Constructed Wetlands
Constructed Wetlands: A New Solution to Excess Flow Storage Tom Foley, P.E.
BACKGROUND
Rock River Water Reclamation District (RRWRD)
›
› › ›
Serves the City of Rockford and 7 neighboring communities totaling approximately 290,000 residents 1,100+ mi of sewer DAF = 40 MGD PDF= 80 MGD – The WRD has passed peak flows in excess of 137 MGD during storm events while still experiencing SSOs
Rock River Water Reclamation District
Why Excess Flow Storage › The RRWRD signed a
Compliance Commitment Agreement (CCA) to handle a 10-year, 24-hour storm event
› The CCA was in response to the Illinois EPA’s enforcement efforts to minimize SSOs.
RRWRD Excess Flow Design Criteria › Green Facility › Minimize Power Requirements › Reduce Hydraulic Load on › ›
Main Pump Station Avoid Internal Process Bypassing Consider Long Term Facility Sizing
Approach › Constructed wetland › Utilize existing sandy › › › ›
soil Utilize wastewater plant effluent Natural appearance Minimize maintenance IEPA Acceptance
DESIGN
Site Plan › 25 MG Basin
› 145.4 MGD Peak Flow
› 19 ac Land
Pump Station
Pump Station
Pump Station
Basin Design
Basin Design
Native Plant Usage
Native Plant Usage › Mesic Prairie Mix – Designed to tolerate brief flooding events – Deep roots of the prairie plants stabilize the side slopes once established
WWTF Effluent Reuse Criteria › Secondary clarifier effluent polishing/irrigation › Wetland plant selection › Nutrient loading based on effluent irrigation of 56,000 gpd
– Avg effluent of 15 mg/l BOD5 = 1 lb/acre/day – Total nitrogen of 20 mg/l = 1.33 lb/acre/day
› Organic loading is negligible, but in the form of nitrates
DESIGN CHALLANGES
Permitting Illinois EPA (IEPA) Wastewater Concept Approval Illinois Historic Preservation Agency Approval
Illinois DNR (IDNR) Office of Reality and Env. Planning EcoCat Project Planning
IEPA Wastewater Construction Permit
IDNR Office of Reality and Env. Planning EcoCAT
City of Rockford, IL Floodplain and/or Wetlands Modification Concept Approval Illinois Joint Construction in Waterways, Floodplains, and Wetlands Permit
Consultation for Threatened and Endangered Species Compliance (after Joint Permit Submittal) IEPA Illinois Water Pollution Control Board Approval as required by IEPA Water Quality Certification pursuant to CWA Section 401
US Army Corp of Engineers (USACE) Wetland Jurisdictional Limits Determination Possible Clean Water Act Section 404 Permit
IDNR Office of Water Resources Possible Submittal for Floodway Map Modification to IDNR and FEMA
Permitting › › › ›
Long history of land treatment – Septic leach fields – Cattle feed lots Constructed wetlands in Illinois – Approved for polishing – Approved for overall treatment Issue, bacterial (fecal coliform) level at property line Monitoring wells required
Wet Weather Loading ›
›
What about the loading during a storm event?
– 48 lbs BOD5 / acre / event – 7.5 lbs nitrogen / acre / event – Fecal coliform has a 99% die off rate in 8 days
The net impact of an annual event on the local groundwater is less than 1 cow/acre grazing in the basin
FEMA › Flood maps updated for the river as project was finishing
Wetland Start Up ›
“Inexperienced contractors and inexperienced engineers writing specifications and providing construction supervision have often killed their wetland plants through insufficient soil moisture, excessive water depths, inadequate soil preparation, damaged plant material, inadequate plant spacing, inappropriate planting methods, and bad timing.” – Kadlec, Robert and Scott Wallace. Treatment Wetlands, Second Addition
Wetland Start Up
Wetland Maintenance › Watering – Saturate soils, not standing water
› Establishing plants is critical – Timing – Remove weeds/invasive species – Re-plant if necessary
› No mowing!! › Controlled burn
RESULTS
Wetland Construction
Wetland Construction
Wetland Construction
Wetland Construction
Energy Savings › Project changed the constraints on the main
100%
90%
2 Pumps: 34.6 FT TDH 99.7% @ 80 MGD
91.4% @ 45 MGD 1 Pump: 36.9 FT TDH 2 Pumps: 30.1 FT TDH
80% 70% Occurance, %
›
pump station The District could focus on pumping smaller flows more efficiently
60% 50% 48.9% @ 35.9 MGD
40%
1 Pump: 33.3 FT TDH
30%
1 Pump: 31.4 FT @ 26.3 MGD
20%
Hourly Influent Flow Min Flow Avg Flow Design Peak
10% 0% 0
10
20
30
40
50
60 MGD
70
80
90
100
110
120
Energy Savings 60 50 40 TDH, ft
› 500 hp pump
30 20 C =120 System Curve
10
Design Flow 1 Morris Pump (85% of Full Speed ; 0,431 rpm)
Design Flow 35.9 MGD @ 33.3 ft
0 0
10
20
30 Capacity, MGD
40
50
60
100 C =120 System Curve
Design Flow 35.9 MGD @ 28.4 ft
90
Design Flow
80
1 Morris Pump (90% of Full Speed ; 0,450 rpm) 2 Morris Pumps
70
› 2x 150 hp pumps
TDH, ft
60 50 40 30 20 10 0 0
10
20
30 Capacity, MGD
40
50
60
Questions?
› Tom Foley – [email protected]
BACKGROUND
Rock River Water Reclamation District (RRWRD)
›
› › ›
Serves the City of Rockford and 7 neighboring communities totaling approximately 290,000 residents 1,100+ mi of sewer DAF = 40 MGD PDF= 80 MGD – The WRD has passed peak flows in excess of 137 MGD during storm events while still experiencing SSOs
Rock River Water Reclamation District
Why Excess Flow Storage › The RRWRD signed a
Compliance Commitment Agreement (CCA) to handle a 10-year, 24-hour storm event
› The CCA was in response to the Illinois EPA’s enforcement efforts to minimize SSOs.
RRWRD Excess Flow Design Criteria › Green Facility › Minimize Power Requirements › Reduce Hydraulic Load on › ›
Main Pump Station Avoid Internal Process Bypassing Consider Long Term Facility Sizing
Approach › Constructed wetland › Utilize existing sandy › › › ›
soil Utilize wastewater plant effluent Natural appearance Minimize maintenance IEPA Acceptance
DESIGN
Site Plan › 25 MG Basin
› 145.4 MGD Peak Flow
› 19 ac Land
Pump Station
Pump Station
Pump Station
Basin Design
Basin Design
Native Plant Usage
Native Plant Usage › Mesic Prairie Mix – Designed to tolerate brief flooding events – Deep roots of the prairie plants stabilize the side slopes once established
WWTF Effluent Reuse Criteria › Secondary clarifier effluent polishing/irrigation › Wetland plant selection › Nutrient loading based on effluent irrigation of 56,000 gpd
– Avg effluent of 15 mg/l BOD5 = 1 lb/acre/day – Total nitrogen of 20 mg/l = 1.33 lb/acre/day
› Organic loading is negligible, but in the form of nitrates
DESIGN CHALLANGES
Permitting Illinois EPA (IEPA) Wastewater Concept Approval Illinois Historic Preservation Agency Approval
Illinois DNR (IDNR) Office of Reality and Env. Planning EcoCat Project Planning
IEPA Wastewater Construction Permit
IDNR Office of Reality and Env. Planning EcoCAT
City of Rockford, IL Floodplain and/or Wetlands Modification Concept Approval Illinois Joint Construction in Waterways, Floodplains, and Wetlands Permit
Consultation for Threatened and Endangered Species Compliance (after Joint Permit Submittal) IEPA Illinois Water Pollution Control Board Approval as required by IEPA Water Quality Certification pursuant to CWA Section 401
US Army Corp of Engineers (USACE) Wetland Jurisdictional Limits Determination Possible Clean Water Act Section 404 Permit
IDNR Office of Water Resources Possible Submittal for Floodway Map Modification to IDNR and FEMA
Permitting › › › ›
Long history of land treatment – Septic leach fields – Cattle feed lots Constructed wetlands in Illinois – Approved for polishing – Approved for overall treatment Issue, bacterial (fecal coliform) level at property line Monitoring wells required
Wet Weather Loading ›
›
What about the loading during a storm event?
– 48 lbs BOD5 / acre / event – 7.5 lbs nitrogen / acre / event – Fecal coliform has a 99% die off rate in 8 days
The net impact of an annual event on the local groundwater is less than 1 cow/acre grazing in the basin
FEMA › Flood maps updated for the river as project was finishing
Wetland Start Up ›
“Inexperienced contractors and inexperienced engineers writing specifications and providing construction supervision have often killed their wetland plants through insufficient soil moisture, excessive water depths, inadequate soil preparation, damaged plant material, inadequate plant spacing, inappropriate planting methods, and bad timing.” – Kadlec, Robert and Scott Wallace. Treatment Wetlands, Second Addition
Wetland Start Up
Wetland Maintenance › Watering – Saturate soils, not standing water
› Establishing plants is critical – Timing – Remove weeds/invasive species – Re-plant if necessary
› No mowing!! › Controlled burn
RESULTS
Wetland Construction
Wetland Construction
Wetland Construction
Wetland Construction
Energy Savings › Project changed the constraints on the main
100%
90%
2 Pumps: 34.6 FT TDH 99.7% @ 80 MGD
91.4% @ 45 MGD 1 Pump: 36.9 FT TDH 2 Pumps: 30.1 FT TDH
80% 70% Occurance, %
›
pump station The District could focus on pumping smaller flows more efficiently
60% 50% 48.9% @ 35.9 MGD
40%
1 Pump: 33.3 FT TDH
30%
1 Pump: 31.4 FT @ 26.3 MGD
20%
Hourly Influent Flow Min Flow Avg Flow Design Peak
10% 0% 0
10
20
30
40
50
60 MGD
70
80
90
100
110
120
Energy Savings 60 50 40 TDH, ft
› 500 hp pump
30 20 C =120 System Curve
10
Design Flow 1 Morris Pump (85% of Full Speed ; 0,431 rpm)
Design Flow 35.9 MGD @ 33.3 ft
0 0
10
20
30 Capacity, MGD
40
50
60
100 C =120 System Curve
Design Flow 35.9 MGD @ 28.4 ft
90
Design Flow
80
1 Morris Pump (90% of Full Speed ; 0,450 rpm) 2 Morris Pumps
70
› 2x 150 hp pumps
TDH, ft
60 50 40 30 20 10 0 0
10
20
30 Capacity, MGD
40
50
60
Questions?
› Tom Foley – [email protected]
