Conserving Upton's Mirror Pool

View of yellow digger working in pond

Recently we undertook a project to repair and replace the clay lining of the Mirror Pool which was created during the 1930s. Over the years the thin lining of clay had gradually worn away and the water had penetrated the lining resulting in several leaks.

How was the Mirror Pool repaired?

The first step was to remove the fish and drain the pool of water. The fish were placed in the pond next to the bog garden, until their original home was ready for them again. Water from the natural spring, which normally feeds the Mirror Pool, was diverted away to allow the silt to dry as much as possible (although we could not stop it raining!). 

The next task was to remove all the muddy silt and vegetation from the pool. This was quite a tricky task as the steep-terraced garden is not easy for diggers to access and work in.

Once this had been done we cleaned and repaired the walls, adding a protecting sealant to the walls that bonds with the new clay lining and help seal the pool and hold the water.

The final stage was to add the new clay lining, Sodium Bentonite. This came in large rolls with a built in lining on both top and bottom. It is thin and flexible, and is easy to transport and install: great for our hard-to-reach terraced garden. When water is added, the clay swells and creates a seal. It is also self-healing if it is punctured, so we should have fewer problems in the future.

The pool then refilled slowly from the natural spring in the garden, and the fish were happily returned home. 

This conservation work took about 12 weeks and was completed in June 2017. With this very thorough replacement of the pool's lining, hopefully it will continue to reflect the beautiful green space around it for many years to come.

Summer lupins reflecting in the mirror pool at Upton House
Summer lupins reflecting in the mirror pool at Upton House
Summer lupins reflecting in the mirror pool at Upton House

Work like this is funded by our visitors: every time you visit us at Upton House and Gardens, you are supporting our continued conservation so that future generations can enjoy this beautiful place. Thank you.

Did you know?

During the Second World War pilots would follow waterways and lakes, which would reflect light, enabling them to navigate across the land to their destination. The Mirror Pool and the Temple Pool, further down the valley, would have both been drained in the 1940s to prevent this from happening.

Upton's mirror pool in the 1940s drained of water to prevent enemy navigation
Seipa photo the mirror pool in the 1940s without water showing the large crack in the clay liner
Upton's mirror pool in the 1940s drained of water to prevent enemy navigation

Want to know more? Read the week by week developments of the project.

Mirror Pool update - week 12

The Pool starting to fill up. The southern path way will remain closed next week whilst work is still in progress.

This week:

  • The top soil is being put down along the top of the stone wall ready to be finished with turf on Tuesday.
  • Replacement drain cover along the out let pipe inspection chamber to be replaced.
  • Southern path way will be reinstated and levelled as the team start to pull out.
  • Followed by the west grass pathways and slope
  • These two areas will be cultivated, aerated, and top dressed and levelled before being laid with turf.

Mirror Pool update - week 11

The last stretch of clay matting and clay substrate going down as the large JCB left the Pool on Wednesday. The stock valve is now closed and the Pool is starting to fill up. 2-10 months depending on rain fall. The southern path way will remain closed until the rest of the stone facing is complete. This week:

  • The last 15 tonnes of concrete will be poured onto the under pinning to reach the corner.
  • Stone facing is progressing well and the wall should be completed by the end of next week.
  • In the Sunken garden the grass seed has started to germinate.

Mirror Pool update - week 10

The contractors at work securing the next fix of shuttering and stone facing the shoring.  The team should be nearly at the corner by the end of next week all going well. The southern path way has now been closed as work progresses this week on the rest of the repairs along the wall. 

  • Shoring and under pinning have begun on the southern end of the wall. This will take approximately 3-4 weeks.  
  • Progress will be slow due to allowing time for the concrete to go off before pouring in the next layer.
  • Concrete and shoring will take about 2 weeks to complete 
  • Stone facing will take another 1 -2 weeks to complete
  • Sunken garden has now been cultivated and over seeded

Mirror Pool update - week 9

The contractors at work securing the shuttering ready for the next mix of concrete to arrive. Progress is still going well and the sacks of stone are all ready to go on to the wall once the shoring has been completed. The southern path way has now been closed as work progresses this week on the rest of the repairs along the wall. 

Slow progress due to the extra under pinning and shoring required. Stone facing will begin next week:

  • Shoring and under pinning have begun on the southern end of the wall. This will take approximately 3-4 weeks.  
  • Progress will be slow due to allowing time for the concrete to go off before pouring in the next layer.
  • Concrete and shoring will take about 2 weeks to complete 
  • Stone facing will take another 1 -2 weeks to complete


Mirror Pool update - week 8

Progress is still going well after yet another few dry days. The southern path way has now been closed as work progresses this week on the rest of the repairs along the wall. 

  • Shoring and under pinning have begun on the southern end of the wall. This will take approximately 3-4 weeks.  
  • Progress will be slow due to allowing time for the concrete to go off before pouring in the next layer.
  • Concrete and shoring will take about 2 weeks to complete 
  • Stone facing will take another 1 -2 weeks to complete


Mirror Pool update - week 7

Progress was really good last week with lots of dry and sunny weather.  This enabled the team to make rapid progress across the pool with the clay liner and substrate. The southern path way has now been opened to enable visitors to access around the southern side of the pool, whilst the machinery is working at a safe distance.  This will close down again when works start on the wall. 

  • The stone facing on the south wall is now completed.
  • Due to the poor condition of the existing wall a further 10-15m will now be replaced.
  • Another 32cubic m of blue clay arrived to transport down to the Pool this will to act as a buffer cover for the clay liner
  • The clay liner installation is rapidly being laid out in the bottom of the pool over 2/3 of the liner has now been laid out and covered with clay substrate.
  • The spring water feed is now being pumped around the south side of the pool to the out flow to allow the area near the spring in take to dry out whilst work is in progress.