alextangofuego
Civil/Environmental
- Feb 18, 2010
- 2
dam is 25' wide across the top...50' wide across at the toe...150' long...constructed with 4' boulders and rubble fill...then topped with concrete...several times because the first and each successive time they did a crappy job without much thought to what they were actually trying to do and the extreme hydraulic force of flowing water...6' deep x 120' water behind it...
The hole is big enough to fish a 40 foot long 24" diameter CMP (corrugated metal pipe) into it...with about 10-12 feet protruding from the upstream side...do this with a Komatsu PC400 trackhoe...a piece of iron big enough to handle the pipe with the swift flow of water pulling on it/flowing through it as the pipe is submerged...so the trackhoe doesn't get pulled into the creek (really a river) by the hydraulic force of the flowing water...also with a boom/stick length long enough so that the trackhoe isn't close to the (substantially) undermined portion of the concrete roadway across the top of the dam...you could drive a go-cart through the hole...
also, make sure no one drowns during the above process of fishing the pipe in...I'm considering having a swift-water rescue team standing there while this is going on...
then start backfilling the upstream end of the pipe (projecting out 10-12 feet past the dam) with 3"-6" screen crushed rock...some of this material will be swept into the void along the sides of the pipe...which is the goal...keep back filling (with the trackhoe) until the flow is minimal through the hole, and most of the water is going through the 24" pipe...... See More
then begin backfilling with flex base (crushed limestone roadbase)...not so much of this material...the fines will be carried into the voids of the 3"-6" rock...at this point the hole should be plugged on the upstream side of the dam...
problem...I've just installed a 24" dia pipe where there was a hole with the equivalent flow of a 48"-60" diameter pipe with a 1-2 fps flow...so, I've constricted the flow, and the dam will start to do it's job...the water will begin to rise behind the dam and begin to overtop the dam...within a day or two or possibly less...be running over the top of the low water crossing...as it is supposed to...but I have not dealt with the void/cavity under the concrete roadway, and now it's underwater...
no bueno...
my other option is to build a fifty foot long temporary dam from the shore...isolating the hole so we can install the pipe and effect repairs on the hole/cavity/roadway...basically filling with high-strength flowable grout...but would need to bypass the 3,000-5,000 gallon per minute flow with a 10"-12" self-priming trash pump...probably two of them...one as a backup/standby...with a day tank to run continuously for the 3-4-5 days it would take to do all the repairs...
any ideas?
The hole is big enough to fish a 40 foot long 24" diameter CMP (corrugated metal pipe) into it...with about 10-12 feet protruding from the upstream side...do this with a Komatsu PC400 trackhoe...a piece of iron big enough to handle the pipe with the swift flow of water pulling on it/flowing through it as the pipe is submerged...so the trackhoe doesn't get pulled into the creek (really a river) by the hydraulic force of the flowing water...also with a boom/stick length long enough so that the trackhoe isn't close to the (substantially) undermined portion of the concrete roadway across the top of the dam...you could drive a go-cart through the hole...
also, make sure no one drowns during the above process of fishing the pipe in...I'm considering having a swift-water rescue team standing there while this is going on...
then start backfilling the upstream end of the pipe (projecting out 10-12 feet past the dam) with 3"-6" screen crushed rock...some of this material will be swept into the void along the sides of the pipe...which is the goal...keep back filling (with the trackhoe) until the flow is minimal through the hole, and most of the water is going through the 24" pipe...... See More
then begin backfilling with flex base (crushed limestone roadbase)...not so much of this material...the fines will be carried into the voids of the 3"-6" rock...at this point the hole should be plugged on the upstream side of the dam...
problem...I've just installed a 24" dia pipe where there was a hole with the equivalent flow of a 48"-60" diameter pipe with a 1-2 fps flow...so, I've constricted the flow, and the dam will start to do it's job...the water will begin to rise behind the dam and begin to overtop the dam...within a day or two or possibly less...be running over the top of the low water crossing...as it is supposed to...but I have not dealt with the void/cavity under the concrete roadway, and now it's underwater...
no bueno...
my other option is to build a fifty foot long temporary dam from the shore...isolating the hole so we can install the pipe and effect repairs on the hole/cavity/roadway...basically filling with high-strength flowable grout...but would need to bypass the 3,000-5,000 gallon per minute flow with a 10"-12" self-priming trash pump...probably two of them...one as a backup/standby...with a day tank to run continuously for the 3-4-5 days it would take to do all the repairs...
any ideas?