Assessing performance characteristics of sediment basins constructed in Franklin County.

Details

• Creators:
  Fang, Xing ; Zech, Wesley C. ; Logan, Christopher P. ; Clement, T. Prabhakar
• Corporate Creators:
  Auburn University. Highway Research Center
• Corporate Contributors:
  Alabama. Dept. of Transportation
• Subject/TRT Terms:
  • Sediments
  • Detention basins
  • Evaluation and assessment
  • Runoff
  • Erosion control
  • State of the practice
  • Surveys
  • Water quality management
• Publication/ Report Number:
  ALDOT Project 930-791
• Resource Type:
  Tech Report
• Geographical Coverage:
  Alabama
• Corporate Publisher:
  Auburn University. Highway Research Center
• NTL Classification:
  NTL-ENERGY AND ENVIRONMENT-ENERGY AND ENVIRONMENT ; NTL-HIGHWAY/ROAD TRANSPORTATION-Construction and Maintenance ; NTL-HIGHWAY/ROAD TRANSPORTATION-Design ; NTL-HIGHWAY/ROAD TRANSPORTATION-Soils and Geology ; NTL-PLANNING AND POLICY-Surveys
• Abstract:
  The objective of the research project was to monitor the performance of newly designed ; sediment basins that were constructed on the ALDOT 502 project in Franklin County. The ; project included four tasks: (1) assess performance characteristics of sediment basins on the 502 ; project, (2) collect cost data and perform a literature review, (3) perform a survey of the current ; state-of-the-practice, and (4) prepare project reports. All tasks proposed have been completed. ; Through completing the study, the following conclusions have been developed: ;  A field-scale data collection plan to monitor and evaluate sediment basin performance was ; developed and implemented using ISCO 6712 portable automatic stormwater samplers, ; flow modules, a rain gauge, and weirs. ;  Sediment basin 4 on the 502 project did effectively remove sediments at the early stage of ; the construction when the basin’s influent most likely contained relative large percent of ; large-size sediment particles. For example, sediment basin 4 removed 97.9% and 83.7% of ; sediments generated by rainfall events on 11/16/2011 and 12/5/2011. ;  A floating skimmer allowed for effluent to be discharged uniformly and slowly, providing ; longer detention time for sediments to settle in the basin. Data analyses on decay ; (reduction) coefficients for total suspended solids (TSS) and turbidity allowed us to ; quantify the sediment-settling rate of soils on the 502 project in Franklin County, AL. ;  Appropriate PAM (or floc log) added into inflow is crucial to aid sediment settling and ; reduce turbidity of effluent. For example, the performance of the basin 4 was superior for ; the rainfall event on 11/16/2011 when correct PAM was used in the inflow channel than the ; performance for the rainfall event on 12/5/2011 when wrong PAM was used. ;  Rainfall events with subsequent high rainfall intensity impulses generated high turbidity ; inflows from the construction site and suddenly increased in-basin turbidity that could be ; several times higher than turbidity of water already in the basin. ;  Resuspension of settled sediments significantly increased in-basin sediment concentration ; and turbidity when the basin has experienced a number of rainfall events with large amount ; of settled sediments inside basin. ;  An under-designed sediment basin (from a volumetric standpoint) more frequently allowed ; highly turbid sediment-laden runoff to directly flow over the emergency spillway to ; downstream receiving water body. ; Based upon the results of the data collected and observed site conditions throughout the research ; period, the following recommendations are provided to ALDOT to improve sediment basin ; design and installation to maximize performance efficiency and cost effectiveness: ;  Use at least 3,600 cubic feet per acre draining to the basin from the contributing area to size ; the sediment basin. ;  Increase the number of PAM floc logs placed at the bottom of inflow channel to properly ; dose for the average flow rate of 2-yr 24-hr runoff. The number of floc logs should be ; based on the manufacturer recommended dosage and the expected inflow rate of ; stormwater runoff. ;  Consider increasing the number of floc logs placed on the sides of inflow channel to dose ; for the average flow rate of 10-yr 24-hr runoff. These storms will have higher water ; depths, resulting in a greater amount of inflow, therefore requiring a higher dosage of ; PAM. ;  The height of the baffles, once installed, should match the full depth of the sediment basin ; and not be installed below the minimum elevation of the emergency spillway. ;  Include a sediment storage volume (e.g., 500 ft3/acre disturbed) into the design ; specifications of sediment basins and a requirement to remove the sediment when it reaches ; one third of the height of the sediment storage volume.
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• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/23154/dot_23154_DS1.pdf
• File Type:
  [PDF - 3.57 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:64f798dd9fcf7768e07e5beb1b704d66172e4c315a591bb3089fcb6b24cdf6e0c469399e0775c46bfff96bb9d49dd583056acc58d14c5495a00cf76811f6967f