HI Sally
I can offer some thoughts on how the sandpit could be constructed, although I should warn you that I've never actually DONE this activity, so pinches of salt at the ready!
Assuming that you aren't going to be able to just dig a shallow trench in the ground and fill it with sand I reckon that the best way to construct a temporary sandpit is to pile up the sand on the ground with a perimeter of boards to keep it in place. The best things to use for the boards are something like 150 x 25 mm sawn softwood shuttering boards. These need to be held in place by being nailed to pegs driven into the ground at say 450 mm centres. Pegs should be 50 x 50 mm sawn softwood with one end cut to a blunt point. They need to be about 450 mm long and driven in with a hammer.
Before you start lay out a plastic sheet - 1200 g polythene DPM will do - over the ground you intend to cover, and hold this down by driving the pegs through it. Once you've got the shuttering boards in place you can fill the sand pit with sand to a depth of 150 mm - level with the tops of the boards, burying your 'finds' as you go.
A sand pit big enough for an entire class to work on will be quite big - if we allow each child a 600 mm width to work on you'll need 18 m of frontage. Suppose we make the thing 9 m long, so we've got two rows of kids digging, then we need to make it wide enough so that the patches don't overlap across the width, so we need a width of about 1500 mm.
How much sand will you need?
The volume of the sand box is going to 9x1.5 x 0.15 = 2.025 cu m. Sand weighs about 2 tonnes to the cubic metre, so you're looking at about 4 tonnes of sand to fill this design. Buy your sand from a builders' merchant who will be able to deliver the stuff to site for you.
Things to beware of:
Don't use 'sharp sand' - this will cause cuts and abrasions as it is made of very angular grains- ordinary builders sand or sandpit sand is the stuff to go for.
The sawn softwood may be considered to be a hazard because of splinters. You could replace this with planed softwood, but this is significantly more expensive. It might be better to just run a plane over the top edge of the timbers in situ, to produce a smooth edge.
Don't use treated timber - it costs more and isn't required for a temporary structure
You need to consider how you're going to dispose of the sand etc when you've finished with it, so you should factor disposal costs, ie skip hire, into the budget. As the sand should remain clean you may be able to persuade a local supplier to lend you what you need, which would help to keep the cost down.
And what are the kids going to put the excavated sand into as they dig? Builders' buckets would probably be the best thing to use as they are cheap, but a 10 lt bucket full of sand will weight about 20 kg, so you need to think about how they will be handled. Barrows are more expensive, and harder for kids to use, but can be hired wheras buckets need to be bought.
Not sure why you need plastic trowels, unless you can get them cheaper than metal ones. Kids should not be mollycoddled by being given inferior 'safe' tools to keep the health and safety crowd happy. If you can afford the proper tools, use them. This will make for a much more authentic experience.
You should cover the sandpit when not in use - more heavy gauge polythene sheet held down by bricks/blocks round the edges is probably best.
And the best people to build this for you - try local builders or groundworks contractors.
Hope this helps
Cheers
Richard.
Richard Ellam
L M Interactive
Science Shows and Hands-On Stuff
On 19 Dec 2010, at 21:26, Sally Russell wrote:
Dear all,
I have to put together a plan and costings for building an archaeological trench for children to have an archaeology day (3-4 hours of activities)- and have to do it in the next 3 weeks!
If anyone has and advice/ warnings about doing this I would really appreciate it!
I am also looking for a supplier that can build a sandpit big enough for a class to all dig at once which can be covered/locked up at the end of the day.
If anyone has any good suppliers for adjustable waterproof outfits for the children to wear, plastic trowels for them to dig with would all be appreciated!
I am sure there are many other things I haven't even considered yet- so all advice would be most welcome!
Thanks
Sally
Chertsey Museum
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