• geometry, result in losses of morphology and in-stream habitat and produce fish passage issues where gradient changes or channel widening occur.
• Obstruction of fish passage as a result of poor construction techniques, particularly where encroachment into a channel to install a structure or realignment of channel sections is required. Potential seasonal or permanent barriers can also develop over time as a result of poorly installed structures, or possibly as a result of erosion and sedimentation triggered through destabilization of the channels following vegetation removal. The effects to water quality from storm runoff are addressed through implementation of stormwater management (SWM) measures. However, the outlet from these facilities can also produce potential impacts to receiving watercourses (i.e. Detroit River). Specifically, improperly designed or sited outfalls can create erosion impacts as discharge flows are conveyed toward the receiving watercourse, or at the point of discharge in the watercourse.
• Short-term impacts to fish and fish habitat from temporary dewatering. Construction often requires work to temporally be completed under dry conditions. The temporary dewatering can, in some situations, reduce baseflow contributions to groundwater fed systems. This temporary reduction in groundwater can potentially affect localized water temperatures and / or fish passage in smaller systems.

In addition the above construction-related impacts, temporary impacts may also occur as a result of maintenance or replacement activities during a project’s operational phase. Under this category, common potential impacts include those associated with the permanent removal or reduction of riparian vegetation. This effect can result in reduced input of organic material and nutrients (allocthanous input), increased solar inputs that influence water temperatures and localized destabilization of banks.

Depending on the severity of the latter effects, potential changes in channel form and morphology (e.g., widening, loss/reduction of pools) may occur.

With reference to border services plaza and bridge crossing components of the DRIC project, each of the above potential impacts will either be avoided (e.g. no in-water works at all associated with the Detroit River) or mitigated (e.g. stormwater runoff from the border services plaza or bridge crossing will be treated prior to discharge).

Mitigation measures are presented in Section 4.2 below.