Inflow & Infiltration Reduction Program

A Public Forum will be held Wednesday March 4^th to review the I&I Reduction Program and Proposed Lateral Replacement Policy, which would require property owners to cover the cost of replacement. The program is a significant and costly infrastructure improvement and will also mean an increase in St. Helens city water rates. The city is researching solutions for low-income property owners.

The geology of St. Helens poses challenges to storm and wastewater management. Situated on a hillside adjacent to the Columbia River, the portion St. Helens east of US Highway 30, sits on a thin layer of clay soil over shallow bedrock. These unique geologic conditions have required many of the waste water main lines and private service lateral lines to be built in blasted rock or clay trenches that act as less permeable conduits for groundwater and percolating rainfall to flow and collect. As a result of these factors, and the age of some of the St. Helens waste water collection system, the City is faced with some of the worst inflow and infiltration (I/I) numbers on record in Oregon.

Inflow occurs when water from any source other than sinks, showers, or toilets, is intentionally introduced into the waste water system.

Infiltration is a result of weaknesses in the wastewater collection system manholes, mainlines, and service laterals.

Responsibility for the environmental quality of America's lakes and rivers was placed squarely upon the shoulders of industrial and municipal point dischargers beginning with the Federal Clean Waters Act of 1972.

As the state agency that enforces the Clean Waters Act, the DEQ allows municipalities and other agencies to collect and treat waste water under a National Pollutant Discharge Elimination System (NPDES) Permit. In order to comply with NPDES permit requirements, the DEQ has required St. Helens to eliminate overflows, except during storms that are greater than the 1-in-10-year, 24-hour summer event and the 1-in-5-year, 24-hour winter event, by January 1, 2010. For reference, the December 2007 storm was categorized as a 1-in-500-year winter event.

St. Helens, currently home to more than 12,000 residents, produces both point and non-point discharge through its wastewater and storm water management systems. The City currently operates a Waste Water Treatment Plant (WWTP) and collection system that serves more than 4,700 residential, commercial, and industrial customers, including Boise Cascade.
In the early 1990's the city completed a program to eliminate all direct inflow points. Over time new direct inflow points such as yard and field drains, down spouts, sump pumps and floor drains have been introduced into the waste water system. This adds significantly to the overall I/I problem, with peak winter flows at the WWTP reaching 25 million gallons per day (mgd), while average dry weather flows are below 2 mgd.

At this time the City has started a program that will reduce I/I into its wastewater collection system. Flow monitoring and collection system modeling have defined the extent of the problem and identified the areas the produce the greatest I/I impact. Inspection of all wastewater mainlines, manholes and storm water management system, is underway. This inspection will provide the city needed information to bring the city into compliance with state and federal regulations.

Many of the oldest wastewater mainlines in the city are constructed of 2-foot lengths of clay pipe that have severely offset joints, structural problems, and deteriorated or non-existent joint gaskets. As a result, the collection system in these areas suffers from very high rates of infiltration during storm events. Water in the trenches enters the waste water system through defects in manholes, mainlines, and service laterals.
However, repair of mainlines and manholes alone will only reduce I/I by 20%. The water that was infiltrating into those lines before they were repaired will simply find another way into the system through the 4,700 privately owned service laterals. The condition of those laterals can only be guessed at. Flow monitoring confirms that the older parts of the city have the worst I/I problems, with ratios of as-much-as 32:1, or 32 gallons of I/I for every gallon of normal flow during heavy rainfall.

Repair of the privately owned service laterals will be critical to bring the city into compliance. City officials and staff are looking into options for this part of the program.

The impact of these repairs on water and sewer rates is not clear at this time.

The city held its first I&I Public Forum July 16^th, 2008. A second Public Forum is scheduled for March 4^th at 6:00 p.m. in council chambers at St. Helens city hall.
Amber Dennis, Principal
Dandelion Communications

GOOD IDEAS FOR GOOD ENDEAVORS

Serving as Public Relations Director for:
- City of St. Helens
- Columbia County Tourism
dandelioncommunications@comcast.net
503.804.0087