By: Martin Lee, Jey Hwan Lee, Wilson Leung. Background Former HKIA, replaced in 1998 ▫World’s busiest in 1997 ▫Overcrowded World famous difficult landings.

By: Martin Lee, Jey Hwan Lee, Wilson Leung

Background• Former HKIA, replaced

in 1998▫ World’s busiest in 1997▫ Overcrowded

• World famous difficult landings into runway 13▫ North end: 6 stories high

buildings▫ Often used due to

prevailing wind directions▫ Visual approach required

After retiring…• Land used for

development▫ Sports Stadium▫ Cruise Terminal▫ Hotel▫ Etc…

From Maunsell AECOM Asia Ltd

• Contaminated land detected:▫ Ex-Government Flying

Services (ex-GFS)▫ South of North Apron▫ South Apron

Causes & Hazards• Causes:

▫ Underground fuel hydrant leakages▫ Oil Companies Tank Farm leakages▫ Workers pouring fuel over pavement

• Contaminants:▫ Total Petroleum Hydrocarbon (TPH)

Toluenes and Xylenes (BTEX) Methane (in explosive concentrations)

▫ Heavy Metals Polyaromatic Hydrocarbons Polychlorinated Biphenyls

• Hazards:▫ No explosive hazard as concrete layer seals underground

contaminants from open air▫ Toluene causes Nausea▫ Xylenes cause headaches, lung issues, muscle co-ordination

problems

Remediation Options

•Bioremediation•Soil Vapour Extraction•Air Sparging•Dual-phase extraction•Low-Temp. Thermal Desorption•Chemical Oxidation•Bio-pile•Capping•Cement stabilisation/solidification•Landfarming

Remediation Adopted

1. Soil Vapour Extraction (SVE)▫ Air Sparging

2. Bio-pile3. Bioremediation

• Mitigating Environmental Effects:1. Vapour Emission Treatment Systems2. Oil Interceptors3. Noise Silencers

Soil Vapour Extraction/Air Sparging - Method

• Method1. Drill Wells into soil

above W.T.2. Apply Vacuum

Pressure3. Underground vapour

pulled out4. Air treatment system

collects vapours5. Separates

contaminants from air6. Contaminants

disposed safely

Soil Vapour Extraction/Air Sparging - Application• Pros:

▫ Simple to install & maintain

▫ Safe and natural process▫ Minimal disturbances to

soil profile

• Cons:▫ Empirical Design, no

theoretical equations▫ Doesn’t deal with soils

under W.T.▫ Cannot deal with low

conc.

• In-situ• Removes subsurface

contaminants, such as Volatile Organic Compounds (VOC)

Bio-pile - Method• Method

1. Identify soil characteristics

2. Excavate soil3. Mix excavated soil with

soil amendments4. Heap contaminated soils

into piles5. Enclose the

contaminated soil6. Contaminants removed

through controlled aerobic microbial activity

Bio-pile - Application• Pros:

▫ Simple to design and implement

▫ Short treatment times (6 months – 2 years)

▫ Relatively cheap (30-90 USD/ton of contaminated soil)

▫ Closed system (vapor emissions controlled)

• Cons:▫ Require a large land area for

treatment▫ Not effective for high

constituent concentrations ▫ Volatile constituent tend to

evaporate rather than biodegrade during treatment

• Ex-situ• Used to reduce concentrations

of petroleum constituent products through biodegradation

Bioremediation - Method1. Wells injected to

groundwater level2. Calcium Nitrate solution

is pumped into soil through wells

3. Oxygen and water is occasionally supplied to wells

4. Solution is spread throughout contaminated areas

5. Extraction wells collects groundwater for further water treatment.

Bioremediation - Application• In-situ• Injection of calcium nitrate to promote growth of

NRSOB• Eliminates odour from degradation of organic

compounds caused by SRB• Pros:

▫ Natural process▫ Easily conducted on-site▫ Efficient, Satisfactory result, short time ▫ Little or acceptable environmental impact▫ Low cost

• Cons:▫ Requires constant monitoring to ensure effectiveness▫ Takes a little longer than some techniques▫ Little knowledge on its long term effect on areas of

multiple contamination

Conclusion• First and largest of its kind in HK

▫ No effective legislation to guide decontamination in right direction

• Combined methods protected 700,000 people incl. residents & workers

• Effectively cleaned almost 19000m2 of contaminated land