1 background

1.1 Introduction

1.1.1.1 Redevelopment of the Yau Tong Marine Lots (the Site) is being proposed by a consortium of developers. The first stage of the re-development involves the decommissioning of the existing operations which includes shipyards amongst other operations, and the second stage reclamation of the Yau Tong Bay. Both stages are classified as designated projects under the EIA Ordinance.

1.1.1.2 As per the requirements of the EIA Ordinance, a study brief was applied for in August 1998 for the proposed decommissioning of shipyards and reclamation works. The study brief issued by EPD in October 1998 (Brief no.: ESB-0010/1998) prescribed that a land contamination impact assessment should be conducted as part of the EIA study. A Contamination Assessment Plan (CAP) has then been compiled which included methodologies for detailed site investigation (S.I.) works involving the sampling and analysis of soil and groundwater to detect for any signs of contamination. The CAP has been endorsed by EPD earlier this year.

1.1.1.3 The said S.I. works as detailed in the CAP have been completed except for sites that are inaccessible to the Consultant. The inaccessible sites shall be assessed when the sites become available. For the purpose of this RAP, results from the accessible lots are extrapolated to give an estimate on the likely extent of contamination. Reference is also made to Section 8 of this report on Future Works.

1.1.1.4 This Remediation Action Plan (RAP) contains a section on Contamination Assessment Report (CAR) covering the findings from the S.I., as well as having outlined the methodology of site remediation work required for the Yau Tong Marine Lots which were found to be contaminated.

2 Contamination Assessment

2.1 Overview

2.1.1.1 Site investigation and laboratory analyses on the samples collected were carried out in accordance with the approved CAP in early 1999. The following sections report on the site sampling works and subsequent results of laboratory analysis for each of the individual marine lot that was in concern.

2.2 Parameters Considered

2.2.1.1 The sampling and testing schedule for site investigation at the concerned marine lots was detailed in the CAP and will not be repeated here. Due to a rich site history of the marine lots, a comprehensive list of parameters for likely contaminants at the shipyards, motor vehicle repair workshops, and machinery repair works were adopted for each of the site suspected to have been contaminated. Parameters tested were also detailed in the CAP which included:

· Total Petroleum Hydrocarbons, TPH;

· Aromatics (BTEX);

· Polynuclear Aromatics, PAH

· Metals which include Cr, Cu, Ni, Pb, Hg;

· Polychlorinated Biphenyls (PCB);

· Tributyl-Tin (TBT)

2.3 Soil and Groundwater Remediation Criteria

2.3.1 Soil Remediation Criteria

2.3.1.1 The Dutch criteria is considered by EPD as the appropriate set of land contamination assessment standard and has hence been applied to assess the soil condition at the Yau Tong Marine Lots. The Dutch criteria comprise three levels of standards : A, B and C, which are generally interpreted as follows:

· A-level implies unpolluted;

· B-level implies potential pollution present and requires further investigation or remedial action; and

· C-level implies pollution which requires remediation

2.3.1.2 For Yau Tong Bay, the following assessment and remediation criteria have been applied:

· where contaminant levels are found to be less than the Dutch B-level, no action is required; and

· where contamination levels are found to exceed Dutch B-levels, soils will be remediated.

2.3.1.3 Because the Dutch standards do not have explicit criteria for total petroleum hydrocarbons (TPH), the criteria for mineral oil and gasoline have been combined and used as the default TPH standard which will be applied to the Yau Tong Marine Lots. Gasoline is also quoted as a separate parameter due to its difference in physical characteristics from that of mineral oil.

2.3.1.4 The Dutch standards relevant to the Site are summarised in Table 2‑1. A complete list of Dutch standards is provided in Annex I for reference.

Table 2‑1 Dutch Soil Contamination Standards

Parameter	Dutch B-Level (mg/kg)	Dutch C-Level (mg/kg)
Mineral Oil (taken as standard for TPH)	1,100	5,800
Gasoline	100	800
Benzene	0.5	5
Toluene	3	30
Ethybenzene	5	50
Xylenes	5	50
Polynuclear Aromatic Hydrocarbons (PAH)	20	200
Chromium	250	800
Copper	100	500
Nickel	100	500
Lead	150	600
Mercury	2	10
Polychlorinated Biphenyls (PCB)	1	10
Naphthalene	5	50

2.3.2 Criteria for Tributyl-Tin (TBT)

2.3.2.1 Tributyl-Tin (TBT) is a specialised chemical used as anti-fouling agent in paint coated on ships and hence considered a possible contaminant at shipyard sites. TBT was later found to be a toxin to human being and marine animals. It is usually detected in coastal waters and sediments. The Dutch List does not include criteria for TBT in soil and groundwater and hence other reference was sought. The US-EPA has a risk-based concentration (RBC) table for a spectrum of contaminants and the RBC values are quite often referenced as the contamination cleanup standard. The RBC for TBT-Oxide is 11 mg/L for tap water, 610 mg/kg for industrial soil, and 23 mg/kg for residential soil. As the future land use at the concerned sites are mainly residential, 11 mg/L for tap water and 23 mg/kg for residential soil were adopted as the land contamination criteria for groundwater and soil respectively.

2.3.2.2 It should be noted that groundwater in Yau Tong is not used for potable use and RBC for tap water was adopted as a very conservative standard in the absence of other standards.

2.3.2.3 There are a number of reasons supporting the use of TBT-oxide standards instead of TBT. Firstly, according to the Extension Toxicology Network maintained by Cornell University, Michigan State University, Oregon State University, and University of California at Davis, TBT by itself is unstable and will break down in the environment unless it is combined with an element such as oxygen. One of the most common TBT compounds is bis(Tributyltin) Oxide, or TBTO. Furthermore, it has been reported that commercial products of TBT are typically available in the form of bis(Tributyltin) Oxide[1]. For such reasons, it can be deduced that the TBT found at shipyards should predominantly be in the oxide form.

2.3.2.4 On the analysis side, the laboratory analysis method gives a result of total TBT, which has included the predominant TBTO, as well as other forms of TBT that might have existed. Following the argument under paragraph 2.3.2.3 above, the TBT in soil is expected to be largely TBT-Oxide. As such, the standard for TBT-Oxides should be considered applicable.

2.3.2.5 Since the laboratory results for soil and groundwater in determining the concentration of TBT were reported in terms of tin content, i.e. mg/kg Sn in soil or groundwater, the RBC criteria for TBT oxides have been converted to equivalent concentration of tin for comparison with the laboratory results.

2.3.2.6 Given the chemical formula for TBT oxide as C₂₄H₅₄OSn₂, 23mg of TBT oxide (the RBC for TBT oxide) in 1 kg soil is equivalent to 9mg/kg of Tin in soil.

2.3.2.7 Similarly, the RBC for TBT oxide in groundwater is found to be equivalent to 4.3mg/L of Tin in water.

2.3.2.8 Hence, the assessment criteria for TBT oxide, in terms of Sn, in soil and groundwater have been taken to be 9mg/kg and 4.3mg/L respectively.

2.3.3 Groundwater Remediation Criteria

2.3.3.1 The establishment of the stringent Dutch levels for groundwater was based on the assumption that the groundwater may be used for drinking. This is obviously very different from the situation in Hong Kong where in the urban area, groundwater will not be extracted for potable use.

2.3.3.2 Dutch B levels is deemed unnecessary given the fact that the groundwater will not be consumed or used in a manner that will pose a risk to the receptors. As a result, a human health risk assessment was used to derive risk-based criteria for groundwater at the site.

2.3.3.3 The risk assessment was based on human and environmental responses to contaminated land. The risk assessment had taken into account the measured groundwater contaminants level, future land use of the site and potential pathway of exposure. Details of the risk assessment are presented in Annex 3.

2.3.3.4 The source concentration used for each of the parameter is shown below. They are derived from the maximum concentration of that parameter found on site irrespective of their locations. However, if they were not detected, the detection limits were used. Also, chromium is all assumed to be Cr (VI) for conservative assessment.

Table 2‑2 Source Concentrations and Oral Slope Factor/Oral Reference Dose Used for the Risk Assessment

Parameter	Source concentration (mg/L)	Oral slope factor 1/(mg/kg-day)	Oral reference dose (mg/kg/d)
Mineral Oil and Gasoline (TPH)	1.3	N.A.	4.00E-02 to 5.00E+00 [2]
Benzene	2.0E-3	2.90E-02 ³	3.00E-03 [3]
Toluene	2.0E-3	N.A.	2.00E-01 ²
Ethybenzene	2.0E-3	N.A.	1.00E-01 [4]
Xylenes	6.0E-3	N.A.	2.00E+00 ²
Chromium (VI)	3.8E+0	7.30E-03 ²	3.00E-03 ²
Copper	7.2E-1	N.A.	4.00E-02 ²
Nickel	4.6E-1	N.A.	2.00E-02 ²
Mercury	6.0E-3	N.A.	3.00E-04 ³

2.3.3.5 The only pre-requisite to derive a risk based groundwater remediation target (RBSL) for a parameter is that it should have a recognised oral slope factor or oral reference dose. This is the reason why the remediation target for lead cannot be derived this way.

2.3.3.6 The targets for TPH were derived for each of the individual TPH constituents. The remediation targets calculated from the risk assessment was above the limit of solubility in water, therefore the criteria has been specified as No Free Product for TPH.

2.3.3.7 Derived groundwater remediation targets are summarised in Table 2‑3.

Table 2‑3 Derived Groundwater Contamination Targets

Parameter	Remediation Targets(mg/L)
Mineral Oil and Gasoline (TPH)	No Free Product*
Benzene	17
Toluene	520*
Ethybenzene	170*
Xylenes	200*
Chromium (VI)	21
Copper	280
Nickel	140
Mercury	0.081*

“*” Indicates solubility value of that contaminant in water is below the risk-based target concentration, i.e. concentration of the contaminant in water will not exceed the derived target.

3 Contamination Assessment report

3.1.1.1 Soil and groundwater samples taken at each of the Yau Tong Marine Lots that were subject to site investigation were analysed with results summarised in the following sections. Only those samples with contamination level above Dutch ‘B’ level are presented. A detailed breakdown of all the results are given in Annex 2 for reference.

3.2 YTML 5

3.2.1.1 Three sampling points (T5A to T5C) were selected for the site. Only one soil sample at ~0.5m could be taken at location T5A as bed rock was encountered at ~0.5m below ground. The laboratory analysis results showed no evidence of soil or groundwater contamination.

3.3 YTML 6-11

3.3.1.1 A total of 14 sampling locations were proposed at this site to cover the existing jetty area, operating workshops, location of a suspected underground oil storage tank, and area where oil staining was apparent.

3.3.1.2 Sampling points T6A, B, E, F, G, and K were selected to cover potential contamination at locations at the three workshops. Results indicated that soil at T6F and T6K were contaminated with lead and petroleum hydrocarbons respectively.

3.3.1.3 Copper and high concentration of petroleum hydrocarbons were found in the soil samples collected at T6I, where the sampling location was at the approximate location of the underground fuel tank. The high TPH in the sampling results indicated that the underground fuel tank could have contaminated the soil.

3.3.1.4 High concentration of Lead was found in the soil samples collected at the oil stained spot, at T6L. Sampling results however, showed that the soil was not contaminated with petroleum hydrocarbons as suggested by the oil stain. The oil stain observed on the ground may only be an incidental spillage of oil product during transportation within the site. Such spillage is expected to be incidental as the site is not used for storage of petroleum or oily product.

Table 3‑1 Soil Contamination Summary for YTML Lot No. 6-11

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T6F	0.5	Soil	Pb	216	> B
T6F	1.2	Soil	Pb	247	> B
T6I	1.5	Soil	Cu	128	> B
T6I	1.5	Soil	TPHs	6,508	> C
T6I	1.5	Soil	Naphthalene	6.3	> B
T6I	2.3	Soil	TPHs	4,004	> B
T6K	0.5	Soil	TPHs	7,432	> C
T6K	0.5	Soil	Naphthalene	9	> B
T6K	1.5	Soil	TPHs	9,617	> C
T6K	2.2	Soil	TPHs	5,402	> C
T6L	1.5	Soil	Pb	987	> C
T6L	2.3	Soil	Pb	995	> C
T6M	0.5	Soil	TPHs	3,150	> B
T6N	1.2	Soil	TPHs	1,320	> B

3.3.1.5 T6M and T6N were proposed at the centre line of the existing three lines of jetties. Results revealed that the soil at the jetty was contaminated with petroleum hydrocarbons. Since the jetties were still in use during the sampling exercise, a continuous source of contaminants polluting the soil and groundwater could have occurred. This provided an explanation on the high level of contamination. As soil samples were only taken from one of the three jetties, and exhibited high level of contamination, soil at the other two jetties next to the sampled one were also presumed to have been contaminated with heavy metals and petroleum hydrocarbons.

3.3.1.6 All measured contaminants concentration for groundwater samples collected from YTML6-11 can complied with the derived remediation target. However, elevated concentration of TPH can be found in groundwater samples collected from some of the locations, free product will be removed according to the method to be detailed in later section of this report, if necessary.

3.4 YTML 12

3.4.1.1 The main concern at this site is the motor (cement lorries) repair area and the two petroleum product storage areas, one near the entrance alongside with two emergency electricity generators and another along the same side of the site near the shore where oil stains were observed.

3.4.1.2 The laboratory analysis results showed no evidence of contamination to either soil or groundwater. Although traces of heavy metal were found in the soil samples, their concentrations were well within the Dutch ‘A’ level. From records of site history, the site has been used as timber factory since 1973. The current operation as a motor repair area has not led to elevated contamination of the soil since it was protected by a concrete slab, which was in good condition. It is still worth noting that during decommission of the site in the future, the two petroleum storage tanks should be removed properly and the surface cleaned prior to breaking the concrete slab to avoid contamination to the soil beneath.

3.5 YTML 15

3.5.1.1 Three sampling points were selected for this site. Oil staining of the ground was observed from aerial photos and two of the three sampling points T15B and T15C were selected to cover this potential contamination hot spot. Soil analysis results showed that the site was contaminated with heavy metals.

3.5.1.2 At sampling point T15A, only soil samples down to 1.7m from surface was taken as bed rock was encountered. The samples at this point have revealed no signs of contamination.

Table 3‑2 Soil Contamination Summary for YTML Lot No. 15

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T15A	0.5	Soil	Cu	170	> B
T15B	1.5	Soil	Cu	277	> B
T15B	1.5	Soil	Pb	188	> B
T15C	1.5	Soil	Pb	429		> B

3.6 YTML 19-21

3.6.1.1 There is little evidence of contamination at this site, except for a small amount of engine oil suspected to have leaked from trucks parked in the area. A sampling point T19A was selected to cover this oil stained area. Two sampling points (T19B - T19C) were selected to cover a previous car repair area as suggested in the site history so as to ascertain whether the land was contaminated.

3.6.1.2 Lead was the only contaminant found in the soil samples that have exceeded the Dutch ‘B’ level. Lead concentration in the soil sample obtained from T19A is given in Table 3‑3 below. Samples at point T19B and T19C showed no sign of contamination.

Table 3‑3 Contamination Summary for YTML Lot No. 19

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/L)	Categorisation in “Dutch List”
T19A	1.5	Soil	Pb	205	> B

3.7 YTML 22A and 22B

3.7.1.1 These two pieces of marine lots are joined lands and will be collectively discussed. Four sampling points, viz., T22A-A, T22A-B, T22B-A & T22B-B, two at each site, were proposed to cover this site due to an uncertainty site history.

3.7.1.2 As shown in Table 3‑4, exceedance in the lead level was found in soil samples at T22B-A and T22B-B. High copper concentration was also revealed from the bottom level soil sample collected at T22B-B. These are summarised below.

Table 3‑4 Soil Contamination Summary for YTML Lot No. 22A and 22B

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T22BA	0.5	Soil	Pb	238	> B
T22BB	2.2	Soil	Cu	2,642	> C
T22BB	2.2	Soil	Pb	408	> B

3.8 YTML 22RP

3.8.1.1 The site was being used for manufacturing of bricks and material transfer. No physical evidence of land contamination was observed except an oil stain was found on the ground under a vehicle during the site survey, which was believed to be an incidental spillage. The two numbers of samples (T22RP-A & T22RP-B) were proposed, one at the stained area and the other at a representative location near the entrance of the site. Sampling results have confirmed that the site was not contaminated.

3.9 YTML 28

3.9.1.1 This site was, at the time of the survey, being used as a car repair workshop with services ranging from general servicing to vehicle body painting. Four sampling points were selected to cover the site. T28A was selected at an oil-stained area near the entrance of the workshop. T28B was selected at the body painting area inside the workshop where land contamination from the painting process is suspected. The remaining two sampling points (T28C and T28D) were selected at car repair bays in the workshop.

3.9.1.2 Soil samples collected from T28A were found to be contaminated with petroleum hydrocarbons and copper, whereas soil samples collected from T28B contaminated with petroleum hydrocarbons and lead. High concentration of mercury was found at soil collected from T28C.

3.9.1.3 Samples that revealed contamination are tabulated Table 3‑5 below.

Table 3‑5 Soil Contamination Summary for YTML Lot No. 28

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T28A	0.5	Soil	TPHs	4,753	> B
T28A	2.4	Soil	TPHs	2,050	> B
T28A	2.4	Soil	Cu	496	> B
T28B	1.5	Soil	TPHs	1,140	> B
T28B	1.5	Soil	Pb	9,112	> C
T28B	2.5	Soil	TPHs	6,380	> C
T28C	1.5	Soil	Hg	82.7	> C

3.10 YTML 32-33

3.10.1.1 Five sampling points were selected to cover the car repair workshop and the filled jetty. Sampling locations T32A and T32B covered the indoor car repair areas where oil stains were observed, while T32C covered the outdoor car repair station. T32D & E covered the filled jetty area.

3.10.1.2 Exceedance in lead was found in the deepest soil sample collected from the outdoor car repair station, i.e. 3 metres below ground. Top layer of soil collected from the filled jetty also exhibits contamination of lead, PCB and petroleum hydrocarbons. The contamination profile is summarised in Table 3‑6 below.

Table 3‑6 Soil Contamination Summary for YTML Lot No. 32 to 33

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T32C	3	Soil	Pb	205	> B
T32D	1	Soil	TPCB	2.4	> B
T32E	0.5	Soil	Pb	160	> B
T32E	0.5	Soil	TPHs	7490	> C
T32E	0.5	Soil	TPCB	41.2	> C
T32E	1.5	Soil	TPCB	1.8	> C

3.11 YTML 35

3.11.1.1 This site was being used as a machinery workshop but details of the activities involved were not known. There were also no physical signs of land contamination from the visual inspection. Three number of sampling locations were selected. T35A and T35C were chosen to cover the two previous machine repair workshops while T35B was selected to cover the driveway of the site.

3.11.1.2 T35A was originally proposed inside a sub-surface service bay in one of the workshops. However the ground of the bay was covered with metal plates and was inaccessible for sample collection. T35A was located at the ground right beside the service bay.

3.11.1.3 Petroleum hydrocarbon contamination was confirmed at all three locations in the soil samples collected. Sampling results exceeding the criteria are as listed under Table 3‑7.

Table 3‑7 Soil Contamination Summary for YTML Lot No. 35

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T35C	0.5	Soil	TPHs	13,910	> C
T35C	1.5	Soil	TPHs	1,750	> B

3.12 YTML 36-37

3.12.1.1 Machine repair works were being the main operation at this site. Six sampling locations were selected to cover the two areas of most likely contamination: three numbers of samples (T36A,B&C) were proposed to cover the machinery workshop area and three others (T36D,E&F) to cover the dissembled parts storage area.

3.12.1.2 Lead contamination was confirmed in the soil sample collected from T36A as shown in Table 3‑8.

Table 3‑8 Soil Contamination Summary for YTML Lot No. 36 to 37

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T36A	0.5	Soil	Pb	178	> B

3.13 YTML 38

3.13.1.1 This site was a piece of vacated land with clean concrete floor. However, historical information suggested that the site has previously been used as a shipyard dated back to 1973. Due to the lack of further information, 4 sampling points (T38A - T38D) were selected to cover the potentially contaminated area although there was no physical evidence on land contamination observed during the site survey.

3.13.1.2 Soil samples collected from T38A and T38C, locations of two demolished ship repair workshops, showed contamination with heavy metals and petroleum hydrocarbons while samples taken from T38B and T38D were free of contaminants. The samples results are summarised under Table 3‑9.

Table 3‑9 Contamination Summary for YTML Lot No. 38

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T38A	1.9	Soil	Cu	224	> B
T38A	1.9	Soil	Pb	253	> B
T38A	1.9	Soil	TPHs	1510	> B
T38C	1.5	Soil	Cu	137	> B
T38C	1.5	Soil	Ni	190	> B
T38C	1.5	Soil	Pb	1229	> C
T38C	1.5	Soil	Hg	2.27	> B
T38C	1.5	Soil	TPHs	1350	> B
T38C	3	Soil	Cu	347	> B
T38C	3	Soil	Pb	220	> B

3.14 YTML 41- 43

3.14.1.1 There were no active ship repairing works observed as the structures at this site were being demolished at the time of the site investigation. Historical information however, suggested that ship repair works were active up to 1993. Due to the lack of further information and that the whole site was extensively used as ship repair, eleven sampling points were selected to cover this large site. They were selected to cover the jetty area and the previous ship repair works area. There were no physical signs of land contamination, hence the sampling points (T41A to K) were spread out evenly to cover the whole site.

3.14.1.2 Soil collected from T41C, F, H, I and K were found to be heavily contaminated with heavy metals and petroleum hydrocarbons. The contamination profile is summarised under Table 3‑10.

Table 3‑10 Soil Contamination Summary for YTML Lot No. 41 to 43

Sampling Location	Depth (m)	Sample type	Contaminants	Concentration (mg/ kg)	Categorisation in “Dutch List”
T41C	0.5	Soil	Cu	1,188	> C
T41C	0.5	Soil	Pb	1,374	> C
T41C	0.5	Soil	TPHs	2,190	> B
T41C	1.5	Soil	TPHs	2,190	> B
T41F	0.5	Soil	Cu	128	> B
T41F	0.5	Soil	Pb	163	> B
T41F	1.5	Soil	Cu	248	> B
T41F	1.5	Soil	Pb	182	> B
T41H	0.5	Soil	Pb	1,420	> C
T41H	0.5	Soil	TPHs	1,950	> B
T41H	1.5	Soil	Pb	490	> B
T41H	1.5	Soil	TPHs	1,286	> B
T41I	0.5	Soil	TPHs	5,820	> C
T41K	0.5	Soil	Cu	524	> C
T41K	0.5	Soil	Pb	413	> B

4 Extent of Contamination

4.1 Soil Contamination

4.1.1.1 Based on the soil remediation criteria described in Section 2.3.1 and the identified soil contamination outlined above, it is apparent that there are a number of areas on the site where soil contamination level will be in excess of the Dutch C-levels and further areas where contamination exceeds Dutch B-levels. The approximate extent of soil contamination is shown schematically in Figure 4‑1.

4.2 Estimation on Contaminated Soil

4.2.1.1 Volumes of contaminated soil have been estimated based on a linear interpolation of contamination levels between sample locations in conjunction with best professional judgement and experience. That is, it has been assumed that the rate of change of contamination between sampling points is linear. The linear assumption was applied to mainly horizontal distribution of contaminants. For the vertical distribution, an additional 0.5m above and below the sampling point which showed exceedance in Dutch B standard was taken.

4.2.1.2 Where on site sampling locations are far apart and contaminants were believed to be localised, the linear interpolation method was not considered appropriate. For such cases, a conservative estimation of a 5m radius circle encompassing the contamination area for contamination in the magnitude of between Dutch B and C, and 7m radius circle for contamination in the magnitude above C was adopted. The depth of the contamination soil was taken to be, for the former, 0.5m above and below the sampling point, and the latter 1m above and below the sampling point. This is typical of the sites contaminated with metals only.

4.2.1.3 There were a number of inaccessible marine lots that were not assessed: YTML2-4, YTML25-26, YTML27, and two pieces of government land between YTML13-14 and YTML15, and between YTML26 and YTML27. YTML2-4 has been an active shipyard. From assessment results of other shipyard operations at Yau Tong Bay such as YTML6-11, it can be established from extrapolation that YTML2-4 is likely to be under the same type and extent of contamination. Using a “size vs contaminated soil” extrapolation, ~43% of YTML6-11 area would be under remediation. Applying this percentage to YTML2-4 which is ~4,640m², the area of contamination is ~1,995m². Assuming the conservative case of contamination down to 3m, the additional volume of contaminated soil would be 5,985m³.

4.2.1.4 YTML 54, YTML 44, YTML 45-46, the existing site for the Gas Pigging Station, CED’s maintenance depot and the salt water pumping station were only available for inspection, but not for sampling due to their on-going operation. Information collected from land use history review and on-site investigation suggested that land contaminating activities could have been carried out in all of the above sites some time in the past. Employing the same assumptions in Section 4.2.1.3, the estimated volume of contaminated soil is ~5,321m³, ~2,206m³ and ~4,177m³ respectively for the YTMLs and ~2692m³, ~4025m³ and ~4666m³ for the other three sites respectively.

4.2.1.5 However, the above estimated volume are for reference only and are subject to confirmation sampling should the owner of the site become a consenting partner in the development or available for sampling.

4.2.1.6 Regarding the other inaccessible sites YTML25-26, YTML27, and the two pieces of government land between YTML13-14 & YTML15, and between YTML26 and YTML27 respectively, there is no site history that suggest land contamination. Upon availability of access, a visual inspection will be carried out to ascertain the status of these marine lots. As above, this will only be carried out if the land owners become consenting partners of the development.

4.2.1.7 Volume of soil contaminated with different contaminants are calculated with the assumptions detailed above and tabulated in Table 4‑1.

4.3 Groundwater Contamination

4.3.1.1 Based on the groundwater remediation criteria described in Section 2.3.3, it is apparent that only groundwater where free product is present requires remediation. From the field observations and analytical results, it is evident that this includes only those groundwaters in the immediate vicinity of the underground fuel storage in Lot 6-11.

4.3.1.2 However, based on an area of contamination of approximately 3,000m² and an estimated average free product thickness of 2mm, the total volume of free product is estimated to be approximately six cubic metres.

Figure 4‑1 Extent of Soil Contamination at Yau Tong Marine Lots

Table 4‑1 Volume Estimation of Contaminated Soil

5 Assessment of remedial options

5.1 An Overview

5.1.1.1 As seen from the results tabulated in the foregoing sections, parts of the site were found to have soils contaminated by heavy metals (Cu, Pb, and Hg), TPH (mostly diesel and fuel oils), PAH and PCBs.

5.1.1.2 At certain locations, heavy metals (Cr, Cu, Ni, Pb, and Hg) and TPH (mostly diesel and fuel oils) were found in the groundwater samples. Tributyl-Tin (TBT) was also detected at a few locations but the levels are well below the required standards as referenced to USEPA.

5.1.1.3 Where these contaminants in soil were detected at concentrations above Level B of the “Dutch List”, site clean up is considered necessary.

5.1.1.4 To assist in the development of suitable remedial options to address the contamination, most of the currently available treatment technologies for the above-mentioned contaminants and affected media were examined based on the following criteria :

· Technical effectiveness - treatment technology should be technically effective for at least one of the above-mentioned contaminants.

· Development status - treatment technology should work in full-scale application.

· Availability - treatment technology should be commercially available.

5.1.1.5 The treatment technologies for heavy metals, TPH, PAH, or PCBs contaminated soil and for heavy metals or TPH contaminated groundwater are presented in Table 5‑1 and Table 5‑2 respectively.

5.1.1.6 The screened treatment technologies presented in these tables are technically effective for the above-mentioned contaminants and media, work in full-scale application and are commercially available in the U.S. and other places of the world. In both tables, treatment technologies are classified into in-situ and ex-situ methods, and are further sub-divided into biological, physical/ chemical, and thermal treatments.

5.1.1.7 A comparison of the merits and demerits amongst the different treatment technologies for soil and groundwater are shown in Table 5‑3 and Table 5‑4 respectively.

5.1.1.8 The comparison is based on the following criteria :

· requirement of treatment train (a series of treatment process) - whether additional supporting treatment technologies are required to complete the remediation. This excludes the treatment of off-gas generated as a by-product of the treatment technologies;

· generation of residuals - whether solid, liquid, or vapour residuals are produced;

· intensity of operation & maintenance (O&M) requirements or capital - whether the treatment requires intensive labour involvement in O&M or significant capital investment in set up and operation;

· reliability or maintainability of the system - whether the system is reliable or maintainable during its operation.

· duration of cleanup - whether cleanup time is reasonable and acceptable;

· cost - whether the total treatment cost is acceptable.

5.1.1.9 A comparative rating was given to the performance of different treatment technologies to assist in the selection of the most suitable and cost effective remedial methods. Treatment technologies that are capable of removing at least two of the contaminants found in the assessment, namely heavy metals, TPH, PAH, and PCBs, were identified. These technologies are referred to as candidate treatment technologies. Candidate treatment technologies for soil remediation are solidification/ stabilisation (in-situ treatment), biopiling, soil washing, chemical extraction, separation, incineration, and thermal desorption.

5.1.1.10 There is no single-stage treatment technology that can treat both TPH and heavy metals in the groundwater because of the contaminants’ difference in characteristics.

Table 5‑1 Treatment Methods for Heavy Metals/TPH/PCB Contaminated Soil

Treatment Technologies	In Situ Treatment	Ex Situ Treatment (assuming excavation)
Biological Treatment	· Bioventing · Enhanced Bio-remediation · Land Treatment · Natural Attenuation	· Biopiles · Composting · Landfarming · Slurry Phase Biological Treatment
Physical/Chemical Treatment	· Electrokinetic Separation · Soil Flushing · Soil Vapour Extraction · Solidification/Stabilisation · Capping	· Chemical Extraction · Chemical Redox · Separation · Soil Washing · Solidification/Stabilisation
Thermal Treatment	N/A	· Incineration · Thermal Desorption

Table 5‑2 Treatment Methods for Heavy Metals/TPH Contaminated Groundwater

Treatment Technologies

In Situ Treatment

Ex Situ Treatment

(assuming pumping)

Biological Treatment

· Enhanced Bio-remediation

· Natural Attenuation

· Bio-reactors

Physical/Chemical Treatment

· Aeration

· Air Sparging

· Bioslurping

· Dual Phase Extraction

· Fluid/Vapour Extraction

· Passive/Reactive Treatment Wells

· Ion Exchange

· Precipitation/Coagulation/

· Flocculation

· Separation

· Sprinkler Irrigation

· UV Oxidation

Table 5‑3 A Comparison of Treatment Technologies for Heavy Metals/ TPH /PAH/ PCB in Soil

Treatment Technology	Treatment Train Requirement	Residuals Produced	O&M or Capital Intensive	System Reliability/ Maintainability	Cleanup Time	Overall Cost
In Situ Treatment:
Bioventing	No	No	No	N.A.	Site Specific	Low
Enhanced Bio-remediation	No	No	O&M	N.A.	Site Specific	Site Specific
Land Treatment	No	No	No	N.A.	Site Specific	Site Specific
Natural Attenuation	No	No	O&M	N.A.	Long	Site Specific
Electrokinetic Separation	Yes	Liquid	O&M	Medium	Medium	Medium
Soil Flushing	No	Liquid	O&M	Medium	Long	High
Soil Vapour Extraction	No	Liquid	O&M	High	Medium	Low
Solidification/ Stabilisation	No	Solid	Both	Medium	Medium	Medium

Ex Situ Treatment:
Biopiles	No	No	No	High	Medium	Low
Composting	No	No	No	High	Medium	Low
Landfarming	No	No	No	High	Long	Low
Slurry Phase Biological Treatment	No	No	Both	Medium	Medium	Medium
Chemical Extraction	Yes	Liquid	Both	Medium	Long	High
Chemical Reduction/ Oxidation	Yes	Solid	No	High	Short	Low
Separation	Yes	Solid	O&M	Medium	Short	Medium
Soil Washing	Yes	Solid/Liquid	Both	Medium	Short	Medium
Solidification/ Stabilisation	No	Liquid	No	High	Medium	Low
Incineration	No	Liquid/Solid/Vapour	Both	Medium	Short	High
Thermal Desorption	Yes	Liquid/Solid	Both	Medium	Short	Medium

Note:

O&M: Operation and Maintenance.

N. A.: Not Applicable.

Reference: Federal Remediation Technology Roundtable

Table 5‑4 A Comparison of Treatment Technologies for Heavy Metals/TPH in Groundwater

Treatment Technology	Treatment Train Requirement	Residuals Produced	O&M or Capital Intensive	System Reliability/ Maintainability	Cleanup Time	Overall Cost
In Situ Treatment:
Enhanced Bio-remediation	No	No	O&M	N.A.	Site Specific	Site Specific
Natural Attenuation	No	No	O&M	N.A.	Site Specific	Site Specific
Aeration	Yes	Vapour	No	Medium	Short	Low
Air Sparging	Yes	Vapour	No	High	Short	Low
Bioslurping	Yes	Liquid/ Vapour	No	Medium	Medium	Low
Dual Phase Extraction	Yes	Liquid/ Vapour	O&M	Medium	Medium	Medium
Fluid/Vapour Extraction	Yes	Liquid/ Vapour	O&M	Medium	Medium	Medium
Passive/Reactive Treatment Walls	No	Solid	Capital	N.A.	Long	N.A.

Ex Situ Treatment:
Bio-reactors	No	Solid	Capital	Medium	Medium	Low
Ion Exchange	Yes	Solid	No	High	Medium	Low
Precipitation/Coagulation/Flocculation	Yes	Solid	No	High	Medium	Low
Separation	Yes	Solid	Both	High	Short	High
Sprinkler Irrigation	Yes	Solid/Liquid	No	Medium	Medium	Low
UV Oxidation	No	No	Both	Low	N.A.	Medium

Note:

O&M: Operation and Maintenance.

N. A.: Not Applicable.

Reference: Federal Remediation Technology Roundtable

5.2 Factors for Consideration

5.2.1.1 According to the Practice Note for Professional Persons : Contaminated Land Assessment and Remediation (ProPECC PN 3/94) issued by the EPD, the selection of appropriate remedial measures should consider the following factors :

· Contamination nature: (refer to Section 3)

· Contamination degree: (refer to Section 3)

· Potential sensitive receivers: receivers that may be exposed to the contaminants are construction workers, residents, and marine life in the Yau Tong Bay area;

· Time constraint;

· Treatment cost;

· Local expertise availability - whether the expertise - staff and equipment are available locally. Some of the equipment might need to be fabricated or procured or leased from overseas suppliers.

6 Recommended REMEDIAL MEASURES

6.1 Remediation of Contaminated Soil with TPH and Heavy Metals

In order to minimise the soil volume required for solidification, soil only requiring biopiling will be separated from those requiring both biopiling and solidification.

6.1.1.1 A schematic diagram of the proposed remediation strategy is presented in Figure 6‑1.

6.1.1.2 There are mainly three categories of remediation: 1) soil with TPH and metals, 2) soil with metals only, and 3) soil with TPH only. There are also separate categories for PAH contaminated soils, PCB & Hg contaminated soils, and the underground storage tank at Marine Lot 6-11. Table 6‑1 gives an outline of each of the treatment category.

Table 6‑1 Remediation Method for each of the 3 Contamination Scenarios

Type of Contamination Scenario	Steps of Remediation
1. TPH & Metals	1. Dig out soil column. 2. Biopile and then solidify in concrete following section 6.6.2
2. Metals only	1. Dig out soil column. 2. Solidify in concrete following section 6.7.
3. TPH only	1. Dig out soil column. 2. Biopile 3. Backfill on-site.
4. PAH contaminated soil	1. for isolated spots with PAH contamination at T6I and T6K, the contaminants levels are 6.3 and 9mg/kg respectively, which are only slightly over the Dutch B standard of 5mg/kg. This PAH soil will be excavated with the rest of the TPH contaminated soil (T6-1 and T6-2) and biopiled.
5. PCB & Hg*	1. Delineate exact soil volume to be excavated for landfill following 6.4.1.1 if required for that particular spot. 2. Disposal to landfill
6. Underground storage tank	1. Decommission the underground following section 6.3.1.1. 2. Further sampling to delineate extent of contamination in TPH and carry out remediation as necessary subject to sampling results.

* for isolated spots with PCB & Hg contamination at T32D&E & T28C respectively, the soils will be excavated and landfilled off-site. The PCB contaminated soil shall be disposed because they are only present at isolated locations, and Hg because it is highly toxic rendering solidification on-site undesirable.

6.1.1.3 Further description of each of the proposed remediation methods including justification for their selection is provided below.

Graphical delineation for individual lots are provided in Annex 4. An estimate of the contaminated soil areas and volumes for 1) Biopiling only, 2) Biopiling followed by Solidification, 3) Solidification only, are provided below under Table 6‑2, Table 6‑3 and Table 6‑4 respectively. The areas and volumes are estimates only.

Table 6‑2 Estimated Area and Volume of Contaminated Soil for Biopiling Only (TPH Contamination)

Table 6‑3 Estimated Area and Volume of Contaminated Soil for Biopiling followed by Solidification (TPH and metal Contamination)

Table 6‑4 Estimated Area and Volume of Contaminated Soil for Solidification only (Metal Contamination)

6.2 Remediation of Soil Contaminated with PCB and Hg

6.2.1.1 All PCB/Hg contaminated soil will be excavated for landfill disposal due to their high toxicity. This will be carried our prior to proceeding to deal with soil with other contaminants. Estimated volumes of soil to be disposed to landfill were estimated and included under Table 6‑5. The actual volumes shall be subject to delineation through further soil sampling during the site remediation stage. Further soil samples shall be taken at 0.5m intervals from all six directions (above, below, and four sides) from the located point of contamination. Sampling shall continue until the contamination level of the contaminant falls below the required Dutch B standard. The volume of soil to be disposed at landfill shall then be calculated by taking the contamination boundaries to be at the sampling locations which showed level of contamination to be below that of Dutch B.

6.2.1.2 Soil will be only be excavated for biopiling at T32E upon verification sampling can show that all PCB contaminated soil were removed for disposal.

6.2.1.3 The Hg level located at T38C at 1.5m below ground is relatively low at 2.27mg/kg which is only slightly above the Dutch B requirement of 2mg/kg. In light of this, no further sampling shall be required for Hg, but a volume of soil at 0.5m above, below, and to 4 sides of this location shall be excavated and disposed at landfill, subject to acceptability of the TCLP test. However, as there are other contaminants that exceeded Dutch B standards at this location (Cu, Ni, Pb, TPH), verification samples shall be carried out at a rate of 4 samples in the four perpendicular directions and 2 samples at the bottom of the pit. Should the sampling results exceed Dutch B standards, further excavation will be carried out at steps of 0.5m outward and downward from the pit and treated in accordance to the test results, i.e., solidification, or biopiling, or one after another.

6.2.1.4 As PCB is an organic compound for which leachibility is unrelated to pH, TCLP test shall not be applicable.

Table 6‑5 Estimated Area and Volume of Contaminated Soil for Disposal to Landfill (PCB & Mercury Contmination)

6.3 Remediation Strategies – Underground Storage Tank

6.3.1.1 In the lack of a detailed standard in Hong Kong, the underground fuel tank at YTML 6-11 shall be removed in accordance to the Model Code of Safe Practice for the Petroleum Industry Part 2: Design, construction and operation of distribution installations 1st ed., Sept 1998, issued by the Institute of Petroleum, London. The following is an outline of the method:

1. Sludge and micisible water shall be pumped out from the underground tank and transferred to the groundwater treatment system as described under section 6.8 for treatment;

2. The oil tank shall then be flushed with steam to allow the tank temperature to reach 60°C until all residues come off from the tank surface;

3. The oil tank shall be allowed to cool down to room temperature;

4. All effluent shall be drained to drums for recovery of oil product and subsequently treated by the groundwater treatment system as described under section 6.8;

5. The interior of the tank shall be inspected visually to determine if all oil residues have been removed. If necessary, steam will be applied to remove local residue and Step 4 shall be repeated;

6. Gas free status inside the tank will be checked and if necessary, repeat the steaming out process;

7. Upon achieving gas free status, the tank shall be flame cut to convenient size for disposal.

8. The scrap metal shall be collected by waste collector for recycling.

6.3.1.2 Further sampling shall be taken to delineate the extent of soil contamination. Upon a visual inspection, a sampling strategy shall be submitted as part of the supplementary CAP for endorsement. Further sampling shall be carried out in accordance to this supplementary CAP and remediation action recommended accordingly. Also refer to Section 8 of this report.

6.4 Remediation Strategies - General

6.4.1.1 Based on the evaluation in the previous chapter, the Consultant would recommend the following remediation strategies for contaminated soils where one or more contaminants have exceeded the Dutch B-levels.

6.4.1.2 Summaries of Soil Volume for each of the specified treatments are given under Table 6‑2, Table 6‑3, Table 6‑4 & Table 6‑5 respectively. The volumes given are raw soil volumes. Treatment method such as solidification will elevate the final volume.

6.5 Excavation

6.5.1.1 Contaminated soil will be excavated mainly with conventional earthmoving equipment such as excavators. Dust will be well controlled by the use of water sprays and other standard construction techniques. Workers, vehicles, instruments, and equipment will be decontaminated before leaving the site. Because TPH contamination has been detected on site, a Combustible Gas Indicator (CGI) shall be used to detect explosive vapour in enclosed and semi-enclosed sites to ensure safety.

6.5.1.2 Excavated soils will be placed in stockpiles with drainage diversions to prevent surface water runoff from entering the stockpile and entraining contaminants in the flow. In addition, silt fences and hay bales will be used to prevent the release of sediment-laden rainwater from the stockpile area.

6.5.1.3 Such techniques for control of soil stockpiles are well established in the construction industry both in Hong Kong and overseas. In Australia, such methods are recommended by the Victorian Environment Protection Authority in its Best Practice Environmental Management Series, “Environmental Guidelines for Major Construction Sites – Publication 480”.

6.5.1.4 Where contaminated soils are located below a layer of uncontaminated soil, the clean soil will be removed and stockpiled separately to the contaminated soil. Following excavation of the contaminated material, the clean soil shall be backfilled and/or retained for use as a clean cap.

6.5.1.5 Emission of volatile organic compounds (VOCs) is not likely to be an issue during excavation or remediation. As described in Annex 2 of this report, all sample results indicate that the TPH contamination is mostly long-chain hydrocarbons with extremely low volatility. The short-chain (less than C9) compounds that would typically cause emissions of VOCs during excavation and bioremediation were found not to be present in the soils at Yau Tong Bay. However, in spite of the low risk of VOC emissions, exhaust air from the bioremediation will be scrubbed through activated carbon beds prior to emission to atmosphere to provide as further level of risk reduction. Further details are provided in Section 6.6.2.3.

6.5.1.6 The concentration of TVOC in air at which point additional controls would be required shall be proposed and agreed with EPD if this monitoring is deemed necessary.

6.6 Bio-remediation

6.6.1 Estimated Volume of TPH Contaminated Soil

6.6.1.1 As discussed under section 4.2 above, the volume of contaminated soil with TPH levels exceeding the Dutch B level has been estimated to be ~16,623 m3 (TPH only) and ~1,053 m3 (TPH and metals). Because of the high TPH level in groundwater at hot-spot T6-2 and the presence of a disused underground storage tank (UST) in the vicinity, there is a likelihood of further TPH contamination to the intervening soils in this area which might not have been discovered in the site investigation. Therefore it is prudent to verify on site when the soils are excavated and, if necessary, treat those soils that are obviously contaminated by TPH.

Figure 6‑1 A Schematic Diagram of the Proposed Remediation Strategy

6.6.2 Biopiling

6.6.2.1 It is proposed to bio-remediate the TPH contaminated soils by the biopile method. Biopiling is a commonly accepted bio-remediation method and is recommended in a number of USEPA guidance documents and its web site. It uses the same biological principle as bioremediation where naturally occurring organisms, most commonly under aerobic conditions, consume petroleum hydrocarbons as a food source and break them down into harmless compounds such as carbon dioxide and water. However, to accelerate the rate of remediation and therefore reduce the time and/or area needed for remediation, biopiling forces air thorough the soil pile, increasing the oxygen exchange rate, enabling the micro-organisms to metabolise and reproduce at a greater rate.

6.6.2.2 For biopiling, contaminated soils are piled into a pyramid-shaped heap or windrow to a height of approximately 2 - 3m, depending on the characteristics of the soil. Because of the greater depth of soil in these biopiles, artificial aeration is required to ensure that oxygen supply is maintained for the biological degradation process. It is proposed to aerate the soil by drawing air through the pile from the top and sides via a network of perforated PVC pipes positioned in a grid at the base of the pile.

6.6.2.3 A suction fan will draw air through the PVC pipes and exhaust to atmosphere. Although there were no volatile TPH compounds detected during the sampling program, it is still proposed to include air treatment of the exhaust air. It is highly unlikely that the levels of VOC would be of any significance because firstly, the sampling results had shown no short-chain TPH component in the soil, and secondly, any traces amount of VOC will be released before the biopile is formed. As there is no short-chain TPH component in the soil, VOC emission is also expected to be insignificant. The activated carbon filter is a prudent precautionary measure only. Exhaust air will be passed through the activated carbon filters prior to discharge to the atmosphere to remove any contaminants. Spent activated carbon will be removed from the site by contractors for regeneration and/or disposal. As such, any minor odour and air emission will be filtered by the activated carbon filter. The exit stream will by and large be normal atmospheric air made up of oxygen and nitrogen. No additional mitigation measure is therefore anticipated.

6.6.2.4 Moisture will be periodically added to the soil. The rate of moisture application will be determined based on the moisture content, which will be affected by prevailing local weather conditions during the period of remediation. The aim will be to maintain a soil-moisture content of approximately 30 % although this figure will be confirmed by soil specific tests prior to remediation. Daily soil-moisture tests will be conducted to assist in the management of the bio-remediation process.

6.6.2.5 Regular visual monitoring of the condition of the soil will be conducted, supported by targeted sampling and TPH analysis to enable the appropriate bio-remediation conditions to be maintained and to determine when TPH levels have been reduced to or below the Dutch B levels.

6.6.2.6 The biopile remediation shall be conducted at four locations across the site. The locations and approximate volume of soil to be treated at each location are shown in Figure 6‑2.

6.6.2.7 All biopile remediation shall be conducted on sealed surfaces under cover of existing warehouse and factory buildings at the site. This will prevent any contamination of soils and also prevent contamination of rainwater that might occur if these works were conducted without cover.

6.6.2.8 The duration of biopiling treatment varies with environmental conditions. It has been estimated that half a year to nine months would be a realistic time span.

6.6.2.9 Soil contaminated with TPH only and with both TPH and metals will be biopiled separately. So that the soil contaminated with TPH only can be backfilled into the site after the bioremediation and the rest can be shipped for solidification afterwards.

6.6.3 Verification

Site Cleanliness Verification

6.6.3.1 At the completion of excavation, verification samples shall be taken at a rate of 1 number per 10m³ of excavated soil. The location of the samples shall be spread out along the perimeter of the excavated area and at the bottom of the pit. There should be no further excavation if there is no further sign of contamination, otherwise, further outward and downward excavation at steps of 0.5m shall be conducted until the confirmatory samples are negative.

Biopile

6.6.3.2 The biopile shall be tested regularly for TPH level to monitor its rate of degradation. Soil samples shall be taken fortnightly at 1 sample for every biopile of 360m³ for process monitoring. When these monitoring levels have dropped to the required standard, final verification shall be carried out at 1 sample per 76.5 m³ of soil. Samples shall be taken in the following manner.

6.6.3.3 Soil samples shall be shovelled into 1-L darken glass bottles provided by the laboratory. All containers shall be pre-washed and pre-treated by the laboratory before use. Sample containers shall be tightly sealed as soon as the samples are taken. The samples shall be refrigerated to 4°C as soon as possible. Refrigeration shall be maintained until analysis, and the samples shall be analysed as soon as possible. Wet samples shall be dried before testing. Collected soil samples shall be sent to a HOKLAS accredited laboratory for analysis.

6.6.3.4 The tools to be used for collecting the soil samples shall be cleaned after each sample taking to avoid cross contamination. They have to be cleaned in the following manner:

Ø initial removal of soil by scrubbing in tap water;

Ø wash/scrub in detergent; and

Ø final rinse in tap water followed by wiping with a paper towel.

6.6.3.5 The process of Biopiling is taken to be completed when all sampling results showed a TPH level below or equal to that of the Dutch B standard. The soil can then be backfilled on-site as clean soil.

6.6.4 Method Statement

6.6.4.1 A method statement shall be prepared detailing the biopiling, monitoring and verification procedures, which is to be submitted to EPD for comment and endorsement prior to commencement of work.

6.7 Solidification

6.7.1 Estimated Volume of Metal Contaminated Soil

6.7.1.1 As discussed under section 4.2 above, the volume of soil contaminated with metals and proposed for solidification is estimated to be approximately ~2,102m³ (metals contaminated soil only) and ~1,053m³ (TPH and metal contaminated soil). The contaminants of concern are lead, copper and mercury. Mercury contaminated soil shall be separated and disposed to landfill instead of on-site disposal because of its high toxicity. Refer to section 6.2 for details.

6.7.1.2 Solidification proposed here refers to the process where cement, fly ash and other inert solids such as sand are physically blended with the soil to and allowed to set into a solid monolithic block. The metal contaminants become physically bound into the matrix of the concrete monolith and are extremely resistant to re-release except under the most aggressive acidic conditions.

6.7.1.3 Typically, between 5 and 30 percent cement will be added to the soil to form a mixture that will set. The total volume of the concrete block will be an increase by up to 50 percent from the original soil volume. Soils contaminated by heavy metals will be excavated and transferred to the solidification compound. The batching of the blocks would be conducted in a series of in-ground, compacted pits, approximately 20m x 10m x 1m(deep) in size. The soil, cement, water and other additives (if required) will be poured in pre-determined proportions into the pit and blended using an excavator or physical mixing tools. The effectiveness of mixing the pre-determined proportions of soil, cement, water and additives by excavator or physical mixing tools shall be demonstrated through pilot trials. The solidified blocks shall be broken up into manageable size blocks using a Breaker before transfer to designated locations.

6.7.1.4 Each batch will be covered during the entire setting time to prevent water entering the mixture. In addition, drainage bunds will be placed around each batch to prevent rainwater from entering the batch.

6.7.2 Verification

Site Cleanliness Verification

6.7.2.1 At the completion of excavation, the boundary of the pit shall be sample at steps of 0.5m increment in radius at 4 samples per pit in the four perpendicular directions. Furthermore, 2 nos. of confirmatory samples shall be collected at the bottom of the pit. There should be no further excavation if there is no further sign of contamination, otherwise, further outward and downward excavation at steps of 0.5m shall be conducted until the confirmatory samples are negative.

Toxicity Characteristic Leaching Procedure

6.7.2.2 Typically the mixture will solidify within about 4-5 days and will then be tested for leachability and compressive strength. The tests will be conducted for every 50m³ of solidified soil. If the blocks fail either test, the batch will be crushed and returned to the batching process.

6.7.2.3 Because of the stable and inert structure of the solidified blocks, once they have passed the compression and leachability testing, they would then be kept on-site. Table 6‑8 summarised the on-site disposal options.

6.7.2.4 The Toxicity Characteristic Leaching Procedure (TCLP) limit as published under EPD’s Guidance Notes for Investigation and Remediation of Contaminated Sites of Petrol Filling Stations, Boatyards, and Car Repari/Dismantling Workshops are standard leachability test standards. However, this set of standards is only applicable to disposal to landfill sites. For on-site disposal, a more stringent set of leachability limit is required.

6.7.2.5 In determining the standards for leachability test for on-site disposal of treated soil, reference has been made to the USEPA Federal Register: May 26, 1998 (Volume 63, Number 100), Rules and Regulations, Page 28555-28604, “Land Disposal Restrictions Phase IV: Final Rule Promulgating Treatment Standards for Metal Wastes and Mineral Processing Wastes; Mineral Processing Secondary Materials and Bevill Exclusion Issues; Treatment Standards for Hazardous Soils, and Exclusion of Recycled Wood Preserving Wastewaters; Final Rule”.

6.7.2.6 This document is about Land Disposal Restrictions treatment standards for metal-bearing wastes, including toxicity characteristic metal wastes. The set of standards being applied to these wastes is the “Universal Treatment Standards” (UTS), 40 CFR Section 268.48. These standards were derived from the performance of the Best Demonstrated Available Technologies for treating these, or similar, wastes.

6.7.2.7 The UTS standard for Copper is unavailable in the above-mentioned reference. In determining the UTS-TCLP standard for Copper, a comparison has been made between Drink Water Standards of the USEPA and the said USEPA Federal Register. It was found that the 2 sets of standards differ by a factor of ~6 (Chromium) to ~2950 (Cyanide). Taking the lowest factor of 6 as the more conservative value. Hence the Universal Treatment Standard for Copper is taken to be the Drinking Water Standard value of 1.3mg/L times a factor of 6 to give 7.8mg/L as shown below.

Table 6‑6 Universal Treatment Standard for Solidified Soil

Constituent	Universal Treatment Standard (mg/L)
Lead	0.75
Copper	7.8 (extrapolated value)

6.7.2.8 Mercury contaminated soil will be disposed to landfill and hence the TCLP value from the EPD guidance note shall be used. This is shown under Table 6‑7.

Table 6‑7 TCLP Limit for Soil to be Disposed in Landfill

Constituent	TCLP (ppm)
Mercury	1

6.7.2.9 A pilot test shall be conducted to ascertain the concrete mix recipe and leachability of the product prior to a full scale solidification.

Compressive Strength Test

6.7.2.10 Compressive strength of at least 150 psi shall be achieved for solidified soil.

6.7.3 Backfilling

6.7.3.1 Following successful bio-remediation and/or solidification, treated soils will be backfilled and compacted on site. There exist a number of options for the disposal of the solidified concrete blocks which are all technically feasible. The choice shall depend on factors such as specific site situation at the time of the remediation, reclamation programme, and final layout of the proposed development. These are listed under Table 6‑8. Use of either one of these options shall be deemed acceptable.

Table 6‑8 Backfilling Options for the Solidified Soil

Options	Advantage	Disadvantage
1. As part of the land reclamation component of the development	Blocks are placed below clean reclamation materials	Need to transport blocks from location of solidification
2. Fill hole created by excavation of contaminated soils	Minimal manoeuvring of the blocks	Large surface area required
3. Place under seaside promenard or similar passive functional locations	Minimise disturbance to the blocks through piling and other construction activities	Need to transport blocks from location of solidification

6.7.3.2 Relatively large volume of soil will require solidification. For easy handling, the solidified soil will be broken up into management size blocks using a breaker upon passing the TCLP verification procedures.

6.7.4 Location of Soil Remediation Activities

6.7.4.1 The indicative location of remediation activities, including biopile remediation and solidification are shown in Figure 6‑2.

6.8 Remediation of Contaminated Groundwater

6.8.1.1 As described in Section 4.3, groundwater remediation is only required for TPH free product that might be present. Field measurements and observations indicate that free product is present in Lot 6 only. Because all soils associated with TPH contamination will be excavated and the underground fuel storage tank will be removed, the major sources of TPH contamination of groundwater will be removed.

6.8.1.2 Free product that is present on the groundwater surface will be transferred by suction pump to an oil/water separation unit. The free product will be removed from the surface of the water and transported off site by contractor for recycling. The water will be held in a temporary storage tank. If the water is tested and found to contain floating TPH product, it will be passed through the oil/water separator for a second time to remove any residual oil. Treated water that is free from floating TPH product will be re-injected into the groundwater table at the site.

6.8.1.3 A schematic drawing of the proposed remediation is provided in Figure 6‑3.

Figure 6‑2 Indicative Location of Soil Remediation Activities.

Figure 6‑3 Groundwater Treatment System

7 Conclusion

7.1.1.1 A site investigation for contamination has been conducted in accordance with the approved CAP and revealed moderate contamination of soil and groundwater at various marine lots by TPH and metals as a results of previous industrial uses at the individual lots. The results indicate that contamination is localised and there appears no sign of migration of the contaminants

7.1.1.2 Various remedial measures have been recommended for the contaminated soils: 1) excavation followed by bio-remediation of TPH contaminated soils by biopile method, 2) solidification of heavy metal contaminated soil by cement, 3) excavate and disposal to landfill site isolated locations contaminated with PCB and Hg, 4) decommission and removal of the underground storage tank followed by sampling of the surrounding soil.

7.1.1.3 The treatment methods suggested in this report are well-established ones with ample references on successful implementations. They are hence considered feasible and effective.

7.1.1.4 It is suggested that the site remediation shall be designed and supervised by competent personnel to ensure that the clean-up is complete and satisfactory and poses no risk to the future sensitive users of the Site.

8 FUTURE WORKS

8.1 Phase 1

Phase 1 of the remediation works shall cover items as described in the current CAP & RAP, which shall include all verification works to ensure site cleaniness upon completion of excavation and acceptability of remediated soil.

8.2 Phase 2

Phase 2 of the remediation works shall cover outstanding items and works on further quantification. The following sections outline the additional works required to cover phase 2 of the remediation.

8.2.1 Inaccessible Sites

8.2.1.1 As described under section 4.2.1.3 to 4.2.1.6 above, there were a number of inaccessible marine lots that were not assessed: YTML2-4, YTML25-26, YTML27, and two pieces of government land between YTML13-14 & YTML15, and YTML26 & YTML27 respectively. Soil sampling were not conducted for YTML 54, YTML 44, YTML 45-46, the existing site for the Gas Pigging Station, CED’s maintenance depot and the salt water pumping station, due to current operations. YTML2-4 has been an active shipyard. Under the condition that the owner of this sites become a consenting partner in the development or cease of operation at the sites, these sites shall be subject to assessment and confirmation sampling, where necessary, to ascertain the land contamination status of these lots. A supplementary Contamination Assessment Plan and Remediation Action Plan shall be compiled to cover these sites.

8.2.2 Further Sampling for PCB/Hg Contaminated Soil for Disposal

8.2.2.1 As described under section 6.2, the exact volume of PCB/Hg contaminated soil would need to be delineated through further sampling.

8.2.3 Removal of Underground Oil Storage Tank and Further Sampling

8.2.3.1 The removal method for underground oil storage tank has been described under section 6.3.

8.2.3.2 A further sampling strategy shall be derived subject to a further visual inspection after the removal of the underground tank. This has also been described under section 6.3.

8.2.4 Further Sampling to Delineate TPH Contaminated Soil for Biopile

8.2.4.1 For sites contaminated with TPH such as Lot 6-11, it is considered pragmatic for further sampling to be conducted to delineate the exact TPH contamination extent. The current calculation is a conservative one based on limited information as site access was restricted. This could potentially reduce the amount soil requiring remediation, or otherwise. In any case, a more accurate picture could be painted with additional sampling exercise. Should this be considered feasible, the additional sampling strategy shall be submitted as part of the supplementary CAP for endorsement before proceeding.

8.2.5 Biopiling Methodology

8.2.5.1 A method statement shall be prepared detailing the biopiling, monitoring and verification procedures, which is to be submitted to EPD for comment and endorsement prior to commencement of work.

8.2.6 Final Reporting

8.2.6.1 A final report with photo log summarising the remediation works should be compiled at the conclusion of the proposed remediation exercise. The report shall be submitted to the authorities for vetting as a final step for discharge of duties.

8.3 Precautionary Investigation for Mitigating Dioxin Contamination

8.3.1 The industrial operations at the Yau Tong Bay marine lots include shipyards, timber saw-mill, cement manufacturing, machine/car repair workshops, and godown for dry goods. Information regarding site history including inspection of aerial photographs, historical search, as well as current operations have been detailed in the Contamination Assessment Plan. From detailed site inspections carried out for potential land contamination assessment, we have found no incineration facilities, burn pits or facilities that utilises high temperature burning at the Yau Tong Bay marine lots. Hence the presence of Dioxin was not considered as an issue.

8.3.2 All the Yau Tong Bay marine lots will be subject to further inspections when they are vacated. Should there be signs of incineration facilities, burn pits or facilities that utilises high temperature burning, soil sampling for Dioxin will be carried out. Details regarding such sampling will be submitted to EPD for approval.

8.3.3 In the event that Dioxin is found at the Yau Tong Bay marine lots, the volume is expected to be small as there has been no indication of such contamination observed. The Dioxin contaminated soil, if any, could be solidified in a cement matrix followed by encapsulation in polythene within steel drums for disposal to landfill site. The solidified material will be subject the TCLP (Toxicity Characteristics Leaching Procedure) prior to disposal. References of similar treatment methods are made to the “EIA (Final Report) for Agreement No. CE 15/99: Demolition of Buildings and Structures in the Proposed Kennedy Town Comprehensive Development Site Area” dated September 2001 and “EIA (Final Report) for Agreement No. CE 15/99: Environmental Impact Assessment for Demolition of Kwai Chung Incineration Plant and Kennedy Town CDA” dated September 2001. A detailed proposal for dealing with Dioxin contaminated soil, if found, will be submitted to EPD for approval.

[1] Tributyltin: case study of an environmental contaminant, Edited by Stephen J. De Mora, Cambridge University Press

1 TPH Criteria Working Group, 1996 (range of oral reference dose depends on the aliphatic and aromatic portion and the chain length/ molecular weight)

2 EPA Region III Risk Based Concentration Table, EPA Region 3, March 7, 1995

3 Standard Provisional Guide for Risk-based Corrective Action, ASTM PS 104-98