Connecting septic system impacts, aquifer vulnerability, and nutrient transport to guide policies protecting lakes, springs, and river systems across Orange County.
Orange County’s lakes and waterways are central to environmental health, recreation, and community quality of life. Nutrient pollution from septic systems and groundwater transport poses an increasing threat to these systems.
Decision-makers needed to understand not only where pollution sources exist, but how contaminants move through the aquifer and ultimately affect downstream waters. Without that insight, policy actions could be ineffective or misdirected.
Drummond Carpenter assessed groundwater vulnerability and pollutant transport across Orange County to determine how septic system pollutants move through the aquifer and affect lakes and rivers.
We developed a vulnerability scoring framework using publicly available environmental data to evaluate the risk septic system pollutants pose to the Surficial Aquifer System.
We then integrated that analysis with a countywide fate-and-transport groundwater model that simulated groundwater flow directions, travel times, and flux to surface waters. Septic plume modeling helped identify the systems most likely to contribute to nutrient loading.
Together, the vulnerability assessment and groundwater modeling showed where nutrient pollution posed the greatest risk and gave the County a scientific basis for targeting policy responses.
The study connected subsurface processes with surface water outcomes to understand how groundwater pollutants affect connected lakes and river systems.
Key components included:
The countywide groundwater model revealed pathways through which groundwater nutrients can reach and pollute surface waters, illustrated here through a visualization of the Wekiwa Springshed.
The findings informed ordinances designed to protect Orange County’s water resources over the long term.
Protecting surface waters requires understanding the pathways pollutants take underground before reaching lakes, springs and rivers. The analysis found administrative rule changes to be the most cost-effective solution for controlling groundwater nutrient pollution.
By connecting aquifer vulnerability, groundwater movement and nutrient impacts on surface waters, Drummond Carpenter gave Orange County the scientific basis to target policies where they could address identified risks.
