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Potential Effects of Structural Controls and Street Sweeping on Stormwater Loads to the Lower Charles River, MassachusettsWater-Resources Investigations Report 02-4220 |
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.
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
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
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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