Rediscovering Bishop Hill Underground Service Reservoir

主教山地下配水庫再發現

Thomas Chung 鍾宏亮 / Yuan Jin 金媛

2020年底主教山配水庫在被拆除過程中被市民意外發現, 引起社會各界廣泛關註。民間保育人士、 學者,建築師等自發整合這百年地下蓄水池歷史及文物價值及其社會意義。幸好結構大部份得以保留,港府也即時回應叫停工程。三個月後配水庫被評為一級歷史建築,在2021年年底完成臨時加固工程,並有限度向公衆開放。為配水庫制定長遠保育策略前必須對文物和其周邊區域進行更深入研究,以及認真考慮鄰近深水埗及石硤尾社區的參與。本文意在追溯主教山配水庫的歷史淵源及其用途和意義的轉化,反思本案在香港文物保育發展中所扮演的角色,在學習同類保育案例的同時思考其長期活化和再利用的可能性。

The revelation of the Bishop Hill Underground Service Reservoir and its century-old brick arches and stone columns, literally coming to light through the jagged oculus pierced by a drilling vehicle, sparked a conservation controversy unlike any other in Hong Kong. Also known as “Mission Hill” due to the presence of nearby missionary establishments or “Woh Chai Shan”, Bishop Hill is an urban oasis of a hillock adjacent Shek Kip Mei and Sham Shui Po, better known for its quirky community-made recreational settings frequented by locals. On 28 December 2020, learning that the dismantling of this forgotten reservoir was underway, a crowd quickly gathered at the summit of Bishop Hill and began to wander through its cavernous ruins. Remarkable photos and clips of its impressive architectural features amid demolished rubble soon went viral, causing an instant public furore on social media.

Aided by the good weather, striking sunlit images of the disused waterworks triggered an overwhelming sense of wonderment online, followed by a chorus of condemnations from citizens, politicians, academics, architects and heritage professionals alike. This pressured the authorities to suspend works by the end of the day, and the Commissioner for Heritage to issue a public apology on site the next day, admitting to “insensitivity and miscommunication” that led to this “mistake” of demolition. Pledges to preserve the ungraded heritage and restore it for public enjoyment also came directly from the government leadership.

The accidental discovery of Bishop Hill was defined by a moment of individual defiance of a local regular confronting the pulsating demolition machine to halt proceedings (p.64). The damage included the collapse of four columns and a gaping hole that literally exposed the subterranean reservoir interiors to the world. Together with the immediate responses that prompted decisive actions all round, the whole incident provided welcoming relief and an unexpectedly upbeat conclusion to a year dominated by the Covid-19 pandemic and political uncertainties.

Three months later in March, with an expedited grading process the 1904 reservoir was accorded Grade I historic building status together with the Ex-Yaumatei Reservoir (1894). In June 2020, the endorsement of Bishop Hill’s listing was announced together with the approval of the same listing for three other pre-war service reservoirs remaining on Hong Kong Island.1 One year on, after the completion of a HK$20 million reinforcement works to install basic amenities such as glass canopy, boardwalks, staircase access, ventilation and lighting, guided tours are now organized to allow a close-up curated experience of the temporarily restored reservoir.

While further research and public consultations will be carried out, the question of how to ensure appropriate conservation for Bishop Hill remains. This article traces the reservoir’s historical origins and its transformation in usage and meaning, reflects on the role this case plays in the rethink of Hong Kong’s heritage conservation development, as well as considers possible directions for its longer-term revitalisation and reuse.

Kowloon Waterworks Gravitation Scheme

Officially named as Ex-Sham Shui Po Service Reservoir2, Bishop Hill was originally called the Kowloon Tong Service Reservoir and was a key part of the Kowloon Waterworks Gravitation Scheme, a larger water supply infrastructure constructed for the sake of modern urbanization in the city’s early colonial years. In 1890, waterworks engineer Osbert Chadwick returned to Hong Kong to implement recommendations he proposed eight years earlier when he was sent to report on the colony’s sanitary conditions. Among many of the public health improvements Chadwick suggested, British Kowloon’s well water supply proposal was completed by 1895. Water drawn from three wells dug north of Yaumatei was supplied directly to users via the Yaumatei Pumping Station.

By 1901, with land reclamation, the building of wharves and cement factories accelerating urbanization, Kowloon’s population had more than doubled within a decade. Coinciding with drought years (1895-1903), freshwater demand had greatly outstripped supply. In 1900, two years after the lease of New Territories, Chadwick already proposed to exploit the newly colonised hilly terrain to create reservoirs at a high elevation for supplying water to urban Kowloon at a lower elevation by gravitation alone, without the need for expensive steam pumping.

The Kowloon Waterworks Gravitation Scheme (KWGS) was prepared by engineer Lawrence Gibbs while working for the Public Works Department. Gibbs was also responsible for designing and supervising its construction after switching to private practice.3 In 1902, the KWGS’ ten works were under way, including the main storage reservoir, filter beds, the Kowloon Tong Service Reservoir (KTSR), as well as connecting mains and distribution pipework.4 The Kowloon Reservoir supplied water to the KTSR, which in turn fed the filtered water into the existing distribution system. Designed as a balance tank, the KTSR had begun storing water in 1904 and became operational in 1906. By 1910, the entire KWGS was completed, signifying the change from a well-and-pump water supply to a reservoir-fed gravitational system for peninsular Kowloon. This rendered the Yaumatei Pumping Station obsolete and it subsequently closed in 1911 after only six years in service.5

The “gravitation scheme” water supply technology emerged in Britain in the 1820s as part of the “water reformation” to produce “physically and morally healthy, productive, modern populace”.6 From the 1840s onwards, urban systems created for modernizing governance such as waterworks infrastructure began proliferating within Britain. By the latter half of the nineteenth century, assist the project of colonial modernization, this techno-environmental transformation of the landscape had been exported to cities like Bombay, Colombo, Singapore and even Yokohama.

For Hong Kong, the KWGS was peninsular Kowloon’s first reservoir-fed filtered rainwater supply, of which the KTSR was an integral part.7 Besides being more reliable and economical, such a steady and clean potable water supply had great hygienic and social value in reducing disease and improving the squalid living conditions of most Chinese inhabitants. While newly added street fountains changed the locals’ water consumption habits, the installation of 158 fire hydrants by 1910 undoubtedly contributed to fire safety, the protection of lives and urban properties generally.

Kowloon Tong Service Reservoir

Serving residents of Kowloon Tong, Sham Shui Po and Tai Hang Tung, the KTSR, with its 9,900m3 capacity, was much larger than its predecessors at Yaumatei (740m3) and Hung Hom (420m3, now demolished). Reportedly falling into disuse due to serious leakage in 1938, it was remodelled in 1951 after the Asia-Pacific War and remained in operation until 1970 until it was decommissioned and replaced by the much larger Shek Kip Mei Fresh Water Service Reservoir (121,000 m3). Finally disconnected in 1984,8 the KTSR’s considerable heritage value lay in it being the second oldest surviving service reservoir built in Kowloon and as bearing witness to the early development of New Kowloon.

Constructed atop Bishop Hill by casting a concrete slab into an excavated pit, the reservoir has a circular plan fitting for the site, a 47m diameter and an area of 1600m2. The slanted retaining perimeter wall of around 6.8m height enhances structural efficiency, while the curved floor junction facilitates maintenance. Inside, there is a total of 108 rusticated granite columns topped by pentagonal spring blocks that carry eleven rows of red brick arches. The “Romanesque” arches in turn support a concrete barrel vault roof holding up the landscape covering above.

The underground reservoir’s cement concrete floor slab, retaining wall and vaulted roof enabled it to withstand the larger vertical and lateral loads of the backfilled earth when compared to earlier reservoirs. Burying the covered reservoir underground also had practical benefits of maintaining water quality and minimizing temperature fluctuations that would cause cracking in the concrete. The concrete was cast without reinforcements as the reinforcement technology only matured in Hong Kong after 1910. This composite use of stone, brickwork and unreinforced concrete at Bishop Hill was the technical solution developed from available construction skills and materials of the time, reflecting the transition from traditional masonry construction to the increasing use of cast concrete.

During 1951-52, a 150 mm thick circular wall was added inside the original perimeter to fix a bad leakage. Compacted soil with cement was used as filling between the two walls and 30 of the granite pillars became embedded, while 78 columns remained freestanding. As a result, the reservoir diameter was reduced, the water level was lowered and the 9,900 m³ storage capacity was more than halved to 4,800 m³. Providing safe drinking water, improvements in public health and fire-fighting, the service reservoir undoubtedly played a key role in Kowloon’s early social history.

From terrain vague to bottom-up place-making After its retirement, the direct social relevance and awareness of this underground waterworks installation began to fade. Its subterranean existence, though, meant that Bishop Hill could not be easily developed. Instead, the hill, also nicknamed “Woh Chai Hill” due to a nearby street name, and its general usage gained in social significance. In the 1950s, the site became a squatter area for post-war refugees from the mainland; it also accommodated victims of urban fires in nearby Sham Shui Po. Squatters remained until the 1970s when they were eventually evacuated and given public housing.

As a species of terrain vague untouched by real estate development, Bishop Hill has been appropriated over the years by residents of adjacent high-density neighbourhoods such as Shek Kip Mei and Sham Shui Po. A local community of morning walkers and frequent visitors have gravitated there, gradually converting it into a series of much-needed outdoor leisure space, especially for the elderly. Often recycling unwanted building materials, they have installed a motley collection of recreational facilities – from rest areas with railings, paved paths, fitness equipment, ping-pong tables to a mahjong shelter, small shrines and tiny cultivated plots.9 Since 2010, these bottom-up, informal public spaces have been created incrementally, turning Bishop Hill into an exemplar of neighbourhood place-making, a well-used community back garden.

In 2017, government officials attempted to remove those makeshift installations under the pretext of the unauthorized installations possibly endangering public safety. The clearance attempt was abandoned after meeting with much resident and user opposition and the intervention of a Sham Shui Po District councillor.10 In March 2019, the community stakeholders, together with supporting Legco members, reiterated their plea urging the authorities to retain existing hillside installations as well as consider the community’s urgent need for green leisure space in their replanning of the hilltop lawn.11

For the reservoir itself, the first alert of safety concerns goes back to 2014. By 2017, due to cracks detected and penetration of tree branches that made it structurally unsafe, the Water Supplies Department had proposed to demolish and backfill the reservoir for other uses, which might necessitate substantial hilltop levelling. In June 2020, demolition work expected to last ten months began in earnest, before being dramatically halted six months later by the chance discovery and the ensuing public outcry. While the historical and architectural values of the exposed reservoir ruins have rightly captured public attention, the social value of the decade-long, community-driven place-making associated with this urban oasis should also feature highly when considering Bishop Hill’s long-term conservation.

A maturing conservation consciousness In many ways, Bishop Hill can be seen as another watershed in Hong Kong’s heritage conservation. Certainly, from the Star Ferry and Queen’s Pier demolitions and the self-inflicted destruction at King Yin Lei in 2006-7 to more recent campaigns such as Wing Lee Street, the West Wing of the Central Government Offices and State Theatre, there was no lack of drama and action from these cases. What was astonishing in the fight to save Bishop Hill was the effective combination of powerful imagery with lightning mobilization of civil society both to stop demolition and elicit decisive reversals from the authorities.

While the wave of popular sentiment generated by the shock that such stunning heritage could remain hidden in the heart of urban Kowloon was understandable, the urgency and outpour of voluntary contributions by citizens on social media to reveal and share information on the different values and significances of Bishop Hill was extraordinary. Extensive expertise involving architects and professionals as well as students and laymen to collaborate, organize and publicise their findings gained widespread support in no time, without which the entire outcome might have been very different. This episode arguably bore witness to a maturing of conservation consciousness in Hong Kong’s civil society.12 setting up clearer guidelines for assessing ungraded heritage and more involvement of experienced conservation practitioners.

For conservationists, a larger ambition would be to revamp the current heritage assessment framework and go beyond the one-size-fits-all, building-centric classification criteria by type and age alone. The Bishop Hill row demonstrates the urgent need to broaden heritage valuation to recognise more diverse appraisal of assets such as infrastructure, military relics, burial grounds and designed landscape. Rather than prioritizing architectural aesthetics of individual buildings, the focus should lie more in the engineering function and design value and the entire system when valuing infrastructure heritage. In fact, when five structures of the Kowloon Reservoir were declared monuments in January 2020, the Bishop Hill reservoir was overlooked precisely because the assessment never considered the complete system of infrastructure as heritage.14

Future Directions

There is general consensus for preserving Bishop Hill’s existing condition as much as possible, including keeping the aperture caused by demolition, and that any repurposing should not further damage its physical fabric.15 Just as any restoration works should be informed by thorough architectural and technical feasibility investigations, the conservation process balancing protection with reuse must consider the socio-historical dimensions before formulating effective strategies that can safeguard heritage place character, be embraced by relevant groups and align with public aspirations at large.

In the continuing public discussion, a whole range of conservation approaches from minimum intervention, museumization to thematized adaptive reuse has been suggested, and various reservoir revitalization examples from abroad cited. There are calls to confer declared monument status to Bishop Hill and to convert it into an educational space to learn about the city’s water infrastructure history. A useful precedent could be the Museum of Drinking Water set within Taipei Water Park, a 19th century pump house for Taipei’s first water treatment plant with original equipment on display. As a destination for heritage tourism, the Basilica Cistern in Istanbul is often mentioned, though its grand scale may not offer most fitting comparison for Bishop Hill. As a public park, a suitable reference might be the Paddington Reservoir in Sydney, also part of a gravitation scheme, whose roof has been opened up to form sunken courtyards and well-designed urban garden.

If we turn to reuse for culture, several cases come to mind. Cisternerne outside Copenhagen adapt a subterranean reservoir into a venue for site-specific contemporary art. Another comparable case is the regeneration of the Buffalo Bayou Park Cistern in Houston into an event space with workshops and changing art installations. The rehabilitated Spring Hill Reservoir in Brisbane goes even further, becoming a performance space for live operas and concerts. In Barcelona alone, there are two reservoir conversions – the Rei Martí Cistern, where Antoni Gaudí built the Bellesguard Tower, has become a district cultural facility, and Les Aigues Library is a respectful rehabilitation of a massive brick water tower into a university library. Closer to home, right next to Bishop Hill in fact, the underground Tai Hang Tung stormwater tank was temporarily transformed into an enormous immersive art experience by a local artist back in 2018.16 (p.65)

As for practical challenges, it is worth remembering that such waterworks facility was never intended for sustained human habitation, so proposals will need to innovate with supporting facilities to ensure visitor safety, comfort and access as well as other statutory compliances that are applicable for the proposed reuse. Lateral thinking will also be required to achieve a robust management and sustainable operation model out of any government initiative or partnership with NGOs or other private entities, ideally also integrating the surrounding landscape into the site’s planning and redesign.

Looking ahead, there is ample potential for Bishop Hill to become a didactic space for interpreting historical heritage, a cultural venue or tourist destination, an urban park, a cherished place for the community or a combined version of all these. Despite public attention and the multiple foreseeable challenges, the revitalisation of this piece of disused waterworks, now treated as an unearthed heritage gem, presents the perfect opportunity for the city to raise the bar in terms of its expectation and commitment to heritage conservation in public discourse, institutional reform as well as imaginative design strategies for adaptive reuse.

Thomas Chung is associate professor at the School of Architecture, The Chinese University of Hong Kong.
Yuan Jin is studying for her PhD at CUHK.
鍾宏亮為香港中文大學建築學院副教授。
金媛為香港中文大學建築學院博士生。

¹ The Antiquities Advisory Board also recommended grade I status to these freshwater reservoirs: Albany at the Mid-levels (1888-89), The Peak (1897) and Mount Gough (1903). All three are still operational, supplying fresh water to the Mid-Levels and Central areas. There was confirmation, however, that ten years ago heritage officials had consented to the demolition and rebuilding of two reservoirs of the same era – Magazine Gap Road (1901) and Hatton Road (1908) – due to leakage and structural concerns.
² Antiquities & Monuments Office (2021) “Historic Building Appraisal: Ex-Sham Shui Po Service Reservoir”. See https://www.aab.gov.hk/form/20210315_historic_3_new_items.pdf

³ Gibbs joined Denison, Ram & Gibbs as partner. The KWGS works was the first time the colonial government commissioned a local private firm to provide consultancy for construction contracts.

⁴ See “Report of the Director of Public Works for the Year 1910”, Hong Kong Government Administrative Reports, 1911, pp.50-56.

⁵ Lee, Cheuk Hei et al (2021)《地水重光 — 主教山配水庫文物價值評估報告》. See https://walkin.hk/wp-content/uploads/2021/03/Bishop-Hill-Assessment-Final-20210228a.pdf

⁶ John Broich (2007) “Engineering the Empire, 1850-1900” in Journal of British studies, vol.46, April, p.349.

⁷ Pokfulam Reservoir (1863-77) on Hong Kong island was the territory’s first to employ the gravitation scheme.

⁸ Tymon Mellor (2021) “Hong Kong Water Supply – Kowloon Tong Water Tank” January 3, 2021. See https://industrialhistoryhk.org/hong-kong-water-supply-kowloon-tong-water-tank/

⁹ In 2008 a retired engineer and SARS survivor Mr. So discovered Bishop Hill. Since then, bringing all the materials himself, he has created a whole gamut of fitness equipment, including exercise bicycle, training bars and swings for community use.

¹º Wong Wing Wah,《主教山隱世晨運樂園遭拆卸 晨運街坊對峙地政職員:想做運動啫》HK01, 14 August 2017.

¹¹ Chan Tsz Ching,《深水埗區議員促維持主教山作 晨運休憩用途》Hong Kong In-media, 6 March 2019.

¹² Paul Chan in保育Live Talk:從主教山風波看古蹟保育制度的漏洞, CACHe webinar, 10 January 2021. See https://www.facebook.com/cache.org.hk/videos/保育live-talk從主教山風波看古蹟保育制度的漏洞/224751232459458/

¹³ See Fredo Cheung, Vice-President of the Hong Kong Institute of Architectural Conservationists (HKICON), and his presentation “Learning from Bishop Hill: Heritage Conservation Perspective”, AIAHK Zoom Webinar, 18 February 2021. https://www.aiahk.org/learning-bishop-hill-february-18-2021/

¹⁴ ibid.

¹⁵ Chee-Kuen Yip,《未來城市:主教山配水庫 保育與發展如何並行?》. Mingpao, 4 April 2021.

¹⁶ After the Deluge is the interactive, site-specific installation by Hong Kong artist Kingsley Ng where he turned the Tai Hang Tung stormwater tank into an immersive experience where visitors listened to a soundtrack of music with headsets before entering the space and watching the movements of long pieces of fabric that imitated water.

Bishop Hill Reservoir’s cavernous interior with Piranesian chiaroscuro 
(Courtesy Hong Kong History Study Circle).

Drawings for repairs of “Kowloon Tong Balance Tank”, 1951-52.
(Credit: Water Supplies Deparment)

Reservoir interiors in December 2020
(Courtesy Hong Kong Reminiscence).

Reservoir interiors in December 2020
(Courtesy Hong Kong Reminiscence).

Aerial view of Bishop Hill showing gaping hole from halted demolition.
(Credit: Wpcpey, 2021).

Top left: locals exercising on hill summit (Image by HK01, Cheung Ho Wai, 2017)
Top right: home-made exercise equipment; bottom  left: outdoor table tennis in progress.
(Courtesy: Dr Chloe Lai)

Reservoir interiors, December 2021 after temporary restoration works, showing new boardwalk and metal stairs access.
Right: early drainage pipe in foreground; float ball valve tower in background
(Courtesy Hong Kong Heritage Exploration).

Reservoir interiors, December 2021 after temporary restoration works, showing new boardwalk and metal stairs access.
Right: early drainage pipe in foreground; float ball valve tower in background
(Courtesy Hong Kong Heritage Exploration).

Top left: Glass canopy and new access stair. (Courtesy Hong Kong Heritage Exploration).
Top right: temporary reinforcement works to concrete barrel vault, bottom
left: view towards new entrance stairs and bottom right: guided tours started in December 2021.
(Images credit: Hong Kong History Study Circle).