e Historic combined sewer systems or sewer conversion — Contributing areas that were once
serviced by a combined sewer system but have been separated and contributing areas that were
once serviced by septic systems but have been converted to sewer connections may have a high
illicit discharge potential. Separated systems were assigned a level value of 3, converted systems
were assigned a level value of 2, and areas still on septic were assigned a 1.
e Surrounding density of aging septic systems — Septic systems 30 years or older in residential
land use areas are prone to have failures and may have a high illicit discharge potential. Outfalls
with surrounding septic systems over 30 years old were assigned a level value of 3, outfalls with
surrounding septic systems between 20 and 29 years old were assigned a level value of 2, outfalls
with surrounding septic systems between 10 and 19 years old were assigned a level value of 1,
and outfalls with surrounding septic systems less than 10 years old were assigned a level value of
0.
e Discharging to an area of concern to public health — Outfalls that discharge to or in the
vicinity of any the following areas:
© Public beaches
© Recreational areas
o Drinking water supplies
o Shellfish beds
Outfalls discharging to areas of body contact or drinking water inlets were assigned a level value
of 10, outfalls discharging to areas of high recreation or boat ramp access were assigned a level
value of 5, and outfalls discharging to areas with limited or no recreation were assigned a level
value of 0.
e CCTV storm drain data — Outfalls with hard pipe connections were assigned a level value of
10, outfalls with significant structural defects were assigned a level value of 5, and outfalls with
neither were assigned a level value of 0.
The following is an initial outfall prioritization flowchart, see Appendix C for an outfall
inventory and priority ranking matrix:
Hic it Discharge Detection and Himination Plan 11
