The SMC recently developed a novel method for quantifying the effectiveness of routine street sweeping in removing contaminants that would otherwise enter storm drains and contribute to runoff pollution.

The method relies on a rainfall generator that was custom-built for the study to simulate rainfall conditions across about 74 square feet of roadway.

After the rainfall generator was built, researchers isolated segments of a Long Beach parking lot. One side of the parking lot was swept, while the other side that served as the experimental control was not swept.

Then, researchers looked for differences in the pollutant levels from the runoff that was generated from each roadway segment.

Based on data from this single site, researchers were able to identify quantifiable differences in the levels of pollutants in runoff from the swept vs. unswept roadway segments.

These differences are described in a technical report summarizing the SMC study’s findings; however, researchers caution that this initial application of the SMC’s new street sweeping evaluation method was not designed to quantify the overall total pollution removal efficiency of street sweeping.

The SMC is now working to finalize the design of a follow-up study that will expand testing to multiple sites to quantify street sweeping’s effectiveness with statistical confidence. Sites will be selected based on a common characteristic they share, such as being the same type of roadway or undergoing the same frequency of street sweeping. Significantly, this characteristic will be one that the SMC believes has an influence on street sweeping’s effectiveness.

The SMC is still in the process of deciding which characteristic that sites will share. Once a decision has been made, sites will be selected accordingly, and field testing could begin as early as Fall 2025.