Benchmark Adjustments: Follow Up 1

[usaedy]

Just wanted to provide some follow up to a previous thread located here:

http://www.eng-tips.com/viewthread.cfm?qid=169526#postform

Site work is complete using the approved benchmark adjustment and there were no issues with regard to utility tie-ins or making the grade work around the perimeter of the site. We have installed all utilities, paved all roads, and padded all lots with topsoil stockpiled and ready for respread.

Using the benchmark adjustment specified, the site contractor gave us a balanced site. Where the site was calculated to be 60,000 c.y. heavy, using the benchmark adjustment we have only exported 6,780 c.y. of dirt. About half topsoil, half fill dirt.

The way this was made successful was by up front communication with both the surveyor and the site contractor. I had personal meetings with the site contractor where we shared our takeoffs and planned for the BM adjustment together. The contractor provided us with a great level of customer service that is rarely seen in this industry. The communications were then carried over to the surveyor for them to provide us with cut sheet calculations. Of course, they were able to use the proposed plan grades, and the only information that changed would have been the cut/fill depths. The surveyor also provided us with red-line markups showing the changes needed to tie in to existing utilities and that was carried out with no issues.

BM adjustments can be made successful and we will be using them in the future. I think the way to acheive success is to get rid of the adversarial business relationships on site and work together to get a difficult job done right.

 

[civilperson]

A misnomer at best. You adjusted the site elevation to get a balance between cut/fill. The BM used DID NOT change, perhaps your datum (quantity to add/subtract to BM to get site reference elevation), changed and thus all tie-ins were adjusted accordingly. It hurts my surveying soul to hear that term,"benchmark adjustment".

 

[tsgrue]

.
It sounds like you adjusted your median finished site elevation (proposed grade). That would not be changing the benchmark elevation.

For example, I might have a site with several benchmarks with elevations relative to NGVD29, NAVD88, local, or some other vertical datum. The final graded elevations on the site might be adjusted up or down, but the benchmarks would not change. Hopefully, the only reason a benchmark elevation would change is to correct an error in establishing the benchmark or adjusting the indicated elevation if the benchmark was disturbed.

Adjusting finished elevations (final grades) over the entire site or in a localized area is pretty common in my experience. It is often done on a project during construction, especially if limited (or no) site geotechnical testing/analysis information was available or utilized during design. Even when such geotechnical information is available, earthwork volume estimates are only estimates and some earthwork deviation from the plans should be expected. Such adjustments can save a lot of money and time. Be careful to run all earthwork changes by the designer prior to undertaking these (which it looks like you did) as these directly affect utilities cover, stormwater management, roadway slope, and other items - which can cause both regulatory requirement problems and long term performance problems.
.


tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation

http://hhwq.blogspot.com