2022-008 Update on the January 13, 2021 Sanitary Sewer OverflowDate: January 21, 2022 Report No. 2022-008
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
Update on the January 13, 2021 Sanitary Sewer Overflow (SSO)
BACKGROUND:
On January 20, 2021, staff informed Council via the Friday Report about an SSO that occurred on
January 13, 2021, near 6404 Crapemyrtle Drive (Attachment 1). The cause of the overflow was
determined to be vegetation grown into the manhole invert. Within hours of notification about the
discharge, field crews removed the vegetation and cleaned the sewer main downstream of the
overflowing manhole, restoring flow and stopping the overflow. During the overflow,
approximately 120,000 gallons of sewage were discharged into an unnamed tributary that flows
into Pecan Creek.
Cleanup efforts for improving water quality in the tributary and visits with investigators from the
Texas Commission on Environmental Quality (TCEQ) continued for six days, concluding on
January 19, 2021. Signage was posted notifying the public to stay out of the affected area and
avoid any exposure to the surface water. Regular monitoring of water quality parameters and E.coli
continued until January 27, 2021, when results indicated the water in the tributary returned to
normal water quality conditions.
Since concluding cleanup and mitigation efforts, the sanitary overflow response plan (SORP)
underwent an annual update.
The January 13, 2021 sewer overflow resulted in a violation of the Texas Water Code and TCEQ
regulations for which an $11,812 administrative penalty was assessed. On January 7, 2022, TCEQ
mailed Mayor Hudspeth and City staff an Agreed Order intending to expedite the enforcement
action. In addition to the fine, TCEQ established technical requirements to be met within 30 days
after signing the Agreed Order for a date to be determined. The technical requirements include the
removal of any sludge within the creek channel 1,000 ft downstream of the overflow, updating the
SORP, and conducting employee training. Staff proactively met most of the TCEQ’s technical
requirements prior to receiving the Agreed Order. Staff training for wastewater personnel is
scheduled for next month.
ATTACHMENT(S):
January 20, 2021 Sanitary Sewer Overflow near 6404 Crapemyrtle Dr Memorandum
STAFF CONTACT:
Stephen D. Gay, Director of Water Utilities
Water/Wastewater Department
901-B Texas Street, Denton, TX 76201
MEMORANDUM
DATE: January 20, 2021
TO: Terry Naulty, Interim Director Water/Wastewater
FROM: Casey Bowles, Interim Superintendent Field Operations– Utilities
SUBJECT: Sanitary Sewer Overflow near 6404 Crapemyrtle Drive
On January 13, 2021, at 4:44 pm, city Wastewater staff were notified of a potential sanitary
sewer overflow. Wastewater Collections on-call staff were dispatched to investigate. Upon
arrival, they noticed a manhole overflowing into a wet weather tributary. They discovered the
cause of the blockage to be vegetation grown into the manhole invert. These staff members
immediately started working to clear the vegetation and restore a clear path for the wastewater to
flow through the manhole. They removed the vegetation and cleaned the sewer main downstream
of the overflowing manhole, restoring flow and stopping the overflow at 9:00 pm.
Clean up Effort
On January 14, 2021, we met on site with the Watershed Protection Team to create plan to clean
the SSO and improve the water quality in the tributary. That day, we began cleaning the area
between the tributary and the manhole, removing debris from the tributary, and flushing the
tributary with reclaimed water.
On January 15, 2021, we met on site with Robin Pugh, Aquatic Scientist, from TCEQ. She
recommended that we pump the water out of the tributary and then continue our flushing efforts.
That day, we collected three, 3” pumps and began pumping water from the wet weather tributary
to manholes in the area and erected signs along the waterway to warn residents of the sanitary
sewer overflow and to not enter the area and to avoid any exposure to the water We continued
our pumping efforts until Tuesday, January 19, 2021. Approximately 14,400 gallons of water
was pumped out of the tributary. Tuesday morning, we began flushing the tributary with
reclaimed water. We have added about 40,000 gallons of reclaimed water to the tributary and
spent a total of 140 manhours on this SSO through January 19th. Before and after cleanup
pictures adjacent to the overflow area are attached.
Monitoring and Data Collection
After the pumping phase of remediation was completed, staff began adding dechlorinated reuse
water to the affected tributary upstream of the discharge at the Shady Shores Road bridge. Water
quality is being monitored at three locations. In-situ data collected with a sonde includes
Water/Wastewater Department
901-B Texas Street, Denton, TX 76201
dissolved oxygen, temperature, pH, conductivity, Total Dissolved Solids (TDS), salinity and
turbidity. E. coli samples are being collected and submitted to the Denton Municipal Lab which
is NELAP certified for this analyte.
Sampling and flushing will continue until the impacted wet weather tributary and downstream
intermittent stream water returns to baseline conditions with E. coli meeting Texas Surface
Water Quality Standards for Segment 0823.
Staff has been collecting water samples at the three monitoring stations along the tributary and
testing them periodically. Also, during the next seven days, it is anticipated that staff will be
collecting water samples for testing on Thursday (1/21/21), Monday (1/25/21) and Wednesday
(1/27/21) and staff will be monitoring the overall condition of the tributary.
The testing results for the first day (Thursday 1/14/21) and Tuesday (1/19/21) are attached.
Based on the comparison of the tests conducted on water samples collected on Thursday
(1/14/21) the day after the spill was reported and Tuesday (1/19/21) the day after the cleanup
efforts (remediation) were completed, it is evident that there is significant reduction in E-coli
levels (from 900,000 to <1,000 MPN/100 ml) and considerable increase in Dissolved Oxygen
(DO) levels (from 4.1 mg/L to 9.4 mg/L).
Hence, it can be concluded that the remediation effort was successful in significantly improving
the surface water quality of the impacted area along the tributary. As discussed earlier, staff will
continue to monitor conditions along this tributary and conduct periodic water testing in the next
seven days.
Water/Wastewater Department
901-B Texas Street, Denton, TX 76201
Sanitary Sewer Overflow near 6404 Crapemyrtle Drive - Water Quality Analysis
Location: Upstream of discharge in ephemeral tributary at Shady Shores Rd
date event color odor
Temperatur
e (°C)
DO
(mg/L)
pH
(units)
Conductivit
y (uS/cm)
TDS
(mg/L)
Salinity
(ppt)
Turbidity
(NTU)
E. Coli
(MPN/100ml)
1/12/2021 dry weather screening - baselineclear none 4 10.33 8.0 747 486 0.36 1.65 N/A
Location: immediately downstream of discharge in ephemeral tributary
date event color odor
Temperatur
e (°C)
DO
(mg/L)
pH
(units)
Conductivit
y (uS/cm)
TDS
(mg/L)
Salinity
(ppt)
Turbidity
(NTU)
E. Coli
(MPN/100ml)
1/14/2021 following response to abate SSOmedium gray strong sewage 12.4 4.1 6.99 760 494 0.37 90.22 909,000
1/19/2021 initiation of flushing clear none 8.7 9.4 7.51 755 491 0.37 3.15 <1,000
Location: approximately 1,000 feet downstream past abandoned Swisher Rd
date event color odor
Temperatur
e (°C)
DO
(mg/L)
pH
(units)
Conductivit
y (uS/cm)
TDS
(mg/L)
Salinity
(ppt)
Turbidity
(NTU)
E. Coli
(MPN/100ml)
1/12/2021 dry weather screening - baselineclear none 5.5 7.16 7.8 640 416 0.31 2.68 N/A
1/14/2021 following response to abate SSOclear none 9.2 4.5 7.26 733 477 0.36 8.37 285,100
1/19/2021 initiation of flushing clear none 9.5 9.1 7.57 748 486 0.37 5.35 1,000
Location: approximately 3,400 feet downstream at Burr Oak Dr
date event color odor
Temperatur
e (°C)
DO
(mg/L)
pH
(units)
Conductivit
y (uS/cm)
TDS
(mg/L)
Salinity
(ppt)
Turbidity
(NTU)
E. Coli
(MPN/100ml)
1/19/2021 initiation of flushing clear none 9.5 8.9 7.64 926 602 0.46 1.71 323
Water/Wastewater Department
901-B Texas Street, Denton, TX 76201
Sampling Locations
Water/Wastewater Department
901-B Texas Street, Denton, TX 76201
Spill Area Near Manhole (1/14/21) Area After Remediation (1/19/21)