Rediscovering Bishop Hill Underground 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 rediscovery of the Bishop Hill Underground Service Reservoir with its century-old brick arches and stone columns, literally coming to light through a jagged oculus pierced by a drilling vehicle, sparked a conservation controversy unlike any other in Hong Kong. Also known as both ‘Mission Hill’ due to the presence of nearby missionary establishments and ‘Woh Chai Shan’, the Bishop Hill hillock is an urban oasis, adjacent to Shek Kip Mei and Sham Shui Po, best 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, quickly followed by a chorus of condemnations from citizens, politicians, academics, architects and heritage professionals. This anger pressured the authorities to suspend works by the end of that day, while on the next one, the Commissioner for Heritage went to the site and issued a public apology, admitting to “insensitivity and miscommunication” that led to this “mistake” of demolition. Pledges to preserve the ungraded heritage site and restore it for public enjoyment came swiftly and directly from the government leadership.

The defining moment in the accidental rediscovery of Bishop Hill was when a regular local visitor to the site confronted a pulsating demolition machine to halt proceedings. The damage done at that point included the destruction of four columns and the creation of a gaping hole that exposed the subterranean reservoir’s interior to the world. Together with the immediate public and expert response that prompted decisive action from officials, the incident provided welcome relief and an unexpected upbeat end to a year until then dominated by the Covid-19 pandemic and political uncertainties.

Three months later, following an expedited grading process, the 1904 reservoir, together with the Ex-Yaumatei Reservoir (constructed in 1894), was accorded Grade I historic building status. In June, 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 HK$20-million of works installed basic amenities such as a glass canopy, boardwalks, staircase access, ventilation and lighting, guided tours now allow people to view 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 and considers possible directions for its longer-term revitalisation and re-use.

Kowloon Waterworks Gravitation Scheme
Officially named the Ex-Sham Shui Po Service Reservoir,² 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 in Hong Kong’s early colonial period. In 1890, waterworks engineer Osbert Chadwick returned to Hong Kong to implement recommendations he had proposed eight years earlier when he was sent to report on the colony’s sanitary conditions. Among the many 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.

In 1901, thanks to land reclamation and the building of wharves and cement factories that had accelerated urbanisation, Kowloon’s population had more than doubled in just a decade. With supplies also hit by a drought that ran from 1895-1903, freshwater demand had greatly outstripped supply. In 1900, two years after Britain signed its lease for the New Territories, Chadwick had proposed to exploit the hilly terrain of the newly colonised area to create reservoirs at high elevations that would supply water to urban Kowloon using gravitation alone, with no 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, construction started on the KWGS’ ten works, among them its main storage reservoir, filter beds, the Kowloon Tong Service Reservoir (KTSR), connecting mains and distribution pipework.⁴ The Kowloon Reservoir supplied water to the KTSR, which in turn fed filtered water into the distribution system. Designed as a balance tank, the KTSR began storing water in 1904 and became operational in 1906. By 1910, the entire KWGS was completed, marking the point at which the previous well-and-pump water supply was replaced with to the new reservoir-fed gravitational system. The Yaumatei Pumping Station was now obsolete. It subsequently closed in 1911 after only six years in service.⁵

Gravitation water-supply technology had been developed in Britain in the 1820s as part of a ‘water reformation’ aimed at producing a ‘physically and morally healthy, productive, modern populace’.⁶ From the 1840s onwards, urban projects for modernising governance such as waterworks infrastructure began proliferating within Britain. By the latter half of the 19th century, such techno-environmental schemes were being used to assist ‘colonial modernisation’ in cities such as Bombay, Colombo, Singapore and even Yokohama.
For Hong Kong, the KWGS was peninsular Kowloon’s first reservoir-fed filtered rainwater supply.⁷ Besides being more reliable and economical, the provision of a steady supply of clean potable water had great hygienic and social value in reducing disease and improving the living conditions of most Chinese inhabitants. Newly added street fountains changed the locals’ water consumption habits and the installation of 158 fire hydrants by 1910 contributed to fire safety and so to the protection of lives and urban properties.

Kowloon Tong Service Reservoir
Serving residents of Kowloon Tong, Sham Shui Po and Tai Hang Tung, the KTSR, with its 9,900 cubic metres capacity, was much larger than its predecessors at Yaumatei (740 cubic metres) and Hung Hom (420 cubic metres, 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, when it was decommissioned and replaced by the much larger Shek Kip Mei Fresh Water Service Reservoir (121,000 cubic metres). Finally disconnected in 1984, the KTSR’s considerable heritage value lay in it being the second-oldest surviving service reservoir built in Kowloon and so a witness to the early development of New Kowloon.⁸

Constructed atop Bishop Hill by casting a concrete slab into an excavated pit, the reservoir had a circular design, 47 metres in diameter and with an area of 1,600 square metres. A slanted retaining perimeter wall of around 6.8 metres in height enhanced structural efficiency, while a curved floor junction facilitated maintenance. Inside, a total of 108 rusticated granite columns topped by pentagonal spring blocks carried 11 rows of red-brick arches. These ‘Romanesque’ arches in turn supported a concrete barrel-vault roof holding up a 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 the practical benefits of maintaining water quality and minimising temperature fluctuations that might have caused cracking in the concrete. The concrete was cast without reinforcement as the appropriate reinforcement technology was only developed in Hong Kong after 1910. The composite use of stone, brickwork and unreinforced concrete at Bishop Hill was the technical solution available from the construction skills and materials of the time, reflecting a transition from traditional masonry construction to an increasing use of cast concrete.

Between 1951-52, a 1.5-metre-thick circular wall was added inside the original perimeter to fix a serious leakage. Compacted soil with cement was used as filling between the two walls, embedding 30 of the granite pillars but leaving 78 columns freestanding. As a result, the reservoir’s diameter was reduced, its water level lowered and its 9,900 cubic metres storage capacity was more than halved to 4,800 cubic metres.

From terrain vague to bottom-up place-making
After being taken out of service, awareness of this underground waterworks installation and its social relevance began to fade. Its subterranean existence, though, meant that Bishop Hill could not easily be developed. Instead, the hill, also known as ‘Woh Chai Hill’ after a nearby street, gained 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 lived at the site until the 1970s, when they were finally evacuated and given public housing.

As a species of terrain vague untouched by real estate development, Bishop Hill was 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, many of them elderly, gravitated there, gradually making it into a much-needed outdoor leisure space. Often recycling unwanted building materials, these people installed a motley collection of recreational facilities, among them rest areas with railings, paved paths, fitness equipment, ping-pong tables, a mahjong shelter, small shrines and tiny cultivated plots.¹⁰ Created incrementally since 2010, these informal public spaces turned Bishop Hill into an example of neighbourhood place-making – a kind of well-used community back garden.

In 2017, government officials attempted to remove those makeshift installations using the pretext that these unauthorised installations possibly endangered public safety. The clearance attempt was abandoned after it met with much resident and user opposition and the intervention of a Sham Shui Po district councillor. In March 2019, the community stakeholders, together with supporting LegCo members, reiterated their call to the authorities to retain the existing hillside installations as well as consider the community’s urgent need for green leisure space in a proposed replanning of the hilltop lawn.¹¹

Concerns about the reservoir’s safety date back to 2014. By 2017, following the discovery of cracks and the penetration of tree roots that had made it structurally unsafe, the Water Supplies Department proposed to demolish and backfill the reservoir for other uses, work which might have necessitated substantial hilltop levelling. In June 2020, demolition work expected to last ten months began in earnest only to be dramatically halted six months later by the chance rediscovery of the reservoir 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 community-driven place-making associated with this urban oasis over the previous decade should also be taken into account when considering Bishop Hill’s long-term conservation.

A maturing conservation consciousness
Bishop Hill is another watershed in Hong Kong’s heritage conservation. From the Star Ferry and Queen’s Pier demolitions and the destruction at King Yin Lei in 2006-07 to more recent campaigns such as that over Wing Lee Street, the West Wing of the Central Government Offices and State Theatre, there has been no lack of drama and action. What was astonishing in the fight to save Bishop Hill was the lightning-fast mobilisation of civil society first to halt the demolition and then to secure a decisive reversal of policy from the authorities.

While the wave of popular sentiment generated by the shock at discovering such a stunning piece of 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 about the value and significance of Bishop Hill was extraordinary. The expertise of architects and professionals combined with the passion of students and laypeople led to collaboration, organising and publicity that generated widespread support in almost no time at all. Without this, the entire outcome might have been very different. Instead, the episode bore witness to a maturing of conservation consciousness in Hong Kong civil society.¹²

Learning from Bishop Hill
On 29 December, a day after the reservoir’s rediscovery, a government official publicly apologised for miscommunication between heritage officers and waterworks engineers who mistook the reservoir as just a ‘water tank’ when approving the demolition plans. While answering accusations of negligence ensured that accountability was seen to be done, there appears to be a telling admission of inadequate inter-departmental coordination and openness to review critical feedback. Professional groups have called for drawing up clearer guidelines for assessing ungraded heritage sites and greater 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.¹³ 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 a 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 all restoration works should be informed by thorough architectural and technical feasibility investigations, so the conservation process balancing protection with re-use must consider all relevant socio-historical dimensions before formulating strategies that can safeguard the character of heritage sites. This should help such plans be embraced by relevant groups and aligned with public aspirations.

As public discussion continues, a range of conservation approaches has been suggested for Bishop Hill, from minimum intervention and museumisation to thematised adaptive re-use, back by various reservoir revitalisation examples from abroad. There have been calls to confer it declared monument status and to convert it into an educational space to learn about the city’s water infrastructure history, for which 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 a well-designed urban garden.

If we turn to re-use for culture, several cases come to mind. Cisternerne, outside Copenhagen, has adapted 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 having become a performance space for live operas and concerts. Barcelona has two reservoir conversions: the Rei Martí Cistern, where Antoni Gaudí built the Bellesguard Tower, is now a district cultural facility, while Les Aigues Library is a respectful conversion of a massive brick water tower into a university library. Closer to home – 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 in 2018.¹⁶

As for practical challenges, it is worth remembering that waterworks facilities were never intended for human habitation, so proposals will need to find ways of ensuring visitor safety, comfort and access as well as other statutory compliances for any proposed re-use. Lateral thinking will also be required to put in place a robust management and sustainable operation model either with the government or in partnership with NGOs or other private entities – ideally one that integrates the surrounding landscape into the site.

Looking ahead, Bishop Hill has ample potential to become an educational space for interpreting historical heritage, a cultural venue, a tourist destination, an urban park, a cherished place for the community or some combination of all these. Despite facing many challenges, the revitalisation of these disused waterworks presents Hong Kong with the perfect opportunity to raise the bar in terms of its commitment to heritage conservation and development of imaginative design strategies for adaptive re-use.

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.