Expensive Earthworks in Winter

[WantToSucceed]

We are doing a development in Perth.
It's a subdivision work for 8 units in Cannington.
I am one of the shareholders and it is managed by someone that I know.
We have someone that is helping us with the works to get the council approval.
We received 2 quotes for earthworks from a couple of builders through him, both around $100K.
Based on the reports from the earthmovers he recommended that we do the work in Summer because that will save us $30K or more.
Also in the event high level of ground water presence, dewatering may be required which is not included in the quote which can be around $50k
He also thinks that the property market is bad at the moment.

I am very unhappy with how the project is managed.
It started in July 2010 and after 2 years we have very little to show.
Mainly caused by a choice of a bad builder at the beginning.

Have anyone gone through with a similar situation related to earthworks in winter?

 

[Tools]

Why are they saying i will be cheaper during summer? Do they have cheaper tipping that is only accessible when it is dry?

Tools

 

[Doovalacky]

I am assuming you must have a low lying block. Possibly with wet areas already?

I have had issues before were the water table in winter was so high the 0.5m soakwells I had brought were 1/2 full and I had to put in extra sub surface slotted drainage pipe.
Then during leveling the bobcat got bogged and after dragging that out had to level by hand.

If the area is wet machines get bogged, trenches fill with water etc making extra work thus increasing the cost. Also delays due to rain.

A small auger dug hole down to a meter or so would soon give an indication on how high the water table is. That's if its not obvious from just looking, ie swamp.

 

[Jake D]

I'm just making an educated guess because I don't know your site or it's earthworks design, but...

A lot of Perth properties have cheap earthworks because it's free draining sand. All they have to do is compact it before pouring their concrete slab. Then they hook up all their drainage to a couple of soakwells and the surface stormwater discharges into the sand and flows away. You may have had, or heard of experiences where "earthworks" wasn't really a requirement or a problem, and It sure didn't cost $100k

In areas where clay is present, it will not allow free drainage of surface stormwater. they still use a concrete slab laid on a compacted sand pad, but the sand has to be imported from somewhere else. AND the clay underneath has to be shaped to allow drainage away from buildings and in most cases into a council drainage system. It's pretty much an underground slide where water drains through the sand, along the top of the clay and intro the drainage system. Errors in designing this will mean your houses are floating in a sandy pool over a solid clay base.

Firstly, $100k is not remotely expensive for cut-base works on an 8 unit site. i've seen quotes for $50-60k for single houses. A not-insignificant part of the cost comes from importing the clean sand and disposing of the excess clay they cut out. Secondly, running heavy machinery is a lot easier on solid, dry clay, as opposed to wet soggy clay. (as stated above) Thirdly, cutting and shaping clay using that heavy machinery is a lot easier when it's dry too.

Hope this is of some help to you.

 

[Tools]

Things must be different over in the west. We are just about to start excavation on a basement 4.5m deep and there is no additional cost for the earthworks contractor for doing it in winter.

Tools

 

[matto_]

Winter=, rain delays.

Nothing on a building site goes quickly when it rains (or is hot)

 

[WantToSucceed]

Yes, the site has clay.

1) Complex and extensive earthworks to be carried out which involves removal of 500mm deep of water impervious clay soil and refill with 900mm high of clean sand as recommended by geotech engineer.

2) Due to the recent heavy rain in winter season, above works required by machine will be much harder due to the presence of high ground water level and to be remove very wet muddy clay.

I guess we have no other good choice other than to wait for a dry season.

I can't believe a subdivision work (excluding the building) has taken 2 years and still more to go.

How a bad management can stuff things up.

 

[Jake D]

Yes, the site has clay.

1) Complex and extensive earthworks to be carried out which involves removal of 500mm deep of water impervious clay soil and refill with 900mm high of clean sand as recommended by geotech engineer.

2) Due to the recent heavy rain in winter season, above works required by machine will be much harder due to the presence of high ground water level and to be remove very wet muddy clay.

Nice guesswork by me, then? Alright.

I can't believe a subdivision work (excluding the building) has taken 2 years and still more to go.

How a bad management can stuff things up.

I am not remotely surprised that a subdivision takes that long. I've never done one myself, but I've been involved in the engineering design side of tons. I know exactly how slow these things can be.