PLANNING STORMWATER FACILITIES

Planning stormwater facilities to achieve the optimum benefit at the least cost is a complex mix of engineering, hydrologic, economic and legal issues.  A stormwater storage facility can only be constructed where the terrain will allow.  Different locations differ in cost of construction and hydrologic effect - for example, relocating storage downstream may increase the volume required to achieve a given reduction in downstream flows.  Economic issues arise regarding the benefit in terms of damage reduction that would accrue from the cost required to build a particular configuration of improvements.  Legal issues dictate whether a given property can be acquired.  Engineering issues may arise if the soils cannot be used for dam construction.

Engineering - even preliminary engineering - of stormwater facilities is expensive because it is a specialized field that requires very technical analyses of hydraulic and hydrological factors.  As a result, conceptual planning is a very important part of the process, since it is done without a large expenditure of funds.  Ideally, conceptual planning continues throughtout the design process, as information becomes available about alternatives.