Grading - Stormwater pond closure.
Grading - Stormwater pond closure.
(OP)
I am working on the grading for the closing of an existing storm water facility with fill and stone (6 inches) of almost 1 acre size in area and 10 feet deep. The closure should provide positive drainage to a regional detention basin
Downstream. Because of the enormous size of fill involved I kept the top of the berm and grades on the other side of the embankment intact (3:1) intact and graded the whole area at 3% close to where the outlet structure of the old detention basin was located. I did not want to create a high point anywhere in the middle of the pond to avoid an increase in fill required for the same. Also, there is a large pipe 48" which is located on one side of the pond. I am not sure on how the drainage from that area will be transmitted downstream. Should I design a pipe extension to the downgrade area?
In summary, all I want to do is close the pond, fill it with stone and fill, take care of the drainage from one of the inflow points and provide a positive drainage flow to the downgrade area (i.e. old outlet structure area).
Any comments and suggestions will be greatly appreciated on the concept based on the information provided above.
Downstream. Because of the enormous size of fill involved I kept the top of the berm and grades on the other side of the embankment intact (3:1) intact and graded the whole area at 3% close to where the outlet structure of the old detention basin was located. I did not want to create a high point anywhere in the middle of the pond to avoid an increase in fill required for the same. Also, there is a large pipe 48" which is located on one side of the pond. I am not sure on how the drainage from that area will be transmitted downstream. Should I design a pipe extension to the downgrade area?
In summary, all I want to do is close the pond, fill it with stone and fill, take care of the drainage from one of the inflow points and provide a positive drainage flow to the downgrade area (i.e. old outlet structure area).
Any comments and suggestions will be greatly appreciated on the concept based on the information provided above.





RE: Grading - Stormwater pond closure.
With an acre to play with, and only 10 feet drop across, you should be able to keep all final grades inside under 10%, so you can re-use the land area.
Engineering is the practice of the art of science - Steve
RE: Grading - Stormwater pond closure.
Is this a right approach...
Thanks.
RE: Grading - Stormwater pond closure.
Why is the client so eager to fill the pond and not demo the berm and outlet structure? This client must have a use for the area in mind.
RE: Grading - Stormwater pond closure.
RE: Grading - Stormwater pond closure.
The idea of keeping the berm intact is to keep the drainage pattern on the other side of the berm intact and not modify anything since there is a rail road on one side of the berm. The use of the area after the basin is closed is to have a open space area to satisfy local officials.
I am planning to use a doghouse manhole or some new drainage boz near the endwall which has the 48
" pipe and tie in to the proposed inlet and then connect it downstream. Because of cover conditions, i am planning to tie the existing 48" pipe to a new inlet box and then use a equivalent elliptical pipe on the other side of the proposed inlet to handle existing flow and also drainage from the filled in area of the basin to the downstream area....
Again thanks for the input and let me know if the above is a good approach.
RE: Grading - Stormwater pond closure.
Also, consider the migration of soil through the rock fill. You may see some soil loss on the top, if the materials differ significantly (as in: doesn’t act as a filter to keep it in place). Also consider that water infiltrating into the stone will be trapped. Do you still have an outlet for it at the bottom of the fill?
RE: Grading - Stormwater pond closure.
RE: Grading - Stormwater pond closure.
RE: Grading - Stormwater pond closure.
Thanks for your message Ron.