Diggin' in the Lowcountry -- Advice needed - 05/31/21 01:37 AM
Hey y'all.
Names Abraham and I'm plannin' on diggin' a pond on Johns Island, SC. I'm in the planning phase and hoping to get yalls advice.
First about the project.
We plan on digging a 3/4 acre to an acre pond on our 8 acres.
The future use would be for farm irrigation, aquaculture, rainwater and flooding mitigation, soil extraction, and general enjoyment.
I have a John Deere 120c with a yard bucket available to me for the job.
I got a quote of 38k to do this job and hoping to save some money by DIY (cause I don't have 38k).
I work 24 hr shift every third day so I can dig 2 out of 3 days.
I did 3 years operating work in the past and am an average to above average hoe operator. Dug a bunch of detention ponds and deep ditches, but no retention ponds.
Next about the site.
The soil is pretty much straight sand. Won't hit anything else at the depth of the dig. Expecting (and hoping) to hit some shell sand at the further depths of the project
The water table is extremely high--less than 2'.
The property is flat as an old mans backside.
There are old farm drainage ditches on the property. All the surrounding properties had them and they drained to the swamp but some have since been filled in by new land owners and now all the surface water from them and surround properties sits in the 'S" portion of the deepest ditch--where we want the pond to go.
There are two ponds north of the site, one an acre and one 4 acres, which are connected and drain to the swamp/river. This will be the overflow discharge space.
Both those ponds north of the site didn't require any liner and filled up/stay full from water table alone.
I plan on damming up the ends of the ditches and putting a vertical spillway connected to the neighbors ponds for appropriate drainage.
Things I'm unsure about.
Has anyone dug in a super high water table with soil like this? I'm going to have to use a trash pump to keep up with the water coming in. Unsure what to use 3", 4" or 6". I have looked at prices of rental and the 4" and 6" are insane (almost 4k a month). I assume I'll be at it at least 3 months weather pending so that's unaffordable. Can I get away with a couple 3"ers? Any other suggestions?
Environmental control has rules of 3:1 for banks and 2:1 below water level. This is what I did all my dirt calculations at. I then spoke to an old timer and he stated that those only work for mainland, not sea islands and I'd need to do a 3:1 to 4:1 below water level to keep the banks from collapsing as it repeatedly refills as I'm digging. This would really mess up the shape of the pond. He has also told me some other farming advice that has been disproven too so I'm leery with his advice. Has anyone dug in pretty much sand? What strategies have you used?
Finally, it has been suggested to take the pond as close to 20' deep to get to that shell sand. That is incredibly deep. What would be ideal for pond health in a place that has such hot summers? I'd like that good sand to build roads with but with such a small excavator would it even be possible?
I have attached two aerials, one of my future pond shape, and one of the neighbor's to give yall an idea of flow. Any help y'all can give would be most appreciated.
_abrahammer.
Names Abraham and I'm plannin' on diggin' a pond on Johns Island, SC. I'm in the planning phase and hoping to get yalls advice.
First about the project.
We plan on digging a 3/4 acre to an acre pond on our 8 acres.
The future use would be for farm irrigation, aquaculture, rainwater and flooding mitigation, soil extraction, and general enjoyment.
I have a John Deere 120c with a yard bucket available to me for the job.
I got a quote of 38k to do this job and hoping to save some money by DIY (cause I don't have 38k).
I work 24 hr shift every third day so I can dig 2 out of 3 days.
I did 3 years operating work in the past and am an average to above average hoe operator. Dug a bunch of detention ponds and deep ditches, but no retention ponds.
Next about the site.
The soil is pretty much straight sand. Won't hit anything else at the depth of the dig. Expecting (and hoping) to hit some shell sand at the further depths of the project
The water table is extremely high--less than 2'.
The property is flat as an old mans backside.
There are old farm drainage ditches on the property. All the surrounding properties had them and they drained to the swamp but some have since been filled in by new land owners and now all the surface water from them and surround properties sits in the 'S" portion of the deepest ditch--where we want the pond to go.
There are two ponds north of the site, one an acre and one 4 acres, which are connected and drain to the swamp/river. This will be the overflow discharge space.
Both those ponds north of the site didn't require any liner and filled up/stay full from water table alone.
I plan on damming up the ends of the ditches and putting a vertical spillway connected to the neighbors ponds for appropriate drainage.
Things I'm unsure about.
Has anyone dug in a super high water table with soil like this? I'm going to have to use a trash pump to keep up with the water coming in. Unsure what to use 3", 4" or 6". I have looked at prices of rental and the 4" and 6" are insane (almost 4k a month). I assume I'll be at it at least 3 months weather pending so that's unaffordable. Can I get away with a couple 3"ers? Any other suggestions?
Environmental control has rules of 3:1 for banks and 2:1 below water level. This is what I did all my dirt calculations at. I then spoke to an old timer and he stated that those only work for mainland, not sea islands and I'd need to do a 3:1 to 4:1 below water level to keep the banks from collapsing as it repeatedly refills as I'm digging. This would really mess up the shape of the pond. He has also told me some other farming advice that has been disproven too so I'm leery with his advice. Has anyone dug in pretty much sand? What strategies have you used?
Finally, it has been suggested to take the pond as close to 20' deep to get to that shell sand. That is incredibly deep. What would be ideal for pond health in a place that has such hot summers? I'd like that good sand to build roads with but with such a small excavator would it even be possible?
I have attached two aerials, one of my future pond shape, and one of the neighbor's to give yall an idea of flow. Any help y'all can give would be most appreciated.
_abrahammer.