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The present paper presents a generalized solution for the hydrologic and hydraulic design of small to medium-sized storm-water pumping stations. The solution enables determination of pump capacity and the corresponding storage capacity. The benefits of the solution include: (1) the ability to consider the effects of storm duration rather than the fixed hydrology assumed in other methods; (2) a simpler and more intuitive design procedure than other available methods; and (3) enabling the calculation of storage requirements independent of the geometry of the wet well and any inundated upstream area. The relation of the method presented herein to several other available methods is presented and the other methods critiqued conceptually and by example. The example is favorably tested using commercial software, and the constant-pumped-discharge assumption of the example is further tested using that software for an actual pump discharge-total dynamic head and system flow-head relationship. Extension of the metho...

The hydraulic design of certain types of subsurface drains has recently been put on a more rational footing, and deficiencies in earlier design methods have been demonstrated. However, significant limitations remain in hydraulic design methods for geosynthetic and aggregate subsurface drains. It is important to decouple the groundwater hydrology from the internal hydraulics of the drain, and properly design subsurface drains for open-channel rather than pressurized conditions. Present design methods can inadvertently result in pressurized flow. The assumption of uniform flow (Manning’s equation alone) is also improperly made in some present design methods. Consequences can include unintended pressurized flow and attendant nonuniformity of inflow on the one hand and uneconomical design on the other. Current standard guidelines provide relatively little guidance for the design of geosynthetic and aggregate drains. A current ASTM standard, commonly referenced by geosynthetic manufacturers, has significant li...

Collection conduits flowing full with nonuniform inflow (variable rate of increase in flow with distance along the conduit length) include well screens (vertical and directionally drilled); submerged effluent collectors; and certain types of inboard weir configurations for settling tanks. Certain subsurface drains used in environmental engineering applications and civil engineering more generally may be inadvertently designed for full-flowing conditions. Formulation of the problem for such collection conduits is presented in terms of the applicable differential equation, slope invariance, the frictionless solution for a general cross section, a uniform-inflow solution, and the difference formulation. The importance of checking inflow uniformity is discussed and exemplified. Dimensional analysis is then employed to demonstrate the relationship between variables, leading to a new generalized numerical solution. That solution is presented in a graphical form which provides further useful display of the relationships between variables and quantitative information for design and analysis. The detrimental effects of flowing-full conditions in subsurface drains is demonstrated, and it is noted that existing design methods may unintentionally cause such conditions to occur.

Numerous types of pipes and channels with spatially increasing flows in environmental engineering applications are identified by type and function and referred to as collection conduits. An overview of methods for designing and analyzing collection conduits is provided. Full conduits with nonuniform and uniform inflow are first considered. Dimensional analysis is then employed to demonstrate the relationship between variables for open channels; that leads to the identification of possibilities for generalized numerical solutions. Prior collection conduit applications are discussed within the framework of the dimensional analysis (which also pertains to some constant-flow applications). A previously unpublished generalized numerical solution for rectangular collection conduits is presented. Subsurface drains are addressed with particular emphasis, including the use of numerical methods to develop a new generalized chart and relation to other design methods. Among the important conclusions for subsurface drains is that the somewhat common practice of using Manning’s equation alone for such problems is not generally adequate. Examples and practical design suggestions are included, and the use of computer-based numerical methods is discussed more generally.