Design of Runoff- and Sediment-Control Plans

Water, water everywhere...  EarthFax has evaluated numerous industrial and residential sites and designed runoff and sediment-control facilities to minimize both the on-site and downstream hydrologic impacts of these developments.  Our experience has included: 

DESIGN OF RUNOFF-CONTROL FACILITIES FOR A HAZARDOUS WASTE DISPOSAL AREA. EarthFax performed an evaluation of hydrologic conditions and designed flood control facilities for a proposed hazardous waste disposal site in western Utah.  We evaluated design storms, calculated storm hydrographs, assessed diversion channel hydraulics, and estimated sediment volumes. Run-on drainage bypass channels, diversion ditches, and a sediment basin were recommended for the active portion of the site. A temporary diversion ditch was recommended to prevent runoff from the inactive portion of the site from contributing to the active portion of the site.  We also modeled the extent of the floodplain associated with the drainages in the area during the occurrence of the 100-year flow event.
 
DESIGN OF SURFACE-RUNOFF AND SEDIMENT-CONTROL FACILITIES. EarthFax has designed numerous surface-runoff and sediment control facilities for surface and underground coal mines, active and inactive uranium mills, and hazardous-waste management operations. Facilities have included sedimentation ponds, diversion channels, riprapped channels, land reclamation, check dams, and culverts. State-of-the-art models have been used to determine peak design flows and to aid in design of the structures. Design considerations have included subcritical versus supercritical flow, avoidance of maximum permissible velocities, cost-effective erosion control, water-surface profile analyses, and selection of the appropriate design storm. Liaison has also been provide between the client and the appropriate regulatory agencies.

CATCHMENT DAM DESIGN. Catchment dams were designed downstream from solar evaporation ponds in southeastern Utah to prevent brine seepage to the Colorado River from the ponds. Field and laboratory investigations were performed to determine the engineering properties of the local soils. Dams were designed to be stable on the saturated silty foundations under both seismic and static conditions. Interceptor drains were designed for the dams to prevent subsurface seepage from reaching the river and to maintain the stability of the dams.

DEVELOPMENT OF FLOOD CONTROL PLANS FOR A URANIUM MILL. Surface hydrologic conditions were investigated by EarthFax at an existing uranium mill in southeastern Utah to aid in the development of flood-control plans. These plans were developed to comply with regulations promulgated by the U.S. Nuclear Regulatory Commission for both the operational (existing) and post-reclamation (proposed) periods. Design flows were determined based on the probable maximum precipitation event, diversions were designed to bypass the mill site and tailings ponds, and flows were routed through the proposed diversion network to model the adequacy of the proposed design. Due to the magnitude of the design flood, special care was taken to avoid unstable conditions in the diversion channels which might result in system failure.

STORM DRAINAGE EVALUATIONS OF A PROPOSED 1700-UNIT DEVELOPMENT. Storm drainage conditions were evaluated for a major, 1700-unit residential and commercial development in northern Utah to assist in the development of runoff-control plans. Both existing and probable future conditions were evaluated, accounting for the proposed final build-out conditions (residential areas, commercial areas, roads, golf course, and undisturbed areas). Previous evaluations by other engineers were reviewed for the applicability of their assumptions in the present study. Field data were also collected to fill data gaps and provide an improved basis for design decisions. A design precipitation event was then selected, and runoff from the watersheds and subwatersheds was modeled. Based on the results of the modeling effort, required sizes for drainage control structures (e.g., culverts, detention basins, etc.) were recommended. The effects of the development on downstream conditions were also estimated.

DESIGN OF STREAM CHANNEL REPAIRS. An intermittent stream channel draining a 2,900-acre watershed had been damaged by flood flows in a residential area of northern Utah. EarthFax surveyed the damaged and adjacent section of the channel to obtain cross sectional, profile, and plan topographic data from the site. Stable channel sections were then designed to safely convey the peak flow resulting from the 100-year event. The stabilization measures included a sloped concrete inlet and headwall at the culvert which existed at the downstream end of the damaged section, welded-wire soil retaining walls near the culvert inlet, and a riprapped channel with backfilled sideslopes through the remainder of the affected area. Stabilization methods were also designed at the headcut which had developed in the channel as a result of the flood. Special care was taken during design of the channel repair to ensure that the project would be not only hydraulically functional but also aesthetically pleasing and minimize further damage to the adjacent residential lots during construction.

STORM SEWER TRUNK LINE SYSTEM DESIGN. Construction drawings and technical specifications were prepared by EarthFax personnel for a major storm sewer trunk line at a university in Utah. Plan and profile design drawings were prepared for 3 miles of 15-inch through 42-inch diameter storm sewer. The project included hydraulic modeling of drainage basins for pipeline sizing, design of manhole and stilling basin structures, and detention ponds. In addition, excavation and bedding requirements were developed, along with subsurface utility investigations and roadway pavement redesign. Construction management and inspection were also provided as part of the project.

DESIGN OF EXPANDED STORM SEWER COLLECTION SYSTEMS. Numerous projects have been completed by EarthFax personnel for the extension of storm sewers collection systems within residential and industrial subdivisions in northern Utah. These projects have included the identification of the location and sizing of existing storm sewer mains, submains, and branch lines, as well as the design of new submains and branch lines. Plan and profile drawings were developed along with specifications for the expansion of the existing systems. Construction management services were provided for several of the projects.