|Click to download the METRIC model files.|
Items can be added to the plan and connected individually, or drawn as a connected Treatment Train using the Add Train tool in the Build menu. The former approach, adding items individually, will be used here. The treatment train begins with the Inflow Area of the Developed Area that drains to a Manhole, from here the site runoff is conveyed to a Dry Pond.
- Make sure you are still working in the Developed Phase
First, the Inflow Areas must be defined for our developed site. For our example we will be placing two inflows onto the area to better represent the drainage characteristics of the developed site. Ensure that Snap is turned on, this can be done in the Plan ribbon. Then outline the two inflow areas as shown below, selecting Catchment Area from the Add Inflow drop down menu.
Now that we have placed our catchment areas, we will modify their templates so that they contain the characteristics of our developed land. Right-click the first inflow area and select Change Template. In the window that opens, select Urb-Res-Dev from the list of available templates and change the label to Inflow 1.
Repeat this for the second inflow area, this time labelling it Inflow 2.
Double-click each inflow area to see how the software has automatically calculated the size of the area based on the points we selected. We can also see that there is the ability to edit the seasonal Volumetric Runoff Coefficient (Cv) values for the specific inflow area. As can be seen for both inflows, the Winter Cv value has not yet been specified. To rectify this, we will input 0.84 as our Winter Cv value, in line with the Wallingford Procedure, for both inflow areas. Once completed click Apply and then OK.
Under the Build ribbon, select the Add Junction option and then Shallow MH. Move the pointer to the location on the site where the manhole will be installed and use the left mouse button to place the manhole. You will notice that the software automatically assigns the inflow area to the junction when it is placed in Plan View.
- Place another manhole on the site to receive runoff from Inflow 2.
- We will now add some further manholes to our system. Under the Build ribbon, select the Add Junction option and then Shallow MH as before.
- Move the pointer to the location on the site where the additional manholes are to be located and place them there as shown below. We could also use the Add Train tool rather than placing manholes and pipes individually.
Under the Build ribbon, select the Add Stormwater Control option and then the Dry Pond Stormwater Control. Move the pointer to the location on the site where the Dry Pond will be installed and use the left mouse button to draw the outline of the Dry Pond SWC (similar to the outline shown in the figure below). When you have finished drawing the polygon, use the right mouse button to end the drawing action.Stormwater Control (SWC) outlines can be redrawn at any point by right-clicking the SWC and selecting Replace Outline.
Right-click the manhole receiving flow from Inflow 1 and select Add Connection, choose the Standard Pipe template. Then left-click the manhole directly North.
After connecting the first manholes together, the Standard Pipe connection remains active, connect the two manholes further upstream as below. When connecting to the manhole receiving flow from Inflow 2 you are presented with the option to attach to an existing inlet or to create a new one, select the New button.
One final connection needs to be made from the most northern manhole and the Dry Pond. Follow the same process as before, however when attaching the pipe to the pond click on the bottom left area as opposed to the pond icon, this creates an icon to show where the inlet is positioned within the SWC outline.
To understand what elevations are adopted and how well the treatment system connects, right-click the Flow Paths item at the bottom of the Tree View and select Add (or alternatively by right-clicking the most southerly manhole and select Add Flow Path/Profile). Then select the southern Manhole and then click the Dry Pond icon. Hit the Esc key in order to stop tracing. You can rename the flow path if you wish by right-clicking and selecting Rename on the flow path in the Flow Paths tree.
Note: You can turn off labels on Plan using the Display Settings accessible from the right-click menu.
Right-click the new Flow Path and select Show Profile (alternatively, select the Flow Path under View, Profiles) to display a profile of the flow path.
Edit the Dry Pond SWC by double-clicking it from the Profile View or on Plan. Note that by using the template, we have a 1.5 m deep pond with a top area automatically set based on how the outline was drawn. The base area needs to be set. Before modifying this, we will change the top area to 500 m2 to maintain similar results. Use the Sizing Calculator and select side slope, input 1:2 slope. We will maintain the Top Area. Select OK and note how the depth-area-volume table and associated schematic have been updated.
The values will vary depending on the exact drawing of the dry pond.
If Inlets and Outlets now fall outside of the SWC, the Inlet and Outlet icons will disappear automatically and the links will connect directly to the SWC icon. The inlets and outlets are not deleted, only removed from the graphical view, they can be redrawn by right-clicking the SWC icon and choosing the Specify Inlet/Outlet Location command.
- Select the Outlets tab, select the + button and from the available Outlet Types select the Multiple option. As is common for a Pond SWC, we will have an orifice outlet to control low flows and a higher-level weir control for more severe rainfall events. We will be using the pond to control the initial runoff by allowing base infiltration (which can be seen in the Advanced tab of the Dry Pond window). This will help us achieve Runoff Reduction and prevent the Water Quality event discharge from leaving the site. Therefore add 0.3 m to the Invert Level automatically picked up as the Base Level of the Pond. This will place our outlet control 0.3 m above the base, preventing any discharge until that depth is reached.
- Select the Edit button above the depth-outflow table. Select the + icon, select Orifice and Weir from the list and click OK.
- We could manually enter some starting values for the orifice and weir or we could use the wizard calculator to help. Use the button to reveal the depth-flow input table. Enter the following design depth-flow values into the wizard calculator.
- Orifice: 0.5 m Design Depth; 20 l/s Design Flow
- Weir: 0.7 m Design Depth; 60 l/s Design Flow.
Save the file as XP_Tutorial4.xpdx