Ducks on the Pond: Stormwater Management Basin Analysis Using AutoCAD Civil 3D and Autodesk SSA

Transcription

1 Ducks on the Pond: Stormwater Management Basin Analysis Using AutoCAD Civil 3D and Autodesk Josh Kehs, P.E. Autodesk, Inc. CI4541 Learning Objectives At the end of this class, you will be able to: Model and analyze detention basins in Civil 3D and Storm and Sanitary Analysis Use tools in Civil 3D and Storm and Sanitary Analysis to determine site hydrology for a number of methodologies Produce reports summarizing the design and analysis of stormwater management basins Account for current regulatory requirements, such as infiltration About the Speaker Autodesk Expert Josh Kehs, P.E. has over 10 years of experience in civil engineering in both the public and private sectors. He has experience in all phases of civil engineering projects from surveying and GIS mapping to construction and project management. Josh has designed various civil engineering projects including commercial sites, residential subdivisions, and state and local roads and highways. Josh has also designed many complex stormwater management systems meeting local, state, and federal water quantity and water quality requirements for private projects. He holds a Bachelor of Science Degree in Civil Engineering from Bucknell University. josh.kehs@autodesk.com

2 Introduction During this 90 minute session, I will discuss and demonstrate the modeling and analysis of detention and retention ponds in AutoCAD Civil 3D and Autodesk Storm and Sanitary Analysis (). We will take a look at a sample workflow in which we create a stage storage curve from a pond surface in Civil 3D, and further model the pond s outlet features in order to analyze the performance of the pond. During the analysis, I will show how to account for infiltration through the bottom of the pond, a requirement of National Pollutant Discharge Elimination System (NPDES) in many areas of the United States. Finally, I will show how to view and report on data from the analysis in. Let s get started! 2

3 Modeling Detention Ponds in Storm and Sanitary Analysis Exercise Introduction: This exercise is intended to show how to setup and analyze detention ponds in Civil 3D and Autodesk Storm and Sanitary Analysis (). Exercise: Stage Storage Tool in Civil 3D Step Action 1. Open Storm Sewer_Final.dwg in Civil 3D. 2. Zoom into the pond on the southern portion of the site 3

4 3. Click on the pond surface and choose the pulldown at the analyze panel of the surface editing ribbon. Choose Stage Storage. 4. Choose Define Basin from the stage storage dialog. In the define basin from entities dialog, make sure Define Basin from Polylines is toggled and then click Extract Objects from Surface. 4

5 Click on the pond surface and the polylines will be extracted from the surface. Next, click Define and pick all of the contours in the interior of the basin up to the berm. Then hit enter. The stage storage table should appear in the dialog: 5

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7 5. Choose Save Table to save the table for later use in. Choose Insert if you wish to place the stage storage table in the drawing. Close the Stage Storage dialog. Exercise: Setup Rain Gage in Rainfall can be setup in for methods other than the Rational Methods using Rain Gages. In order to setup a rain gage, the project options should be first set to something other than the Rational Method. Once this is done, the rain gage entry will appear in the Project Data Tree in. A rain gage can be applied to each separate subbasin or to all subbasins at once, as will be done in this example. Step Action 1. Open 01Pond-Begin.spf in. 2. Open the Project Options and set the following parameters: 7

8 3. Next, Open the Rain Gages dialog, click Add, and then click the ellipses next to the Time Series under Data Source. 8

9 Click Add in the Time Series Dialog and then click Rainfall Designer. Set the following values in the rainfall designer. 9

10 Click close until you get back to the Rain Gage dialog and then choose Assign. Choose yes to assign the rain gage to all subbasins. Close the Rain Gage dialog. Exercise: Create a Storage Node in In, a storage node is used to schematically represent a Stormwater Management Pond. This can be an above-ground retention or detention pond, as well as underground features. Pond volume can be created from a stage-storage curve or from functional dimensions from a chamber-type reservoir. Later, individual elements representing weirs and orifices will be used to model the outlet structure. Step Action 1. Continued from previous demonstration. 10

11 2. Zoom into the area where the pond is and you'll see one outfall entering the pond 3. Select the outfall, right-click and choose Convert to > Junction. 4. Using the Add Storage Node icon on the Elements toolbar, add a new Storage node somewhere near the center of the pond. 5. Use the Select Element icon to double-click on the Storage Node just created. 6. In the Storage Nodes dialog box, change the Storage Node ID to "Pond 1", and enter the following elevation values (from the pond surface or the stage storage table) in the Physical Properties area: Invert Elevation = Maximum Elev = Change the Storage Shape Type to "Storage Curve", and press the ellipses the Storage Curve pull-down to open the Storage Curves dialog box. next to 8. In the Storage Curves dialog box, press the Add button in the top right to create a new curve. Name the new curve "Pond 1 Curve" next to Curve ID in the top left. 11

12 9. Click Load in the Storage Curve Dialog to load the curve that was created from the pond surface in Civil 3D. The file type may need to be changed in order to see the table. 10. Storage Curves created manually in can also be saved for later use using the Save button. 11. Select Close to close the Storage Curves dialog box and then Close to close the Storage Nodes dialog box. 12. Connect the converted junction (step 3) to the Storage Node using the Add Conveyance Link tool. Draw a link from the Junction to the new Storage Node. (Right-click and choose 'Select' to end the command). 13. This last link is really in the pond already and not an actual pipe, so you can model it as a "Direct" link. Double-click on the new link using the select tool; and in the Conveyance Links dialog box, choose the "Direct" shape, and choose 'Close' to close the dialog box. 12

13 14. View a profile of the network through the pond, by right-clicking on the storage node and choosing Start Profile Plot. Then choose structure 14 as the ending node. Click Show Plot. You can see from the profile that the bottom of the pond is below the lowest invert coming into the pond, however, the top of the pond is much higher than the lowest inlet grate elevation (120.8). We ll make an adjustments to the pond design to account for this. 15. Double-click on the Storage Node, and change the following: Maximum Elev =

14 Exercise: Add an Emergency Spillway in An Emergency Spillway is modeled in by the use of the weir element set to specific characteristics. The emergency spillway is a separate outlet from a pond that is not part of the pond s outlet structure. Step Action 1. In order to add an Emergency Spillway we first need to place a junction to represent where the spillway will overflow. Add a new Junction using the Add Junction icon on the Elements toolbar, and place it just outside the pond to the southeast (see image below. 2. Use the Add Weir icon to connect the Storage node to the new Junction. 3. Double-click on the Weir link to open the Weirs dialog box. 4. Enter a Crest Invert elevation of (This is the overflow elevation of the weir, 1 ft. below the lowest inlet rim elevation). 14

15 5. Enter a Crest length of 10 feet. (This is the length of the weir measured perpendicular to the flow direction) 6. Enter a Weir total height of 2.2 feet (this is the height between the crest of the weir and the top of the pond). 7. Choose a Type of Trapezoidal with 1:1 side slopes 8. Choosing the ellipses next to Discharge Coeff. will provide C d values for weir shapes. Since an emergency spillway is a broad-crested weir, we ll use a value of Change the contraction type to Both Ends 10. Select Close to close the Weirs dialog box. Exercise: Model an Outlet Structure A pond outlet structure is modeled using individual weir and orifice elements going into a junction from a storage node representing a pond. This allows endless configurations for outlet structures, while other pond analysis applications have a limitation on the number of weirs and orifices that can be part of a single outlet structure. Step Action 1. Continued from the previous demonstration. 2. Using the Add Junction icon represent the outlet structure., place a junction on the south side of the pond to 15

16 3. Use the Add Orifice icon to connect an orifice link from the Storage node to the new structure. 4. Use the Select icon to double-click on the new Orifice link. 5. In the Orifice ID, enter a description as follows: Outlet orifice 2 Year, as this will be the low orifice set to balance the outflow for the 2 year storm. 6. Set the Type to Side 7. Set the Shape to Circular (this should automatically change the Orifice coefficient to to match the shape). 8. Set the diameter to 3 inches. 9. Set the Crest Elevation to To add an additional orifice, select the Add button in the top right, and change the Crest 16

17 Elevation to 118 and the diameter to 6 inches. Name this Orifice Outlet orifice 10 Year. Select Close to exit the Orifices dialog box. 11. Since the two orifices were created without changing the From and To connectivity nodes, they have been drawn on top of each other. To separate them, left-click on the link to select it, then right-click and choose Edit Vertices. Drag the black grip that appears to pull it off the other Orifice Link. You can select the other link and move the two around so they are easy to see. When you're finished, right-click and choose Quit Editing. Set the following values I the physicl properties of the outlet structure. 17

18 12. Place an outfall just outside the basin near the outlet structure. Then, connect the outlet structure to the outfall with an outfall pipe using a conveyance link. Double-click on the outfall and set an invert of Double click on the outfall pipe and set the inverts by clicking the arrows next to the appropriate fields: 18

19 Exercise: Configure Exfiltration To account for infiltration through the bottom of the basin, exfiltration needs to be configured in both the Project Options and the Storage Node dialog. Once exfiltration is turned on, a volume of water will infiltrate through the bottom of the basin. This will be quantified and a summary of the data can be viewed in the time series plots. Step Action 1. Continued from the previous demonstration. 2. On the element tree double click on Project Options (or from the pull-down menus choose Input > Project Options) 3. Inside the Project Options dialog box, select the Storage Node Exfiltration Method pulldown and choose "Constant rate, wetted area"; and select OK to close the box. 4. Double-click on the Storage node element, and set the Exfiltration type to "At all elevations" 5. For the Exfiltration rate, enter.1 inches per hour. 6. Close the Storage node dialog box. 19

20 Exercise: Perform Analysis and Create Report An analysis can be performed with the click of a button in for a single storm or for multiple storms. In addition, a solution file can be generated and loaded at a later date to compare results. The performance of the stormwater management basin can be viewed in a number of ways, including in plan, profile, and even animated in plan and profile. has a robust set of reporting features, ensuring that a report can be generated in the format required by a client, customer, or regulatory agency. The example below scrolls through a few of the reporting methods in. Step Action 1. Continued from the previous demonstration. 2. Use the Perform Analysis icon to run the analysis. 3. View an animation of the the analysis by choosing the Output tab and Output Animation 4. Double-click on the Storage node and view the Analysis Summary section. Be sure the node is not flooded, and that the maximum elevation is at least.5 feet below the emergency spillway, or Double-click on the Weir link and view the Analysis Summary section. 6. Double-click on each Orifice link and view the Analysis Summary sections. 7. Click on Time Series Plot in the lower left hand corner to view a summary time series for all of analysis data. Multiple solution files can be loaded for quick comparisons 20

21 across storm events. 8. From the Output pull-down choose Generate Custom Report. Allow a few moments for the report to be created and opened. 9. Scroll through the report reviewing the storage related data. The Storage node specific information should be at the end. 21

22 Additional Information on Reporting: To view time series data, including infiltration data, choose the Time Series button in the lower left Tip: The exfiltration parameter for the storage node will quantify the amount of stormwater infiltrated during the analyzed storm. Data from previous analysis runs can be loaded from solution files by right clicking in the Time Series Plot area and choosing Open Solution Tip: Multiple solution files can be compared to determine if requirements have been met. For example, the pre-development and post-development data could be loaded at the same time to compare the difference in flow and quantity values. Multiple storm analysis is set up in Analysis Options. 22

23 Reporting Results In, the user can produce reports in a number of ways. Report format can be customized by choosing Custom Report Options from the Output menu. A report of the entire project can be created in one click by choosing a report button on the toolbar. Reports can also be created from element dialog boxes Data can also be exported to Word or Excel from the Time Series Plot data chart 23