Fluid Migration in Utility Trenches 2

[SanEnr1]

I am doing research for a paper regarding fluids (either liquids or gasses) that follow utility trenches after construction is complete. I have seen groundwater follow porous stone bedding materials downgradient and volatiles follow the same type material upgradient where the fluid is then released into the environment.

If anyone has experience regarding this topic or has read other papers on the issue, I would like to hear the story of the problem and how it was resolved.

Thank you.

 

[bimr]

Nobody has solved this problem yet. Try the following posts:

http://www.eng-tips.com/viewthread.cfm?qid=109240&page=1

 

[cvg]

trench plugs using low permeability material can be used to disrupt the migration. Plugs can be clay or flowable concrete backfill.

 

[4tuna]

Wow, where to begin. This is not an uncommon problem, especially in areas where groundwater is shallow.

One of my sites was a bulk petroleum distribution site, with another bulk petroleum distribution site across the street to the south. Groundwater was shallow (~5-8 feet with seasonal variability) with flow to the east toward a seasonal canal. Betweeen the two sites in the center of the road, there was a deeper (10~12') sewer lateral in permeable backfill that sloped to the east and acted as a drain on the site, affecting both groundwater levels and contaminant transport. By the time the problem was fully uncovered, MTBE had travelled east in the utility corridor to the canal, which acted as a shallow barrier to fluid migration, and spread laterally (to the north and south) almost 1/2 mile in each direction. BIG PROBLEM!!!

In general, utility trenches are more permeable than surrounding soils, and they may serve as collection sumps for surface runoff/infiltration of water and contaminants, even where the groundwater table is deeper than the trenches. Becasue of their higher permeability, any material that enters the trenches can travel some distance before fully percolating into underlying soils.

One approach for your research is to talk to municipal city workers - they will know which trenches are good and bad. I have often heard things like "Oh, yeah, everyone knows that stretch of trench is contaminated.....it stinks so bad I get a headache everytime I go in there." Whenever I think utility corridors may have an impact on my site, I consult workers ASAP.

 

[daddymem]

One solution to help mitigate the problem:

http://www.epa.gov/boston/assistance/ceit_iti/tech_cos/mcr.html

There may be more info on the EPA website.

 

[SanEnr1]

4tuna,
Your story sounds very interesting. Could you contact me directly at v o e r g c (at) c o l o n i e (dot) o r g with more details? (Please note that there are no spaces in my contact info, this is only used to throw off spammers.)
SanEnr1