Virginia’s Septic System Strategy Is Missing a Crucial Timing Factor and a New Study Explains Why
Virginia has spent years trying to reduce pollution flowing into the Chesapeake Bay, and septic systems are a big part of that challenge. A new study from the University of Maryland now suggests that while the state’s intentions are solid, its current septic management approach is missing something essential: timing. According to the research, septic system failures are not just about where systems are located or how old they are. They are deeply connected to changing water conditions over time, and overlooking that relationship may be limiting how effective Virginia’s policies can be.
The study was conducted by Jerin Tasnim, a researcher at the University of Maryland, and is scheduled to be presented on December 8 at 10:30 A.M. ET during the Society for Risk Analysis Annual Meeting in Washington, D.C. The findings raise important questions about how septic systems are monitored, maintained, and prioritized for intervention—especially in coastal and rural areas of Virginia.
Why Septic Systems Matter So Much in Virginia
Septic systems are a major source of nitrogen pollution in the Chesapeake Bay watershed, particularly in rural communities that are not connected to public sewer infrastructure. When septic systems fail or function poorly, nitrogen can leak into groundwater, rivers, and tidal waters, eventually making its way into the Bay. Excess nitrogen fuels algal blooms, reduces oxygen levels in the water, and harms aquatic life.
Virginia’s Phase III Watershed Implementation Plan aims to reduce this nitrogen loading through measures such as inspections, regular pump-outs, and system upgrades. These steps are important, but the study suggests that how and when these actions are taken may be just as critical as the actions themselves.
The Problem With Static Risk Indicators
Currently, septic management strategies in Virginia rely heavily on static indicators. These include factors like the age of a septic system, how close it is to surface water, and general soil conditions. While useful, these indicators assume that septic risk is relatively constant over time.
The new research challenges that assumption. Septic systems are influenced by dynamic hydrological stressors, including rainfall, river flooding, rising groundwater, and tidal inundation. These factors change daily, seasonally, and annually, and they can dramatically affect how well a septic system performs.
By focusing mostly on static factors, Virginia’s current approach may miss opportunities to anticipate failures before they happen, rather than responding after problems become severe.
A Closer Look at the Data and Methods
To better understand how septic systems respond to environmental stress, Tasnim analyzed daily septic maintenance call records from 2011 to 2023 across coastal Virginia’s river basins. This long-term dataset allowed the study to detect patterns that shorter analyses might miss.
Instead of using traditional statistical tools, the research applied cross-wavelet coherence analysis. This advanced method examines how two variables—such as hydrological conditions and septic maintenance calls—interact across both time and frequency. In simple terms, it helps reveal when and how strongly environmental stressors and septic problems are connected.
This approach uncovered relationships that conventional methods often overlook, especially when those relationships vary over time.
Key Findings That Stand Out
One of the clearest findings is that septic issues do not occur randomly. Maintenance calls follow strong and consistent patterns that closely align with seasonal cycles. This means septic problems tend to rise and fall at predictable times of the year.
The analysis revealed major maintenance peaks at six-month and one-year intervals. These cycles suggest that public outreach, inspections, and maintenance reminders could be far more effective if they are timed to match these high-risk periods, rather than spread evenly throughout the year.
Another important finding is that patterns vary by river basin. Some areas experience stronger or more frequent stress cycles than others, indicating that a one-size-fits-all strategy may not be the best approach. Regional targeting could significantly improve outcomes.
Hydrological factors also play a major role. Higher water levels, increased precipitation, and tidal influences were all closely linked to spikes in septic maintenance calls. Even subtle changes in water conditions were shown to place high stress on septic systems, increasing the likelihood of failure.
Perhaps most concerning is the nature of many of these calls. A large portion were related to pumping events, which usually occur only after systems are already experiencing serious problems. This suggests that many homeowners are reacting to failures rather than preventing them, increasing the risk of nitrogen pollution entering nearby waters.
What This Means for Policy and Equity
The study highlights a clear opportunity for improvement in how the Virginia Department of Health prioritizes septic interventions under the Chesapeake Bay Watershed Implementation Plan. By incorporating time-frequency signals, agencies could identify systems that are repeatedly stressed—even if they do not appear high-risk based on static criteria alone.
This approach also has important equity implications. Underserved and unsewered communities may experience recurring hydrology-driven septic failures that are currently overlooked. Better timing-based analysis could help ensure that assistance reaches communities that need it most, rather than those that simply meet traditional risk thresholds.
Preparing for Climate Change Pressures
Climate change adds another layer of urgency to these findings. Rising sea levels, more intense rainfall, and increased flooding are expected to intensify hydrological stress across coastal Virginia. Septic systems that are already vulnerable may face even greater pressure in the coming years.
The research suggests that assistance programs and maintenance schedules should be adapted for future climate conditions, accounting for both spatial and temporal changes in risk. Proactive planning now could reduce costly emergency repairs later while protecting water quality and public health.
How Smarter Timing Could Help Everyone
By anticipating when septic problems are most likely to occur, Virginia could send time-sensitive maintenance reminders, schedule inspections more strategically, and deploy resources where they will have the greatest impact. This would not only reduce nitrogen pollution but also help homeowners avoid expensive, last-minute repairs.
The study ultimately shows that septic systems behave less like static infrastructure and more like systems responding to environmental rhythms. Recognizing and working with those rhythms could make septic management more effective, fairer, and better prepared for the challenges ahead.
Research Reference
Society for Risk Analysis / University of Maryland
Study by Jerin Tasnim, presented at the Society for Risk Analysis Annual Meeting, December 8, 2025
https://www.sra.org
