For discussion PWSC(96-97)84
on 18 December 1996


Air and Sea Communications - Port works
112AP - Update on cumulative water quality and hydrological effect of coastal
developments and upgrading of assessment tool

Members are invited to recommend to Finance Committee the upgrading of 112AP to Category A at an estimated cost of $69.1 million in money-of-the-day prices for the collection and analysis of oceanographic data to enable a more accurate assessment of the effect of coastal developments on the quality and hydrology of Hong Kong’s coastal waters.


We do not have up-to-date field data necessary to assess the cumulative effects of coastal developments on water quality and hydrology.


2. The Director of Environmental Protection, with the support of the Secretary for Planning, Environment and Lands and the Director of Civil Engineering, proposes to upgrade 112AP to Category A at an estimated cost of $69.1 million in money-of-the-day prices to collect current oceanographic field data from Hong Kong waters. T tohis field data will be beneficial for the purpose of calibrating new mathematical models being developed by the Civil Engineering Department (CED) which will assess comprehensively, and with greater precision, the cumulativecumlative effects of coastal developments onto the quality and hydrology of Hong Kong’s watersin.


3. The project we propose to upgrade to Category A comprises -

  1. oceanographic surveys of hydrological conditions, water quality sampling and laboratory testing of water quality;
  2. calibration of CED’s new mathematical models using the data collected under (a);
  3. interpretation of the collected data and modelling the results with respect to the cumulative effects of coastal developments on water quality and hydrology; and
  4. transfer of the techniques in handling the data and models from the consultants to Government staff.


4. Hong Kong’s hilly terrain has requiredled to a major part of our land and infrastructure beingto be developed in the coastal areas. This has had an impact on the hydrological conditions and quality of our coastal waters. We therefore need accurate data on the hydrological conditions and quality of Hong Kong waters in order to enable us to assess the cumulative effects of such developments. We made our first assessment of the Water Quality and Hydraulic Models (WAHMO) to assess the cumulative water quality impacts of large-scale coastal developments in 1982 under the Study on Harbour Reclamation and Urban Growth using the Water Quality and Hydraulic Model (WAHMO) operated by the CED. In the late 1980s under the Port and Airport Development Strategy (PADS) and the Metroplan, we used the same models to further assess the feasibility of new developments and to identify environmental constraints at the strategic planning level. With carefulmodelling assessment of the data provided by the models, appropriate planning and the provision of suitable mitigation measures, we have managed to keep the cumulative effects of the developments within acceptable limits. Background information on the application of the WAHMO is at Enclosure 1.

5. The last time we collected hydrological and water quality survey data was for PADS. This study was conducted nearly seven years ago. Given the changes in the general environmental conditions since then, we need more recent data on Hong Kong waters to update our database. There is also an increasing concern at the international level about the cumulative effects of coastal developments on the ocean. The need to improve oceanographic models and databases has been discussed on the agenda of international foraums like such as the Asia-Pacific Economic Cooperation.

6. The oceanographic survey now proposed will enhance the accuracy of our predictions on the effects of future coastal developments on the marine environment in Hong Kong. pPopulation growth and economic developmentgrowths have createdcaused increasing pressure for further land and infrastructure development. The Territorial Development Strategy Review published in July 1996 has proposed a number of strategic growth areas to meet the demand for additional land requirements in both the medium and long term. Some of these involve the development ofareas would involve coastal areas. In response to this, CED is procuring new models under 106AP - Port and Airport Development Strategy with a view to upgradinge the WAHMO. These new models when put to use will produce a finer resolution of the effects of relatively small developments and cover a larger geographical area than that covered by as compared with the original WAHMO.

7. In updating itsBefore putting the new models to use, however, CED will benefit directly from oceanographic need data as direct inputs (such as data on polluting loads and boundary conditions) and the establishment of yardstick measurements for the calibration of the WAHMO models’ calibration (the adjustment of model coefficients until a satisfactory relationship is achieved betweenof model simulation and field data) which will derive from the oceanographic survey. If such inputsEPD could not conduct an oceangraphic survey are not availableto collect new data from our waters, CED will have to rely oncould only use the old data collected under PADS someabout seven years ago to calibrate the upgraded WAHMOits new models. AResults of the modelling assessment based on such these outdated data will then be not able to truly reflect the cumulative effects of coastal developments at the present time.

8. With Ttupdated If CED could calibrate its new models with the new water quality data collected under EPD’s proposed oceanographic survey, CED it willould be able to produce more reliable modelling results. The consultants will then interpret these results to provide forgive Government and the public an up-to-date and more accuratebetter picture of the cumulative effects of proposed coastal developments. We willould closely monitor the consultants’ work and ensure that Government staff willould eventually be trained to handle the enhanced data and models for future applications.


9. We estimate the capital cost of the study to be $69.1 million in MOD prices (see paragraph 10 below), made up as follows -

$ million

(a) Oceanographic surveys and data collection


(b) Laboratory testing


(c) Consultants' fees for -


(i) planning and supervision of hydrological surveys


(ii) calibration of mathematical models


(iii) data interpretation, assessment of cumulative water quality impact


(iv) transfer of techniques from the consultant to Government staff on handling the data and models


(v) report preparation


(d) Contingency



(at December 1995 prices)


(e) Inflation allowance



(in MOD prices)



A breakdown by man months of the estimate for consultants’ fees is at Enclosure 2.

10. Subject to approval, we will phase expenditure as follows -


$ million
(Dec 1995)


$ million

1997 - 98




1998 - 99




1999 - 2000






11. We have derived the MOD estimate on the basis of the Government's forecasts of trend labour and construction prices for the period 1997 to 2000. We will tender the consultancy services (Item c (i), (ii), (iii) (iv) and (v) of paragraph 9 above) under a lump sum contract because the scope and quantity of the services are well defined. The consultancy will be subject to adjustment for inflation because it will last for more than 21 months. We will tender the data collection and laboratory testing components of the contract under re-measurement contracts because the scope and value of these activities cannot be exactly quantified at this stage. The tender price for this component will not be subject to subsequent adjustment for inflation because the contract period is shorter than 21 months.

12. The proposed study will not give rise to recurrent expenditure.


13. We consulted the LegCo Panels on Environmental Affairs and Planning, Lands and Works on 7 November 1996. The Panel noted the proposalpurpose of the proposal should be clearly explained.


14. The project is an environmental investigation involving field measurement and water sample collection. It has no adverse environmental implications.


15. This project does not require land acquisition.


16. The upgrading of the WAHMO mathematical models under 106AP started in December 1995 and will be completed by December 1997.

17. We intend to start the proposed project in April 1997 for completion in May 1999.


Enclosure 1 to PWSC(96-97)84

Background information --Model Applications on Water Quality Impact Assessment for Coastal Development

The government uses mathematical computer models to predict the effects of changes in coastal landform, and new infrastructure projects such as bridges or sewage outfalls, on the current flows and water quality in our territorial waters.

2. The models simulate water quality and hydraulic behaviour in the marine environment by solving mathematical equations representing the physical, chemical and biological processes in nature. To ensure accuracy, we calibrate (adjust the model coefficients) and validate the models by using field data. With the calibrated models, we predict the likely changes in flow pattern and water quality caused by reclamation or additional pollution factors, analyse this information and compare it against our Water Quality Objectives. As and when we predict significant impact, we use the models to identify mitigation measures or to draw up viable options.

3. Our existing models were first developed in 1982 and upgraded in 1987 to provide a comprehensive tool for assessing likely changes in a wide range of environmental conditions such as water flow, wave propagation, sediment transport and water quality. Using these models we have made fundamental decisions on the acceptability and location of major infrastructure developments. For example the application of the models in the Studies on Harbour Reclamations and Urban Growth in the early 1980s demonstrated the importance of dealing with our urban sewage problem if reclamations in the harbour were acceptable. The application of the models to the Port and Airport Development Strategy (PADS) projects in the late 1980s was critical in confirming the environmental acceptability of the major reclamations required.

4. The models, therefore, have served as a fundamental and very valuable tool for managing the water environment. Without these models, we might not have been able to manage our water environment.

5. The accuracy and reliability of our models depend critically on the following factors -

  1. The area of coverage. When the coverage is too small, the boundaries of the model would become too close to the area of interest and the results would be distorted and unreliable.
  2. The extent to which the models are able to resolve small scale effects. When boundaries are set sufficiently far from the area of interest, our models would have a grid-size of 250m, and the effects on a scale smaller than this cannot be predicted.
  3. The accuracy of calibration with existing field data.

6. Until now, we have been able to use our models effectively because the primary area of interest has been the inner harbour and the Western Anchorage which is sufficiently far from the model boundaries, and we have updated the field data in 1990. However, it is likely that any new proposed developments would be outside the main harbour areas and comparatively nearer to the boundaries of the existing models. It is also likely that any proposals for further infrastructure developments within the harbour would be on a comparatively smaller scale or in critical locations. In these cases, we would not be able to assess accurately the effects with the existing models. We therefore need to take action now to ensure that we can be in a position to assess their impact effectively.

7. With regard to paragraph 5(c) above, PADS projects were assessed using models calibrated with 1987 data. The completion of core PADS projects have brought about significant changes in the hydraulic conditions in the harbour. To ensure accuracy in predicting future impacts it is important that we should collect new data and recalibrate our existing models.

8. If we do not carry out a fresh data collection exercise, we will not be able to assess the impacts of any proposed infrastructure developments outside the central harbour area, which may affect water quality. Similarly we will not be able to assess the effects of developments in narrow or semi-enclosed areas where critical distances are less than 250m.

9. If we can carry out an updating exercise, we will have a robust modelling platform to assess the cumulative effects of future strategic coastal developments and to tackle transboundary pollution problems. We will then be able to ensure that Hong Kong’s continuing development and post-1997 economic integration with the Guangdong hinterland will not be at the expense of the sustainability of our marine environment.


Enclosure 2 to PWSC(96-97)84

112AP - Update on cumulative water quality and hydrological effect of coastaldevelopments and upgrading of assessment tool

Breakdown of estimates for consultants' fees
Consultants’ staff costs

Category of Works/Items




($ million)

(a) Planning and supervision of hydrological and water quality surveys











(b) Calibration of mathematical models











(c) Data interpretation, assessment of cumulative water quality impact











(d) Transfer of techniques from the consultant to Government staff












Total consultants’ staff cost



Out-of-pocket expenses

(a) Report production



Total out-of-pocket cost




1. A multiplier factor of 3 is applied to the average MPS point to arrive at the full staff costs including the consultant’s overheads and profit, as the staff will be employed in the consultant’s offices. (At 1.4.95, MPS pt. 40 = $51,440 p.m. and MPS pt. 16 = $17,270 p.m.).

2. Out-of-pocket expenses are the actual costs incurred. The consultant is not entitled to any additional payment for overheads or profit in respect of these items.

3. The figures given above are based on estimates prepared by the Director of Environmental Protection. We will only know the actual man months and actual fees when we have selected the consultant through the usual competitive lump sum fee bid system.


Last Updated on 16 August 1999