San Diego hopes to balance its mix of vacuum and mechanical sweepers.
In 2008, the City of San Diego Storm Water Department implemented a Street Sweeping Pilot Study to determine if enhanced sweeping is a cost-effective solution for reducing pollution and meeting existing and regulatory requirements mandated by the state of California. The project compared sweeping frequencies as well as different types of machines.
Preliminary results indicated that street sweeping has a positive impact on water quality by providing an effective means of reducing pollutant concentrations in storm water runoff. Survey results indicated that 93% of businesses and 78% of residents believe that street sweeping was a good use of public money. The city currently is evaluating the scientific results, community feedback and financial data from the pilot study to apply a triple-bottom-line analysis (environmental, social and economic factors) with the goal of identifying cost-effective opportunities to improve its street sweeping program. Near-term opportunities and potential long-term modifications are being developed as follows.
At the completion of the pilot study, the department discontinued aggressive street sweeping in one of the pilot study areas. Upon evaluation, other areas in San Diego were determined to be of a higher priority with regard to water quality protection; sweeping along this route resumed its previously unposted schedule.
The department has identified the following near-term, cost-neutral opportunities for improving its street sweeping program:
- Maximize pollutant removal by utilizing vacuum sweepers on flat routes. The study results show that the city’s vacuum sweeper is more effective than its mechanical sweeper at removing debris and fine particulates, including metals, along flat routes in good condition with well-defined curb and gutter. This sweeping modification will allow the city to benefit from improved water quality without impacting existing budgets and resources.
- Engage communities in advance of implementing posted sweeping. The feedback survey results indicate that the majority of residents and nearly all business owners feel that street sweeping is beneficial and a good use of public funds. The department has been tracking requests for increased street sweeping and is incorporating a request recommendation into the planning process.
Potential Long-Term Modifications
Long-term, programmatic modifications to the city’s street sweeping program will impact future fiscal year budgets and resources. Potential long-term modifications may include:
- Transitioning the city’s fleet of sweepers to a more equitable mix of vacuum and mechanical sweepers commensurate with the city’s hilly/uneven vs. flat street characteristics;
- Identifying residential areas interested or requesting enhanced (e.g., weekly) sweeping;
- Identifying commercial and industrial routes for aggressive (e.g., twice a week) sweeping; and
- Sweeping center medians along high-traffic roadways.
The department will be assessing the fiscal and logistical impacts of these potential modifications to the current street sweeping program. In addition, it will be comparing the cost-effectiveness of these potential modifications with other best management practices (BMPs) in order to make more comprehensive and balanced decisions toward meeting water quality objectives.
This assessment, along with the comparative analysis of other BMPs, will ultimately guide the city’s decisions on making sustainable, programmatic changes to the department’s sweeping program and allow for maximum compliance under local, state and federal clean water regulations.
Editor’s note: This article is a follow-up to the July/August Storm Water Solutions article “To Sweep or Not to Sweep?”