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Stormwater Sampling


Stormwater Sampling

Certain industrial, construction, and municipal facilities in California must conduct stormwater sampling to comply with National Pollutant Discharge Elimination System (NPDES) permit requirements. Samples must be collected at discharge points during the rainy season, generally twice per year. The samples are analyzed for pollutants, pH, TSS, and more. Facilities must upload the lab results to the Stormwater Multiple Application and Report Tracking System (SMARTS) within 30 days of receiving them. Previously, results were only reported on the Annual Report.

Meeting these stormwater sampling and reporting requirements can be burdensome for companies. CDMS can provide turnkey stormwater sampling kits containing bottles, chain of custody (COCs), pH strips, a cooler, and instructions customized to your facility’s discharge points. CDMS will track the lab results and load them into SMARTS by the regulatory deadline, ensuring you meet the stormwater sampling requirements with ease.

Regulatory bodies
  • Environmental Protection Agency (EPA)
  • State Water Resources Control Board (SWRCB)
  • Regional Water Quality Control Boards (RWQCB)
  • Local Municipalities
Who needs it

Facilities must conduct storm water sampling at each of the discharge points from the facility (storm drains or other areas where the storm water leaves the property). Samples must be taken twice per rainy season.

Samples are analyzed for certain required items as well as any pollutants they may have on site.

Sample results are required to be uploaded to Stormwater Multiple Application and Report Tracking System (SMARTS) within 30 days of receiving the lab results. Previously facilities need only report on the Annual Report.

Regulation reference
  • Clean Water Act
  • 40 CFR 122 – EPA stormwater regulations
  • Industrial General Permit Order 2014-0057-DWQ
  • Construction General Permit Order 2009-0009-DWQ
  • Small MS4 Permit Order 2013-0001-DWQ
  • Individual NPDES permits
  • Municipal stormwater ordinances
  • California Water Code Section 13383
What our service provides:

CDMS can provide sampling kits to companies to meet storm water sampling requirements. The kits will include sample bottles labeled for each sample point, pH paper, a pre-prepared chain of custody, and instructions for sampling. All materials will be contained in a cooler for shipping to the lab and the sample results will be returned to the companies

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How often does stormwater sampling need to be conducted?
Typically twice per rainy season for industrial stormwater permit holders in California.

What are facilities looking to test for in stormwater?
pH, TSS, O&G, heavy metals, pollutants related to the site’s activities that could contaminate stormwater runoff.

When does stormwater sampling need to be completed by?
Samples must be taken within the first 4 hours of discharge during qualifying rain events during operating hours.

How are discharge points/samples determined?
Samples are taken at locations where stormwater exits the property, such as outfalls, drains, or streams.

Who conducts stormwater sampling?
Permit holders can use qualified personnel or contract consultants/labs to perform sampling.

What type of documentation is required?
Chain of custody (CoCs) forms with sample details, dates, times, signatures, etc.

How are stormwater samples shipped to the lab?
Samples are packed in coolers with ice packs and sent to the lab via overnight delivery.

How long does the lab need to analyze the samples?
Testing is typically completed within 5-10 business days.

Where are the lab results reported?
To Stormwater Multiple Application and Report Tracking System (SMARTS) and the Annual Report within 30 days of receiving results.

Can stormwater samples be mixed or composited?
Yes, composite samples from multiple points meeting certain criteria are allowed.

What are common mistakes facilities make with sampling?
Collecting samples too late after discharge starts, improper labeling, broken custody chain.

What are the consequences of improper stormwater sampling?
Permit violations, fines, required additional sampling events.

How long must stormwater sampling records be kept?
At minimum 3 years, but 5 years or more is recommended.

Who enforces stormwater sampling requirements?
The Regional Water Quality Control Board (RWQCB) issues fines and violations.

How much does compliant stormwater sampling typically cost?
From $1,500 to $5,000+ per rainy season with lab analysis.

Can facilities sample less frequently after demonstrating compliance?
Potentially, sampling reductions can be requested but are not guaranteed.

What triggers a facility being subject to stormwater sampling?
Location in an industrial sector, construction activity, stormwater permit requirements.

Are temporary waste piles or storage subject to stormwater sampling?
Yes, runoff from temporary outdoor storage/processing areas usually requires sampling.

Does stormwater from vehicle maintenance shops need sampling?
Yes, vehicle maintenance areas exposed to precipitation will require sampling.

Is training required for personnel conducting stormwater sampling?
Yes, annual training is required to ensure proper sampling procedures are followed.