Urban Connections: Legacy Sewer Systems and Groundwater Plumes

In the digital age, we are more connected than we ever thought possible.  Our connections also relate to old technologies, such as sewers.  Sewers connect us in a way that was not considered decades ago when vapor intrusion models were developed, and consequently, VOCs in sewer air are free to enter buildings when vapor seals and plumbing fixtures are compromised. Buildings might contain a musty, moldy or rotten-egg odor which could indicate degraded indoor air quality.   Toilets which wobble even a small amount can indicate a compromised vapor seal on a toilet wax ring. Water traps that dry out from lack of use (basement P-traps or unused bathrooms) can allow sewer air into occupied spaces.  Leaking plumbing fixtures and loose or cracked fittings can contribute to sewer air entering occupied spaces.  

(1) SEWER AIR TESTING SERVICES - Clearwater Group provides sewer air testing services.  Individual buildings are tested after a site inspection defines plumbing layout and utility conduit locations.  Air sampling varies, but can include the use of a variety of vapor meters, sorbent tube samplers, active samplers and passive samplers to evaluate whether sewer air is entering an occupied space.  If sewer air is entering an occupied space, the concentrations and composition of the contaminants in the sewer air can be identified, and mitigation measures can be implemented;

(2) LEGACY SEWER AND GROUNDWATER PLUME INTERSECTION MAPPING STUDIES - Clearwater Group provides regulatory agencies, sewer agencies and others a map of the condition of sewer lines based on video camera inspection and smoke testing, overlain with maps of known soil contamination and groundwater plumes.  These studies allow agencies to prioritize sewer replacement projects, which typically are multi-million dollar capital improvement projects.  Mitigation measures in occupied buildings are also performed. 

(3)  WORKSHOPS AND TRAINING - Clearwater Group has developed workshops and training regarding sewer air investigations and sampling methods for sewer districts, consultants or regulatory agencies;

(4) COST ALLOCATION STUDIES - Typical of urban sewer agencies with legacy systems which are impacted by industrial contaminants, Clearwater Group provides sewer agencies or regulatory agencies independent cost allocation services to address cost sharing of sewer air mitigation measures.  The firm also provides information to help sewer agencies to define responsibilities of the potentially responsible parties (PRPs) for the contaminants in the sewer systems; and

(5) COMMUNITY SUPPORT SERVICES - Sewer air contaminated with volatile industrial compounds can be an issue of environmental justice, as a disproportionate number of low-income, frequently minority residents live near industrial urban areas with impacted soil and groundwater. Clearwater Group provides public outreach and community communication regarding environmental issues, building inspections for sewer air intrusion into occupied structures, sewer air sampling design, and if exposure issues are discovered, design and implementation of mitigation measures.