Sanitary Sewer Overflows Select Slides from PowerPoint Presentation - - PowerPoint PPT Presentation

Slide 1

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.

Slide 3 Sanitary Sewer Overflows

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

• ccur in almost every sewer system.

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

Slide 4 Sanitary Sewer Overflows

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

Slide 5 Sanitary Sewer Overflows

Charles County Sanitary Sewer Overflows and Rain-Caused Overflows

Slide 6 Sanitary Sewer Overflows

4 5 5 3 10 1 22 20 15 15 18 9 10 R² = 0.8123 4 8 12 16 20 24 28 2004 2005 2006 2007 2008 2009 2010

Number of SSO Events Year

Charles County DPW - Utilities SSO 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

Slide 7 Sanitary Sewer Overflows

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)

Slide 8 Sanitary Sewer Overflows

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)

Slide 9 Sanitary Sewer Overflows

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

Slide 10 Sanitary Sewer Overflows

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

Slide 11 Sanitary Sewer Overflows

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

Slide 12 Sanitary Sewer Overflows

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

Slide 13 Sanitary Sewer Overflows

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

• nly a few feet wide.

Slide 14 Sanitary Sewer Overflows

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. Slide 15 Sanitary Sewer Overflows

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. Slide 16 Sanitary Sewer Overflows