Agenda

8 Training

7 Catchment Investigations

Once stormwater outfalls with evidence of illicit discharges have been identified, various methods can be
used to trace the source of the potential discharge within the outfall catchment area. Catchment
investigation techniques include but are not limited to review of maps, historic plans, and records;
manhole observation; dry and wet weather sampling; video inspection; smoke testing; and dye testing.

6.1.3 Sample Collection and Analysis

If flow is present during a dry weather outfall inspection, a sample will be collected and analyzed for the
required permit parameters’. The general procedure for collection of outfall samples is as follows:

1. Fill out all sample information on sample bottles and field sheets
Put on protective gloves (nitrile /latex/other) before sampling

3. Collect sample with dipper or directly in sample containers. If possible, collect water from the
flow directly in the sample bottle. Be careful not to disturb sediments.

6.1.2

Field Equipment

Table 6-1. Field Equipment —- Dry Weather Outfall Screening and Sampling

Equipment

Use/Notes

Clipboard

For organization of field sheets and writing surface

Field Sheets

Field sheets for both dry weather inspection and Dry weather sampling
should be available with extras

Chain of Custody Forms

To ensure proper handling of all samples

Pens/Pencils/Permanent Markers

For proper labeling

Nitrile Gloves

To protect the sampler as well as the sample from contamination

6 Dry Weather Outfall Screening and Sampling

Dry weather flow is a common indicator of potential dlicit connections. The MS4 Permit requires all
outfalls (excluding Problem and Excluded Outfalls) to be inspected for the presence of dry weather
flow. The Engineering Department is responsible for conducting dry weather outfall screening, starting
with High Priority outfalls, followed by Low Priority outfalls, based on the initial priority rankings
described in the previous section by the end of Year 3.

Hic it Discharge Detection and Eimination Plan

12

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 Determined by the permittee as high priority based on the characteristics listed in
Appendix C.

4. Low Priority Outfalls: Outfalls determined by the permittee as low priority based on the
characteristics listed below or other available information.

5 Assessmentand Priority Ranking of Outfalls

The MS4 Permit requires an assessment and priority ranking of outfalls in terms of their potential to
have ilicit discharges related public health significance. The ranking helps determine the priority order
for performing IDDE investigations and meeting permit milestones.

5.1 Outfall Catchment Delineations

4 Sanitary Sewer Overfiows (SSOs)