ABALONE COVE LANDSLIDE

ABATEMENT DISTRICT(ACLAD)

Board of Directors Sharon Nolan Mary Sheridan Neil Siegel Emily Vaughan Robert Douglas, ChairmanMgr. Well Operations Daphne ClarkSecretary Sandy Marshall

• Geological Hazard Abatement (GHAD) District– created by the Beverly Act (SB1195) of l979;

ACLAD was the first district formed (1981)• Governed by a Board of Directors (5 persons)

elected from property owners in the District– Assisted by a Secretary and Manager of Well

Operations • ACLAD assesses property owners in the

district to pay for construction and maintenance of abatement measures– Example: Dewatering wells

• GHADs are a means by which homeowners can “help themselves”

ABALONE LANDSLIDE ABATEMENT DISTRICT

(ACLAD)

Abalone Cove Landslide

Altamira ShaleBasalt

SLIDE SURFACE (IMPERMEABLE LAYER)

Rain

GROUNDWATER BUILDUPS WITHIN LANDSLIDE

FRACTURES/FISSURES - CONDUITS FOR INFLITRATING WATER

RESULT:•INCREASE WEIGHT•INCREASE PORE PRESSURE•MOVEMENT

GROUNDWATER AND LANDSLIDES

?

Toe

Head

TRAPPED WATER

Wells added after l985

ACLADDewatering

Wells2006

1980 wells

WW6WW1WW14

WW12WW13

WW11WW8

WW16

WW15

WW17

Abalone CoveLandslide

WW18

WW19

WW9

WW20

WW5

WW2 WW4

WW7

WW10WW3

(Aver. daily production forFebruary and September)

Well Production 1980-2006Aver. Production approx.150,000 gals/day

First wells drilled

Upslope wells added

WW1

WW14

WW12

WW13

WW15

WW16

WW8

WW11

WW17

WW6

WW7

WW3

WW2

WW4WW

9

WW5

WW19

WW18

Abalone Cove Landslide >6,000 gal/day

1-6,000 gal/day

<1,000 gal/day

>20,000 gal/day

ACLADOriginal set of wells

1980-81

Abalone Covelandslide

WW2

WW3

WW5 REDRILL

Major Maintenance

Project

Proposed

Completed

WW1

WW6

Aver=15 in/yr

RAINFALL ANDWELL PRODUCTION

WELL PRODUCTION

RAINFALL

WET YEARS

DRY YEARS

RAINFALL THRESHOLD21-23 in/yr

RAINFALL AND MOVEMENT IN THEABALONE COVE LANDSLIDE

WET YEARS

DRY YEARS

CREEP (mm/yr rate)

ENSO cycles (5-8 yrs)

Highly Developed

Sparsely Developed

INCREASERAINFALL

WITH ELEVATION

40% increase

SUMMARY

• ACLAD Dewatering wells currently pumping ~ 200,000 gals/day; nearly 300 acre-feet water annually

• Since l980, water table elevations have dropped:– 25-60+ feet in Abalone Cove Landslide wells– 8-10 feet in upslope well

• Creep (mm/yr rate) in Abalone Cove Landslide occurs when rainfall totals >~22 inches/year

• Need to rehab older wells and drill new wells in upslope areas

(wet years)

ABALONE COVE LANDSLIDE ABATEMENT DISTRICT

(ACLAD)

1980-2006: TWENTY-SIX YEARS OF

PROGRESS AND SERVICE

• DEWATERING WELLS• GPS MEASUREMENTS

ACLADProduction

Wells2006

>6,000 gal/day

1-6,000 gal/day

<1,000 gal/day

WW1

WW14

WW12

WW13

WW15

WW16

WW8

WW11

WW17

WW6

WW7

WW3

WW2 WW4WW9

WW5WW19

WW18

Abalone Cove Landslide

>20,000 gal/day