Pond Boss Forums POND CONSTRUCTION Building a dam Question on measuring height of dam

I came across this link to a PDF on Indiana Dams:
http://www.state.in.us/dnr/water/files/damguidelines.pdf

This is a cut and paste on the part in question:

Prior IDNR approval (permit) should be obtained by anyone desiring to construct
or significantly modify (work that is not routine maintenance) a dam before work
begins, if the dam meets any one of the following criteria:
- The drainage area above the dam is one (1) square mile or greater.
- The height of the dam, measured from the natural streambed below the crest of
the dam to the lowest point on the crest, is equal to or greater than 20 feet.
- The volume of water impounded by the dam at the emergency spillway elevation,
is 100 acre-feet or more.


I am a little confused on the way this is written (about the height). So would the height of the dam be measured from A to C, B to C or A to Spillway elevation?
A is the orginal dirt grade before construction.

The way thaat is worded, I would vote for A to C. Because it says " Below the crest".

How large is your pond? Does it have a watershed larger than 660 acres (one sq mile), or more than 100 acre feet of water? Finally, does your pond dam a seasonal or a normally flowing creek?

DC, if you contact an NRCS agent, they can tell you if any permit is required and can/will help you through the process.

Rainman, My pond is 2.5 acres with approx 50 acres watershed. I have had two different excavators tell me two different things. One said A to C, and the other told me it was measured from the toe of the dam B to C. Mine is pushing the max and just wanting to see how others interpret this guideline.

Federal dam measurments are from the lowest to the highest points in a dam. In reading throught he link you gave, I would feel pretty confident in saying that IN requires the measurement to be from the ORIGINAL elevation of the stream bed under the center of the dam to be where either the max water level is or the top of the dam.

Again your local NRCS agent can answer these questions and pu the regs in laymans terms.

If you are under the 20 foot threshold and your water shed is way below the sq mile threshold and 2.5 ac is not going to be near 100 acre feet of volume, you have no permit issue or requirement.

I've always understood dam ht to mean A - C
also....
don't forget this resource of mind-blowing tables, charts, and mental stimulators

DC70,

Be sure that you check with your county plan commission. Dept. of Soil & Conservation explained to me the same guidelines and that I wouldn't need a permit. When the Hamilton County Plan Commission saw the newly constructed pond via. eye in the sky...

They came looking for reasons to pull the plug on my investment (excuse the pun). Thank goodness I had built a good relationship with the Soil & Cons. guy, he backed my design and location. Plan Commission couldn't find any violations so they approved my permit request only after levying a hefty fine for not procuring permit before starting work.

My pond is the same size, similar shape and watershed area as yours, I'm even surrounded by trees like you. Just my experience. Better safe than sorry.

I was considering a pretty big dam/pond in my main streambed several years ago. NRCS explained it as measured from "original" streambed to the emergency overflow level. That was the kicker...in order to get what I really wanted out of my investment, the height would have be about 22 feet. Lots of permits, and NRCS would step away and not do the design work. I would need an engineer, would have involved the CoE, probably major liability insurance for downstream structures...too much risk involved. Had to settle for the 2 smaller ones....

Just what I was told...opinions vary.

Matt and rainman are correct it is original streambed and/or highest to lowest. This means you have to consider slope of dam on backside. If say on a 3:1 and 18 feet tall you have to measure elevation at lowest point 54 feet below center of dam. Where you have elevation changes like we do in North Ga this will add several feet as well. Hope I explained that well. The reason I know this is that we planned a dam for client only to findout about this. The creek dropped over 8 feet in elevation not far behind the dam, we had to move it up to not get in this rapid change and stay under the 20 feet requirement.

In GA it also is considered a class one dam if potential loss of life if the dam wwer to breech. Out in the country no biggie in metro Atlanta with school downstream good luck with that enginerring.