HomeMy WebLinkAboutSouth Hilo Sanitary Landfill Final Closure PowerPoint PresentationCounty of Hawai'i
Department of Environmental Management
Solid Waste Division
South Hilo Sanitary Landfill
Final Closure
District of South Hilo, Island of Hawaii, Hawaii
TMKs (3) 2-1-013: 152, 156, and 162
November 7, 2017
Aupuni Center
November 8, 2017
West Hawai'i Civic Center
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South Hilo
Sanitary Landfill
The South Hilo Sanitary Landfill
(SHSL) is an unlined municipal
solid waste landfill comprising
41.3 acres at the eastern edge
of Hilo.
Located on land owned by the
State of Hawai'i and under the
control and management of the
County of Hawaii for sanitary
landfill purposes under
Executive Order.
Existing Landfill Capacity
SHSL is expected to reach its permitted maximum capacity in
approximately 1.5 years based on the available airspace and
current daily loads.
An expansion permit would be required for continued operation
of the landfill beyond current capacity.
When capacity is reached, the SHSL must be closed in
compliance with state and federal laws, rules, and regulations.
Regulatory Requirements
Resource Conservation and Recovery Act (RCRA) Subtitle D
(40 CFR Parts 257 to 258) requires:
Preparation of a closure plan.
Installation of a final cover system that is designed to minimize
infiltration and erosion.
Preparation of a post -closure plan.
Post -closure monitoring and maintenance for 30 years.
Expansion/New Landfill Constraints
Various options to expand the existing landfill or find an
alternative site in East Hawai'i have been explored. There are
significant constraints:
Leachate management — Subtitle D Federal regulations require
the collection, treatment, and proper disposal of landfill leachate.
The existing landfill is unlined which does not meet current
federal regulations. Since East Hawaii in general is a region of
significant rainfall, leachate volumes would be high and
treatment options costly.
Permitting of an expansion at a landfill site or establishment of a
new landfill is a multistep, multiyear process with an uncertain
outcome.
Expansion/New Landfill Constraints
Subtitle D, Location Restrictions, states that owners or operators
of new municipal solid waste landfills and lateral expansions that
are located within 10,000 feet of any airport runway end used by
turbojet aircraft must demonstrate that the units are designed
and operated so that the landfill does not pose a hazard to
aircraft.
Proposed Action
Proposed improvements consist of:
Installing a final cover system on the top and side slopes of the
landfill;
Installing a new passive landfill gas venting system; and
Constructing a new storm water detention and infiltration basin, and
other storm water management structures.
Prior to installation of the cover, the landfill will be slightly regraded
to the final design grades to manage storm water runoff, stabilize
the slopes, and prevent adverse effects of Tong -term settlement.
A maintenance access road will be provided for post closure
maintenance activities.
A perimeter swale will be provided to facilitate control and
containment of storm water runoff onsite.
Cover Alternatives Analysis
The criteria for selecting the final cover alternatives that can
potentially be deployed included:
Does it meet regulatory requirements for infiltration?
Does it meet engineering design requirements for
constructability, slope stability and Tong -term performance?
Does it meet physical site specific performance parameters for
rainfall, wind, and natural exposure?
Is it economically feasible?
What are post -closure repair and maintenance requirements?
Cover Alternatives Analysis
Alternative 1: Polyethylene Geomembrane Overlain by
Engineered Synthetic Grass
INTEGRATED STUDS FOR
HIGH CAPACITY DRAINAGE
GIEDMEMEIRANE —
!MIGRATED SPIKES TO
ENSURE HIGH FRICTION
SYNTHETIC GRASS
GRADING LAYER
DETAIL 1: SIDE SLOPE
4 v 'NUS S,19aAsE=-. -.=--:
SND LAYER WITH
FX/NDING AGENT
WOVEN
GEOTEXTILES
,
1.0.
INTERMEDIATE COVER
471
SYNTHETIC GRASS/GEOMEMBRANE COVER DETAIL
NOT TO SCALE 'JOT `::ALE
lI(RQSPIKE LINER
SAND LAYER
WOVEN
GEOTEXTILES
ja1,111.730111-r-
ASTE
DETAIL 2: TOP DECK
SYNTHETIC CRASS/GEOMEMBRANE COVER DETAIL
Cover Alternatives Analysis
Alternative 1: Polyethylene Geomembrane Overlain by
Engineered Synthetic Grass
Advantages Disadvantages
• Geomembrane layer is essentially • Generates more storm water runoff
impermeable. than other alternatives.
• Shorter construction time. • Sand layer and binder mixture
• Reduced post closure maintenance required and must be reapplied
costs. periodically.
• Will not provide a habitat for birds • Repair and replacement of the
that may pose a hazard to air cover may eventually be required.
navigation.
Cover Alternatives Analysis
Alternative 2: Combination of Evapotranspiration for the Side
Slopes and a Geosynthetic/Soil Composite for the Top Deck
PLANT COVER
vl
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50IL LAYER
INTERMECIATE
COVER
DETAIL 1: SIDE SLOPE - EVAPOTRANSPIRATION COVER
1. 21- si:ALE
T
PLANT COvER
— TOP SOIL
- VECETATNE SLIE3LLIL
1607/SY GEOTExTILE
60 SAIL HDPE
'VC
/R ` ` GEOMEMBRANE LINEk
1 6oz/SY CEOTExTILE
-- INTERMEDIATE
COVER
DETAIL 2: TERRACE AND TOP DECK
GEOSYNTHETIC/SOIL COMPOSITE COVER
NST T_ CALE
Cover Alternatives Analysis
Alternative 2: Combination of Evapotranspiration for the Side
Slopes and a Geosynthetic/Soil Composite for the Top Deck
Advantages Disadvantages
• Landfill gas venting system may not • Still needs additional review for
be necessary. regulatory approval.
• Lowest storm water runoff than any • May be vulnerable to significant
other option. erosion during vegetation
• Infiltration lower than prescribed establishment period.
cover. • Intensive and challenging
cover/vegetation maintenance.
• Potential habitat for wildlife.
Grass on the side slopes compared to
engineered synthetic grass on the top deck
Cover Alternatives Analysis
Alternative 3: U.S. Environmental Protection Agency (EPA)
Subtitle D Prescribed Cover System
RANT COVER
TOP SOIL
— BENTONITE AMENDED SOIL
(K< 1)(10-5 cm/sec)
INTERMEOIATE
.rte COVER
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PRESCRIBED COVER DETAIL
NOT T: .Sc.LE
Advantages
• Straightforward permitting process.
• No veneer stability issues on side
slopes
Disadvantages
• Need to amend soils with bentonite to
meet minimum permeability
requirements.
• Possible variability of cover soil
conditions.
• Challenging to meet soil compaction
requirements.
• Intensive and challenging maintenance
requirements.
Cover Alternatives Analysis
The three alternatives were evaluated on the basis of:
Closure construction cost
Overall site work cost
Technical feasibility
Construction complexity
Specialized expert labor and equipment
Post -closure care
Prior EPA Region 9 approval for similar closure systems
FAA and State DOT Airports Division acceptance
Cover Alternatives Analysis
Preferred Alternative:
Alternative 1— Polyethylene Geomembrane Overlain by
Engineered Synthetic Grass
Closed Landfill with Engineered Synthetic
Grass over Geosynthetic Membrane in Florida
Project Cost and Schedule
Cost —Approximately $20 million.
Schedule —
Submit
Final
Closure Plan
to DOH
Award NTP issued
October
I Cg Construction
completed
November
June 2018 August 2018
Out to bid Bid opening
2018 2018 May 2020on
Impacts and Mitigation Measures
Temporary Impacts:
Closure construction activities may result in some temporary soil
erosion, noise level, air quality, and water quality impacts.
Impacts will be mitigated by implementation of best
management practices and compliance with county, state, and
federal rules and regulations.
No significant impacts on federally -listed endangered or
threatened species is anticipated. Conservation measures will
be incorporated into the project plans and specifications to
avoid or minimize impacts during construction.
No impacts on historic or archaeological resources is
anticipated.
Impacts and Mitigation Measures
Decomposition of the organic material in the landfill will result
in the release of landfill gas (roughly 50% methane and 50%
carbon dioxide with trace amounts of non -methane organic
compounds).
These levels will be the same
with or without the project.
Passive gas vents will be
installed to allow venting of
landfill gas.
Coverage of Passive Gas Vents
Impacts and Mitigation Measures
Release of landfill gas (cont.)
These levels will be the same with or without the project.
Six (6) gas monitoring wells are installed along the perimeter of
the landfill to monitor landfill gas concentrations.
To date, no environmental releases in exceedance of state and
federal regulations have been detected.
These wells will continue to be monitored for 30 years after the
landfill closes in compliance with RCRA Subtitle D and HAR 11-58.
It is anticipated that landfill gas levels will reduce over time and
approach zero.
Impacts and Mitigation Measures
Additional storm water runoff will be generated by the
installation of a geomembrane layer.
The additional runoff will be
controlled and contained.
A new detention and
infiltration basin is
proposed at the northwest
corner to accommodate the
additional runoff.
No leachate generation from
storm water infiltration as
the geomembrane layer is
impermeable.
New Detention Basin
Impacts and Mitigation Measures
Long-term impacts on groundwater quality will continue to be
monitored.
Groundwater beneath the SHSL is monitored by four monitoring
wells, one upgradient and three downgradient.
To date, no environmental releases in exceedance of state and
federal regulations have been detected.
These wells will continue to be monitored for 30 years after the
landfill closes in compliance with RCRA Subtitle D and HAR 11-58.
Runoff with traditional cover (left) vs. engineered synthetic turf (right)
MSW Destination
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Closure Operational Plans
Current plan is to consolidate certain waste at the East Hawaii
Regional Sort Station in Hilo where reusable or recyclable
materials will be removed from the waste stream, and residual
waste will be directed to the WHSL in Pu'uanahulu.
Should the logistics and mechanisms for this plan not be in
place by the time SHSL accepts its final load, county trailers,
commercial haulers and other government agencies may be
required to haul waste directly to the WHSL.
Secondary Impacts and
Mitigation Measures
Increased impacts on traffic, noise levels, and air quality are
anticipated to be negligible.
Traffic study by Wilson Okamoto Corporation (October 2017)
concluded that the traffic Level of Service (LOS) on all routes is
not degraded as a result of the project.
Waste will be properly contained during transportation as
required by law.
Vehicles transporting waste will be advised to route directly to
WHSL.
Continue current driver training program.
Continue existing waste diversion efforts and exploring new
strategies intended to reduce the amount of waste disposed at
landfills.
Mahalo
The Draft EA is available online for review at:
http://oegc2.doh.hawaii.gov/EA EIS Library/2017-10-23-HA-DEA-South-Hilo-Landfill-Final-
Closure.pdf
To submit comments on the Draft EA, please send to:
Department of Environmental Management
County of Hawai'i
Attn: Gene Quiamas
345 Kekuanaoa Street, Suite 41
Hilo, HI 96720
swd@hawaiicounty.gov
with a copy to:
Wilson Okamoto Corporation
Attn: Rebecca Candilasa
1907 South Beretania Street, Suite 400
Honolulu, HI 96826
rcandilasa@wilsonokamoto.com