Community Forum Berm Mitigation at Ascon Landfill April 2, 2020 De - - PowerPoint PPT Presentation

▶
community forum berm mitigation at ascon landfill april 2
SMART_READER_LITE
LIVE PREVIEW

Community Forum Berm Mitigation at Ascon Landfill April 2, 2020 De - - PowerPoint PPT Presentation

Aug 01, 2023 178 likes •579 views

Community Forum Berm Mitigation at Ascon Landfill April 2, 2020 De pa rtme nt o f De pa rtme nt o f T T o xic Sub sta nc e s o xic Sub sta nc e s 1:30 p.m. to 3:30 p.m. Co ntro l Co ntro l SITE MITIGATION AND RESTORATION PROGRAM

slide-1
SLIDE 1

De pa rtme nt o f T

  • xic Sub sta nc e s

Co ntro l De pa rtme nt o f T

  • xic Sub sta nc e s

Co ntro l

Community Forum Berm Mitigation at Ascon Landfill April 2, 2020 1:30 p.m. to 3:30 p.m.

SITE MITIGATION AND RESTORATION PROGRAM DEPARTMENT OF TOXIC SUBSTANCES CONTROL (DTSC)

slide-2
SLIDE 2
  • https://primetime.bluejeans.com/a2m/live-event/tjxabyex

Click on Join Meeting: Call in: (415) 466-7000 Enter Passcode: 4768832

  • Community Forum is being recorded.
  • After one week you may view it at: YouTube channel

(DTSCGreen).

L OGIST ICS

4/2/2020 Department of Toxic Substances Control

slide-3
SLIDE 3
  • All attendees' mics are muted
  • Click icon on right hand side to post your

questions

  • We will respond to the questions during the Q&A

session

  • Technical difficulties – let us know

Guidelines for Today’s On-Line Community Forum

4/2/2020 Department of Toxic Substances Control

slide-4
SLIDE 4

Agenda

4/2/2020 Department of Toxic Substances Control

Welcome and Introductions

  • Maya Akula, DTSC Public Participation Supervisor

Ascon Project Overview

  • Grant Cope, Deputy Director, Site Mitigation & Restoration Program

Why the Emergency Berm Repair Work?

  • Ed Morelan, Branch Chief, Site Mitigation & Restoration Program

Next Steps & Closing Remarks: Grant Cope, Deputy Director Questions and Answers Session, Maya Akula, DTSC Public Participation Supervisor Wrap Up

slide-5
SLIDE 5

Grant Cope Deputy Director, DTSC Site Mitigation & Restoration Program

Department of Toxic Substances Control 4/2/2020

slide-6
SLIDE 6
  • DTSC’s mission is to protect California’s

people and environment from harmful effects

  • f toxic substances
  • Responsible for overseeing the investigation

and cleanup of contaminated properties

  • Lead Agency for Ascon Landfill Project

DTSC’s Role

4/2/2020 Department of Toxic Substances Control

slide-7
SLIDE 7

Community Concerns and Enhanced Safeguards

Department of Toxic Substances Control 4/2/2020

Community Concerns

Additional Safeguards

  • Health concerns
  • Dust
  • Odors
  • Storm water runoff
  • Constructed new fence height to 16

feet

  • Additional off-site air monitoring
  • Technical Advisor
  • Concrete tested for asbestos
  • Tenting and enclosure system at

permitting stage with AQMD

slide-8
SLIDE 8

Why DTSC Recommends Emergency Berm Repair to Protect Public Safety

  • Berm (slope) on Hamilton Ave. showing signs of

failure

  • Tension cracks
  • “Hummocky” surface at its base

4/2/2020 Department of Toxic Substances Control

slide-9
SLIDE 9

Safety Threats of a Landslide

  • Contaminated material could enter Hamilton Avenue
  • Could result in uncontrolled release of VOCs, odors & dust
  • Emergency response would be needed
  • Rains increase chances of failure

4/2/2020 Department of Toxic Substances Control

slide-10
SLIDE 10

Safety is Our Number One Priority

DTSC Recommends:

  • Minimal rate of excavation – 92% smaller that last year’s average
  • Maximum amount of dust and odor controls
  • Further reduction if odors effect people sheltering in place
  • Stop excavation if odors cannot be controlled
  • Work conducted while Edison High School is out of session

4/2/2020 Department of Toxic Substances Control

slide-11
SLIDE 11

92% Smaller rate than last year

2019 2020

600 Cubic Yards per Day

50 Cubic Yards per Day

200 Cubic Yards per Day

4/2/2020 Department of Toxic Substances Control

slide-12
SLIDE 12

Ed Morelan, PG, CEG Branch Chief, DTSC Cypress Cleanup Branch

Department of Toxic Substances Control 4/2/2020

slide-13
SLIDE 13

Background

  • Tension cracks on the embankment – December 31
  • DTSC directed Project Navigator to monitor the tension cracks
  • Monitoring found additional cracks – February 6
  • DTSC directed Project Navigator to develop proposed actions –

including emergency response

  • Estimated a Medium to High Potential Risk of Slope Failure

4/2/2020 Department of Toxic Substances Control

slide-14
SLIDE 14

De pa rtme nt o f T

  • xic Sub sta nc e s

Co ntro l De pa rtme nt o f T

  • xic Sub sta nc e s

Co ntro l

slide-15
SLIDE 15

TENSION CRACKS IDENTIFIED (Looking West)

4/2/2020 Department of Toxic Substances Control

slide-16
SLIDE 16

TENSION CRACKS IDENTIFIED (Looking East)

4/2/2020 Department of Toxic Substances Control

slide-17
SLIDE 17

Interim Measures

  • Slope covered with plastic when it rains
  • Additional barriers on south side of Hamilton
  • Initial visual observations of cracks
  • Subsequent monitoring with electronic devices

4/2/2020 Department of Toxic Substances Control

slide-18
SLIDE 18

INITIAL OPTIONS EVALUATED

  • Toe Buttress with Soil
  • Slope Flattening with Soil
  • Slope Flattening with Soil and Mechanically Stabilized Earth
  • Toe Buttress with Retaining Wall
  • Slope Flattening Under a Tent
  • Slope Flattening by Managed Excavation

Department of Toxic Substances Control 4/2/2020

slide-19
SLIDE 19

Department of Toxic Substances Control 4/2/2020

Toe Buttress with Soil

slide-20
SLIDE 20

Department of Toxic Substances Control 4/2/2020

Slope Flattening with Soil

slide-21
SLIDE 21

Department of Toxic Substances Control 4/2/2020

Slope Flattening with Soil and Mechanically Stabilized Earth

slide-22
SLIDE 22

Department of Toxic Substances Control 4/2/2020

Toe Buttress with Retaining Wall

slide-23
SLIDE 23

Department of Toxic Substances Control 4/2/2020

Slope Excavation Under a Tent/Enclosure

slide-24
SLIDE 24

Department of Toxic Substances Control 4/2/2020

Managed Slope Excavation

slide-25
SLIDE 25

Limitations of Initial Six Options

  • Any disturbance to the slope could trigger a failure
  • Engineered structures (retaining walls, buttresses, MSE

walls) require geotechnical study and engineering design

  • Tent fabrication and permitting review could delay work for

several months (assuming that permit is approved)

4/2/2020 Department of Toxic Substances Control

slide-26
SLIDE 26

Subsequent Options Identified

  • DTSC directed that additional options be evaluated -
  • Especially those that involve limited slope disturbance
  • Additional options reviewed included soil “nailing”, in-

place soil stabilization, and hybrids of the initial options

4/2/2020 Department of Toxic Substances Control

slide-27
SLIDE 27
  • Utilizes a tie-back system to hold back the slope from collapsing
  • Requires stable and uniform soil to anchor the “nails” or tie backs
  • Ascon soils are low-strength and very likely unable to support “nails”
  • Concrete and asphalt could prevent driving of “nails”
  • Extended time frame required for Design and Mobilization

Department of Toxic Substances Control 4/2/2020

Soil Nailing

slide-28
SLIDE 28
  • Strengthening the soils by mixing with cement
  • Drill boreholes within landfill materials to create concrete

“columns”

  • Added weight and vibration while the concrete/soil mixture

is placed increases failure risk

  • Extended time frame required for Design and Mobilization

Department of Toxic Substances Control 4/2/2020

In-Place Soil Stabilization

slide-29
SLIDE 29

Combined or Partial Options

  • Project Consultant directed to evaluate partial performance
  • f the original options, or combinations of them
  • Combinations were considered viable, but still subject to

geotechnical evaluation / engineering design

  • Decreased volume of excavation reduces the risk of slope

failure – but doesn’t eliminate it

4/2/2020 Department of Toxic Substances Control

slide-30
SLIDE 30

Limiting Factors of Additional Options

  • All require geotechnical and engineering evaluations
  • In-place Stabilization could actually increase the risk of

slope failure

  • Partial excavation before getting to a 5:1 slope angle:
  • Still involves excavation, and does not definitively eliminate

the risk of a slide

4/2/2020 Department of Toxic Substances Control

slide-31
SLIDE 31

Slope Stabilization Recommendation

  • All options evaluated have drawbacks – but we do need to act
  • Quickest and most certain approach: minimized excavation rate –

“Managed Slope Excavation”

  • Would only be approved with a dramatically slower rate of excavation
  • Maximum amount of controls over odors and dust (foam, soil, and

plastic covering)

4/2/2020 Department of Toxic Substances Control

slide-32
SLIDE 32

92% Smaller rate than last year

2019 2020

600 Cubic Yards per Day

50 Cubic Yards per Day

200 Cubic Yards per Day

4/2/2020 Department of Toxic Substances Control

slide-33
SLIDE 33

DTSC’s Recommendation: What you can expect

  • Conduct minimized excavation rate
  • Ensures a maximum amount of controls over odor

and dust

  • Barring any additional information - limited

excavation would be authorized very soon

4/2/2020 Department of Toxic Substances Control

slide-34
SLIDE 34

Critical Differences from Past Excavations

  • Dramatically limit daily excavation rate
  • Close down the excavation if odors cannot be controlled
  • Get as close to the 5:1 angle as possible to reduce risk of a

slope failure

  • Direct the work to occur while Edison High School is closed

4/2/2020 Department of Toxic Substances Control

slide-35
SLIDE 35

Safety Measures to Protect the Community

Controlled rate of excavation DTSC staff on-site when work is conducted Real-time Dust and Odor Monitoring Multiple Approaches to Odor Control

4/2/2020 Department of Toxic Substances Control

slide-36
SLIDE 36

Future Considerations

4/2/2020 Department of Toxic Substances Control

slide-37
SLIDE 37

For More Information on Ascon Project

  • Contact: Safouh Sayed, DTSC Project Manager

Safouh.Sayed@dtsc.ca.gov (714) 484-5478

  • DTSC website:

https://dtsc.ca.gov/smrp-projects/ascon-landfill-site/

  • DTSC EnviroStor:

https://www.envirostor.dtsc.ca.gov/public/profile_report?glob al_id=30490018

4/2/2020 Department of Toxic Substances Control

slide-38
SLIDE 38

DTSC Ascon Team

  • Robert Senga

Supervising Environmental Scientist, DTSC Robert.Senga@dtsc.ca.gov (714) 484-5436

  • Safouh Sayed

Project Manager, DTSC Safouh.Sayed@dtsc.ca.gov (714) 484-5478

  • Maya Akula

Public Participation Supervisor, DTSC Maya.Akula@dtsc.ca.gov (714) 484-5416

  • Gamaliel Ortiz

Public Information Officer, DTSC Gamaliel.Ortiz@dtsc.ca.gov (916) 327-4383

  • Ed Morelan, PG, CEG

Branch Chief, DTSC Alexander.Morelan@dtsc.ca.gov (714) 484-5440

Department of Toxic Substances Control 4/2/2020

slide-39
SLIDE 39

4/2/2020 Department of Toxic Substances Control

Questions & Answers