ENGINEERING TECHNOLOGY

EGTE 321 – Storm-Water Management

Storm-Water Management Design Project

Part II – Estimated Detention Volumes and Preliminary Pond Design

Design the pond and specify its approximate location. Also do a preliminary design for the water quality outlet. Write short narratives describing the design involved with each of the tasks below and include appendices for any supporting documentation (e.g. computer printout or TR-55 worksheets, CAD drawings, etc.):

·  Determine storage volume for the permanent pool (0.5 inches of runoff).

·  Use chapter 6 in TR-55 for help in estimating the storage volumes required to control the 2-, 10-, and 100-yr storms. You will need to look at the drainage area that actually leads to the pond and do the TR-55 calculations based on that area.

·  Develop the contours for the pond and fore bays that will produce the storage required for the permanent pool with 0.5 inches of storage. Permanent pool depth should be on the order of 3 to 4 ft (absolute limits are between 2 and 5 ft). See Pond Code 378 for specifications regarding top widths, side slopes, and level benches. Keep in mind that any runoff in the form of overland flow that goes to the pond must have an unblocked pathway for getting there. Specify location of any drainage easements that may be necessary for surface drainage features such as open channels.

·  By Pond Code 378, a 10-ft level bench will be located one foot below the permanent pool elevation. Another 10-ft level bench will be located one foot above the permanent pool elevation.

·  Determine the runoff depth produced by a 2-inch rainfall event. Use the 2-inch rainfall event as the water-quality storm unless runoff exceeds 1.0 inch. If so, determine the rainfall amount that produces 1.0 inch of runoff and use that rainfall depth for the water quality storm.

·  Do a preliminary design of the water quality outlet structure by locating its invert at the permanent pool elevation. Use PondPack to route the water quality storm through the basin to verify that outflow persists at least 24 hours after runoff commences. You can assume that tail water inside the principal spillway drop structure does not interfere with the performance of the water quality inlet.

·  Develop the additional contours for the pond and fore bays that will produce the storage volume required to control the 2-, 10-, and 100-yr storms as estimated by TR-55. Provide fore bays to the pond for any inlets. Fore bay volume at the 2-yr storage elevation should total 2% of pond volume and should be distributed among the inlets by runoff weighting.

·  Include a graph of elevation vs. storage for the preliminary pond design.

Assessment Form: Relative Contributions of Team Members[1]

Participant: ______Team: ______Date: ______

SWM Design Project Part ______

Storm-Water Management
Group Design Project Team members
(include yourself) / Individual contributions to this team project[2] / Comments
1.
2.
3.
4.
5.


SWM Design Project

Part II: Storage Volumes

Grading Rubric

Task / Highly Competent
(2) / Competent
(1) / Needs Improvement
(0)
Narrative, appendices, and supporting materials as described in assignment. / Report is complete with clear, concise discussion of relevant regulations, assumptions, and design considerations. Analysis is complete and done correctly. All relevant supporting documentation is included in appendices. / Report is complete; design work and analysis are supported with adequate documentation and some commentary regarding major regulatory aspects, assumptions, and design considerations. There may be one or two minor omissions or errors in analysis. / Report incomplete and analysis is inadequate or faulty with little or no discussion of major regulatory aspects, assumptions, and design considerations. There may be significant design errors or the design may be inadequately documented.

Specific Components:

·  Narrative – Provide discussion of these items:

§  Overview of NCC for quantity and quality as related to results from Part I: Hydrology

§  Summary of hydrology for present and developed conditions at a clearly defined point of interest.

§  Calculation of permanent pool volume and data for the water quality storm.

§  Estimation of required storage volumes for 2-, 10-, and 100-yr storms required to attenuate developed peak flows to their present condition values at a clearly defined point of interest.

§  Design of Pond and Fore bays

§  Design of water quality outlet

·  Appendices (Typically, the format for each appendix should be a brief narrative with accompanying computer output or computations.)

§  Contour Map for pond and fore bays

§  Calculations for pond and fore bay volume, Elevation vs. Storage curve for pond.

§  Performance curve for water quality outlet

§  24-hr detention of two-inch rainfall (or 1-inch runoff, whichever is smaller) event verified by routing

[1] After Fletcher, Lugowski, and Stern. 2002. Fluid Power Facilitator Guide. Sinclair Community College.

[2] Allocate 100 points to your team members, including yourself. Base the allocation on your opinion of each individual’s contribution. The sum of all points allocated must equal 100.