TABLE OF CONTENTS

8 Sewerage and Sewage Treatment Implication. 8-1

8.1 Introduction. 8-1

8.2 Description of Environment 8-1

8.3 Design Guidelines and Standards. 8-1

8.4 Sewage Estimation and Impact Assessment 8-1

8.5 Conclusion. 8-7

LIST OF TABLES

Table 8.1 Residents in the Concerned Sewerage Catchment

Table 8.2 Employees in the Concerned Sewerage Catchment

Table 8.3 Students and Staffs in the Concerned Sewerage Catchment

Table 8.4 Swimming Pools in the Concerned Sewerage Catchment

Table 8.5 Summary of Capacity for Concerned Pumping Stations

Table 8.6 Summary of Capacity for the Relocated Sha Tin Sewage Treatment Works (STSTW)

LIST OF FIGURES

Figure 8.1 Layout Plan for Proposed Dry Weather Flow Interceptor (DWFI) System for Fo Tan Nullah (Sheet 1 of 3)

Figure 8.2 Layout Plan for Proposed Dry Weather Flow Interceptor (DWFI) System for Fo Tan Nullah (Sheet 2 of 3)

Figure 8.3 Layout Plan for Proposed Dry Weather Flow Interceptor (DWFI) System for Fo Tan Nullah (Sheet 3 of 3)

LIST OF APPENDIX

Appendix 8.1 Hydraulic Performance of Existing Sewers

8 SEWERAGE AND SEWAGE TREATMENT IMPLICATIONS

8.1 Introduction

8.1.1.1 This section presents the assessment on potential sewerage and sewage treatment impacts on the downstream public sewerage, sewage treatment and disposal facilities arising from the Project, which has been conducted in accordance with the criteria and guidelines as stated in Section 6.5 of Annex 14 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) as well as the requirements given in Clause 3.4.9 and Appendix G of the EIA Study Brief (No. ESB-319/2019).

8.2 Description of Environment

8.2.1.1 Fo Tan Nullah is located within the catchment of Sha Tin Sewage Treatment Works (STSTW). The land uses nearby the Project site are mainly industrial and residential uses, as well as commercial uses such as some restaurants and shops.

8.2.1.2 Due to the possible ageing of drainage systems and individual direct discharge to Fo Tan Nullah, a number of water quality pollution incidents have been reported and there remains some polluting sources. Installation of dry weather flow interceptors (DWFI) system is considered as one of the options to enhance water quality in the Nullah.

8.3 Design Guidelines and Standards

8.3.1.1 The design guidelines and standards adopted in the sewerage and sewage treatment assessment are:

· DSD Sewerage Manual Part 1 (2013 Version);

· DSD Sewerage Manual Part 2 (2013 Version);

· DSD Technical Circulars and Practice Notes;

· EPD Guideline for Estimating Sewage Flows for Sewage Infrastructure Planning Version 1.0 (Report No. EPD/TP 1/05); and

· Environmental Impact Assessment Ordinance (EIAO), Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM), Annex 14 Section 6.5.

8.4 Sewage Estimation and Impact Assessment

8.4.1 Dry Weather Flow Intercepting System

8.4.1.1 Due to possible ageing drainage systems and possible expedient connection made in the past to Fo Tan Nullah, there still remains a portion of polluting sources. Hence, a dry weather flow intercepting (DWFI) system is proposed to improve the water quality in the nullah.

8.4.1.2 With the proposed DWFI system, polluted dry weather flows from drainage outlets would be intercepted by two dry weather flow channels, running along both sides of the nullah bed (see Section 2). The dry weather flow will be carried downstream eventually joining the nearby existing sewerage system. The dry weather flow then follows the existing sewage route to existing sewage pumping stations and eventually reaching the relocated Sha Tin Sewage Treatment Works. Proposed alignment of DWFI system is shown in Figures 8.1 to Figures 8.3.

8.4.2 Estimation of Existing Sewage Flow

8.4.2.1 The DWFI system is proposed to discharge into an existing 1200mm dia. sewer between manhole FMH4038367 and FMH4038368. To assess the hydraulic performance of the existing 1200mm dia. sewer, existing sewage flow from the concerned sewage catchment was estimated.

8.4.2.2 The sewage flow from the concern sewage catchment comprises several components: residential, industrial, commercial, and institution/schools. Population from each of the components were estimated and the average dry weather flow (ADWF) were calculated based on the “Guidelines for Estimating Sewage Flows for Sewage Infrastructure Planning” (GESF) from Environmental Protection Department.

8.4.2.3 The existing development parameters in the concerned sewerage catchment are estimated and summarised in Table 8.1 to Table 8.4.

Table 8.1 Residents in the Concerned Sewerage Catchment

Residential Buildings ^[1]	Population ^[2]	Unit Flow Factor ^[3] (m^3/day)	ADWF (m^3/d)
Jubilee Garden Block 1	762	0.27	236.5
Jubilee Garden Block 2	762	0.27	236.5
Jubilee Garden Block 3	762	0.27	236.5
Jubilee Garden Block 4	762	0.27	236.5
Jubilee Garden Block 5	762	0.27	236.5
Jubilee Garden Block 6	762	0.27	236.5
Jubilee Garden Block 7	762	0.27	236.5
Jubilee Garden Block 8	762	0.27	236.5
Ficus Garden	269	0.27	83.5
Royal Ascot Block 1	538	0.27	166.9
Royal Ascot Block 2	538	0.27	166.9
Royal Ascot Block 3	622	0.27	193.0
Royal Ascot Block 5	622	0.27	193.0
Royal Ascot Block 6	554	0.27	172.1
Royal Ascot Block 7	554	0.27	172.1
Royal Ascot Block 8	896	0.27	278.2
Royal Ascot Block 9	896	0.27	278.2
Royal Ascot Block 10	896	0.27	278.2
Royal Ascot Block 11	896	0.27	278.2
Haywood Villa Block 1 - 6	17	0.37	7.1
Rosary Villas Block 1	11	0.37	4.8
Rosary Villas Block 2	11	0.37	4.8
Rosary Villas Block 3	11	0.37	4.8
Rosary Villas Block 4	11	0.37	4.8
Rosary Villas Block 5	11	0.37	4.8
Rosary Villas Block 6	11	0.37	4.8
Rosary Villas Block 7	11	0.37	4.8
Rosary Villas Block 8	11	0.37	4.8
Rosary Villas Block 9	11	0.37	4.8
Rosary Villas Block 10	11	0.37	4.8
Ascot Heights	34	0.37	14.3
Valley View	22	0.37	9.5
Juniper Villa A1	22	0.37	9.5
Juniper Villa A2	22	0.37	9.5
Juniper Villa B1	22	0.37	9.5
Juniper Villa B2	22	0.37	9.5
Pine Villa Block C	22	0.37	9.5
Pine Villa Block D	22	0.37	9.5
Pine Villa Block E	22	0.37	9.5
Pine Villa Block F	22	0.37	9.5
Pine Villa Block G	22	0.37	9.5
Pine Villa Block H	22	0.37	9.5
The Morning Glory Block 1	22	0.37	9.5
The Morning Glory Block 2	22	0.37	9.5
The Morning Glory Block 3	22	0.37	9.5
Houses near Tsun King Road	342	0.27	106.1
Fo Tan Village	434	0.19	94.8
Fo Tan Kuk San Tsuen & Kwai Tei New Village	193	0.27	60.0
Houses near Wong Chuk Yeung Tsuen Path	120	0.27	37.4
Fung Yue House	1089	0.27	338.2
Fung Yat House	1089	0.27	338.2
Fung Lin House	1089	0.27	338.2
Hing Wan House	1089	0.27	338.2
Hing On House	1089	0.27	338.2
Hing Sing House	1089	0.27	338.2
Wing Mau House	1089	0.27	338.2
Wing Cheung House	1089	0.27	338.2
Wing Hing House	1089	0.27	338.2
Scenery Garden Block A	157	0.27	48.7
Scenery Garden Block B	291	0.27	90.4
Scenery Garden Block C	269	0.27	83.5
Scenery Garden Block D	246	0.27	76.5
Oriental Heights	146	0.27	45.2
Phoenix Heights	146	0.27	45.2
Queen's Heights	146	0.27	45.2
Rhine Heights	146	0.27	45.2
Hong Kong Baptist University Staff Quarters	316	0.27	98.2
Votre Palais	17	0.37	7.1
Garden Villa	25	0.37	10.7
Mei Wo Circuit	31	0.37	13.1
Ville De Cascade	302	0.27	93.9
Greenwood Terrace	736	0.27	228.7
Ville De Jardin	115	0.27	35.6
Yuk Wo Siu Chuk	146	0.27	45.2
Pat Tsz Wo Village	185	0.27	57.4
The Grandville	1193	0.27	370.4
Shatin Lodge	168	0.27	52.2
Hill Lodge	67	0.27	20.9
Claymore Garden	67	0.27	20.9
Cloudview Mansion	70	0.27	21.7
Mountainville Court	67	0.27	20.9
Eden Gardens	101	0.27	31.3
6 Lok Fung Path	168	0.27	52.2
10 Lok Fung Path	168	0.27	52.2
Richmond Court	45	0.37	19.1
Lok Lam Garden	78	0.27	24.3
Laurna Villa	3	0.27	0.9
Hong Kong Jockey Club Shatin Staff Quarter	1702	0.27	528.6
Racecourse Villa	56	0.19	12.2
The Palazzo Tower 1	479	0.27	148.7
The Palazzo Tower 2	384	0.27	119.1
The Palazzo Tower 3	398	0.27	123.5
The Palazzo Tower 5	398	0.27	123.5
The Palazzo Tower 6	406	0.27	126.1
The Palazzo Tower 7	308	0.27	95.6
The Palazzo Tower 8	283	0.27	87.8
The Palazzo Tower 9	283	0.27	87.8
The Palazzo Tower 10	406	0.27	126.1
The Palazzo Tower 11	507	0.27	157.4
Shek Shui Wan Village	50	0.27	15.6
Residential Buildings in CDA at Au Pui Wan Street	6840	0.19	1494.6
Choi Wo Court at Wo Sheung Tun Street	2257	0.27	700.7
Chun Yeung Estate	13569	0.19	2964.8
Mount Vienna	34	0.27	10.4
Yuk Wo Court	2324	0.19	507.8
Sub-total=			16,913.9

Notes:

[1] Information on no. of flat of existing residential building is collected from the website of Home Affairs Department https://www.buildingmgt.gov.hk/en/database_of_private_buildings_in_hong_kong/12.htm.

[2] According to statistics on population and households from Census and Statistic Department, an average domestic household size of 2.8 people was adopted in the population estimation.

[3] Unit Flow Factors were obtained from “Guidelines for Estimating Sewage Flows for Sewage Infrastructure Planning” (GESF) from Environmental Protection Department.

Table 8.2 Employees in the Concerned Sewerage Catchment

Commercial Buildings		Nos. of Workers ^[1][2]	Type	Unit Flow Factor ^[3] (m^3/day)	ADWF (m^3/d)
Fo Tan Railway House		1279	J6	0.08	117.7
Commercial Building		163	J3	0.18	33.7
The Palazzo Shopping Centre		72	J4	0.28	23.2
Shopping Centre at Jubilee Garden		408	J4	0.28	131.4
Plaza Ascot		84	J4	0.28	27.0
Fo Tan Railway Station		162	J3	0.18	33.5
Sui Wo Court Shopping Centre		272	J6	0.08	25.0
Fo Tan Cooked Food Market (West)		28	J10	1.58	50.9
Fo Tan Cooked Food Market (East)		33	J10	1.58	60.0
Sui Fai Factory Estate		1665	J3	0.18	344.7
Supreme Industrial Building		240	J3	0.18	49.7
Universal Industrial Centre		681	J3	0.18	141.0
Shatin Galleria		581	J3	0.18	120.3
Goldfield Industrial Centre		853	J3	0.18	176.6
Kerry Godown (Shatin)		934	J3	0.18	193.3
World-wide Industrial Centre		1381	J3	0.18	285.9
Wah Lok Industrial Centre		2801	J3	0.18	579.8
Chun Yeung Shopping Centre		258	J3	0.18	53.4
Wah Sang Industrial Building		1017	J3	0.18	210.5
Sun Hung Kai Logistics Centre (Shatin)		1505	J3	0.18	311.5
Yue Cheung Centre		565	J3	0.18	117.0
Fu Cheung Centre		635	J3	0.18	131.4
Yan Hing Centre		762	J3	0.18	157.7
Wah Luen Industrial Centre		1283	J3	0.18	265.6
Goodman Shatin Logistics Centre Phase 1		378	J3	0.18	78.2
Goodman Shatin Logistics Centre Phase 2		518	J3	0.18	107.2
Wah Lai Industrial Centre		387	J3	0.18	80.1
International Industrial Centre		615	J3	0.18	127.3
Yale Industrial Centre		732	J3	0.18	151.5
Leader Industrial Centre		725	J3	0.18	150.1
Wah Wai Centre		1042	J3	0.18	215.7
Veristrong Industrial Centre Block A		599	J3	0.18	124.0
Veristrong Industrial Centre Block B		599	J3	0.18	124.0
Meeco Industrial Building		283	J3	0.18	58.6
Harry Industrial Building		294	J3	0.18	60.9
Haribest Industrial Building		324	J3	0.18	67.1
Chinachem Wah Yiu Industrial Centre		993	J3	0.18	205.6
Fo Tan Industrial Centre		1205	J3	0.18	249.4
On Wah Industrial Building		289	J3	0.18	59.8
Fonda Industrial Building		290	J3	0.18	60.0
Fo Tan Road 33-35		368	J3	0.18	76.2
Kin Ho Industrial Building		1050	J3	0.18	217.4
Unison Industrial Centre		604	J3	0.18	125.0
Valiant Industrial Centre		1071	J3	0.18	221.7
Tao Miao Institute		169	J10	1.58	307.1
On Shing Industrial Building		418	J3	0.18	86.5
Hopeful Factory Centre		421	J3	0.18	87.1
Wah Wai Industrial Building		281	J3	0.18	58.2
Watson House		704	J3	0.18	145.7
Power Industrial Building		266	J3	0.18	55.1
Leaspont Industrial Building		286	J3	0.18	59.2
CCT Telcome Building		592	J3	0.18	122.5
Sha Tin Industrial Building		232	J3	0.18	48.0
Sha Tin Cold Storage Co. Ltd. No. 1		434	J3	0.18	89.8
Pak Sik Godown No. 1		944	J3	0.18	195.4
Café de Coral Centre		232	J3	0.18	48.0
Pak Sik No. 2 Building		1028	J3	0.18	212.8
Shatin Cold Storage No. 2		1101	J3	0.18	227.9
Sha Tin Communications & Technology Centre		4282	J3	0.18	886.4
Hong Kong Sports Institute		852	J12	0.08	78.4
Eating Place at CDA at Au Pui Wan Street ^[4]		425	J10	1.58	772.2
Shop and Services at CDA at Au Pui Wan Street ^[4]		292	J4	0.28	94.0
	Sub-total=				9,775.0

Notes:

[1] The total area of commercial building is measured using base map.

[2] The worker density per 100m² is based on Commercial and Industrial Floor Space Utilization Survey (CIFSUS) conducted by the Planning Department.

[3] Unit Flow Factors and Catchment Inflow Factor (Sha Tin Catchment) were obtained from “Guidelines for Estimating Sewage Flows for Sewage Infrastructure Planning” (GESF) from Environmental Protection Department.

[4] The floor areas of the eating place and shops and services at the CDA at Au Pui Wan Street are referred to the "Broad Development Parameters of the Applied Use/Development in respect of Application No. A/ST/927".

Table 8.3 Students and Staffs in the Concerned Sewerage Catchment

School/ Institution	No. of Students ^[1]	No. of Staff ^[1]	Unit Flow Factor for Students ^[3] (m^3/day)	Unit Flow Factor for Staff ^[3](m^3/day)	ADWF (m^3/d)
Stewards Pooi Kei Primary School	720	53	0.04	0.28	50.2
Sha Tin College	1200	100	0.04	0.28	87.4
Caritas Resurrection School	80	20	0.04	0.28	10.1
Hong Kong & Kowloon Kaifong Women's Association Sun Fong Chung Kindergarten	86	13	0.04	0.28	8.1
Po Leung Kuk Siu Hon Sum Primary School	100	49	0.04	0.28	20.4
Kindergarten at CDA at Au Pui Wan Street ^[2]	144	22	0.04	0.28	13.7
Sub-total=					189.9

Notes:

[1] Number of students and staffs was collected from the websites of kindergarten, primary school, secondary school and special school.

[2] Since there is no information on the proposed kindergarten at CDA at Au Pui Wan Street, the no. of students and no. of staffs are estimated by the floor area ratio of the proposed kindergarten (842 m²) to the Hong Kong & Kowloon Kaifong Women's Association Sun Fong Chung Kindergarten (505 m²). The proposed floor area of the kindergarten is referred "Broad Development Parameters of the Applied Use/Development in respect of Application No. A/ST/927

(https://www2.ozp.tpb.gov.hk/gos/download.aspx?type=apply&caseno=A/ST/927&lang=0).

[3] Unit Flow Factors and Catchment Inflow Factor (Sha Tin Catchment) were obtained from “Guidelines for Estimating Sewage Flows for Sewage Infrastructure Planning” (GESF) from Environmental Protection Department.

Table 8.4 Swimming Pools in the Concerned Sewerage Catchment

Swimming Pools	Pool Volume ^[4] (m^3)	Backwashing Rate ^[2] (m^3/hr)	Estimated Flow from Pool Backwashing ^[1][3] (m^3/d)
The Palazzo	768	192.0	22.1
Jubilee Garden	864	216.0	24.8
Royal Ascot	1162.5	290.6	33.4
Royal Ascot 2^nd Swimming Pool	1174.5	293.6	33.8
Ascot Heights	214.5	53.6	6.2
Haywood Villa	108	27.0	3.1
Ficus Garden	387	96.8	11.1
Pine Villa	165	41.3	4.7
Juniper Villa	114	28.5	3.3
Rosary Villas	327	81.8	9.4
HK Sports Institute	1950	487.5	56.1
Sub-total=			208.0

Notes:

[1] Assume turnover rate is 4 hrs.

[2] Assume backwash duration is 3min/backwash.

[3] Assume 2 backwash per day.

[4] The total area of each swimming pool is measured from base map, and pool depth is 1.5m.

8.4.2.4 By summing up all the contributing sources in the concerned sewerage catchment mentioned above (Table 8.1 to Table 8.4), the total ADWF that eventually discharges to sewer manhole FMH4038367 is 27,057.0 m³/day.

8.4.3 Estimation of Dry Weather Flow

8.4.3.1 As mentioned in Section 8.4.1, a DWFI system was proposed as a water quality enhancement measure. It will intercept dry weather flows with substandard water quality that would otherwise be discharged to Fo Tan Nullah from drainage outlets.

8.4.3.2 A water quality survey has been conducted under this Project. The water quality survey consists of two parts. The first part is a visual inspection of all the drainage outlets along the nullah with an aim to identify outlets with substandard water quality and odour issues, which will likely be intercepted by the DWFI system. The second part is a water quality sampling and testing to verify the water quality conditions of selected outlets.

8.4.3.3 In addition, a flow survey has also been conducted under this Project. Flow sensors have been installed in major drainage outlets and along the main channel.

8.4.3.4 Based on the results from the water quality and flow surveys, outlets that will likely discharge polluted flow into the nullah have been identified, and the dry weather flow targeted for interception was estimated to be roughly 2,700 m³/day.

8.4.4 Impact Review on Existing Sewerage Network and the Proposed Sewerage Improvement Works

8.4.4.1 To assess the sewerage impact induced additional 2,700 m³/day dry weather flow as mentioned above, the hydraulic performance of the existing 1200mm dia. sewer between manhole FMH4038367 and FMH4038368 was reviewed and the results are shown in Appendix 8.1.

8.4.4.2 The assessment results demonstrate that the existing 1200mm dia. sewer has enough capacity to cater for the additional flow intercepted by the DWFI system. Under current condition, the percentage utilisation of the concerned sewage system is 63%. The percentage goes up to 65% with the additional dry weather flows, which still leaves roughly 35% spare capacity. No mitigation measures are anticipated.

8.4.5 Impact Assessment on Treatment Capacity of Sha Tin Sewage Treatment Works

8.4.5.1 Table 8.5 and Table 8.6 outline information on capacity for concerned pumping stations and sewage treatment works for the DWFI system. The planned ultimate flow to STSTW was 339,000 m³/day, which includes 10% for flow uncertainties. In other words, the relocated STSTW shall be able to take up the dry weather flow whose amount is within the 10% flow uncertainties limit.

Table 8.5 Summary of Capacity for Concerned Pumping Stations

Sewerage Pumping Stations	Existing Maximum Daily Flow 2017 (m^3/day)	Planned Maximum Daily Flow (m^3/day)	Design Capacity (m^3/day)
P7 Sha Tin Main SPS	173,240	547,000	552,960
ISPS ^[1]	-	708,000	708,000

Note:

[1] Intermediate Sewage Pumping Station (ISPS) will be located within the existing STSTW.

Table 8.6 Summary of Capacity for the Relocated Sha Tin Sewage Treatment Works (STSTW)

Relocated Sha Tin Sewage Treatment Works	Flow (m^3/day)
Planned Ultimate Flow (THEES Review Study)	309,000
Planned Ultimate Flow (Cavern Study) ^[1]	339,000
Design Capacity for the Relocated STSTW	340,000

Note:

[1] Cavern study has an additional 10% for flow uncertainties.

8.5 Conclusion

8.5.1.1 A DWFI system is proposed to improve the water quality in the Fo Tan Nullah with intercepted dry weather flow estimated to be at 2,700 m³/day. The sewage impact assessment indicated that existing sewerage system has sufficient capacity to take up the additional dry weather flow intercepted by the DWFI system. Thus, no mitigation measures are required.