Stormwater Sampling

EST is well equipped to support all weather contingent field services related to National Pollutant Discharge Elimination System (NPDES) permits. We have multiple public and private sector clients that rely on us to provide the most cost-effective and reliable stormwater sampling services available. Our staff has collected stormwater samples for NPDES permit compliance for a diverse client base throughout the Northeast including “first flush” and composite samples during qualifying events in accordance with EPA protocol.  EST is also proficient in collecting both 24-hour and week long acute and chronic WET tests. Our clients include public agencies, municipalities, engineering consultants, and private industry throughout the region. In order to provide the most reliable services available, we have self-contained automatic sampling units that can be triggered based on flow or rainfall. These units can also be equipped with telemetry to alert sampling personnel when criteria for sample collection have been achieved.

Common Stormwater Sampling FAQs

How does the scheduling process work if EST is handling my stormwater sample collection?

Once EST has been contracted by a client to conduct their NPDES permit sampling, they are placed on an automatic monitoring schedule based on their sampling and frequency requirements. EST will monitor rain events and mobilize as needed which allows our clients to focus on

How and when does EST mobilize for a stormwater event?

EST’s staff is highly knowledgeable in tracking daily weather patterns that present opportunities to satisfy our client’s NPDES monitoring needs. Each weather system that passes through the area is evaluated to determine if conditions are favorable for mobilization. Due to our client’s diverse geographical footprint, our technicians are often well poised to quickly and efficiently take advantage of favorable conditions as they develop.

What is a “first flush” sample?

First flush samples are wet weather samples collected within the first thirty (30) minutes of rainfall discharge, where practical, but in no case later than the first hour of drainage.

What is a qualifying event?

In general, qualifying events are those resulting from a storm event that is greater than 0.1 inches in magnitude and that occurs at least seventy-two (72) hours from the previously measureable (greater than 0.1 inch rainfall) storm event.

What information is provided with a visual observation?

When EST technicians conduct visual assessments of samples, the technician does so within the first 30 minutes after discharge. A field examination report is then completed containing the following information:

  • Date of sample collection and of visual assessment
  • Time of sample collection and of visual assessment
  • Sample site identification
  • Date of storm event
  • Name and signature of sampling technician
  • Incremental rainfall data and nature of discharge (i.e. runoff or snowmelt)
  • Date and estimated time of end of last rain event
  • Visual observations of samples (color, odor, clarity, floating solids, settled solids, suspended solids, foam, oily sheen, or other indicators of pollution) and probable sources of any observed pollutants.
  • If applicable, why it was not possible to collect a sample within the first 30 minutes of discharge

In the event of unusual or significant observations based on EST’s judgement and experience, the client is notified by email or phone as soon as possible on the sample collection day.

What happens if EST mobilizes but is unsuccessful in collecting my samples due to unexpected changes in the weather?

EST will continue to monitor future rain events during the sample period and target additional opportunities until a sample can be obtained.

New England Office

51 Fremont Street Needham, MA 02494

Mid-Atlantic Office

127-G Gaither Drive Mount Laurel, NJ 08054