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Potential Effects of Structural Controls and Street Sweeping on Stormwater Loads to the Lower Charles River, Massachusetts

Water-Resources Investigations Report 02-4220

By Phillip J. Zarriello, Robert F. Breault, and Peter K. Weiskel

ABSTRACT

The water quality of the lower Charles River is periodically impaired by combined sewer overflows (CSOs) and non-CSO stormwater runoff. This study examined the potential non-CSO load reductions of suspended solids, fecal coliform bacteria, total phosphorus, and total lead that could reasonably be achieved by implementation of stormwater best management practices, including both structural controls and systematic street sweeping. Structural controls were grouped by major physical or chemical process; these included infiltration-filtration (physical separation), biofiltration-bioretention (biological mechanisms), or detention-retention (physical settling). For each of these categories, upper and lower quartiles, median, and average removal efficiencies were compiled from three national databases of structural control performance. Removal efficiencies obtained indicated a wide range of performance. Removal was generally greatest for infiltration-filtration controls and suspended solids, and least for biofiltration-bioretention controls and fecal coliform bacteria.

Street sweeping has received renewed interest as a water-quality control practice because of reported improvements in sweeper technology and the recognition that opportunities for implementing structural controls are limited in highly urbanized areas. The Stormwater Management Model that was developed by the U.S. Geological Survey for the lower Charles River Watershed was modified to simulate the effects of street sweeping in a single-family land-use basin. Constituent buildup and washoff variable values were calibrated to observed annual and storm-event loads. Once calibrated, the street sweeping model was applied to various permutations of four sweeper efficiencies and six sweeping frequencies that ranged from every day to once every 30 days.

Reduction of constituent loads to the lower Charles River by the combined hypothetical practices of structural controls and street sweeping was estimated for a range of removal efficiencies because of their inherent variability and uncertainty. This range of efficiencies, with upper and lower estimates, provides reasonable bounds on the load that could be removed by the practices examined. The upper estimated load reduction from combined street sweeping and structural controls, as a percentage of the total non-CSO load entering the lower Charles River downstream of Watertown Dam, was 44 percent for suspended solids, 34 percent for total lead, 14 percent for total phosphorus, and 17 percent for fecal coliform bacteria. The lower estimated load reduction from combined street sweeping and structural controls from non-CSO sources downstream of Watertown Dam, was 14 percent for suspended solids, 11 percent for total lead, 4.9 percent for total phosphorus, and 7.5 percent for fecal coliform bacteria. Load reductions by these combined management practices can be a small as 1.4 percent for total phosphorus to about 4 percent for the other constituents if the total load above Watertown Dam is added to the load from below the dam. Although the reductions in stormwater loads to the lower Charles River from the control practices examined appear to be minor, these practices would likely provide water-quality benefits to portions of the river during those times that they are most impaired-during and immediately after storms. It should also be recognized that only direct measurements of changes in stormwater loads before and after implementation of control practices can provide definitive evidence of the beneficial effects of these practices on water-quality conditions in the lower Charles River.

CONTENTS

Abstract

Introduction

Purpose and Scope

Acknowledgments

Structural Controls

Removal Efficiencies

Estimated Contaminant-Load Removal in the Village Brook Subbasin

Street Sweeping

Contaminants on Streets

Street Sweeping as a Water-Quality-Management Practice

Sweeper Types and Efficiencies

Factors that Affect Sweeper Performance

Model Simulation

Calibration

Sweeping Efficiencies and Frequencies Evaluated

Model Limitations

Sensitivity Analysis

Simulated Contaminant Removal by Street Sweeping

Calibrated-Model Load Removals

Alternative-Model Load Removals

Potential Effects of Structural Controls and Street Sweeping on Loads to the Lower Charles River

Water Year 2000

Design Year

Design Storms

Summary and Conclusions

References

FIGURES

1. Map showing principal geographic features, precipitation stations, and subbasins of the lower Charles River Watershed, Massachusetts.

2. Box plot showing distribution of constituent removal efficiencies for structural controls, summarized by control type

3. Bar graphs comparing (A) land use and (B) road types in the lower Charles River Watershed and the Village Brook Subbasin

4. Scatter plot showing relation of simulated constituent loads to measured loads for eight sampled storms between January 10 and July 27, 2000, at the single-family land-use subbasin, lower Charles River Watershed

5-9. Line graphs showing:

5. Suspended-solids buildup on streets simulated by the Michaelis-Menton method with and without street sweeping at two sweeper efficiencies and 2-day sweeping intervals by the (A) Stormwater Management Model and (B) an adjusted buildup rate corrected to the load that remains after sweeping

6. Schematic representation of the percent load removed by street sweeping at 2-day intervals when calculated by the Stormwater Management Model and by a buildup rate adjusted for the load remaining after sweeping

7. Sensitivity of (A) annual suspended-solids loads and (B) percent load removed by street sweeping to buildup and washoff variable values in the Stormwater Management Model

8. Simulated constituent-load removal for various sweeper efficiencies at selected sweeping intervals in the single-family land-use subbasin, lower Charles River Watershed, 2000 water year

9. Estimated percent load reduction for the 2000 water year by street sweeping at various efficiencies and frequencies for the (A) lower Charles River (excludes the loads above Watertown Dam) and (B) the entire Charles River Watershed (estimated by the street density ratio)

10. Bar graph showing constituent loads from non-combined-sewer-overflow sources from major subbasins, and estimated load reductions by hypothetical structural controls and street sweeping, lower Charles River Watershed, 2000 water year

11. Box plots and line graphs showing distribution of rainfall and antecedent storm characteristics for the 2000 water year, design year, and 1970­95 period, lower Charles River Watershed

12. Bar graphs showing estimated 3-month and 1-year design-storm loads from non-combined-sewer-overflow sources from each of the major subbasins and estimated load reductions by hypothetical structural controls and street sweeping for (A) suspended solids and total lead loads and (B) fecal coliform and total phosphorus

TABLES

1. Categories of structural-control types, their characteristics, and the major physical or chemical processes that affect water quality
2. Inventory of structural controls identified by the Center for Watershed Protection for the Village Brook Subbasin, lower Charles River Watershed
3. Estimated removal efficiencies in stormwater loads and total loads by hypothetical structural controls in the Village Brook Subbasin, lower Charles River Watershed
4. Reported and simulated constituent loads for the single-family land-use subbasin, 2000 water year, lower Charles River Watershed
5. Calibrated Stormwater Management Model variable values for constituent buildup and washoff for the single-family land-use subbasin, lower Charles River Watershed
6. Measured and simulated storm runoff and constituent loads for sampled storms in the single-family land-use subbasin, lower Charles River Watershed
7. Efficiencies of street sweepers simulated for removing selected contaminants
8. Measured and simulated loads of suspended solids for sampled storms, single-family land-use subbasin, 2000 water year, lower Charles River Watershed
9. Percent removal of constituent loads by street sweeping simulated with the highest efficiency sweeper once every two days with the calibrated and an alternative Stormwater Management Model in the single-family land-use subbasin, lower Charles River Watershed
10. Subbasin street length and density, lower Charles River Watershed
11. Street and subbasin contaminant loads used to calculate the weighting factor for estimating potential contaminant removal by street sweeping, 2000 water year, lower Charles River Watershed
12. Estimated range in the percent decrease in annual loads by hypothetical structural controls, lower Charles River Watershed
13. Simulated percent annual-load reductions to the lower Charles River, Massachusetts, by street sweeping with the highest efficiency sweepers at various sweeping intervals and the (A) calibrated model and (B) an alternative model
14. Percent annual-load reductions by combined hypothetical structural controls and street-sweeping practices, lower Charles River Watershed
15. Simulated runoff volume for the 2000 water year and the design year, lower Charles River Watershed
16. Estimated design-year constituent loads from non-combined-sewer-overflow sources for each of the major subbasins to the lower Charles River

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The citation for this report, in USGS format, is as follows:

Zarriello, P.J., Breault, R.F., and Weiskel, P.K., 2003, Potential Effects of Structural Controls and Street Sweeping on Stormwater Loads to the Lower Charles River, Massachusetts: U.S. Geological Survey Water-Resources Investigations Report 02-4220, 48 p.

For more information about USGS activities in Massachusetts-Rhode Island District, visit the USGS Massachusetts-Rhode Island Home Page.




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