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The network that is being designed is to enter an attenuation pond around Manhole MH14. The allowable discharge is 10 l/s.
- Continue with your previous file or open Completed Analysis.iddx.
- Save the file as Pond Design.iddx.
- We are now going to open a background layer showing an outline of the pond. Right-click the CAD data in the Tree View and select the Import Data option.
- Select the file Pond Outline.dwg. Click Next and then Finish.
- In the Plan ribbon, make sure the Snap is switched on.
- Select the Surface Colour Fill check box from the Tree View.
- Go to the Build ribbon, and select Add Stormwater Control > Pond.
- Snap the outline of the pond to the imported CAD file.
- Right-click to finish the pond, then select the Select tool from the Toolbox.
- Right-click MH14, and then select Add Connection > Pipe. Then click on the blue + that appears.
- Connect the manhole to the pond and you will see the inlet appear.
- Switch to the Select tool in the Toolbox.
- Double-click the Pond to bring up its properties. With Base Level selected, enter 1.5 m as the Depth, then add a row to the table at 1.5 m Depth, entering the same Area of 123.51 m2.
- The pond is currently straight sided but in reality a pond would have sloping sides. Select the Sizing Calculator (near the top-left corner of the Pond dialog box) and in the Method drop-down select Side Slope. Set the Side Slope value to 4 and then press OK.
- Click OK. This adds sloping sides to the pond.
- The next task is to provide an initial estimate of the size of the pond.
- Set the Freeboard value to 300 mm.
- Select the Sizing Calculator again. Change the Method to Quick Storage Estimate. In the Design up to field, select Freeboard from the drop-down list.
- Click the smaller calculator icon next to the Volume field.
- For Input Type, we can leave it as Use Plan Data which automatically uses the Catchment Area details entered and the Rainfall selected for Analysis. Enter a Discharge Rate of 10 l/s. Make sure that the Safety Factor is set to the default value of 2. Click Calculate.
This returns an upper and lower estimate for the storage volume required.
Pressing OK will then take the mean of the two values and put it in the Volume field, clicking OK to the Sizing Calculator will update the pond dimensions.Note: We selected update method Depth / Area / Volume in the previous step which changes both the area, depth and volume of the pond while maintaining the slope. If you were to select Depth, the volume would be altered but the slope would change too.
- Click OK and the outline has increased to reflect the space the pond will take up on site. You may wish to move the inlet closer to the edge of the pond to get a more accurate pipe length.
- At this point, the original pond outline CAD layer can be turned off from the Tree View.
- Right-click the main flow path (labeled Train if you have followed the entire tutorial) in the Tree View and select Edit. Add on the additional pipe from MH14 to the pond.
- From the Results ribbon, select Show Profile and the profile view will now include a graphical representation of the pond. Update the Diameter of the final pipe to 375 mm by double-clicking on the value in the table below to match the US pipe. As this was added after the Network Design Wizard, it has not been sized.
Adding a Hydro-Brake®
A discharge rate of 10 l/s from the attenuation pond should now be defined.
- Use the Select tool to double-click the newly created pond and select the Outlets tab.
- Click the + icon on the Outlets tab and under Outlet Type, use the drop-down menu to select a Hydro-Brake®.
- Enter a Design Depth of 1.2 m and a Design Flow of 10.0 l/s. Press the Calculator then the Calculate button and this will run the analysis via the Hydro International Servers to calculate the appropriate Hydro-Brake, reference number and Depth/Flow relationships available.
- Click OK.
- Save the model.
- From the Results ribbon, click the Analysis Criteria button and make sure that 18 storms are to be simulated. Also check that the model validates with no errors.
- Click the Go button to simulate the model. Once the simulations have finished, the Stormwater Controls Summary will automatically open.
Click the Critical Storm button to show the highest level in the pond during any of the 18 storms. From the results we can see that the 120 minute winter storm was the worst, producing a maximum depth of 1.1 m in the pond. This is below the 1.2 m necessary to meet the freeboard and is therefore acceptable.
- From the Results ribbon, open the Connections table and press the Critical Storm button. From here we can see that some of the manholes flood.
Save the final version of the model Pond Design.iddx.
As a separate exercise, you may want to manually upsize some of the pipes to resolve the flooding.
If you are planning on sending the design to someone (like Innovyze Support). The transmit feature is the best way to do this as it keeps together all relevant files in a compressed format.
Go to File > Transmit Design, and then select the appropriate layers and choose the appropriate destination. And then click OK.