Combined Sewer System Long Term Control Plan - DC Water

Table 15-3
Phase 3 Monitoring
Post Construction Monitoring
Monitoring Type Anacostia River Potomac River Rock Creek Frequency
Rain Fall Monitoring 1 gage in Northeast
Boundary
1 gage in Tiber Creek
1 gage in Slash
Run
1 gage in College
Pond
1 gage in Piney
Branch
Continuous
CSO Overflow
Monitoring and
Diversion to Storage
Monitoring
Tunnel Storage Level
Monitoring
CSO Overflow
Sampling
Receiving water
Monitoring- Dissolved
Oxygen
Receiving Water
Monitoring- Bacteria,
Field Parameters
Northeast Boundary
CSO 019
Fort Stanton CSO 007
B ST/ NJ Ave Pumped
Overflow CSO 010
Potomac Pumping
Station CSO 021
College Pond CSO
029
Piney Branch
CSO 049
Continuous
1 sensor in Tunnel 1 sensor in Tunnel 1 sensor in
Tunnel
Continuous
1 sampling station at 1 sampling station
-- 4 storms per year
Northeast Boundary at CSO 021
Approx 1 hour
sample interval
D.O. monitors
operated by DOH
Use data from other
existing programs
D.O. monitors
operated by DOH
Use data from
other existing
programs
for each storm
-- Approx 30
minute intervals
-- Frequency of
existing
programs
Phase 3 monitoring will be conducted for 12 months.
15.7 NPDES PERMIT CONDITIONS
Because the operation of the District’s combined sewer system is addressed in NPDES Permit No.
DC0021199, permit conditions will need to be developed to monitor and measure compliance based
on operation of the LTCP. A potential framework for defining an acceptable level of performance
and permit compliance would contain the requirements such that the CSO control system would be in
compliance when:
Transfer facilities from CSO outfalls to storage are conveying flow up to prescribed rates.
An outfall is not discharging when its associated storage facility is not filled to capacity and
the transfer facility is conveying flow up to prescribed rates.
The BPWWTP is operating at prescribed treatment rates and capacities.
An outline of permit conditions is as follows:
Discharges from permitted individual combined sewer system outfalls are prohibited except
during wet weather events when:
o The associated combined sewer overflow storage facilities are filled to capacity:
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