Strategic Approach to Infiltrating Industrial Stormwater
In line with the conference theme, infiltration best management practices (BMPs) “connect the drops” from runoff to recharge. Infiltration basins, subsurface galleries, and deep infiltration drywells recharge groundwater aquifers while reducing discharge to surface waterbodies.
Historically, infiltrating storm water at industrial sites has been discouraged by regulatory agencies and municipalities because of the perceived risk of adversely impacting soil and groundwater. Increased demand on groundwater supply coupled with increasingly stringent discharge limitations to surface waterbodies are motivating industrial dischargers and regional stakeholders to consider infiltration. Furthermore, upcoming amendments to California’ Industrial Storm Water General Permit (IGP) are expected to incorporate discharge reduction as a compliance strategy. The proposed compliance alternative is providing a strong incentive for industrial dischargers to evaluate infiltration as part of their long-term storm water management strategy, especially for dischargers located in watersheds facing proposed Total Maximum Daily Load (TMDL)-based Numeric Effluent Limits.
This presentation will summarize the standard of practice for evaluating and sizing infiltration systems for industrial dischargers, and discuss the tools and strategies industrial dischargers and consultants should consider when designing an infiltration system including:
• Evaluating pre-existing soil and groundwater conditions;
• Selecting infiltration test methods to calculate infiltration rate;
• Identifying and mitigating potential risks of adversely impacting soil or groundwater;
• Understanding permitting and regulatory requirements;
• Applying hydrologic modeling and vadose zone modeling techniques to size the infiltration system;
• Selecting appropriate pre-treatment methods; and
• Implementing an infiltration system monitoring program.
I will also discuss a case study to demonstrate how these steps were applied at a metal-scrap processing facility near Riverside, California to evaluate risks associated with infiltration, identify appropriate pre-treatment, and design an infiltration BMP to satisfy the proposed IGP compliance alternative criteria. The objective of the presentation is to promote discussion of the standards of practice for evaluating and installing infiltration BMPs at industrial sites.