Conditions to Justify Residential Slope Assessment

[mudandsnow]

I want to buy a house but there is a hill behind it. If it needs a retaining wall, I don't want to buy it.

If it most likely needs a wall, I will probably walk away before spending money on assessment.

I'm sure this is hard without seeing it in person but any rough guess would be appreciated. What are the odds that it will need a retaining wall?

What factors do you consider when deciding whether a hill should be assessed or not?

Slope: about 45°
Height: about 100ft
Soil Type: silt
Vegetation: grass and small shrubs
Above the hill: flat orchard / vineyard
Climate: Western Canada, multiple freeze thaw cycles in spring and fall and snow melt water runoff in spring.
Features: looks like there used to be a 1 car wide road diagonally up the hill. Does that mean it's packed down and thoroughly tested?
House age: 50 years

I don't think the hill has moved in the 50 years the house has been there but there have been slides in the area lately, often in spring and usually attributed to snow melt runoff and multiple freeze thaw cycles.

 

[ATSE]

To MTNClimber: You and I agree.
My comment about the 90% should have been followed by:
"Be skeptical of the confidence placed in 2H:1V slopes."
My local jurisdiction in Northern California allows 2H:1V for cut slopes and fill slopes; slopes on residential properties where less than 50 cubic yards are cut or otherwise moved do not require a grading permit or geo report. This probably works well most of the time, but this gives me a little heartburn, so I err on the side of caution.

 

[cvg]

The geo data recon and lab testing necessary to render a high-confidence opinion on a questionable slope is disproportionate to the value of most single family dwellings.

on Eagle Point, I would have to place some fault with the building and safety department. safety is their middle name, but apparently there were not safety issues anticipated with building residential inside a quarry without adequate grading and drainage requirements put in place to mitigate what was arguably a very high risk slope. certainly, the developer should have done a risk assessment and the city should have required the engineer to submit a geotechnical study which addressed the high wall. if not, than they should be held accountable for the damage.

 

[mudandsnow]

Still haven't managed to get an appointment with a geotech. Is there a big shortage of geotechs?

Half my city is built on hills, I'm surprised how hard it is to get a pre-purchase inspection. It is making me think no one bothers. Is it common for people to have geotechs look at hills before buying houses?

Any ideas how I convince a local geotech to meet with me?

 

[cvg]

good luck hiring an engineer.
you are asking for a professional opinion on a high risk project with a small budget. the risk vs reward is high. Insurance companies frown on these types of projects.

you may just have to educate yourself and do your own due diligence. a trip down to city hall / building department on a fact finding mission might yield some results.

 

[oldestguy]

I hate to say it but money speaks. If you offer to pay on the job at a few bucks above their hourly rate, that may do it. At the time make a call to the bank to verify the money is there. A down payment also helps. My guess is they can't verify anything until test borings are done and then it is unlikely that they can 100% say it is safe. I'd go mainly on the history of the area and land slide histories and skip the geotech..

 

[PEinc]

Homeowners too often cry over any engineer's invoice that is over a few hundred dollars. Sometimes it's just not worth working on residential projects.

http://www.PeirceEngineering.com

 

[MTNClimber]

You may have to find a one-person shop to help you out. If a bigger firm turns you down ask if they know of anyone that is out on their own.

Yes it's common in certain areas to have someone do an inspection or even a full subsurface investigation. In Colorado, the soils are so bad in areas that cities, towns, or counties require borings be performed on a lot before construction. Prior to moving out here, I never heard of such a thing.

As a side note, often homeowners (or future homeowners) are the most difficult to work for. Not only do they cry about a few hundred dollars but they can be reluctant to pay. I've heard stories of homeowners having to sell tractors or pianos to pay the engineering fee and then cry to the engineer that their fee is costing them their potential dream house... blah blah blah. So yeah, money talks. If you pay upfront or partially pay upfront that may get you somewhere.

 

[mudandsnow]

Pretty much all the city said was 'ask a geotech'.

I work for tech start ups, I am familiar with difficult clients with no money.
Never seen anyone cry but I've also never seen a hill run through someone's house.

I am not asking for a study or a report or any kind of definitive answer. Just a quick consult to get a rough idea of the area. Do they recommend most hills around here get studied? Approx what H:V is their threshold? If they think its worth it, a quick visit to see if there are any concerning features. Maybe do all that at once.

I'd also like to ask about the history of the area. Figure they would know that better than anyone. Is there anywhere I can get record of slides or sink holes or other problems in the area?

It seems weird to offer payment, isn't payment implied when asking for a professional's time?

Should I say, "please chat with me, I'll pay you?" Or should I offer a fixed amount?

 

[oldestguy]

My suggestion was early payment, since some might be slow to pay. Who wants slow payers?

As an alternative, is there a city engineering or public works dept with an engineer? They may be of some help, since they might have to deal with problems related to slopes.?

If I was in town, I might (that is might) have experience with such slopes and could comment. However, if there is a significant risk, it would take on site soil examination, with test borings, lab tests, etc. Cost maybe a few thousand. A simple look and comment maybe a few hundred. That likely means getting access to the slope for the drill rig. Would disturb things and might not be wise. It costs to work on sites like that.

 

[MTNClimber]

MudandSnow - I think you have the right idea with just getting someone to comment on if it should be a concern. I don't think a full slope stability analysis will be likely required. Just someone with experience in that area that can comment on how high the risk is from the 30,000' view.

My wild guess is that the slope is probably fine. From the aerial photos it looks like it may have been developed from historic erosion from the water. But this guess doesn't mean much compared to having a local geotechnical engineer's opinion with access to the site.

 

[mudandsnow]

The conclusion: someone else bought it.

They supposedly had multiple offers, multiple times. Someone after us had an accepted offer for a little while but they too backed out and then someone else bought it.