Abstract
Utility vaults and underground structures house essential telecommunications, gas, and electrical infrastructure (e.g., transformers, copper wiring) that could contaminate water which accumulates in them. Water is removed from utility vaults during routine infrastructure maintenance. That water is typically released to the storm drain system, raising concerns that polluted water could reach receiving waters. However, no one has measured pollutants in utility vault water. The State Water Resources Control Board (SWRCB) has mandated such measurements as a condition of renewing the National Pollutant Discharge Elimination System Utility Vault Permit. We analyzed 126 priority pollutants in 20 utility vault water samples collected throughout California by Pacific Gas and Electric Company (PG&E). We also estimated the volume of utility vault water discharged and calculated loads. Twenty-one priority pollutants were detected. Metals were commonly found. Only copper (Cu) and zinc (Zn) exceeded water quality criteria. Their maximum concentrations were 791 and 386 μg/L, respectively. Median Cu and Zn concentrations of 9.66 and 81.6 μg/L were representative of urban stormwater, suggesting runoff is a source of metals in utility vault water. For San Francisco Bay, Cu and Zn loads from PG&E's utility vault water (0.06 and 0.5 kg/year) were inconsequential compared to previously reported total loads (74,000 and 320,000 kg/year) from stormwater, wastewater treatment plants, etc. For California, utility vault water loads were 5 and 40 kg/year of Cu and Zn. We are the first to report pollutant concentrations in utility vault water. Utility vaults are not a major source of pollutants to receiving waters.
Highlights
In the USA, the Clean Water Act of 1972 successfully addressed many point sources of pollution, providing funding and reducing pollutant loads into surface waters (Sanudo-Wilhelmy et al 2004)
All samples were analyzed by Eurofins/Calscience labs in Southern California, using the Environmental Protection Agency (EPA) methods specified within the 2014 National pollutant discharge elimination system (NPDES) Utility Vault Permit and listed within PG&E’s Characterization Study Plan (California State Water Resources Control Board 2014a; Pacific Gas and Electric Company 2015f)
The thresholds for the SIP were used as a comparison for the utility vault water data only when the methods of analysis were unable to meet the limits required in the 2014 NPDES Utility Vault Permit
Summary
In the USA, the Clean Water Act of 1972 successfully addressed many point sources of pollution, providing funding and reducing pollutant loads into surface waters (Sanudo-Wilhelmy et al 2004). Non-point source pollution is one of the major global threats to water quality, especially in urban areas where stormwater run-off can mobilize pollutants (Fraga et al 2016; Gilbreath and McKee 2015). Consistent with this focus, diffuse sources of pollution have come under scrutiny. Utility service companies install and maintain subsurface structures, called utility vaults (Fig. 1) These structures hold equipment used by gas and electrical industries as well as phone, cable, and internet service providers (California State Water Resources Control Board 2014a). The accumulated water must be removed (i.e., dewatering) to safely access the equipment (California State Water Resources Control Board 2014a)
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