City of Modesto — Rockwell Assessment

LWA designed a study to help the City of Modesto meet their 2009 NPDES Stormwater Permit requiring the evaluation of the impact of infiltrated runoff on groundwater quality and the effectiveness of the rockwells in removing pollutants of concern (POCs). LWA services included:

  1.  Identification of the Pollutants of Concern (POCs),
  2. Characterization of groundwater hydraulics,
  3. Design and installation of continuous groundwater monitoring sensors,
  4. Set-up and maintenance of a website to display real-time water quality data from the sensors,
  5. Collection of groundwater samples,
  6. Oversight of the groundwater well installation, and
  7. Analysis and evaluation of the groundwater data in conjunction with the urban runoff data to determine the pollutant removal effectiveness.

To guide the locations for the up- and down-gradient monitoring wells at each rockwell site, LWA worked with the University of California, Davis to build a local groundwater flow model for the area of interest, and incorporated it in an existing larger scale regional computer model to determine water table elevations and flow direction.