Southern Kent Island, Maryland (SKI) Sanitary Project Annual...Southern Kent Island, Maryland (SKI)...
Transcript of Southern Kent Island, Maryland (SKI) Sanitary Project Annual...Southern Kent Island, Maryland (SKI)...
Southern Kent Island, Maryland (SKI)Sanitary Project
National Onsite Wastewater Recycling Association
2017
www.skisewer.com1
Southern Kent Island Sanitary Project
• Project overview
• Problems & challenges faced
• Smart growth considerations
• Climate change & rising sea level “risks”
• Project system
• Phasing & construction status
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Correct a long-standing public health problem within existing 1950’s
& 60’s-era communities that were developed before modern public
health and land use regulations.
• Affordably
• Growth limits
• Permanent
• Robust
Southern Kent Island Sanitary Project Goal
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Failing onsite septic systems
• 1,518 existing homes
• 1,600 vacant lots of record
80% of existing homes discharging directly into groundwater
Communities situated miles away from public sewer service area
Environmentally sensitive region – 70% of project within
Chesapeake Bay Critical Area
Public concerns about growth from a sewer line extension
Southern Kent Island Sanitary Project Problem
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Public Health and Environmental Issues
• High groundwater
• Soils with poor permeability
• Small lot sizes
3 Strikes and You’re Out!
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Historical County Efforts
2008 – Retained engineering/planning firm (JMT) to evaluate
options for a public sewer system to serve South Kent Island
2010 – Comprehensive plan adopted reflecting future public
sewer service to SKI communities
2011 – Local Advisory Board concludes that “public sewer
collection and treatment is warranted”
• Limit infill
• Establish an Economic Benefit Premium (EBP)
• Obtain state grants
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Began regular meetings with MDE & MDP to craft a plan to balance
infill development with project financing and costs to residents
• Bay Restoration Fund
• State revolving loans
Local health department adopts “holding tank policy” for failed septic
system areas
• 7 homes and 2 businesses currently on holding tanks
• 500+ additional homes identified for holding tanks
Smart Growth Considerations
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Avoid Holding Tanks
Average House:
$200 - $400 per pump out
$7,200 - $8,640 per year
About $600 a month
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Introduced Lot Consolidation Ordinance #13-24
• Merged adjacent lots under common ownership
• Must conform with existing zoning district NC-20
Final project service area boundaries established
• Denied access force main
• Only offer service to vacant interspersed lots / avoiding
undeveloped blocks of lots from service area
• Vacant lot inventory reduced – from 1,600 down to 632
Appraisal to set EBP range and introduced Special Benefit Resolution
#14-07 to levy project cost
Smart Growth Considerations
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Researched and developed public sewer system design concept using Septic
Tank Effluent Pumping (“STEP”)
• Best suited for areas with limited topography
• Simple and efficient design technology
• Low-pressure system
• Easy to retrofill
MDE sponsored legislation HB 11 to change state law, which made BRF funds
eligible for the project
State & County Efforts - Planning
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Serving the 9 communities at SKI with the sanitary project
will:
• Help prevent future growth
• Provide a cost-effective solution
• Eliminate pathogens
• Provide superior reduction in nitrogen loads
Best Alternative for SKI
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EXISTING CONDITIONS – Septic Systems NITROGEN LOAD - LBS/YEAR
Septic Systems
940 homes - Critical Area 17,446
113 homes - near a stream 1,311
465 homes beyond the Critical Area 3,236
vacant lots 0
Non-point
1,518 homes - 878 acres 6,895
vacant lots - 327 acres 1,528
About 30,400 lbs/yr TOTAL
Nitrogen Loads – Existing
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FUTURE CONDITIONS – Connect to WWTP NITROGEN LOAD - LBS/YEAR
ENR
1,518 existing homes on ENR and
560 new homes on ENR 4,987
Non-point
1,518 existing homes - 878 acres and
560 new homes - 327 acres 8,158
About 13,100 lbs/yr TOTAL
Nitrogen Loads – Future
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Existing septic and non-point N loads 30,400 lbs/yr
Future ENR and non-point N loads - 13,100 lbs/yr
Reduction in Nitrogen Loads 17,300 lbs/yr
Reduction in Nitrogen Loads
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Approval of SKI sewer extension and eligibility for use of BRF funds
and SRL grants
1. Limited to 1518 existing homes and max of 632 infill vacant lots
2. Report new connections annually to MDP
3. Limit treatment capacity to 500,000 gpd
4. No increased capacity for existing non-residential uses
5. Denial of service for any future connection outside of SKI
service area
6. Adopt MD model floodplain ordinance with a 2-foot freeboard
requirement
7. Evaluate climate change vulnerability and outline strategies to
enhance resilience
State Smart Growth Committee
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“Thoroughly assess climate change impact vulnerability
and outline specific strategies for enhancing resilience to
the impacts of sea level rise and coastal flooding.”
Climate Change
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• Infrastructure impacts
– EMS
– Evacuation routes
– Roads
– Schools
– Wastewater facilities
– Water supply
– Residential property/structures
– Commercial property/structures
• Natural resource impacts
– Wetlands
– Critical area
– Agricultural land
Scenarios and Impacts
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Study Area Scenario 1 Scenario 2 Scenario 3
1 0.5% 0.8% 1.1%
2 2.5% 3.7% 5.6%
3 13.7% 22.8% 34.2%
4 11.1% 18.9% 31.9%
Countywide 2.6% 4.1% 6.3%
Percent of Land Impacted
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• Avoid
• Accommodate
• Protect
• Retreat
• Build adaptive capacity
Climate Change Protection Strategies
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• Identify areas of high vulnerability
• 2014 FEMA flood insurance rate maps have reduced flood
zone compared to prior maps by 313 acres or 70% in SKI
communities
• County floodplain ordinance proposed to increase freeboard
requirement from 1 to 2 feet
• Evaluate changes to zoning
• Application of building code will mitigate future property
damage from flooding
Climate Change Risks Mitigated
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• Environmental degradation from effluent backwash much greater
with storm surge over individual failing septic systems than over
proposed closed STEP sewer system
• Participate in FEMA’s Community Rating System
• Employ CRS activities
• Evaluate feasibility of land acquisition of vulnerable properties
Climate Change Risks Mitigated
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• Plan for mobilizations of EMS services
• Kent Island can be evacuated within 24 hours
• DES will begin advanced notifications 7 days prior to a potential
threat that may result in an evacuation
• Reverse notification system “Everbridge” and other media
sources will be used to notify and provide frequent updates
• EOC will be activated and a decision to evacuate will be made at
least 2 to 3 days prior to a potential threat
Climate Change Risks Mitigated
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System Alternatives
Selecting the Right Sewer System
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• Vacuum Sewers (majority of connections in SKI are vacuum
sewers)
• Gravity Sewers
• Grinder Pump Low Pressure Sewers
• Septic Tank Effluent Pumping (STEP) Low Pressure Sewers
Choosing a System Type
Selecting the Right Sewer System
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Vacuum Sewers
• Vacuum Pit at each house
• Solids handling vacuum sewer mains, laid below frost line in saw-tooth pattern
• Wastewater collected at Central Vacuum Pump Stations
• Sewage is then pumped to WWTP
• Little to no storage in Vacuum Pit –problems in pit are an emergency
• Vacuum Pump Stations are expensive to build, require property purchase and regular maintenance
Choosing a System Type
Selecting the Right Sewer System
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Gravity Sewers
• 4” or 6” lateral pipe from home to gravity sewer
collection main
• Gravity sewer collection main is minimum 8”
diameter, typically 8’ to 15’ or deeper below
grade, laid at a constant downslope
• Manholes required throughout collection system
• Large Main Pumping Stations required
• Gravity sewers are not water tight (subject to
infiltration and inflow (I/I))
• Construction is very expensive and highly
disruptive
• Regular maintenance required at Main
Pumping Stations and to control I/I
Choosing a System Type
Selecting the Right Sewer System
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Grinder Low Pressure Sewers
• Grinder Pump Basins at each house
• Grinder Pump grinds solids, fats, oils and greases into a slurry
• Grinder pump then pumps slurry through small diameter low pressure sewer mains to WWTP
• Must maintain minimum scour velocity to keep main unclogged and free flowing
• Little to no storage in Grinder Pump Station – problems in pump station are an emergency
• Grinder pumps and cutters require maintenance
Project SystemSTEP System On-lot Component Overview
• Solids are retained on site
• Minimum of 24-hours of storage
in the interceptor tank
• Only clear septic tank effluent is
pumped to the treatment plant
• Low installation costs
• Low energy use
• Simple to operate and maintain
Project SystemSTEP System On-lot Component Overview
• Watertight, 1,000 or 1,500 Gallon Septic
Tank
• Effluent Pumping package
– Pump vault
– High-head effluent pump
– filter cartridge
– Float assembly
– Discharge assembly
– Splice box
• Control Panel
Project SystemSTEP System On-lot Component Overview
High-Head Effluent Pump
• Non-corroding stainless steel
• Typically 115V
• Lightweight; under 30 pounds
• Long life; 20 to 30 years
• Easy to maintain
• 10-year warranty
Project SystemSTEP System Low Pressure Sewer Component Overview
• Shallow burial depth
• Laid to contour of land
• Low minimum velocities
• No oversized designs (due to little I/I)
• Low operation and maintenance costs
EDUs QpPipe Size,
Inches
Head Loss,
ft/1000 ft
10 20 1 1/4 35 +
100 65 2 54 +
500 265 4 32 +
1000 515 6 16 +
• Uses directional drill technology (HDD)
• Closed system minimizes I & I
• Eliminates need for intermediate pump stations
• Provides emergency storage during power outages
• Service call issues are minor (isolated to individual home vs. hundreds of
homes)
• Easy to pinpoint and correct problems
• Pumps are economical, yet robust
• Use of seamless concrete tanks
• Adaptable to varying site conditions
• Can be integrated into existing sewer infrastructure
• Abuses stay in septic tank
Project SystemSTEP System Advantages
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• Thousands of Orenco
Effluent Sewers have
been installed for
Municipal and
Commercial projects in
virtually every U.S. state
and Canadian province.
• Systems with up to ~
4,000 connections
Project SystemResearch into Other Communities with STEP Systems
Project SystemResearch into Other Communities with STEP Systems
• 35+ years of documented system performance
– Glide, OR, 1,100+ connections, installed in 1980
• Officials at Queen Anne’s County visited similarly sized systems
– Yelm, WA, 1,100; Lacey, WA, 4,000+; Montesanto, WA, 2,000; Coborg, OR, 400
• Other Regional examples and number of connections
– Northern: Southwest Barry County, MI, 1000+
– Mountain: Missoula, MT, 2000
– Central: Bucyrus, KS, 80
– Southwest: Penn Valley, CA, 240
– Southeast: Ariton, AL, 340
– Northeast: Hillsdale, NY, 130
– Northwest: Camas, WA, 2,900
Phase 1 - Kent Island Estates & Romancoke
Construction contracts awarded August 2016
Construction is now underway!
• STEP systems contract #16-01
• Transmission main contract #16-02
• Community mains contract #16-03
Community public outreach continuing
SKI Current Status
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• Estimated total cost of infrastructure: $50 million
• Phase 1 cost: $32 million
• State Revolving Loan with 30-year term
• Assessments will be levied as work is completed
• BRF offsets expense to existing homes: $10,000 per home
• Vacant lots pay EBP charge: $25,600
• Final cost to homeowners: $100/month
• Final cost to vacant lot owners: $159/month + allocation fee with an
option to defer for up to 10 years
Financial Parameters
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Queen Anne’s County Department of Public Works
Todd R. Mohn, PE
Director
www.skisewer.com
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Julie Barown, P.E.
Northeast Regional Engineer
Orenco Systems, Inc.
www.orenco.com
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