Greater Detroit Regional Sewer System

Transcription

1 Utilization of Water Quality Monitoring Data to Support the City of Detroit s Long Term CSO Control Plan Mirza Rabbaig, Detroit Water & Sewerage Department Imad Salim, Wade-Trim Tony Igwe, Wade-Trim Julie Aichler, CDM State of the Strait Conference 2004 Wade-Trim

2 Objective Define level of combined sewer overflow (CSO) control required for the protection of public health and meet Water Quality Standards at the time of discharge.

3 Greater Detroit Regional Sewer System Oakland County Macomb County Canada Service Area Statistics 3 million people 78 communities 900 square miles (35% Combined) City of Detroit 3,500 miles of combined sewers 78 outfalls 3 major interceptors Wayne County

4 CSO Control Enforcement Clean Water Act and Amendments State of Michigan Act 451

5 What CSO Control is Required? Basins Tunnels Disinfection Screening $$$$$$$ $$$$$$$$$$ $$$$ $$ $$$$$ Screening and Disinfection

6 Demonstrative Approach for Type and Size of Required CSO Control Receiving Water Quality Data Treatment Performance Data + = Protection of Public Health and Water Quality Standards

7 City of Detroit Demonstration Projects CSO Basin CSO Basin Water Quality Monitoring CSO Basin CSO Basin S/D Facility S/D Facility Water Quality Monitoring S/D Facility

8 Water Quality Monitoring 1. Spatial extent of CSO impacts 2. Dissolved oxygen (DO) depression 3. Aesthetic and bacterial impairments 4. Ecological impacts

9 1. Spatial Extent of CSO Impacts A. Objective: Define horizontal and vertical extent of the Detroit River area influenced by DWSD CSOs. B. Monitoring: and 2001 CSO Plume Tracking Turbidity Measurement Surveys Near and Off Shore Dye Plume Studies CSO Plume Tracking E-Coli Bacteria Levels Surveys 4. Ongoing TRC Downstream of Pilot Facilities

10 Estimated Plume Edge from Multiple Survey Data Conner Creek Gregory's Detroit Intake Leib St. Aubin Windsor Intake Legend estimate plume edge_2001 turbidity tracking Bacteria shp N Plume101502_dye study.shp Coastline.shp River_Depth_contour.shp g://_project/22723/wqwg/2003map.apr 4000 Feet

11 Plume Tracking and Dye Tracer Monitoring Findings 1. Plume remains within 500 feet of shoreline and impact 20% or less of the total Detroit River channel width. 2. Detroit and Windsor water intakes are located outside DWSD CSO plume. 3. Plume was well mixed in the water column.

12 2. Dissolved Oxygen Depression A. Standard: Minimum DO level is 7 mg/l B. Monitoring: Four Continuous water quality monitors ( ) : from May through November 2002 : from June through October : from June through September

13 Locations of Continuous Monitors 4P r 3P St. Aubin r Leib &\ &\ $Z 2P 1P-Windmill Pointe 2P- Gregory's Boat Basin 3P-Riverfront Apartments 4P-ACOE at Ft. Wayne 5P-Jefferson Bridge 6P-Dix Bridge Conner Creek r Windsor Intake $Z &\ DWSD Intake Belle Isle 1P &\ Pilot CSO Control Outfalls r Long Term Monitors N $Z Public Water Intakes Uncontrolled CSO Depth_contour.shp Miles r

14 Dissolved Oxygen Monitoring Data DO (m g /L) Rainfall(in) 7 Freud P S : 57 M G Freud P S : 45 M G /14/03 12:00 8/15/03 0:00 8/15/03 12:00 8/16/03 0:00 8/16/03 12:00 8/17/03 0:00 8/17/03 12:00 1P -W indm illp ointe 2P -G regory's B oat B asin 3P -R iv e rfro n t A p ts S a tu ra tion D O (at 2P ) Avg H ourly R ainfall 0.90

15 Dissolved Oxygen Monitoring Findings 1. DO drops from CSOs are temporary/localized. 2. All monitored DO levels above 7 mg/l. 3. DO reductions are attributed to mixing with low DO concentrations in the CSO not due to DO demand of discharge.

16 3. Aesthetic and Bacterial Impairments A. Standard: - Restricts presence of unnatural physical properties including: turbidity, color, oil films, floating/ suspended/ settleable solids, foam, etc. - E. Coli event geometric mean less than 300 cfu/100 ml for full body contact B. Monitoring: and 2000: Shoreline Surveys to evaluate the appearance of the water body and debris that may have been deposited along the shore : In-stream bacteria sampling

17 Aesthetic and Bacterial Impairments Findings 1. The Detroit River was found to be clear, colorless and generally had no odor during surveys performed during dry weather and following major rainfall events. 2. Majority of locations had no debris or only natural debris during surveys performed. 3. The presence of foam and oil films at few locations during several dry and wet weather surveys. 4. Bacteria concentrations higher than standard were found following rainfall events.

18 4. Ecological Impacts A. Standard: No adverse impact on the biological community B. Monitoring: Benthic Macroinvertebrate Surveys: Artificial Substrate Samplers 8 Near and 7 Offshore Sampling Sites 4-6 samples per site Upstream & Downstream of each Pilot CSO facility

19 Benthic Sampler Locations

20 Ecological Impact Findings There is an observable decrease in the number and quality of Macoinvertebrates in the near shore stations from the head of the Detroit River to downstream urban area. No consistent impact from CSO discharge has been observed to date. Surveys will continue after pilot facilities are in operation to further evaluate ecological impacts of treated CSO effluent.

21 Conclusions To Date The CSO plume affects 500 feet; 20% of channel width. The CSO plume is well mixed in the water column. Public water intakes are not impacted by DWSD CSO plume. Dissolved oxygen levels are always >7 mg/l standard. The Detroit River was found clear, colorless and generally had no odor. Bacteria levels exceed standards within the CSO discharge plume. No consistent impact from CSO discharge has been observed to date.

22 Next Steps Continue post CSO pilot facility monitoring through 2006 Pilot facility performance Receiving water quality impacts Determine adequate CSO controls Update City of Detroit Long Term CSO Control Plan