Looking for advice...
I've been called out to an issue where a property is suffering from ground heave. Immediately north there's a row substantially lapsed Leyland Cypress hedging. To the west, an old Cypress (no doubt another Leyland) stump which looks older than 5 years since it's dismantlement.
The cracks inside and outside the property widen and close throughout the year suggesting desiccation of the soil caused by the trees. My desk study from SoilScapes shows the area where the property is situated is in fact "clay with impeded drainage." Heave happens throughout the summer months suggesting a dramatically reduced moisture content which, in turn suggests the possibility of clay soil.
Over the past few years I've had a handful of cases with mature broad leaf species along the clay belt in Norfolk causing ground heave. We have dismantled the trees over the course of 3 years in dormant months reducing radical moisture content changes within the ground.
Year 1: Pollard to secondary scaffold.
Year 2: Pollard to primary scaffold.
Year 3: Remove.
So far its worked on properties without substantial foundation footings (but still monitoring) resulting with manageable outcomes where our repairs company can rectify the issues.
Now, in this case we have a substantial amount of conifer. To my understanding; conifers are never fully dormant although the winter months have shown less water demand with the cracks closing on the external wall. I cannot carry out the same procedure to these Conifers as by pollarding will ultimately lead to its terminal decline near instantly. So with that in mind I should remove the trees to ground level in one go.
My question is simply; When is the best time? The evidence suggests winter but...
My concern is if the ground has impeded drainage and I've left the area with a substantial amount of moisture, can the clay swell causing a more positive heave? I have information given to me from our consulting engineers whom state that elsewhere in the village is 20m thick boulder clay. If there wasn't so much boulder clay in the area then I would've just removed the trees in winter and rectified the property issues.
Am I over thinking this? Part of me is thinking "what ever happens...happens" as I can't see many options.