2010 Stormwater Management Report (PDF) - US Environmental ...

2.4 OUTFALL SCREENING
a. Dry Weather Outfall Screening 1999-2004
Between 1999 and 2004, the Commission completed dry weather screening of its major
outfalls in accordance with the permit requirements. Screening consisted of visual
inspection of the outfall structure after 24 to 72 hours of antecedent dry weather, and
completion of a field inspection form. If the outfall structure was not accessible, the
nearest upstream manhole not subject to tidal influence or backflow was inspected. If
flow was observed, the physical characteristics (e.g. color, visible sheen, turbidity,
floatables, smell, and estimate of flow) were recorded and grab samples were collected
and analyzed for surfactants and ammonia using portable field test kits. The results of the
1999-2004 dry weather outfall screening were presented in previous annual reports.
b. Dry Weather Outfall Screening 2010
In the last several years, illegal connection investigations have expanded into many new
areas and many illegal connections have been identified and corrected. To evaluate
current conditions in the drainage system the Commission performed dry weather
screening of all its outfalls (major and non-major) in 2010. The screening method used in
2010 was the same as that used during the 1999-2004 screening, except that samples
were also analyzed in a laboratory for bacterial indicators. The 2010 dry weather outfall
screening was completed towards the end of the year and data is currently being verified
and compiled. A report on the results and findings of the screening is expected to be
completed by the end of April 2011.
2.5 DRAINAGE AREA INVESTIGATIONS
The Commission is currently advancing illegal connection investigations in all of the
major watersheds within Boston. New areas opened for investigation in 2010 included
the recently separated 15L088 and 15L089 drainage areas and several drainage areas
located in Charlestown. Figure 1-1 provided at the end of Section 1 shows the locations
of the Commission’s outfalls and their tributary areas. The map also illustrates the
current status of illegal connection investigations in each drainage area. Table 2-1 is a
tabular representation of all of the Commission’s outfalls/ drainage areas, including their
size category (major vs. non major), and current investigation status. Currently there are
101 drainage areas under investigation. Investigations have been completed in 61
drainage areas.
In 2010, investigations in drainage areas tributary to outfalls discharging in close
proximity to beaches continued to take first priority. To ensure efficient use of resources
and avoid fragmentation in the program approach, investigations in areas started during
SBI and Phase 1 were given the next level of priority. The next priority for investigations
was given to the areas already opened for investigation under Phase 2. Areas receiving
lower priority were generally those that are very small in size and have few buildings,
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