Saturday, September 20, 2008
H2OMAP SWMM and InfoSWMM Sediment Transport Modeling
Sanitary and combined sewer systems can carry substantial loads of suspended solids (waste solids) which can accumulate and cause blockages thereby impairing the hydraulic capacity of the sewer pipes (by restricting their flow area and increasing the bed friction resistance). H2OMAP SWMM and InfoSWMM can simulate the transport and gravitational settling of (total suspended solids including grit) over time throughout the sewer collection system under varying hydraulic conditions. As long as flow velocity exceeds the critical/terminal velocity, H2OMAP SWMM and InfoSWMM assumes that the sewage flow has the capacity to transport all incoming . Deposited particles are also assumed to be scoured and transported downstream when velocity of the sewage flow exceeds the terminal velocity. Settling starts when flow velocity falls below the critical velocity. In the model, transport of thet particles is governed by advection implying that the particles are transported at local flow velocity.
The sediment transport modeling using H2OMAP SWMM and InfoSWMM requires only few inputs, namely limiting flow velocity, particle settling velocity, and source node(s) and initial concentrations (in mg/l) at the source nodes.
In order to specify the first two inputs (i.e., limiting flow velocity and particle settling velocity), the user should first select from the quality tab which in turn activates the editing tabs for particle settling velocity and limiting flow velocity. Specification of source node(s) and its/their initial concentration is similar to the method described above in relation to pollutant transport. The default values used by the model for limiting flow velocity and particle settling velocity are 2 ft/s and 0.1 ft/s, respectively. User specified values over rid these default figures .
H2OMAP SWMM and InfoSWMM deposition (in kg) in pipes and concentration (in mg/l) at manholes, wet wells, and outlets are the outputs reported following successful simulation of transport for a collection system.
There is a rule in SWMM 5 that the depth cannot be less than half the bottom width for a modified basket handle(see below). You always have to have a maximum depth less than 50 percent or 1/1 of the bottom width, If you do not meet this criterion then the program will generate an invalid number warning. This is the code from xsect.c that checks the validity of the cross section data:
if ( p <= 0.0 || p <>
xsect->yFull = p/ucf;
xsect->wMax = p/ucf;
Saturday, September 13, 2008
Wave Of Sewage Flows Toward Bay
Tribune photo by CANDACE C. MUNDY
Workers with Spectrum Underground Inc. work to repair a 20-inch sewage pipeline which broke in Town 'N Country this afternoon.
The Tampa Tribune
Published: September 13, 2008
TOWN 'N COUNTRY - Approximately 200,000 gallons of untreated sewage spilled into Sweetwater Creek on Friday afternoon, prompting a warning to residents along the creek to avoid the water, Hillsborough County officials said.
The spill occurred along Comanche Avenue just east of Hanley Road when a 20-inch sewage pipeline ruptured. The break was at a connection point to a section that had been replaced about eight weeks ago, officials said.
Because the work had been done so recently, it was under warranty, and the original contractor returned to fix the break, said Bill Bozeman, project manager for the county's water resource services. Bozeman did not know what caused it.
The fracture, reported by a passer-by at about 12:45 p.m., caused sewage to spill onto Hanley Road and ooze down Comanche toward the creek. The flow was contained two hours later. After five hours, a cloud of sewage still fogged the water along one of the creek's banks.
The section of Comanche where the spill occurred is home to a couple of businesses and a small strip of offices under construction. A narrow bridge over Sweetwater Creek leads to a neighborhood and to Sweetwater Organic Community Farm.
The farm does not rely on the creek for irrigation and the creek in that section is too shallow and choked with overgrowth in places for kayaking or swimming. County workers posted signs in English and Spanish notifying visitors of high bacterial levels and a health risk, telling them not to swim, wade or fish in the water.
Residents along the creek, which flows south to the Courtney Campbell Parkway area, are urged not to have any contact with the water for the next several days in the creek or the area where it flows into Tampa Bay.
While the contractor worked to repair the pipe, the county diverted the flow from nearby lift stations that serve the areas into tanker trucks.
The spill did not affect home use of water, Bozeman said.
The Water Resource Services staff will notify local and state environmental agencies, take samples and monitor the area where the spill occurred.
Sunday, September 7, 2008
SWMM 5 View Variables
There are four types of graphical variables in SWMM 5: (1) Subcatchements, (2) System, (3) Nodes and (4) Links. The SWMM 5 Hydrology binary graphics file consists of 21 view variables for each subcatcment simulation in SWMM 5. The variables are:
|SUBCATCH_RUNOFF||total runoff flow rate|
|SUBCATCH_RUNOFF_IMPZero||runoff flow rate from zero imp area feb 2007|
|SUBCATCH_RUNOFF_IMP||runoff flow rate from imp area feb 2007|
|SUBCATCH_RUNOFF_Pervious||runoff flow rate from pervious area feb 2007|
|SUBCATCH_LOSSES||total losses (infil)|
|SUBCATCH_EVAP||watershed evaporation loss|
|SUBCATCH_GW_FLOW||groundwater flow rate to node|
|SUBCATCH_GW_FLOW_A1||groundwater flow rate to node|
|SUBCATCH_GW_FLOW_A2||groundwater flow rate to node|
|SUBCATCH_GW_FLOW_A3||groundwater flow rate to node|
|SUBCATCH_GW_ELEV||elevation of saturated gw table|
|SUBCATCH_GW_PERCOLATION||aquifer deep percolation|
|SUBCATCH_SNOWMELT||watershed snow melt|
|SUBCATCH_SNOWDEPTH||watershed snow depth|
|SUBCATCH_FREEWATER||watershed snow depth|
|SUBCATCH_COLD||watershed cold content|
|SUBCATCH_SNOWAREA||watershed snow coverage|
|SUBCATCH_FTOT||infiltration during an event|
|SUBCATCH_FU||current value of F|
|SUBCATCH_FUMAX||maximum value of F|
|SUBCATCH_MOISTURE||current soil mositure (less than porosity)|
|SUBCATCH_IMD||current IMD (Porisity - Moisture)|
|SUBCATCH_IMDbyEvent||IMD at the beginning of an event|
|SUBCATCH_SAT||Flag for saturation (1 is saturated)|
|SUBCATCH_INFIL_TIME||GA infiltration time|
|SUBCATCH_WLMAX||current infiltration RATE|
|SUBCATCH_BUILDUP||pollutant buildup concentration|
|SUBCATCH_WASHOFF||pollutant washoff concentration|
|SYS_LOSSES||evap + infil|
|SYS_DWFLOW||dry weather inflow|
|SYS_GWFLOW||ground water inflow|
|SYS_INFLOW||total lateral inflow|
|SYS_CE||continuity error for the basin|
|SYS_ITERATIONS||average iterations over the basin|
|SYS_COLD||cold storage for the basin|
|SYS_SNOWMELT||snowmelt for the basin|
|SYS_RAINMELT||rainmelt for the basin|
|SYS_TS||time steps during the simulation|
|SYS_DWFLoad||total K3 line DWF load|
|SYS_WWFLoad||total K3 line WWF load|
|SYS_WWFLoadExtra||agency extra WWF Load|
The SWMM 5 Node graphics binary file consists of 20 variables on one line for each junction/storage/outfall/divider simulated in SWMM 5. The variables are:
|NODE_DEPTH||water depth above invert|
|NODE_VOLUME||volume stored & ponded|
|NODE_LATFLOW||lateral inflow rate|
|NODE_IIFLOW||total rdii inflow rate|
|NODE_UH1||total rdii inflow rate from UH 1|
|NODE_UH2||total rdii inflow rate from UH 2|
|NODE_UH3||total rdii inflow rate from UH 3|
|NODE_DWFFLOW||total DWF inflow rate|
|NODE_INFLOW||total inflow rate|
|NODE_OUTFLOW||total outflow rate|
|NODE_AREA||node surface area|
|NODE_DQDH||node surcharge dqdh|
|NODE_DENOM||node surcharge dqdh|
|NODE_ITERATIONS||node iterations to this time step|
|NODE_TIMESTEP||node iterations to this time step|
|NODE_CONVERGENCE||node iterations to this time step|
|NODE_QUAL||concentration of each pollutant|
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