[scott C]

I am working on aprice for a srw retaining wall to be installed on a lakeside. I am currently awaiting info from the engineer but I have a couple of questions for those of you that may have installed a wall in water applications.

1) Our crusher run footer will be below water level. I will be using a sump pump tp remove the water as we are digging but the sub surface will be consistently wet. Not an ideal situation. How does one handle this.

2) how do srw hold up along a lakeside. does undermining occur even with rip rap installed in front of the wall.

3) are there better materials to use other than srw's.????

[Stonehenge]

I've done some reading, and even bid on a couple projects like this, but never landed any. And frankly, I'm OK with that.

From the info I've read from the folks at Versa-Lok, and through some chate with people here, you essentially have to build two walls. The first wall is constructed, not from SRW, but from some other material that is easily removed. This wall is built outside the area you'll be building the primary wall. This wall's function is hold back the water to allow you to work. Once this wall is constructed, you have to de-water the area. Versa-Lok has a nice Tech Spec on this application, and involves using grid folded over itself in the base prep, plenty of clear stone behind the wall, and plenty of rip-rap in front.

As a side note, from what I understand, if there are ice shoves or ice floes on the body of water where you're working, and they hit your shore, there's no SRW out there that can stop them.

Oh yeah - another side note - make sure you or the client has contacted the DNR - they tend to be humorless about building walls that don't allow wildlife to easily enter or exit the water.

Hopefully that'll give you a start, but I'm sure there are others that have 'lived the dream', and will be able to give you more info.

[Paul]

I don't know what type of SRW you are going to use on this project or how big of a job it is. Having done a few wet work jobs you need to understand the forces applied to the SRW's.

I wouldn't use standard crusher run material, My thinking is using a 3" gravel under your SRW units encased in a UV resistance geo fabric. This may be as thick as 3' depending on the soils under it'. It may need to be tied into the supporting soils behind the wall. This may be done with a geo-grid half way thru the 3" stone. One other option is to use a reinforced concrete footer under the SRW.

Dewatering and water devertment; this can be as simple as a sandbag and visquine reinforced wall to special water filled bags and desilting equipment.

I like to use larger units for this type of work Unilock makes some that work very well in water and have specs that will help you in finding what you are looking for.

We have done natural stone in rivers but we were able to rewrite the specs for this job and still ran into problems, we ended up pouring a footer in the river to support the stone do to lack up natural solid footing that we and the engineer had expected to find from their soil borings.

[Paul]

Here's another picture of natural stone beening used in a river.

[scott C]

Thanks for your replies, I realize that all of you are busy and do appreciate your time.. I hope to hear even more feedback from others so keep it coming.

There will be a total of 2 walls each one 100 + feet long. The space between the walls is yet undertimend but is under 20 feet. Total height 14-17 feet.

The blocks we will (hope ) to be using are anchor diamond straight units. Unfortunately ther is no access from the lake side other than barge so srw's seem to be the way to go. the blocks are manufactureded locally which means the cost is low and some help from the manuf. is available.

One good thing about the site is that each winter the lake is lowered so ice jams / damming should not be a problem.

On the down side the engineer is rather old (have not met him yet) and the property owner does not feel he has experience designing this type of wall.

Paul made a good point about soil conditions. The geo tek took some samples of the upper side of the lot.(silty /clay), but the soil conditions where the wall will be is going to be different.

I realize that each site is different but do you feel a poured concrete wall, gabian SP. baskets or other type of material may be better??

This could be a great opportunity for my company since many of the lake front properties need walls. The down side is I am doing a lot of leg work for a job that the homeowner is not fully commited to hiring us for, although I am the front runner.

[Paul]

Soils are going to be your biggest problems, normally a 20' separation on a dual wall, each wall could be considered a separate wall, but knowing the difference in soils and the amount of water they will hold at different times of the year I would quiz the engineer on how he came up with his reenforcement numbers.

I would have a soils report done on the lake side soils before I would commit to anything.

Again I don't know how big the site is or the distance from your easy access side to the wall, but sometimes larger SRW's are better to install then the cheaper ones. On larger units you are installing more sq footage per unit, which means your labor price per unit is cheaper, even if you need to hire a crane to install them, prices for cranes are in the $100 to $300 per hr but installing some units that are 6+ sq ft per unit might mean your installing 100 to 200 sq ft per hr with less labor on your end. But don't think that your going to do these type of walls for $20 per sq ft. You may spend just that for the back fill and geo-grid.

Your biggest wait is going to be on the reports so I wouldn't spend alot of time on this until you know what you are dealing with!

[Tim]

Paul, didn't having your equipment in the water like that make you nervous of hitting a "sink hole" type area? The wall definitely appears it would stand up to the test of time for sure though. Tim

[Paul]

The only thing we worried about was a oil leak, some of those stones weighted a bit more than that machine could handle, EPA clean-up's are big money.

[Tim]

I bet that was scary! EPA has a very small sense of forgiveness. It looks like a pretty pristine environment too. Did you pull it off without any hitches? Tim

[Paul]

Here's some of the problems that can happen when your dealing with water. This shot was right after install....

[Paul]

About 3 weeks after we installed the boulders

[Tim]

Water!! They only thing for sure about it, is it will eventually find a way to do what it wants! Tim

[scl]

Recently I lost a bid on a really big wall to a local builing contractor that bought the forms for something like those big Redi Blocks. About 1/2 yard of crete per block covering close to 4 sq. feet. They had to lift them over the residence with a crane, not much rear access. They're now signed to use them on a seawall I was looking at and I was told they are going in for Paul's magic $20 a foot. They can have it for that money!

I don't like the looks of it myself but it comes back money. People putting this stuff at their houses are high end consumers who hob knob with this builder at "the club". I just don't get how they can do this for that amount!

You figure 1/2 yd crete is $35, cost of forms, trucking, crane is over $2k a day and that may be quite lite. But they do go in quick. Hope they don't start building flower bed out of it LOL. When it comes to bigger stuff I like the bigger Unilock stuff, mostly Sienna, but the cost of material is more than that. Waiting for their first failure for some good pics.. Well I can hope, can't I?

[Tim]

Originally posted by scl

You figure 1/2 yd crete is $35

One way they are probably getting around the cost of concrete is by furnishing their forms to the local redi-mix company(s). The concrete used is just left over wash out from the trucks when they come back off of job sites. The drivers just blast the mud in the forms with a vibrator quick, and then top it off with a mag finish when full. The guys doing it here, pay the yard $5 per block for the driver to put the top finish on. No real skill is involved to do it, the yard solves their waste problem, and they make money on what has already been paid for. It is a good program for everyone. It is unfortunate that it effects bid acceptances for better suited, quality materials. Tim

[Paul]

I don't think they're using waste concrete on those block, at least not if they are going to do any state or government work. Think of it this way they are not getting charged $70 per Cu yd if it mixed on the same site it's poured on.... and their selling them to them selves. Now on to the costs of setting big walls, the more you use a crane or crane service the cheaper it gets, the service having you pay for dead time it's built into their price, now if you can keep one busy.... they can reduce the cost to you and you can pass it along to your customer.