Tuesday, November 17, 2015

"..a pond dug into the subsoil will act as a natural sump for all of the allotment's surface water."

...So I blogged a week or two ago.  But I hadn't really thought through the implications. The fact is, where the flooding is now, the level of the allotment is too low.

When somebody decided to build a big East-to-West greenhouse across most of the width, maybe in the 1920s, or 30s, in the era of No Mean City, they can have had no idea that it would still be effecting the whole allotment well into the 21st Century. But it is, because in the region of the Old Greenhouse the clay subsoil is higher than elsewhere.  The topsoil in the middle of the North beds has become hollowed out, and the water collects there. The very northern boundary is higher than the middle of the beds, so the water can't drain through that way.

This means I need to clear all of the topsoil from the entire area of the Old Greenhouse, and dig a metre down in the middle. That will be the pond. The topsoil will be distributed to raise all the beds. The path at the northern end will need to be raised at least 6ins, but also have a deep foundation, maybe a foot or more. Something similar with the path at the southern end, probably.  The water from the whole allotment will then run into the paths' foundations and down into the pond.

Easier said than done. The Old Greenhouse area is now the high point of the allotment, but must become the low. That's going to involve an awful lot of digging, shovelling and barrowing. Bloody hell. And all during a time when the days are too short to get there in the week, and the weekends marred by the inclement winter weather... I might not finish it before next May.

But at the end of this Herculean business, I'll have an allotment naturally draining into a decent sized permanent clay pond. A pond which isn't just an added "feature" but an essential element. Eureka. I've had a nagging feeling since June that there was Something Not Quite Right about that allotment and this morning I've Got It.