MEASURES TO REDUCE EROSION AND TURBIDITY IN CONSTRUCTION SITE RUNOFF

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 conduced for 11 PAMs on 13 sediment sources from North Carolina Department of Transportation (NCDOT) construction sites around North Carolina. In addition, a field test of two PAMs and 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. Superfloc 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 0.75 mg/L, or a few grams per 1,000 cubic ft of water. The differences between PAMs in reducing turbidity was clearest shortly after mixing the PAMS and soil. 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 NCDOT construction sites failed to show a significant reduction in turbidity or erosion. Erosion rates were 2 times greater on bare soil plots after the first several 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 (11kg/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 flocs from settling.

• Record URL:
  http://www.ncdot.org/doh/preconstruct/tpb/research/download/2001-05FinalReport.pdf
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/39875
• Supplemental Notes:
  • This research was supported by a grant from the North Carolina Department of Transportation and the U.S. Department of Transportation, University Transportation Centers Program. This report available on CD-ROM.
• Corporate Authors:

  North Carolina State University, Raleigh

  Department of Soil Science, Campus Box 7619
  Raleigh, NC  United States  27695-7919

  Research and Special Programs Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • McLaughlin, R A
• Publication Date: 2002-6

Language

• English

Media Info

• Media Type: Digital/other
• Pagination: 131 p.

Subject/Index Terms

• TRT Terms: Clay soils; Construction sites; Drainage; Embankments; Erosion control; Field tests; Flocculating agents; Laboratory tests; Mulching; Rainfall; Runoff; Sandy soils; Sediments; Seeding; Slopes; Turbidity
• Uncontrolled Terms: Polyacrylamides
• Geographic Terms: North Carolina
• Subject Areas: Construction; Design; Environment; Geotechnology; Highways; Hydraulics and Hydrology; Planning and Forecasting; I21: Planning of Transport Infrastructure; I51: Earthworks and Soil Drainage;

Filing Info

• Accession Number: 00941209
• Record Type: Publication
• Report/Paper Numbers: FHWA/NC/2002-023,, Final Report
• Contract Numbers: 98-1783
• Files: UTC, NTL, TRIS, USDOT
• Created Date: Apr 23 2003 12:00AM