- Title
- Measures to reduce erosion and turbidity in construction site runoff
-
-
- Date
- June 2002
-
-
- Creator
- ["McLaughlin, Richard Allen, 1956-"]
-
- Place
- ["North Carolina, United States"]
-
Measures to reduce erosion and turbidity in construction site runoff
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Technical Report Documentation Page
1. Report No.
FHWA/NC/2002-023
2. Government Accession No.
3. Recipient’s Catalog No.
4. Title and Subtitle
Measures to Reduce Erosion and Turbidity in Construction Site
Runoff
5. Report Date
June 2002
6. Performing Organization Code
FAS # 5-45096
7. Author(s)
Richard A. McLaughlin
8. Performing Organization Report No.
9. Performing Organization Name and Address
Department of Soil Science
NC State University
Box 7619, Williams Hall
Raleigh, NC 27695-7619
10. Work Unit No. (TRAIS)
1 1 . Contract or Grant No.
98-1783
12. Sponsoring Agency Name and Address
U.S. Department of Transportation
Research and Special Programs Administration
400 7lh Street, SW
Washington, DC 20590-0001
13. Type of Report and Period Covered
Final Report
July 2000-June 2002
14. Sponsoring Agency Code
HWY 2001-05
15. Supplementary Notes
This project was supported by a grant from the U.S. Department of Transportation and the North Carolina
Department of Transportation through the Center for Transportation and the Environment, NC State
University.
1 6. Abstract
An evaluation of polyacrylamides (PAM) for both erosion and turbidity control for construction sites was conducted
in both the laboratory and the field. A laboratory screening was conducted for 1 1 PAMs on 13 sediment sources
from North Carolina Department of Transportation (NC DOT) construction sites around North Carolina. In
addition, a field test of two PAMs at two rates, with and without straw mulch and seeding, on a 2:1 fill slope, a 4:1
cut slope, and a 4: 1 fill slope were performed. The results indicate that there is no one PAM that is effective for
turbidity reduction on all sediment sources, but several are promising for many soils. Superfloe A- 100 ranked
among the top three flocculants for 10 of 13 sediment sources. Some PAMs are equally effective but at different
doses, some as low as .075 mg/L, or a few grams per 1,000 ft3 of water. The differences between PAMs in reducing
turbidity was clearest shortly after mixing the PAM and soil (30 sec). These turbidity differences were usually
maintained 30-60 minutes after mixing, but allowing the soil/water mix to settle for 24 hours reduced or eliminated
the differences. Tests of PAM with and without mulching on 2:1 slopes at NC DOT construction sites failed to
show a significant reduction in turbidity or erosion. Erosion rates were 20 times greater on bare soil plots after the
first seven events, with or without PAM, compared to those mulched with straw and seeded to grass. During the
eighth and last event, in which over 6 cm of rain was recorded, rates of over 50 tons/ha were recorded for a single,
intense storm event for the bare soil plots compared to 3-9 tons/ha on the mulched/seeded plots. PAM at the highest
rate ( 1 1 kg/ha) was effective in reducing erosion and turbidity on the 4: 1 cut slope with a clay loam texture but the
effect declined with each storm event. On the sandy 4: 1 fill slope, there was no evidence of PAM effects, even at 20
kg/ha. PAM was effective in flocculating turbid water pumped from a borrow pit but turbulence within the basin
tended to keep the tlocs from settling.
1 7. Key Words
mulches, sediments, sedimentation, turbidity,
erosion, polyacrylamide
18. Distribution Statement
19. Security Classif. (of this
20. Security Classif. (of this
21. No. of Pages
22. Price
report)
page)
unclassified
unclassified
131
Form DOT F 1700.7 (8-72)
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