More Civil Engineering in the orchard

We constructed a concrete socket and cantilever beam for the gate post in the orchard today. Thankfully we had help from the volunteer team in mixing the cubic metre of concrete needed for the task. We'd hired an electric cement mixer to assist us Our portable 110V generator provided the power. Whilst the volunteer team had no previous experience of making concrete after a brief demonstration by the management, they were soon enthusiastically hurling shovel loads of aggregate and cement into the mixer, most of which was on target.

During the week, we'd dug the trench and post socket hole. I then fabricated the reinforced steel frame work and fixed it in place in the trench and socket hole. First thing this morning I fixed a steel post socket in place within the rebar. I then used a quarter bag of Quickcrete to fix the socket in a true vertical position. After 30 minutes were were then ready to pour the concrete.

The work was completed within three hours, leaving us with the task of tidying up and loading the vehicles with the equipment. We'll leave the concrete to cure for a month before attempting to mount the gate.

Edit:31/10/16 With our typical luck the weather is turning colder. Let's hope the concrete cures enough to avoid frost damage.

Planning for the orchard gate

The main field of the Turnditch Orchard has a gap in the hedge where a gate used to be located. We have a heavy (more than 50 kilograms) 4 metre steel gate on site which we believe used to be used as the gate for the field. At some point in the past the old gate posts have been removed. We'll need to install some new gate posts so that we can swing the old metal gate.

The old gateway, just after hedges re-laid.

We think the old gate posts were taken out so larger vehicles could gain access to the field to enable dumping of building/construction waste. With the fruit trees in place, we don't want any large vehicles on the orchard, so putting the gate back suits our purposes just fine. The gate will discourage unwanted guests from straying off the public footpath into the orchard field.

The soil where we'll put the gateposts is quite soft and any gatepost footed in a few centimetres layer of postcrete will soon sag under the weight of the gate. We've determined the need to build a concrete beam to provide a secure support for the hinge post. The beam will need embedded steel rebar and approximately 0.7 cubic metres of concrete. We'll mix the concrete on site as it is too far from the road to use a readimix concrete lorry without incurring charges for lorry rental or additional labourers to run around with wheel barrows. The steel work for the re-bar will be designed and ordered from Twiggs in Matlock during this week. A galvanised steel gatepost will be purchased from Lester Lowe.

The beam will be buried out of sight underground when the work is complete. We've used this technique of a concrete beam before  for the roadside gate. In that case we were concerned the gate post and fence posts could cause damage to the top of the river bank. 

Where there's gaps between the hedge and the gate posts we'll build a short section of fence to fill the gap. Later we'll plant hedge plants to grow against the fence to allow its replacement in a few years time.

Good progress on the roadside gate

Yesterday we completed the installation of the metal gate posts for the roadside gates at the Turnditch Orchard. We'd already dug the hole for the right hand side post and lined the bottom with a pad of concrete, but this was to be the acid test of whether we'd got everything in the right position. The gateway is at the top of a sloping ramp leading from the field to the road. At the gateway the ground slopes in two different directions. As we have two gate leaves meeting in the middle it is essential their support posts are accurately aligned in terms of height of the hinges and the vertical aspect of the posts.

When we came to complete the work it was clear that all of the careful pre-preparation has paid off. The volunteer team lifted the heavy metal post into the hole and we commenced the check measurements. After a couple of sideways shuffles of the post we had exactly 12 feet between the posts and they were perfectly level and aligned. The volunteers had not seen the magic of postcrete in action before this installation. We (the volunteers' leader sent a pensioner down the ladder to the river) grabbed a couple of buckets of water from the river and filled the post hole approximately quarter deep with water then poured four bags of postcrete powder in the hole around the post. Using a scrap piece of timber we tamped down the concrete making sure the concrete mix was thoroughly dampened as we poured. Within ten minutes the post was held firmly in place and accurately positioned.

We'll leave the gate post concrete to harden for a couple of days before we mount the gates on their hinges.

We've now turned out thoughts to where we should build the barbecue. I'll be double checking to see whether I need planning permission. The intention is to allow local people to come on to the orchard and make use of the barbecue.

We are currently planning to locate it at the foot of the embankment approximately half way along the orchard. The soil at this location seems to be quite poor and fruit trees and other vegetation does not thrive.

Electric fence energiser housing

We're building a small cabinet in the Orchard to provide security and weather protection for our new electric fence energiser. Today we excavated the base and laid a small reinforced concrete slab to provide a base for the housing cabinet. The base is not large, approximately 100 x 60 cms, so we mixed the concrete by hand from ballast and cement powder (6:1 by volume). Sam's Steps by the river provided a convenient access to fill our water buckets.  The warm humid weather and summer flies buzzing around did not make this work a pleasant experience. Once the base slab has cured we'll build a lockable housing for the energiser and its battery. There will be some additional security features to deter thieves.

After the work had been done I checked the orchard and found four young sheep lurking in a far corner close to the railway. They'd knocked over the temporary electric fence posts  to gain access to our woodland. I spent a couple of hours installing some heavy duty wooden posts, driven firmly into the ground and set up a six strand electric fence to deter these four legged marauders.

Edit 24/06/2016
I found sheep in the orchard again this morning. They'd pushed the six strand electric fence aside. These must be some mighty hungry sheep if they are prepared to tolerate the powerful 3 joule shock this fence gives. I think the problem is they are dumb juvenile sheep not yet "trained" to recognise electric fences. The older sheep steer clear once they realise it is an electric fence.

I've now ripped out the extended section of the electric fence adjacent to the railway line and replaced it with 30 metres of wire stock fence mounted on wooden posts driven in at 10 foot intervals.

I removed the plywood shuttering from the base of the energiser shed. The concrete slab is looking good.

Edit 28/06/2016
The installation of wire stock fence seems to have worked, there have been no further sheep invasions since I upgraded the fence to a permanent structure. Last night I added an insulator mounted electrified high tensile steel wire top strand above the wire stock fence to enhance the sheep resistance. I'd been trying to avoid a permanent fence as we still have to fell some trees in that area, but it seems to be the only solution to deal with the sheep.

Why are things never simple in the orchard?

Finally on Thursday we were able to pour concrete to form a beam to support the new gate post and fence posts on the top of the river bank at the Turnditch orchard. The beam is about two metres long and approximately sixty cm square in profile. It took roughly 2/3 of a cubic metre, about 1.5 tonnes, of ST4 grade concrete with added polyester fibre to reduce cracking to complete the beam.  The actual pour process only took about 30 minutes from the time the mixer lorry arrived. We now have to leave the beam for a couple of weeks to harden somewhat before setting up the posts. 

Concrete beam supporting gate post

In the picture you can see the fence post cast  in place. It looks a bit tilted, but that is just caused by the camera angle. According to the  builder's level it is well squared and vertical. At the base of the post you can make out a couple of layers of plastic bubble wrap. This was added to increase the diameter of the post socket hole in the concrete. We'll lift the post, remove the bubble wrap, and then reinstall the post with dry sand packing. This will allow subsequent removal of the post for maintenance without damage to the concrete beam. 

You can also see a dummy post embedded in the concrete. This also has bubble wrap and acts as a form for the socket hole in the concrete for the gate post. When we are ready to install a gate post we'll pull out the dummy post leaving a clean hole for the new post. 

There is a matrix of steel reinforcing bars hidden and embedded in the concrete to strengthen the beam. The steel is carefully designed to resist the potential stresses from the posts. During the next few days we'll cover up the concrete beam with aggregate/soil from the original hole so people will be unaware of the minor civil engineering buried beneath. As mentioned in an earlier post this work will help to prevent river bank collapse so close to the road bridge. 
It was a lot of work, when all we were expecting was to drive a post in for a short fence on the river side bank.

Civil engineering in the orchard?

As we work through the plans for the gates to the orchard site it is beginning to sound like a civil engineering project. We've worked out we'll need about half a cubic metre of medium strength concrete to cast the beam required to support the riverside gate/fence posts. We've phoned around various suppliers to discuss the options and it seems a mix-to-order truck which mixes the concrete on site is the best option. A local company J C Balls provides a suitable service at a reasonable price. 

Fortunately where we are working is close to the roadside so delivery is not a problem. We'll just need a robust wheel barrow to move the concrete to the place we need to pour. The truck is charged in half-hour timeslots.

We're going for a concrete ST4 mix with polyester reinforcing fibres. We've now received the re-bar for the steel reinforcement of the beam for Twiggs, so all that remains for us to do is to dig out the trench for the beam and install some 18mm plywood shuttering to create a form for the concrete. We'll then position the re-bar and wire tie it in place before pouring the concrete. We need a 7 day period to allow the concrete to cure and gain strength, prior to installing the gate/fence posts.

The rebar awaiting installation, and wire tie equipment.

All this effort is necessary so we can set the gate post and the fence post in such a way that it will provide sufficient strength of support without creating risk of damage to the slope down from the road. The gate post will be exposed to frequent use by the public as they open/close the gate for their dogs as they make use of the public footpath. A gate post just driven or dug into the limestone chippings of the slope will inevitably fail within a few years. We mentioned in an earlier blog posting that we'll leave the historic stone gate posts and stile in place.

Once we have the gateposts installed we'll build a pair of wooden gates to match the distance between the posts. It will not be a standard gate size and we have to allow for footpath access, so using "off the shelf" gates is not an option..

Bending steel

After some spraying of blue marker paint on the ground and lots of measuring, we've specified the steel reinforcing bar for the concrete beam to support the gate posts of the field gate. In an earlier post on here we mentioned the reasoning for constructing a concrete beam. Now we've taken a view on the likely forces that will be imposed on the concrete. We've also considered how the posts will be replaced in future if significant repairs are required.

Some research on YouTube has made us instant experts on how to set out rebar (Steel reinforcing bar) and to create shuttering to hold the concrete used to form the beam. We've had to understand the British Standards for common rebar shapes used in the construction industry. This allowed us to produce specifications for the amount and shape of rebar required for the concrete beam to support the orchard field gate. It is a cantilevered design to prevent the gates from sagging in use. We requested a quotation from a local steel supply firm Twiggs for rebar bent to our custom requirements. The price was so reasonable I actually rechecked they'd included the cost of bending within their price. We've placed the order and await delivery.

The beam will be approximately 200 cm long by 90 cm wide with a depth of approximately 40 cm. It will be capable of withstanding the weight of heavy agricultural machinery which might pass through the gateway. It will be buried from view once the posts are installed.

The reinforced beam will provide reinforced sockets for the gate post (200 mm diameter) and a fence post (100mm). When we're casting the beam we'll mount the gate and fence post in position in the beam. We'll pre-wrap the end of the posts in plastic bubble wrap so we can lift them out once the concrete has hardened. The sockets are also designed to prevent the accumulation of water under the base of the posts. After removing the bubble wrap we'll re-install the posts in the beam using sand to pack the gap between the beam sockets and the posts. This installation method allows the post to be securely mounted, free from rocking/tilt, but allowing for easy removal for future maintenance. If you just mount the posts directly in the concrete when it is poured subsequent maintenance of post removal is difficult.

We are also practising the art of wire tying to fix the rebar in place before pouring concrete. Youtube helps again.  All that remains now is to trick the volunteer team into agreeing to, dig the trench and to mix the concrete when the management team are ready to construct the beam. We'll be incorporating reinforcement fibre into the concrete mix to provide extended life.

Little did we realise when we started the orchard project that we'd become involved in civil engineering and reinforced concrete design.

Preparing the security unit and river erosion

We were able to get on the orchard site today. We started to lay the base of the temporary security box. This unit will store materials and dangerous tools while we work on the site to clear the field, plant the orchard, install drainage and manage the woodland. 

The metal base frame is filled with steel fibre reinforced concrete mounted on a sheet of vapour barrier plastic. This plastic sheet will protect the soil from the concrete for when we come to remove the temporary store unit. Water for the concrete comes from the Ecclesbourne River. 

A toughened steel security chain is embedded in the very heavy concrete base and attached to ground anchors. The chain will be used to secure tools when they are not in use. Other hidden security measures may be in operation. ;-)

The petrol motor brush cutter we're using to clear the field is quite long at 2 metres. We had to chose a large security box to provide space for the brush cutter. The long-handled Stafford Billhook we'll be using for hedge laying is now literally razor sharp. At times we'll be using other power tools. The intent is to be able to safely lock away tools such as these and also angle-grinders and chain saws during the day when we are working at the other end of the field or in the woodland. Better safe than sorry, but if kids were to mess around with those forestry tools they could be become injured. It's unlikely, but the site is very close to the road with a public footpath running next to the river.

Nothing valuable will be stored overnight. We'll even release trespassers from the chains before we pack up for the night.

Update 31/10/13  I've discovered I have muscles involved on concrete mixing (by hand/shovel) which I've not used in a long time. 

We also noticed some exposed flower bulbs, snowdrop, on the river bank. There's probably been some soil erosion during recent years. We may need to consider some method of natural reinforcing to prevent the erosion extending. If we leave this the erosion will eat into the public footpath and endanger the farm access to adjoining fields.

Exposed flower bulbs (Snowdrop) on the bank of the Ecclesbourne

There's some useful information here. Obviously concrete is out of the question and geotextile or wire gabions always looks quite tatty after a couple of years. Tied brushwood bundles (fasces) and/or introducing some live Willow Spiling to replace the undercut elm and ash may be a suitable method of approach. Here's other willow supplier and locally. This requires soon winter work (to allow the live stakes time to take root for the summer), but as we have other more urgent work on the Orchard site the bank reinforcing will have to wait until the 2014 winter.

I suspect some of the erosion is caused by eddies from the road bridge piles when the river is in spate. Note to self: find a source of live native willow stakes

Update 3/11/2013: We've discovered any river bank erosion control scheme needs Flood Defence Consent Approval from the Environment Agency. This will definitely delay the Spiling works until next year. It also implies a £50 fee payment for us doing work to "improve" the river bank and the same forms as if we were constructing flood defences for Derby, ho-hum!. We've contacted the Environment Agency and we'll keep you posted on progress. We'll see if there's bureaucratic overload for the planting  a dozen live willow stakes in the bank and weaving twigs between them.

Update 6/11/2013: The environment Agency Help Desk gave us the wrong information. It looks like Derbyshire County Council look after this. Their documentation is here. Their guidance suggests we need no special permission, but we are in contact to with DCC to confirm.

Update 10.06/2015 We read in the Derby Telegraph newspaper today that volunteers for the Derbyshire Wildlife Trust that they've being undertaking some spiling on the Ecclesbourne river to protect the banks from erosion. Great minds think alike eh?! Here's DWT's report on their work.