Incomplete Topo Survey? 1

[stvnchng]

I'm attaching a a portion of a topographic survey with the hope of soliciting opinions regarding its completeness. I feel that basic data has been omitted, but I'm a bit out of my depth here and would appreciate any input.

Thanks in advance!

 

[msucog]

i would ask the civil/drawer for elevations to the contours. i would also double check the contours to the percent slopes indicated (glancing at the plan, they don't seem to make complete sense to me with the topographic lines).
any particular issue you're worried about?

 

[stvnchng]

The lack of elevations for the contours is exactly what I feel is missing, but I thought I was not reading it correctly somehow.

Would you expand upon your comment regarding the relationship of the contours and the percent slopes?

Thanks for your help!

 

[CarlB]

Wow 24%, that's a steep road!

An example of a slope/contour discrepancy-where a 1.5% cross-slope is shown, contour is parallel to the road which would mean more like a 0% cross-slope.

25% would be a 1' drop in 4' horizontal. Can't tell what the drawing scale is. You could check if the slope along the road shown agrees with the contour spacing. (the slope in percent is the contour elevation interval divided by the spacing, times 100).

 

[msucog]

carlb hit part of what i was getting at. also, the slopes don't appear (at a quick glance) to follow the contour lines. many of the contours at one station are essentially the same going across the road yet the drawing indicates cross slopes and multiple slopes along the sides and middle of the road. a scale or something would be good to see if the indicated slopes work with the contours. there may be reasons as to why the slopes and contours wouldn't match that i'm not aware of, but it doesn't look like what i typically see.

 

[namdac]

When a firm is hired to perform topographic surveys, usually all items required are spelled out in the contract. However if this is an "In House" production, your firm needs to work on it's communication skills. When a crew shoots in a very limited number of shots, the interpelation between them becomes highly exagerrated. This is why I think your contours appear to be a "little" off. When we send out crews it is clearly understood as to how much and what they are required to pick up. In this case I believe that I would have the crew shoot 20' beyond BOC, it would give up at least a better tin to work from.
Regards,
Namdac

 

[stvnchng]

Thanks for the responses. What does BOC stand for?

 

[PELS]

BOC = Back of Curb, sometimes TC or Top of Curb.

I agree with defining the contours but spot elevations would help too because, as others have noted the cross slopes, longitudinal slopes and contours don't seem to relate properly as they should.

Not sure what this is being used for but I would also want ground elevations beyond the edge of roadway. Maybe some typical road sections would help visualise what's going on better too.

 

[stvnchng]

This is a survey for a driveway renovation. I've attached another portion of the survey. This is the area in most need of attention. Of note is a 40+% slope on the downhill side of the driveway. The blue line represents a suggested solution. On the uphill side, a retaining wall would be needed to accomplish this new path. Unfortunately, there is little information about the elevations in this area. In addition, our property line is very close to the uphill edge of the proposed solution; however, this information was not gathered. The company that provided this survey is also an engineering firm. After this work was done, I expressed interest in moving on to the permit drawing phase of the project. At that time, it was disclosed that only grading could be engineered through the firm; retaining walls were not a part of their repertoire. This situation prompted me to investigate the work.

 

[CarlB]

It should be apparent to the survey/grading design firm, as you noted, that the topo is incomplete in a critical area - the uphill area where the wall is proposed. If it was just an as-built survey of the driveway, then it was sufficient, but as a design survey, not enough. he property line locations, & grades in that area must be provided to design a wall or cut slope in that area, if it's even possible.

That's some steep slopes at the end of the driveway. The design makes it marginally better, in my opinion. You might consider steepening a short straight section of the driveway to get a flatter slope at the bottom without offsetting the driveway as much.

 

[PELS]

The "firm" doesn't need to design the retaining wall. There are material suppliers/manufacturers that will provide the structural design just for specifying their product (Keystone, for example

http://www.keystonewalls.com/

). What the "firm" can do is determine the location and varying heights of the wall based on the new driveway design and the existing ground (topo) where the wall needs to be placed. If the "firm" says they can't do this, they shouldn't be in business.

You are getting "second opinions" here on this forum, but I suggest you contact another firm in your area to have a look. I think your eyes will be opened to what a real "firm" is capable of doing.

 

[stvnchng]

I started this thread simply looking for objective information regarding the survey. I really wasn't looking for second opinions on the design. Perhaps I shouldn't have posted the second image, but I thought it would be helpful.

I agree that the firm isn't obligated to design the retaining wall, but I believe that they should have disclosed that they would not do so prior to offering a contract for services, especially when it was a reasonable possibility that a retaining wall would be needed.

I am in the process of interviewing local engineers/surveyors.

Thank you all for the invaluable advice!