A Nautilus Pond™ (U.S. Patent No. 8,333,895; Canada Patent No. 2,704,715) is a high performance surface water treatment environment in both form and function. The core “pond” portion of the environment is specifically designed to allow water that is resident in the pond prior to a stormwater inflow event to be displaced toward a central drain rather than mixing with the inflowing stormwater. Resident water is then preferentially flushed in favour of retaining newly inflowing stormwater to a greater degree than is typically possible using designs consistent with current stormwater best management practices. The result is a longer average stormwater retention time and better opportunities for achieving sediment and nutrient removal objectives.
The conceptual sketch illustrates how a representative forebay cell in a Nautilus Pond™ layout directs water to enter near and generally tangential to the pond perimeter. Water generally follows an inward spiraling path and leaves the pond by a central drain. An inner berm is shown that functionally separates an outer annular channel from the central portion of the pond. This inner berm will be submerged under relatively small inflow events but ensures that the intended general spiral flow pattern will be maintained in the pond even under very large inflow events. Since the inner berm is submerged under relatively low flow events, the illustrated Nautilus Pond™ forebay cell maintains almost the same active storage volume as a simple circular pond with a 100 m diameter.
General hydraulic control over the outflow is achieved within the control structure located outside the pond perimeter for easy access by maintenance staff. A single pipe can be used to draw water from the pond centre and deliver it to the control structure. Water may be drawn from one or multiple elevations in the water column.