Tip #1

How Important is the Sampling Technique?

I receive a lot of questions about sampling techniques and I would love to discuss something truly important.

People ask me if they should hire someone to take a sample for them.  If you are on a budgetand don’t mind standing in the rain for a bit then the answer is “No”.  Stormwater sampling is tricky but it is not rocket science and you can get the best result when you know exactly where and how you sample.  First get some basic training like contacting your lab and ask them about storm water sampling and sometime they might even come out and train you on the sampling.  A few rules of sampling 1) Do not force a sample if there is no discharge.   I see it too many times where staff were asked to take a sample when it rain, but in reality water is in puddle and it wasn’t even discharging out of the facility so the sampler forced a sample by either scraping the bottom of a small puddle (where all the sediment settle). So the best way when it is raining, but not discharging is to do documentation.  Take a picture of the discharge point and note that it is not discharging.  Also don’t think you can fool the Water Boards by always showing a photo that it is not discharging.  Water Boards can look into rain data and your surrounding facility data to see if you are telling the truth.

OK.  So what are some tips on sampling?  1)  Make sure your BMPs are maintained (Ex: dirt and sediment build up needs to be clean up) 2) Field sampler should choose the best sampling point based on field condition and not blindly following the SWPPP.  If there is a better alternate sampling point that can avoid cross contaminant from landscape area or run-on then change the spot and revise your SWPPP and site map to show the alternative sampling spot. 3) Take your sample after any BMPs 4) Sample are required to be taken within the first 4 hours of the first discharge.   Stick your head out of the window and see how heavy the rain is.  If it looks like there will be enough rain for a while then wait a bit before you take a sample because the first rain (especially first of the season) will have the most concentrated discharge due to accumulation (so CLEAN before the first rain of the season).  5)  Make sure you are taking flowing water and an easy way is to create a dam with gravel bag and add a PVC pipe in the middle for your sampling collection point.