By Justin Ramsey
Over the last weekend the Pagosa area observed a ‘Rain on Snow’ precipitation event. Rain on Snow (ROS) events occur when rain falls onto an existing snowpack. The result is runoff that includes both rainfall and melted snow, which can overwhelm drainage structures, causing flooding and sewage leaks. This flooding saturates the soils, enters basements and crawlspaces and infiltrates the sewer system.
Residents and visitors are warned to avoid ‘standing water’ in the Pagosa Lakes area, as the water may be contaminated.
Infiltration refers to groundwater that seeps into sewer pipes through holes, cracks, joint failures, and faulty connections. Inflow is stormwater that quickly flows into sewers via roof drain downspouts, foundation drains, storm drain cross-connections, and through holes in manhole covers.
These two terms — infiltration and inflow — are referred to as I&I.
All of the water that enters the municipal sewer system goes to the Vista Wastewater Treatment Plant. Neither the sewer system nor the treatment plant was designed to handle stormwater, so when all that additional water enters the sanitary sewer system, it can lead to multiple problems:
- Takes up capacity in the collection system and treatment plant and ends up at the wastewater treatment plant where it must be treated like sewage, resulting in higher treatment costs.
- Contributes to sewer system overflows in local homes and the region’s waterways, negatively impacting public health and the environment.
- Results in more energy usage to pump the flow and the unnecessary treatment of storm water.
- I/I can lead to funding a plant upgrade, because I&I flows are exceeding permit and design capacity of the treatment plant.
The ROS event has led to regional flooding in the community. PAWSD crews are monitoring the situation and assuring pump stations are working at their highest capacity and has reported the overflows to the Colorado Department of Public Health and Environment. Archuleta County crews are working to unclog culverts and maintain drainage structures to reduce inundation of flood waters.
PAWSD and Archuleta County realize this is a troubling situation… and will only be exacerbated by the upcoming storms.
Here are some items that you as home and business owners can do to help reduce I&I:
- Do not connect sump pumps to the sanitary sewer.
- Do not connect roof drains and gutters to the sanitary sewer.
- Do not connect foundation drains to the sanitary sewer.
- Keep all cleanouts capped, both inside and outside. This will help keep unwanted water out of the sanitary sewer system.
- Avoid planting trees/shrubs over your sewer lateral, as tree roots can damage sewer piping.
- Keep driveway culverts and bar ditches clear allowing snowmelt and precipitation to flow off your property and out of your neighborhood.
- Report clogged roadway culverts and bar ditches to Archuleta County.
If you live in an area that is prone to flooding and sewer backups PAWSD recommends you install a check valve on your sewer service. Sewer service check valves can be purchased at plumbing stores or directly from PAWSD. These check valves allow sewage to flow only in one direction, away from your home, if the sewer main becomes surcharged the check valve will close and not allow sewage from the main to reverse flow up your service line and into your home. Keep in mind these check valves do need maintenance, over time solid materials can build up not allowing the check valve to operate correctly. These solids must be removed routinely to assure the check valve is protecting your home.
PAWSD is working to minimize the impacts of I&I by:
Main Jetting and Televising
Every year PAWSD hires a local contractor to flush and televise our sewer mains. High pressure water is used to run down the sewer mains removing any materials that may limit flow through the sewer main. After cleaning, a robot camera with the ability to record, moves through existing openings in the sewer pipe. This camara is self-propelled and can inspect the sewer main. The cameras are an essential inspection tool for identifying infiltration and inflow, solids accumulation, root infiltration, pipe defects, and the structural condition of lateral services and mainline sewers.
Manhole Inspections
Inspection methods include visual observation by technicians documenting the condition of the manholes.
Lift Station upgrades
Because we live in a mountainous community the sewer distract operates and maintains 26 lift stations. Lift stations are used to pump sewage uphill when gravity flow is not an option. Many of these 26 lift stations were installed in the early 1970’s and rely on outdated technology. The vaults that house the pumping equipment are decaying and are prone to infiltration. PAWSD is upgrading and replacing these outdated lift stations.
Justin Ramsey is District Manager for the Pagosa Area Water and Sanitation District.