1 Background

A Contamination Assessment Report (CAR) and Remediation Action Plan (RAP) for the site of KCRC Kowloon Southern Link (KSL) (Appendix 10.2 of the KSL EIA Report) were prepared. Groundwater at some spots of the KSL alignment was found contaminated with primarily heavy metals (i.e. Copper, Lead and Mercury) of which their levels exceeded the Dutch C level for groundwater. Within the construction sites of KDB300 & KDB400, water sample collected at borehole KSD100/DHEPZ113 in the vicinity of Tai Kok Tsui petrol filling station at Skyway House exceeded the discharge limit as stipulated in Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters (TM) and Dutch C Levels as indicated in KSL EIA Report.

According to the KSL EIA Report and Further Environmental Permits (FEPs) (EP No. FEP-02/215/2005/A and FEP-03/215/2005/A) for KDB300 & KDB400, direct discharge of contaminated groundwater will not be adopted. Contaminated groundwater should be diverted to pre-determined well(s) for recharging back to the ground. In accordance with the KSL EIA Report and EM&A Manual, recharge wells should be selected at places where the groundwater quality will not be affected by recharge operation. According to Conditions 3.4 and 3.5 of the FEPs for KDB300 and KDB400 respectively, a Working Plan (WP) including a number of recharge wells and their specific locations, baseline parameters of the recharge and monitoring locations, and number of treatment facilities and their treatment capacities should be prepared and submitted to EPD prior to dewatering works.

According to the KSL EIA Report and EM&A Manual, ambient measurements on the groundwater quality at the WKN and the cut-&-cover tunnel to the north of WKN prior to the selection of recharge wells is required. The measurement results will be used to update the potential of groundwater contamination and to form groundwater baseline condition. After performing the ambient groundwater quality measurement, recharge wells would be selected for recharging contaminated groundwater.

A Groundwater Monitoring Working Plan was prepared and endorsed by EPD on 31 October 2006.

In the endorsed Groundwater Monitoring Working Plan, three potential control wells C1, C2 and C3 were identified for groundwater monitoring during the recharge operation. From preliminary investigation, utility as-built records showed that the location of well C2 is full of underground utilities (detailed in Section 4.4). There is much risk involved to drill at this location. In consideration of the extensive underground utilities located at potential control well C2, control wells C1 and C3 will be used for groundwater monitoring during the recharge operation.

From on-site experience it has been observed that the flow rate is lower than previously estimated, hence, the actual dewatering rate is lower than previously estimated. Therefore, only five dewatering zones are required (Zone A, B+C, D+E, F and G) compared to the seven dewatering zones (Zone A, B, C, D ,E ,F and G) stated in the endorsed Groundwater Monitoring Working Plan.

This updated Working Plan (WP) is prepared to:

§ Revise the dewatering zones to take into account the lower dewatering rate than previously estimated;

§ Describe general approach of groundwater monitoring works;

§ Identify ambient groundwater monitoring locations;

§ Formulate ambient/baseline groundwater monitoring programme and stipulate monitoring parameters, reporting limits and analytical method for the ambient, recharge and monitoring locations;

§ Update the extent of potential groundwater contamination;

§ Identify possible areas for recharging groundwater, locations of recharge wells, impact monitoring wells and control wells;

§ Formulate the impact monitoring programme including Limit Level of impact monitoring and Event and Action Plan;

§ Describe the requirements of groundwater monitoring wells, sampling methodology and sample handling requirements; and

§ Identity the number and capacity of the treatment facility required.

2 Groundwater Monitoring Approach

2.1 Ambient Groundwater Monitoring

According to the KSL EIA Report and EM&A Manual, ambient groundwater monitoring should be carried out for updating the extent of the groundwater contamination identified in the KSL EIA report. The ambient groundwater monitoring will also form part of the baseline groundwater monitoring of the groundwater monitoring programme for recharging contaminated groundwater.

Groundwater would be considered as contaminated if it cannot comply with the discharge limits of the relevant flow band as stipulated in Table 9a – Standards for Effluent Discharged into the Inshore Waters of VHWCZ of the TM and it contains any prohibited substance listed in Section 9.2 of the TM.

The following diagram shows the approach of the groundwater monitoring works.

2.2 Groundwater Monitoring Phases

Groundwater monitoring for recharging groundwater work will be separated into baseline and impact phases.

2.2.1 Baseline Groundwater Monitoring

Baseline monitoring will be undertaken at the following monitoring wells:

I. Ambient Groundwater Quality Monitoring Well

II. Recharge Well

III. Control Well

IV. Impact Monitoring Well

Groundwater samples from the above wells will be collected daily for 7 consecutive days. Monitoring will be carried out at ambient groundwater monitoring wells to determine the level and extent of groundwater contamination, if any. If ambient groundwater monitoring results show that the groundwater quality does not comply with the discharge limits ~~as stipulated in TM~~ or ~~the groundwater is contaminated (i.e. concentration of contaminants above the Dutch C Levels)~~contains prohibited substances as stipulated in TM, baseline monitoring will also be carried out at recharge well(s), control well(s) and impact monitoring well(s). Based on the baseline monitoring results, limit levels will be established once the analytical results are available based on the followings:

§ Ambient groundwater quality measurement results; and

§ The groundwater quality of the monitoring wells at the site boundaries will not be affected by the recharging operation.

2.2.2 Impact Groundwater Monitoring

Impact monitoring will be carried out at the recharge wells and monitoring wells in order to ensure the quality of groundwater from dewatering is better than that of the recharge areas. In addition, monitoring will also be carried out at the control well for monitoring the natural variation of groundwater quality.

In case of any exceedance, appropriate action will be undertaken in accordance with the Event and Action Plan as described in Table 7-4.

3 Dewatering Works

3.1 Dewatering Works at KDB400

KSL railway will be laid underground and will be constructed by cut-&-cover. Excavation and dewatering works along the alignment will be required and will be carried out in separate zones within KDB400. Each of the excavation areas will be surrounded by cofferdam walls (by means of sheet-pile or pipe-pile), which restrict the seepage of groundwater into the excavation zones. The first zone of where excavation works will be carried out is Zone A at Nam Cheong Park as shown in Annex 1.

From on-site experience, taking into account the actual permeability of the soils, the flow rate is lower than previously estimated, hence, the actual dewatering rate is lower than previously estimated. Therefore, only five dewatering zones are required (Zone A, B+C, D+E, F and G) compared to the seven dewatering zones (Zone A, B, C, D , E ,F and G) in the previous Working Plan.

Two site areas have been identified for recharging the groundwater from dewatering process. Groundwater from Zones A and B+C will be recharged to recharge area at Nam Cheong Park near Zone A (R2). Groundwater from Zones D+E, F and G will be recharged to recharge area adjacent the KSL alignment near the construction site of Olympic City Phase III near Zone F (R1). Annex 1 shows the identified recharge areas and tentative programme for dewatering works of Zones A to G.

3.2 Dewatering Rate

Dewatering rate depends on the dewatering requirement of each phase of dewatering works. In general, dewatering works will be separated into two phases. Phase I dewatering works include pumping test and full drawn-down of water table and phase II dewatering works control the seepage of groundwater during excavation and tunnel construction works. The estimated average hourly dewatering rate of the dewatering well and the daily dewatering rate of dewatering zones in different phases are given in Annex 1. As dewatering works of different zones will be overlapped in certain time periods, the estimated daily groundwater dewatering rates at different time periods are summarised in Table 3-1.

Period	Zone	Dewatering Works		Estimated Dewatering Rate, m³/day	Recharge Area
Period	Zone	Pumping Test and Draw-down Water Table	Seepage Control	Estimated Dewatering Rate, m³/day	Recharge Area

09 Nov 06 to 15 Nov 06	A	ü		576	Recharge area at Nam Cheong Park near Zone A
16 Nov 06 to 15 Mar 07	A		ü	192
16 April 07 to 23 April 07	B+C	ü		1,440
24 April 07 to 31 Aug 07	B+C		ü	480
23 Mar 07 to 30 Mar 07	D+E	ü		1,440	Recharge area adjacent to the KSL alignment near the construction site of Olympic City Phase III near Zone F
1 April 07 to 24 May 07	D+E		ü	480
25 May 07 to 31 May 07	D+E		ü	1,920
25 May 07 to 31 May 07	F	ü		1,920
01 June 07 to 22 June 07	D+E		ü	960
01 June 07 to 22 June 07	F		ü	960
23 Jun 07 to 30 Jun 07	D+E		ü	2,688
	F		ü
	G	ü
01 Jul 07 to 31 Aug 07	D+E		ü	1,536
	F		ü
	G		ü
01 Sep 07 to 31 Oct 07	F		ü	1,056
01 Sep 07 to 31 Oct 07	G		ü	1,056
01 Nov 07 to 30 Nov 07	G		ü	576

Table 3-1 Tentative Schedule of Dewatering Works and Respective Dewatering Rate

4 Location of Sampling Wells

4.1 Ambient Groundwater Monitoring Wells

According to the KSL EIA report, six sampling locations were identified at five identified potential contaminated areas. Figure 4-1 shows the sections of the construction sites of KSL Contracts KDB200, KDB300 and KDB400. Figure 4-2 shows five groundwater sampling locations identified in the KSL EIA report. Only two sampling locations (KSD100/DHEPZ113 and KSD100/DHE120) are located within the construction site of KDB400. There was no potential contaminated area identified in the construction site of KDB300. The analytical results of these five locations extracted from the EIA report are given in Annex 2.

Groundwater sample from the borehole KSD100/DHEPZ113 in the vicinity of Tai Kok Tsui petrol filling station at Skyway House exceeded the discharge limit of Mercury as stipulated in TM. TPH (C15-C28) was also present in the groundwater sample. As the testing for TPH (C10-C14 and C29-C36), PAHs and BTEX in the EIA study was not up to the required reporting limits, such substances might also be present in the sample.

TPH (C15-C28 and C29-C36) was present in the groundwater sample at borehole KSD100/DHE120 that is located at the former shipyard site in West Kowloon Reclamation Area. Moreover, as the testing for TPH (C10-C14), PAHs and BTEX in the EIA study was not up to the required reporting limits, such substances might also be present in the sample.

Annex 23 shows that there is an old seawall down to –5mPD (approximate 11m below ground level) at Chainage 6+950* (at about the northern end of MTR Olympic Station and the Chainage is referred to Site Layout for KDB400 (Drawing no.: KDB400/HA/Y0001 rev A) as given in Annex 34). This would potentially restrict the migration of groundwater across the seawall.

For updating the extent of the groundwater contamination and to evaluate the groundwater quality at the excavation areas, the ambient groundwater quality monitoring wells are located between Chainage 6+950* and Chainage 7+200* (where it is midway between boreholes KSD100/DHEPZ113 and KSD100/DHE120). Six ambient groundwater quality monitoring wells, AGM 1 to AGM 6, along the alignment are shown in Annex 41.

In addition, one ambient groundwater well (AGM 7) has been identified in the vicinity of KSD100/DHE120 as shown in Annex 41 to update the groundwater contamination at the site of Nam Cheong Park.

All of these ambient groundwater wells are located at the excavation areas where dewatering works will be undertaken to the north of the old seawall. Thus AGM1 to AGM7 can represent the groundwater quality from Zone A to Zone G.

4.2 Recharge Well

Two recharge areas locating recharging wells for groundwater recharge operation were identified. Recharge areas near Zone F and Zone A are identified for recharging groundwater from Zone D+E to Zone G and Zone A to Zone B+C respectively. Two recharge well locations; R1 and R2, for evaluating the groundwater contamination at recharge areas were identified as shown in Annex 41. R1 is located at the site area adjacent to the KSL alignment near the construction site of Olympic City Phase III near Zone F and R2 is located within the construction site of Nam Cheong Park near Zone A.

Pit will be constructed at each recharge area as it is not practicable that recharge groundwater from dewatering works into a single recharge well. The adequacy of the recharge well to accommodate the dewatered groundwater would be subject to the soil permeability data which will be obtained from the pumping test. Pit will be enlarged or additional recharge area will be identified if it is found that the pit at the recharge area is not sufficient to accommodate the dewatered groundwater.

As mentioned in Section 3.1, cofferdam wall will be constructed surrounding the excavation zones to restrict the groundwater seepage. This would also restrict the groundwater recharged to R1 and R2 to migrate seaward across the alignment. Thus, monitoring and control wells as mentioned below are also located to the east side of the KSL alignment where R1 and R2 are located.

4.3 Monitoring Well

Monitoring well locations, M1/AGM5a, M2, M2a and M3, are identified at the site boundary near the recharge wells as shown in Annexes 1 for ensuring there is no likelihood of locally risen groundwater level and transfer of pollutants beyond the site boundary. Due to site constraint, M2 was used for obtaining the baseline groundwater quality near the site boundary while M2a will be the actual monitoring location during impact monitoring ~~and 4~~.

4.4 Control Well

Control well will be used to monitor the natural variation of the groundwater quality. Groundwater quality should not be affected by excavation works and recharge operation. Three potential control wells C1, C2 and C3 were identified for groundwater monitoring during the recharge operation and they are shown in Annex 1. From preliminary investigation, utility as-built records showed that the location of well C2 is full of utilities, e.g. tel-cable, optical cable, town gas pipe, etc and therefore poses too much risk to drill on. In consideration of the extensive underground utilities located at potential control well C2, control wells C1 and C3 will be used for groundwater monitoring during the recharge operation.

The control wells have been identified at the best available locations with the consideration of the followings in order to ensure that the groundwater quality at control wells can represent natural variation but not affecting the KSL construction works:

§ excavation and dewatering works;

§ recharge operation;

§ limited site area (as the site area railway construction is narrow);

§ most of the suitable areas are existing roads and slopes which are not suitable for locating sampling well; and

§ Consideration of underground utilities.

C1/C3 will be used as control well for recharge operation for Zone A as M2a will be used as monitoring well during the recharge operation. C3 will be used as control well for Zone B+C as M3 will be used as monitoring well during the recharge operation. For recharge operation for Zones D+E, F and G, as M1/M1 AGM5a (to be renamed as M4) will be used as monitoring well, C3 will be used as control well.

Table 4-2 shows the respective recharge areas, monitoring wells and control wells for the recharge operation for different excavation zones.

Zone	Dewatering Period	Recharge Area/Well	Monitoring Well	Control Well
Zone A	Nov 06 to Mar 07	R2	M2M2a	C1/C3
Zone B+C	April 07 to Aug 07	R2	M2M3	C3
Zone D+E	Mar 07 to Aug 07	R1	M1/M1AGM5a (M4)	C3
Zone F	May 07 to Oct 07	R1	M1/M1AGM5a (M4)	C3
Zone G	Jun 07 to Nov 07	R1	M1/M1AGM5a (M4)	C3

Table 4-2 Recharge Areas and Monitoring Location

5 Monitoring Methodology

5.1 Baseline Monitoring

Baseline monitoring should be carried out at all sampling wells identified in Section 4.

Baseline monitoring was carried out from 23 June to 29 June 2006 at the sampling wells, AGM1 to AGM4, AGM6&7, M1 and M2, R1 and R2, and C1. Due to the temporary traffic arrangement, access to AGM5 was not available during the baseline monitoring period. Thus, alternative location, AGM5a, was identified. However, due to the site constraint, AGM5a could only be located ~~within the~~ outside the excavation area but at the site boundary near the recharge area near Zone F as shown in Annex 1. Monitoring at AGM5a was carried out from 6 July to 12 July 2006.

Baseline monitoring at M3 and C3 has been scheduled from 24 January 2007 to 30 January 2007.

5.1.1 Sampling Frequency

Groundwater samples from the wells were collected daily for 7 consecutive days in accordance with the KSL EM&A manual.

5.1.2 Testing Parameters

With reference to KSL EIA report, within KDB400 site, only the concentration of contaminant of Mercury (Hg) was found to exceed the discharge limit as stipulated in TM at KSD100/DHEPZ113 and TPH was present in the groundwater at KSD100/DHEPZ113 and KSD100/DHE120. KSL report also shows that the concentrations of Cd, Cu, Pb and Zn at KSD100/DHEPZ113 and Cd at KSD100/DHE120 were close to the discharge limits. Therefore groundwater samples were tested for the parameters as listed in Table 5-3. Table 5-3 also shows the reporting limits and analytical methods of the parameters to be tested. All the analytical works, except pH and Temperature, will be carried out by HOKLAS accredited laboratory. All the surplus groundwater generated from the sampling works will be recharged to the same location.

Parameters	Monitoring Well	Analytical Method	Reporting Limit¹ (mg/L)	TM-Water effluent limit² for inshore waters of VHWCZ (mg/L)
Groundwater Level	AGM1 to AGM7, R1 to R2, M1 to M3, C1 and C3 (14 wells)	In house	0.1m	---
pH		In house	0.1unit	6-9
Temperature °C		In house	0.1°C	< 40°C
TPH C6 – C9		USEPA8015	20 mg/L	---
TPH C10–C14			25 mg/L	---
TPH C15 – C28			25 mg/L	---
TPH C29 – C36			25 mg/L	---
Cd		USEPA6020	0.0002	0.001
Cu	AGM1 to AGM6, R1, M1, C1 and C3 (10 wells)		0.001	0.1 ~~to 0.25~~
Pb			0.001	0.1 ~~to 0.25~~
Zn			0.01	0.1 ~~to 0.25~~
Hg		APHA3112B	0.0005	0.001
Total Toxic Metals	N/A	N/A	N/A	0.22 ~~to 1.6~~

Notes:

1. Lowest detection limits could be achieved by common commercial laboratories in Hong Kong. For those substances not detected using these detection limits, it is assumed that such substances do not exist in the water sample.

2. As the maximum dewatering rate is 3,200m³/day, ~~Subject to actual flow of the groundwater to be discharged or the groundwater discharge license obtained from EPD~~the discharge limits for the flow band of >3,000 and ≤4,000 ~~3,200~~m³/day are adopted.

Table 5-3 Baseline Groundwater Testing Parameters

5.2 Impact Monitoring

Impact monitoring will be carried out at monitoring well, control well and, where appropriate, inlet of recharge well or outlet of treatment facilities according to Table 4-2 as mentioned in Section 4 during the recharge operation.

5.2.1 Sampling Frequency

Weekly monitoring of groundwater quality at the monitoring well, inlet of recharge wells/outlet of treatment facilities and control wells will be carried out during the recharging operation. Groundwater level at the monitoring wells and control wells will also be monitored on a daily basis.

5.2.2 Testing Parameters

As the baseline monitoring results show that only the concentration of TPH in the groundwater does not comply with discharge limit as stipulated in TM (details are mentioned in Section 6), monitoring parameters will only include groundwater level and TPH during the impact monitoring stage. The analytical method and detection limit will be the same as mentioned in Table 4-1.

5.3 Sampling Method

5.3.1 Requirements of Monitoring Wells

Following are the general requirements of the groundwater monitoring wells:

§ Monitoring wells should be constructed to the depth of at least 3m below groundwater table.

§ A well pipe should be placed within a borehole for the formation of well.

§ The well pipe should comprise a well casing and a well screen with an inner diameter of 75mm. The materials for well casing and well screen should be inert not reacting with, releasing and adsorbing contaminants.

§ The well screen, which is the bottom part of the well pipe, should be formed from the bottom end of the monitoring well to the depth of ground water table. The well screen should be a slotted pipe that allows water flow into the well without allowing the entrance of soil particles into the well causing build up of sediment in the well.

§ The well screen should be surrounded by granular material (filter pack) such as gravel in the annular space of the borehole.

§ The well casing should be a solid walled pipe that connects the well screen with the ground surface.

§ Approximate 1m bentonite seal should be placed around the well casing at the annular space of the borehole above the sampling zone of the well screen to prevent migration of contaminants. Above the bentonite seal, the annular space of the borehole should be grouted with cement, bentonite or water slurry.

§ A concrete pad should be constructed at the ground surface around the well casing.

§ Sampling cap and bottom cap should be provided at the top and bottom end of the well pipe.

§ A concrete security casing with lockable cover should be installed at the ground surface for protecting the monitoring well.

§ Following the installation, the well should be developed using pump, bailer or surge block to remove any materials or contaminants that might have entered the well during installation and from filter pack. Development should be continued until the water is visibly clean.

§ After development of the monitoring well, sufficient time for equilibrium should be allowed.

Typical installation details of groundwater monitoring well are shown in Annex 5.

5.3.2 Groundwater Sampling

§ Prior to any groundwater sampling, purging will be carried out for removing stagnant water. No sample will be collected from the well that is not purged within 24 hours.

§ During groundwater purging, at least three volume of groundwater in the well will be purged. The pumping rate for purging will less than the pumping rate in developing the monitoring well.

§ The presence of floating product and its thickness will be recorded at each sampling point before and after groundwater purging.

§ Samples may be taken by pump or Teflon/stainless steel downhole bailer. Sampling equipment should be decontaminated between sampling locations using distilled water.

5.4 Sample Handling

All the groundwater samples collected should be transferred to clearly labelled and pre-cleaned sample containers with necessary preservatives immediately after collection. The sample containers should be provided by HOKLAS accredited laboratory. Sufficient quantity of samples should be collected for all laboratory analyses. Following sampling, samples should be stored in a cool box at temperature of between 0 and 4 ^oC, and transported to the laboratory within the sample retention time as advised by the laboratory under proper chain-of-custody system.

6 Baseline Monitoring Results

6.1 Monitoring Results

Table 6-4 summarises average value of the baseline monitoring results at each sampling location throughout the sampling period. Detailed baseline monitoring results are given in Annex 6.

~~Sampling Well~~Parameters		Discharge Limit	AGM1	AGM2	AGM3	AGM4	AGM6	AGM7	R1	AGM5a	R2	M1	M2	C1
Temperature	Average	< 40°C	27.2	26.9	26.6	27.4	26.5	26.9	27.2	26.2	26.7	26.5	25.6	26.2
Temperature	Range	< 40°C	27.1 – 27.4	26.7 – 27.2	26.4 – 27.1	27.0 – 27.9	26.0 – 27.0	26.4 – 27.5	27.1 – 27.4	26.0 – 26.3	26.3 – 27.0	26.2 – 26.9	25.3 – 26.0	25.4 – 26.7
pH	Average	6-9	7.6	7.4	7.5	7.7	7.5	7.5	7.6	8.1	7.8	7.8	7.5	7.6
pH	Range	6-9	7.6 – 7.8	7.2 – 7.5	7.4 – 7.6	7.6 – 7.8	7.4 – 7.5	7.4 – 7.6	7.6 – 7.8	8.1 – 8.1	7.4 – 8.1	7.5 – 8.2	7.3 – 7.8	7.6 – 7.7
Groundwater Level	Average	-	2.0	2.3	2.5	1.4	2.1	2.4	2.1	2.1	2.8	2.2	5.0	2.4
Mercury	Average	1	0.50	0.50	0.50	0.50	0.50	N/A	0.50	0.50	N/A	0.50	N/A	0.50
Mercury	Range	1	0.5 – 0.5	0.5 – 0.5	0.5 – 0.5	0.5 – 0.5	0.5 – 0.5	N/A	0.5 – 0.5	0.5 – 0.5	N/A	0.5 – 0.5	N/A	0.5 – 0.5
Cadmium	Average	1	0.23	0.27	0.20	0.23	0.21	0.76	0.20	0.20	0.23	0.40	0.43	0.50
Cadmium	Range	1	0.2 – 0.3	0.2 – 0.5	0.2 – 0.2	0.2 – 0.3	0.2 – 0.3	0.4 – 1.0	0.2 – 0.2	0.2 – 0.2	0.2 – 0.4	0.2 – 1.0	0.2 – 0.5	0.2 – 1.0
Copper	Average	100	3.3	7.7	2.0	1.3	1.0	N/A	3.4	1.0	N/A	2.7	N/A	2.9
Copper	Range	100	1 – 7	1 – 20	1 – 4	1 – 2	1 – 1	N/A	2 – 6	1 – 1	N/A	1 – 7	N/A	2 – 5
Lead	Average	100	34.9	42.4	13.4	38.0	7.3	N/A	41.0	5.6	N/A	140.1	N/A	139.1
Lead	Range	100	11 – 50	14 – 97	4 – 28	8 – 75	4 – 23	N/A	26 – 76	4 – 8	N/A	26 – 420	N/A	28 – 327
Zinc	Average	100	51.0	63.3	13.0	12.7	10.0	N/A	15.7	10.0	N/A	13.4	N/A	24.3
Zinc	Range	100	19 – 116	12 – 156	13 – 164	10 – 27	10 – 10	N/A	10 – 25	10 – 10	N/A	10 – 25	N/A	12 – 39
Total Toxic Metals	Average	200	89.9	114.2	29.1	52.7	19.1	0.76	60.8	17.3	0.23	157.1	0.43	167.3
Total Toxic Metals	Range	200	34.7 – 163.7	28.7 – 236.7	18.7 – 196.7	19.7 – 104.8	15.7 – 34.8	0.4 – 1.0	42.7 – 107.7	15.7 – 19.7	0.2 – 0.4	37.7 – 453.5	0.2 – 0.5	42.7 – 372.5
TPH C6 – C9	Average	-	20.00	22.86	20.00	20.00	20.00	78.43	76.43	60.57	20.14	133.71	120.00	54.14
TPH C6 – C9	Range	-	20 – 20	20 – 40	20 – 20	20 – 20	20 – 20	20 – 107	20 – 188	30 – 124	20 – 21	30 – 237	20 – 199	20 – 118
TPH C10–C14	Average	-	36.86	61.29	40.14	33.14	26.57	89.29	197.29	30.57	90.14	53.00	79.57	49.86
TPH C10–C14	Range	-	25 – 78	25 – 166	25 – 58	25 – 45	25 – 36	64 – 123	25 – 588	25 – 42	32 – 262	29 – 80	59 – 102	38 – 62
TPH C15 – C28	Average	-	189.86	431.71	313.86	136.71	150.29	264.14	374.86	784.43	285.86	310.43	255.71	409.86
TPH C15 – C28	Range	-	53 – 342	183 – 971	122 – 448	25 – 235	67 – 210	206 – 301	154 – 797	651 – 913	101 – 552	180 – 533	188 – 318	215 – 580
TPH C29 – C36	Average	-	58.71	136.14	128.14	31.00	26.00	63.00	87.00	30.43	217.43	43.00	39.57	41.00
TPH C29 – C36	Range	-	25 – 138	40 – 335	52 – 214	25 – 48	25 – 29	48 – 110	25 – 123	25 – 40	32 – 506	25 – 53	26 – 52	35 – 45
TPH (Total)	Average	-	305.4	652.0	502.1	220.9	222.9	494.9	735.6	906.0	613.6	540.1	494.9	554.9
TPH (Total)	Range	-	123 – 547	273 – 1492	219 – 740	95 – 331	137 – 291	346 – 588	224 – 1528	738 – 1009	185 – 1311	300 – 768	302 – 616	351 – 696

Notes:

1. All ~~results~~ units are in mg/L except for groundwater level. Groundwater level is in mPD.

2. No groundwater level limit is stipulated in TM.

3. TPH is prohibited substance according to TM.

4. N/A – Testing of the parameters was not carried out. Referring to Section 5.1,, the parameters are not of concern at the relevant locations.

Table 6-4 Summary of Baseline Groundwater Monitoring Results

Baseline monitoring results show that the average concentrations of Hg, Cd, Cu, Pb and Zn and average concentrations of total toxic metals at AGM1 to AGM4 and AGM6, and average concentration of Cd at AGM7 comply with ~~their respective~~ discharge limits of the flow band (of >3000 and ≦4000 m³/day, (i.e. the maximum dewatering rate) as stipulated in the TM.

TPH was found in the groundwater samples from all of the monitoring wells. The average concentrations of TPH were found from the range of 220.9mg/L to 906.5mg/L. The highest average TPH concentration is found at AGM5a which is located within the recharge area near Zone F. AGM5a is outside the tunnel footprint and no water at AGM5a will be dewatered. The average TPH concentrations at R1 and R2 are 735.6mg/L and 613.6mg/L respectively.

It is found that the average TPH concentrations at ambient groundwater monitoring wells, AGM4 and AGM6, are better than that of R1. However, it is found that average TPH (C15-C28 and C29-C36 at AGM2 and C29-C36 at AGM3) concentrations are higher than those of R1. Moreover, average TPH (C6-C9) concentration at AGM7 is higher than that of either R1 or R2.

AGM2 and AGM3 can represent groundwater quality of Zones F and G. AGM6 and AGM7 represents groundwater quality of Zone D+E and AGM7 represents groundwater quality of Zones A and B+C. Thus, groundwater from all Zones should be treated prior to recharge in order to avoid affecting the groundwater quality at the recharge area. Details of the requirements of treatment facility are discussed in Section 8.

6.2 Extent of Contamination

The baseline monitoring results show that TPH and heavy metals wasere found across the site area to the north of the old seawall at KDB400. However, the average concentrations of individual metals and total toxic metals at relevant sampling locations, except for the average concentration of lead at C1, comply with respective discharge limits as stipulated in the TM. As mentioned in Section 4.1, the old seawall would potentially restrict the migration of contaminated groundwater from the petrol filling station at Skyway House to the south of the seawall. Moreover, there was no potential contaminated area identified at the site areas to the south of the seawall at KDB400 in the KSL EIA report. Thus, it is considered that the extent of the contamination of groundwater is from the old seawall to the northern end of KDB400 site.

7 Event and Action Plan

7.1 Limit Level

Limit Levels for the impact monitoring have been developed based on the ambient water quality measurement. Reference is also made to the approach for determining Action and Limit (A/L) Levels in Appendix D2 to the Environmental Monitoring and Audit Guidelines for Development Projects in Hong Kong (EPD, February 1998) and KSL EM&A manual for the inlet of recharge wells/outlet of treatment facilities. The Limit Levels for R1 and R2 of where impact monitoring will be carried out are shown in Table 7-5.

Parameters	Limit Level (95 percentile of baseline data)
Parameters	R1	R2
TPH (C6-C9)	165.5	20.7
TPH (C10-C14)	531.3	227.2
TPH (C15-C28)	711.5	543.9
TPH (C29-C36)	118.8	497.3

Note: Exceedance is considered valid only if there is no justification from the monitoring at the control well.

Table 7-5 Limit Levels of TPH at Recharge Wells/Outlet of Treatment Facilities

Monitoring wells will be used to ensure there is no likelihood of local risen of and transfer of pollutant beyond the site boundary. The limit levels for the groundwater level and TPH at monitoring wells ~~As groundwater level monitoring at recharge wells is not practicable, groundwater level monitoring will be carried out at monitoring wells. Limit Levels for groundwater level at monitoring well~~ are shown in Table 7-6. In order to monitor the natural variation of groundwater, water level at control well will also be monitored.

Parameters	Limit Level ~~(1m above baseline level)~~
Parameters	M1	~~3.2~~AGM5a (M4)	M2a	M3
Groundwater level	3.2	3.1	6.0	To be Determined
TPH (C6-C9)	284.4	148.8	238.8	To be Determined
TPH (C10-C14)	96	50.4	122.4	To be Determined
TPH (C15-C28)	639.6	1095.6	381.6	To be Determined
TPH (C29-C36)	63.6	48	62.4	To be Determined

Notes:

1. Exceedance is considered valid only if there is no justification from the monitoring at the control well.

2. Limit level for groundwater level is 1m above baseline level.

3. Limit level for TPH is 120% of the maximum concentration of the baseline monitoring. As M2a is close to M2, baseline monitoring results of M2 is considered representative for establishing the limit level of M2a. Otherwise, baseline monitoring at M2a is required to determine the limit level prior to the impact monitoring.

Table 7-6 Limit Levels ~~of Groundwater Level~~ at Monitoring Wells

7.2 Event and Action Plan

In case of any exceedance of Limit Levels, actions in accordance with the event and action plan as shown in Table 7-7 should be taken.

Event	Action
Event	ET Leader	IEC	ER	Contractor
Groundwater level exceeds 1m from baseline Level	· Notify IEC and the Contractor. · Carry out investigation. · Report the results of investigation to IEC and the Contractor. · Discuss with the Contractor and formulate remedial measures. · Increase monitoring frequency to check mitigation measures.	· Review with analysed results submitted by ET. · Review the proposed remedial measures by the Contractor and advise ER accordingly. · Supervise the implement of remedial measures.	· Confirm receipt of notification of exceedance in writing. · Notify the Contractor. · Require the Contractor to propose remedial measures for the analysed groundwater problem. · Ensure remedial measures are properly implemented.	· Reduce the recharge rate AND / OR · Suspend the recharge until the groundwater level falls back to less than 1m difference with the baseline
Limit Level Exceedance for TPH	· Notify IEC and the Contractor. · Carry out investigation. · Report the results of investigation to IEC and the Contractor. · Discuss with the Contractor and formulate remedial measures. · Increase monitoring frequency to check mitigation measures.	· Review with analysed results submitted by ET. · Review the proposed remedial measures by the Contractor and advise ER accordingly. · Supervise the implement of remedial measures.	· Confirm receipt of notification of exceedance in writing. · Notify the Contractor. · Require the Contractor to propose remedial measures for the analysed groundwater problem. · Ensure remedial measures are properly implemented.	· Suspended the recharge OR · Treatment of the recharged groundwater until monitoring result shows the compliance of Limit Level

Table 7-7 Event and Action Plan

8 Groundwater Treatment

Based on the baseline monitoring results, recharge areas have been identified for recharging the groundwater. As mentioned in Section 6, groundwater from all zones is required to be treated prior to recharge.

It is considered that treatment process such as chemical enhanced sedimentation, physical filtration and activated carbon filter should be used to remove the suspended solids and organics laden in the groundwater. Groundwater treatment plant with treatment capacity of 40m³/hr (960 m³/day) will be provided. Based on the dewatering rates, the numbers of treatment facilities at different time periods are shown in Table 8-8 below:

Period	Estimated Dewatering Rate, m³/day	Number of Treatment Facilities	Recharge Area
09 Nov 06 to 15 Nov 06	576	1	Recharge area at Nam Cheong Park near Zone A
16 Nov 06 to 15 Mar 07	192	1
16 April 07 to 23 April 07	1,440	2
24 April 07 to 31 Aug 07	480	1
23 Mar 07 to 30 Mar 07	1,440	2	Recharge area adjacent the KSL alignment near the construction site of Olympic City Phase III near Zone F
1 April 07 to 24 May 07	480	1
25 May 07 to 31 May 07	1,920	2
01 June 07 to 22 June 07	960	1
23 Jun 07 to 30 Jun 07	2,688	3
01 Jul 07 to 31 Aug 07	1,536	2
01 Sep 07 to 31 Oct 07	1,056	2
01 Nov 07 to 30 Nov 07	576	1

Table 8-8 Number of Treatment Facilities

Each of the treatment plant will include three treatment components: chemical enhanced sedimentation tank, sand filter and activated carbon filter. The schematic process of the groundwater treatment is shown in Figure 8-3. Suspended solids in the contaminated groundwater will be removed by both chemical enhanced sedimentation and sand filter to approximate 5mg/L in order to avoid blockage of activated carbon filter. Activated carbon filter will be designed to treat the TPH to be half of the Limit Levels of the recharges wells.

Figure 8- 3 Schematic Process of Groundwater Treatment

9 Additional Groundwater Monitoring Works

It should be noted that baseline monitoring results of C3 and M3 were not available during the preparation of this working plan. The baseline monitoring results of these locations is for comparing with the impact monitoring results during the impact monitoring stage for evaluating any significant impact of groundwater by the recharge operation. The identified recharge wells and, if necessary, appropriate treatment facilities would not be subject to the baseline monitoring results of C3 and M3. Baseline monitoring results of C3 and M3 will be submitted to EPD for record prior to any impact monitoring at these locations (i.e. dewatering works of Zones B+C to G).

This working plan has been prepared based on the best available information at this stage. Nevertheless, if additional recharge areas (refer to Section 4.2) and evaluation of contamination of groundwater for further excavation areas are required, baseline monitoring at additional sampling wells will be required to determine the suitable recharge well and ascertain the necessity of treatment prior to groundwater recharge. Additional baseline monitoring and formulation of impact monitoring including the Limit Level for impact monitoring would adopt the same approach of this WP.

* All Chainages are referred to Site Layout for KDB 400 (Drawing no.: KDB400/HA/Y001 rev A) as given in Annex 2.