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Rain Logs: A proactive way to document Stormwater Compliance

CDMS has seen an increase in private entities taking legal action against companies who fail to sample 4 times per year.   

Industrial facilities are increasingly seeing lawsuits filed against them for not taking a sufficient number of samples in addition to other purported violations of the Industrial General Permit (IGP).  


Who needs it and what is it? 

A rain log tracks the amount of rain the facility receives and proves that no sample is needed during days with light rain.   

Anyone in the industrial stormwater program that thinks they could be at risk of being at the receiving end of third-party legal actions can benefit by maintaining a rain log. 


What do you need to do? 

If we already do periodic site visits to your facility as a part of our compliance management service, our project managers will ask if you need a rain log template and give advice on when/what to log.  

All facilities who are in the stormwater program should implement a rain log which documents your facility’s compliance with the Industrial General Permit (IGP).   

If you need help with anything stormwater related, contact us at We look forward to assisting you. 


Why is it important? 

CDMS has noticed a notable uptick in third-party non-profit groups enforcing the Industrial General Permit (IGP) by taking legal action against clients that do not sample and do not have clean samples. As regulatory scrutiny increases, it becomes crucial for companies to adopt proactive measures to demonstrate compliance, and one such effective tool is the implementation of a rain log. 

A rain log serves as a valuable resource for industries covered by the IGP, recording a detailed account of precipitation events and their impact on water runoff from the property.  


Components of an Effective Rain Log: 

Creating an efficient rain log often involves a rain gauge and photographic evidence of stormwater runoff points. The rain gauge provides accurate measurements of precipitation, while photographs offer a visual representation of the site’s condition during and after rainfall. 


CDMS provides Rain Logs for Clients: 

Recognizing the significance of rain logs in maintaining compliance, we have taken the initiative to create a rain log template for our clients who are requited to develop a Stormwater Pollution Prevention Plan (SWPPP). This tool ensures that our clients are well-prepared to address regulatory inquiries and demonstrate their commitment to environmental responsibility. 



As environmental regulations become more stringent, staying ahead of compliance requirements is paramount. Implementing a rain log not only demonstrates a commitment to environmental stewardship but also positions companies to navigate regulatory challenges with confidence. By proactively addressing stormwater management, businesses can protect their bottom line while contributing to a sustainable and responsible industrial landscape. 

Click here for related FAQ and details of Storm Water Pollution Prevention Plan (SWPPP) regulatory requirements