INFLOW AND INFILTRATION (I & I)
First I & I must be defined. I & I is the acronym for Inflow and Infiltration. Inflow is water from rain gutters and sump pumps that enters a sewer line. Also a storm drain could be directly connected to the sewer system. Infiltration is groundwater that seeps into sewers due to cracks in the sewer pipes or misaligned pipe joints.

All of this water makes it way to our wastewater
treatment plant and must be treated. All sewer systems will have some I & I.
The Hartstene Pointe Sewer System has a major I & I problem. During heavy rainfall events, the treatment plant influent flow exceeds the plant design capacity of 350,000 gallons per day. When the treatment tanks are full, the plant operator must allow some untreated wastewater to bypass into Case Inlet. The discharge of untreated water is a violation of our discharge permit (NPDES permit) and such violations must be reported to the Washington State Department of Ecology (Ecology). Ecology has authority under the Federal Clean Water Act to issue orders requiring corrective action be taken and also to assess civil penalties.

On December 12, 2010, Hartstene Pointe experienced a major rainfall and a flow in excess of 350,000 gallons per day entered the wastewater treatment plant (it is estimated to have been at or above 600,000 gallons per day). The operator spent hours trying to control the excessive flow by filling both treatment tanks,(technically referred to as the Sequencing Batch Reactors) (SBRs), to full capacity. When the SBRs became full and threatened to spill over, the operator
had no choice but to bypass untreated wastewater until the flow subsided. To a usually lesser degree, this situation happens whenever there is a severe rainfall event.

This situation is not new. Mason County operators experienced the same problems. In 2008, Mason County contracted for a project to correct I & I involving the main sewer line at a cost of $165,027.17. Twenty-three infiltration points were repaired and several manholes were repaired. While this work was necessary for proper sewer maintenance, it was discouraging to learn that
the influent flow into the treatment plant during a heavy rainfall had been reduced by only a small amount, if at all. The total cost for this project came from the accumulated Hartstene Pointe rate funds.

Excessive flow into the treatment plant places an undue burden on the treatment plant equipment. Pumps and valves must operate more frequently and for longer periods. More chemicals and electricity are consumed. The treatment plant contractor is compensated on an hourly basis, so the additional hours the contractor must spend at the plant increases the labor
cost. All these costs would be lessened if we can reduce excess water flowing to the treatment plant. Rainwater and groundwater do not need treatment, but if they flow into the sewer system with the wastewater, they must receive the same treatment as the wastewater.

These factors should be noted:
1. The increase and decrease in the rate of flow into the treatment plant is quite rapid. Sump pumps are capable of moving large volumes of water. The rapid increase in treatment plant inflow then could be, in part, the result of a number of sump pumps starting to move water at about the same time. Of course, only those sump pumps connected directly to the sewer lines would contribute to this increased flow.

2. The 2008 project did not significantly reduce the influent flow to the treatment plant during periods of heavy rainfall.

3. If infiltration of groundwater were the total problem, the rate of the influent flow increase to the treatment plant would be more gradual and continuous and could continue for some period after the storm ceases.

4. When Mason County owned and operated the Hartstene Pointe plant, their plant operator also witnessed rapid increases and decreases of influent flow into the treatment plant. Tom Moore, Mason County Deputy Waste Management Director, has mentioned that he suspected a number of sump pumps might be discharging to the sewer system.

Ecology requires that all permitted wastewater systems reduce I & I flows. Ecology has placed that requirement in the Hartstene Pointe discharge permit that soon is to be reissued. The same requirement was also in the recently expired permit originally issued to Mason County.

A project to reduce I & I will cost $500,000 or more depending on the number and severity of cracked pipes or misalignments. A contractor would be hired to televise all the lateral sewer pipes. The lateral sewer pipes connect each residence to the sewer main and extend from the sewer main to homeowner’s property. The lateral pipe sewer system here is a complex system that branches off from one lateral pipe to another in various directions and may connect as many as five or six houses. This makes it difficult and expensive to televise and to accomplish repairs. When major leaks are identified, the District would have a contractor make the repairs. Expansion of the treatment plant really is not a solution since the high flows occur only a relatively few times a year during heavy rainfall. Having an oversized plant operate at minimum capacity the rest of the time would result in inefficient and costly operation for much of the year.

The District currently lacks the money for an extensive I & I program and our borrowing capacity is near exhaustion. We believe that we should be able to negotiate a schedule for compliance with Ecology that would allow us 4 or 5 years to complete this work. One reason for the increase in rates this year is an attempt to accumulate at least some of the funds needed for this work.

We are asking property owners to try to determine if a sump pump (if present) and/or the rain gutters are connected to the sewer pipe at their residence. All such connections must be eliminated and the water directed to a storm ditch or piped over the bluff. If you are have a sump pump and/or rain gutters connected to the sewer, please leave a message for General Manager Mont Jeffreys at the Customer Service number, 360-876-2545, and indicate your schedule for
removing the connection. The District will monitor the effect that sump pump and rain gutter disconnections have on the flow rate to our treatment plant.

If you are uncertain about the existence of a sump pump at your house, please call Mont Jeffreys at the above number and he will give you assistance.
Also our treatment plant contractor is trying to find ways to store more wastewater within the system to lessen the volume bypassed during storm conditions. Our small collection system is at a disadvantage in this respect. In larger utilities, the collection system itself has capacity to hold considerable excess volumes of water during storm events and level out flows to the plant.
Our system does not have such surge capacity. Some sort of “surge basin” could help oursystem. We do not have any suitable vessels for this purpose and little, if any, room to construct one – if - we had the funds to do so.

The final solution will almost certainly be as described above. That is, locating the points where storm generated water can enter the collection system and make repairs. The difficulty, as mentioned before, is locating these points. The use of television is useful and effective. The major difficulty is that the lateral sewers are small in diameter and have many lateral connections. Also access to both ends of the line is needed transport the cameras through the sewer.

Take note that 100% of the stormflow does not need to be removed. The flow must be brought down to the point that bypassing is no longer necessary. That flow can be determined, in fact, a suitable maximum flow (the hourly design flow) is shown in the discharge permit.