Have you considered filling it in with soil and creating a bog garden?
From the sacbee.com
Not least, they need the bog conditions of high acidity and poor soil that remains moist but not wet.
From the dailyherald.com
It will perform well in somewhat dry garden soil or is at home in the moist bog garden, too.
From the thestate.com
While they do require moist soil, this type needs good drainage and won't like growing in a bog.
From the dailyherald.com
There it can feed bacteria in the water that break down the peaty soil itself, releasing stored carbon from the bog into the rivers.
From the newscientist.com
The soil in Mellor is fairly rich in peat and can bog easily, but there are no permanent peat bogs within Mellor itself.
From the en.wikipedia.org
You can plant them in the ground, in a pot, or even in a bog or water garden, with an inch or two of water over the top of the soil.
From the dailyherald.com
Unfortunately, it runs every 10-15 minutes and because the soil in this area is clay, it was creating an un-mowable bog in the front yard.
From the tennessean.com
The project then evolved into creating a subtropical oasis using moats, compost hills and planting bog plants in the moats and covering the hills with plants that thrive in soil that drains well.