**ADDITIONAL NOTES FOR POND DESIGN**

**COMPUTER PROGRAM V 1.2 - AL, 12/96**

The following notes are additional notes to the user\'s guide for the
Pond Design Computer Program. This may not cover all of your questions,
but it should be of some assistance. The user\'s guide is pretty
thorough in explaining what to do on a line by line basis. Also, the F1
key is the help key and is extremely useful in using the program. The
following notes will be referenced to page numbers within the user\'s
guide.

**Note:** This program is for hazard class \"a\" dams only. Make sure to
record the class of the dam.

**Note:** A strong familiarity with Tech Guide IV concerning ponds and
some practical experience should exist before using the Pond Design
Computer Program.

**1. Pg. 17** - \"Select Desired Elevation Storage Input Method\" -
Probably select \"Acres\" for most jobs.

**2. Pg. 17** - \"Enter Elevation-Storage Data (Acres Method)\" - If you
prefer to keep this simple then you may just enter the elevation and
pool area at the (1) bottom of the pond (2) normal pool and (3) some
point above the possible top of dam elevation. The most accurate method
of obtaining the elevation-storage data is through field measurement

**3. Pg. 19** - Use F3 key if want to see Elevation-Storage Curves.

**4. Pg. 20** - \"Rainfall Distribution Type\" for most of Georgia is
Type II. For coastal counties use Type III. For questionable counties,
contact your area engineer for assistance. A rainfall distribution type
map is provided in Chapter 2 of NEH 650.

**5. Pg. 20** - \"Flow Length, Ft\" - This is the longest flow path in
the watershed divide to the outlet. The outlet is at the proposed dam
location.

**6. Pg. 20** - \"Freq. (Yrs)\" - Refer to the value taken from Tech
Guide IV, Pond 378 Specs.

**7. Pg. 22** - \"Sediment Storage Req\'d (Ac-Ft)\" - Both values can be
left at zero for most ponds.

**8. Pg. 24** - \"Principal Spillway Info - Inlet Type\" - A riser with
conduit pipe system is known as a drop inlet system. For information on
other pipe systems (siphon, hooded, canopy, etc.), contact the Area
Engineer.

**9. Pg. 24** - \"Conduit Invert\" - For drop inlets, this is also the
elevation of the inlet invert of the drain pipe at the gate. Normally,
this elevation is held constant from the entrance of the drain pipe to
the riser. Then some grade may be placed in the pipe from the downstream
end of the riser tee to the outlet.

**10. Pg. 24** - \"Elbow\" - Usually this will be left blank for drop
inlet systems. Use the F1 key to see the location of the elbow in
question.

**11. Pg. 25** - \"Actual Length - Elbow To Outlet, Ft\" - Usually, this
will be zero for drop inlet systems. Use the F1 key for more details.

**12. Pg. 26** - \"Inlet Extension, Horizontal Distance, Ft\" - Refer to
what you put on Ga-Eng. 27, 28, 29, or 055. Also, make sure the edge of
the trash rack for drop inlet systems is not placed in the slope of the
dam.

**13. Pg. 27** - \"Length, Lin. Ft\" - For drop inlet systems the length
of pipe given by the program will be inaccurate. You should check this
manually using Ga-Eng. 27, 28, or 29

**14. Pg. 27** - \"Entrance Coefficient, Ke\" - Normally use 1.0 for
drop inlet and hood inlet systems.

**15. Pg. 27** - \"Riser Diameter, In.\" - As a rule of thumb, the
diameter of the riser should be approximately 1.5 times the diameter of
the conduit under the dam for pipe flow to control. You will get a
message later if the riser is undersized and the emergency spillway
elevation will automatically be raised to compensate or you will have to
enter a larger riser.

**Note**: The trash rack should be 1.4 times the diameter of the riser
or the cross-sectional area of the trash rack should be twice the
cross-sectional area of the riser computed using the outside diameter of
the riser.

**Note:** Concrete may be needed at the riser base to prevent flotation
of the riser. See the Manual for Erosion and Sediment Control in Georgia
for a sheet titled \"Concrete Volume Required To Prevent Flotation Of
Riser\" to help calculate the volume of concrete needed.

**16. Pg. 27** - \"Crest Radius, In.\" - This will be zero for metal and
pvc risers.

**17. Pg. 29** - \"Job Class\" - This value from the program is usually
incorrect due to changes in job class since the program came out.

**18. Pg. 29** - \"Drawdown Time For Principal Spillway Storm,
Days-Hrs\" - As a rule of thumb, it is good to have 24 hours or less for
drawdown time.

**19. Pg. 29** - \"Emergency Spillway Discharge Determination - Select
Desired Method\" - Select \"Qe values from ESFILE.\"

**20. Pg. 31** - \"Retardance\" - Use F1 key for help. Hit F1 key two
times to get to table called "Retardance". Select appropriate value.
Usually \"Retardance C\" is a good choice.

**21. Pg. 31** - \"Level Section Length, Ft\" - This should probably be
at least 25\'. Use the profile of the emergency spillway to determine if
more than 25\' will be used.

**22. Pg. 31** - \"Side Slope Ratio\" - This should generally be 3:1 or
flatter.

**23. Pg. 31** - \"Exit Channel - Retardance\" - Use F1 key for help.
Hit F1 key two times to get to table called \"Exit Channel Retardance.\"
Select appropriate value. Usually \"Retardance C\" is a good choice.

**24. Pg. 31** - \"Exit Channel - Permissible Vel, FPS\" - Use F1 key
for help. Hit F1 key two times to get to table called \"Exit Channel
Permissible Velocity.\" Select appropriate value.

**25. Pg. 33** - \"Minimum and Maximum Exit Slopes, %\" - Your actual
exit slope should fall within these values. If it does not, then changes
must be made on other inputs so that the actual exit slope does fall
within the minimum and maximum limits. The actual exit slope can not be
changed unless another emergency spillway location is found. Therefore,
changes have to be made to change the minimum and maximum exit slopes.
This may be accomplished by changing the bottom width, flow depth,
permissible velocity or combination of the three.

Filename - PDsupplement.doc