select slides from powerpoint presentation prepared july 2011

Sanitary Sewer Overflows

Select Slides from PowerPoint Presentation

Prepared July 2011

Sanitary Sewer Overflow

• “Sanitary Sewer Overflow (SSO)”

means a discharge of untreated or

partially treated sewage from a

separate sewer system before the

sanitary wastewater reaches the

headworks of a wastewater

treatment facility, pursuant to

COMAR 26.08.10.01.

Slide 2 Sanitary Sewer Overflows

Unauthorized Discharge

• An “Unauthorized Discharge” is

the release of fully treated and

disinfected wastewater at a

location other than the discharge

point, or outfall, listed in the

plant’s NPDES permit.


Sanitary Sewer Overflows

• EPA estimates that nationally there are

at least 23,000 to 75,000 SSOs per year

(not including sewage backups into

buildings). *

• Even though systems are intended to

collect and contain all the sewage that

flows into them, SSOs occasionally

occur in almost every sewer system.

* http://cfpub.epa.gov/npdes/home.cfm?program_id=4


MDE Zero Tolerance• MDE adopted a Zero Tolerance policy in

March, 2005 (effective January 1, 2009) for

SSO events

• Many Maryland wastewater agencies feel that

the policy is unrealistic. SSO’s, while not

desirable, do happen

• MDE has developed a sliding scale of fines

and penalties for SSO events

• Charles County actually has a good record for

SSO’s


Charles County Sanitary Sewer Overflows

and Rain-Caused Overflows


45 5

3

10

10

22

20

15

15

18

910

R² = 0.8123

0

4

8

12

16

20

24

28

2004 2005 2006 2007 2008 2009 2010

Nu

mb

er

of

SS

O E

ve

nts

Year

Charles County DPW - UtilitiesSSO Events 2004 - 2010

Rain SSO's

# of SSO's

SSO Trendline

Charles County Sewer History

• The County’s earliest collection system

lines date from 1950’s and 1960’s and

are still in use

• The collection system as we know it

today is made up of formerly

independent sewer districts

• Construction and Inspection services

were not consistent among the districts


Causes of SSO Events

• Infiltration and Inflow (I&I) (heavy rains, roof

leaders connected to sewer, cracked and

broken pipes)

• Equipment Failure (pipes, pumps, sensors)

• Grease, rags (difficult to control residential

discharges)

• Power Failures (brown outs, black outs and

storm-caused power failures)

• Vandalism (sticks, trash, other debris

deliberately dumped in manholes)


Causes of SSO Events (Cont’d)

• Infrastructure Deterioration (age, cracks,

breaks, pipe / manhole failure due to

corrosion)

• Design and Construction Issues (improper

materials, undersized pipes, improper grade,

“bellies” or humps in pipes)

• Contractor negligence (pipe plugs and

construction debris lost in system)

• 3rd Party Damage (directional drilling through

pipe)


Corrective Actions

• DPW has an on-going I&I capital project

developing and implementing an action

plan

• Utilities has an in-house I&I team and a

sewer cleaning crew to help monitor

SSO “hot spots”

• Westin Project

– SCADA for notification of problems

– INFOR automatically generates cleaning

schedules


Corrective Actions (continued)

• Install redundant alarm sensors

– e.g., a float level sensor to back up a bubbler

system

• Upgrades to the Mattawoman influent /

effluent pump station– Interim plan replaced bar screen and grit

removal units

– Refurbished an existing pump and will install a

new pump


Utilities takes SSO’s VERY seriously

• Staff are trained to deal with SSO’s, including:

– Full investigation of the cause of any SSO

– MDE and CCHD reporting requirements

– Debriefing following an SSO event

– Initiation of follow-up actions, as appropriate,

to prevent SSO re-occurrence

– Clear SSO Standard Operating Guidelines, first

distributed in 2004 and regularly reviewed and

updated


However…

• SSO’s cannot be completely eliminated:

– We simply cannot foresee the unforeseeable

– We cannot stop natural events such as

torrential rains

– We cannot always tell exactly what is

happening underground

– Man made materials and construction

techniques have finite life spans


Mattawoman Creek Flooding Due to

Torrential Rains, May 12, 2008

Note orange manhole location stake in photo on left. The

manhole is completely under water. The creek is normally

only a few feet wide.


Broken Sewer Pipe

Utilities crew is about to install a stainless steel sleeve to repair the

break. This particular pipe is among the oldest in the Waldorf

collection system.


Panda Line Pipe Failure

During construction, the protective lining of the pipe was damaged.

The damage occurred 11 years prior to the pipe failure and resulted

in an Unauthorized Discharge.


select slides from powerpoint presentation prepared july 2011

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