes. Refer to Planning considerations for additional discussion. In general, temporary stream crossings are applicable when heavy equipment must be moved from one side of a watercourse to the other, or where lighter-duty construction vehicles require frequent, short-term access for crossing a stream channel.
Site applicability
Temporary stream crossings should be limited to locations with low erosion potential and should be constructed during dry periods to minimize stream disturbance and reduce costs. Select crossing sites away from trees, steep banks, channel bends, and deep pools. Stream channel conditions, including expected flow rates during the operation of the temporary crossing, should be thoroughly evaluated before choosing the appropriate type of stream crossing. For example, culverts and access fords may not be appropriate for large streams or during high flow conditions, as they may constrict flow and create potential safety hazards. Temporary bridges may be more suitable for these conditions and are also less likely to impede fish and aquatic life passage.
Although bridges are generally the most expensive to design and construct, they are often the preferred method for temporary stream crossings because they provide the least disturbance of the stream bed and constriction of stream flow. Culverts are less expensive than bridges, relatively easy to construct, and able to support heavy equipment loads. Fords are typically the least expensive to construct but are generally not appropriate for construction during rainy periods or on high-flow perennial streams. The table below provides additional information on the applicability of each temporary crossing and limitations of use.