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Advisory Council on the Environment

BEACH WATER QUALITY 1998

 

(ACE Paper 12/99)
for information

INTRODUCTION

The purpose of this paper is to brief Members on the water quality of gazetted beaches in the 1998 bathing season, and the arrangement to be implemented in the coming bathing season to enhance the release of information on beach water quality to the public.

BACKGROUND

2.The Environmental Protection Department (EPD) has a programme to monitor the bacteriological water quality of beaches. Based on the monitoring results, a comprehensive report on beach water quality is published by the EPD annually to provide information on the annual ranking of beaches. The annual ranks are calculated on the basis of the geometric mean E.coli count of all sampling occasions in the bathing season.

3.Besides the annual ranking system, beaches are also classified according to a grading system to inform the public of the short term water quality trends. The beach grades are calculated on the basis of the geometric mean E.coli count of the five most recent sampling occasions, and released to the public during the bathing season.

4.Over the years, the analytical method for E.coli has improved to such an extent that the reporting period could be reduced from 3 days to 1.5 days. As a result, the sampling frequency at all gazetted beaches has been increased from twice per month to weekly since August 1997. Hence, more timely information on beach water quality could be obtained and the beach grading could be made available to the public through press release before each weekend during the bathing season.

BEACH WATER QUALITY IN 1998

5.The 1998 annual beach water quality report is now ready and is enclosed with this paper. The water quality of 41 gazetted beaches is monitored by the EPD. According to the annual ranking system, beaches are classified as "Good", "Fair", "Poor" or "Very Poor". Beaches in the ranks of "Good" and "Fair" meet the relevant Water Quality Objective (WQO).

6.The annual ranks of the gazetted beaches for the year 1998 are shown in Figure 3.1 of the annual report on Beach Water Quality in Hong Kong 1998. In 1998, 16 gazetted beaches were ranked "Good", 16 "Fair", 8 "Poor" and 1 "Very Poor". The only beach with "Very Poor" annual rank was Ting Kau Beach in the Tsuen Wan District which was closed to the public since 1996.

7.The water quality of most gazetted beaches in 1998 had improved when compared with the status in 1997, as illustrated in Figure 3.4 of the annual report on Beach Water Quality in Hong Kong 1998. The percentage of beaches which complied with the WQO had increased from 63% in 1997 to 78% in 1998. Fifteen beaches had improved their annual ranking and only one beach was downgraded. The improvement in the general beach water quality in 1998 is attributed to the completion of some of the sewerage works and the continuous enforcement effort of the EPD to control all the discharges in the beach hinterlands.

NEW INITIATIVES

MODIFIED BEACH GRADING SYSTEM

8.The EPD has reviewed the beach grading system through a Working Group comprising membership from the green groups, academic sector and the two municipal services departments. The present beach grading method which is based on the geometric mean of the five most recent readings may average out any high readings. The Working Group considered that if the last E. coli reading is high, this could reflect recent deterioration of water quality. In order to safeguard public health, the Working Group suggested that in addition to the present beach grading method, a "Very Poor" grade would be given to a beach when its last E. coli reading has exceeded the maximum allowable single sample limit of 1600 count per 100mL irrespective of the geometric mean. The public will be advised to avoid swimming at the "Very Poor" beaches as far as possible until the next grading is available.

9.The maximum allowable single sample limit of 1600 E. coli count per 100mL is derived on the basis of the local epidemiological studies conducted previously and the statistical method recommended by the USEPA. The modified beach grading system (Table 1) will be implemented in the coming bathing season.

Table 1 - Modified Beach Grading System

 

Grade Beach Water
Quality
E. coli level*
(Count per 100mL)
Minor illness rate**
(Cases per 1000 swimmers)
1 Good < 24 undetectable
2 Fair 25 - 180 10 cases or fewer
3 Poor 181 - 610 11 to 15 cases
4 Very Poor > 610
or last reading > 1600#
more than 15 cases

 

* Except where indicated, the E. coli level is the geometric mean E. coli count of the 5 most recent sampling occasions.
** Skin and gastrointestinal complaints.
# The modified system will assign the beach with a "Very Poor" grade if the last E. coli reading is above 1600 counts/100mL.

ENHANCEMENT OF THE WEBSITE ON BEACH WATER QUALITY

10.In order to enhance the dissemination of beach water quality information to the public, a webpage on "Beach Water Quality in Hong Kong" has been made available at EPD's website (http://www.epd.gov.hk) since October 1998. This webpage provides information on the beach monitoring programme and the water quality of individual beaches.

11.To further enhance the information provided in the webpage, starting from the coming bathing season, the trend of beach grades will be included as shown in on the webpage. The webpage will also be updated as soon as the beach grades are available so that the public could obtain the most timely information on beach water quality from the Internet.

ADVISORY NOTICES AT THE BEACHES

12.Despite the progressive implementation of the sewerage improvement works which have brought about gradual improvement of the beach water quality, the hinterland of some beaches is not yet provided with sewers.

13.As observed from the past monitoring records, most of the high E.coli readings are associated with heavy rainfall. Heavy rain will cause sewage to overflow from septic tank and soakaway pit systems or to bypass interceptors, and will also increase polluted surface run-off in the beach hinterland. Hence, pollutants will be flushed by rain into streams or storm drains leading to the beach area, and may cause short term deterioration of beach water quality. The impact of heavy rain on water quality varies to different extent for different beaches depending largely on the nature of the hinterland developments. However, the beach water quality usually recovers within 3 days after rain stops.

14.In order to alert swimmers about the possible short term deterioration of water quality and to avoid swimming at the beach after heavy rain, advisory signs will be erected by the USD and RSD in the coming bathing season at those beaches that are more susceptible to the impact of heavy rain. The beaches which will have rainfall advisory signs are listed in Table 2.

Table 2 - Beaches with Rainfall Advisory Signs to be Erected

 

District Beach
Hong Kong Island South Big Wave Bay, Shek O, Turtle Cove, Hairpin, Stanley Main
Tuen Mun Golden Beach, Old Cafeteria, New Cafeteria, Kadoorie, Butterfly
Tsuen Wan Lido, Casam, Hoi Mei Wan, Gemini, Tung Wan (Ma Wan)
Outlying Islands Silvermine Bay, Cheung Sha Lower, Pui O, Tong Fuk, Kwun Yam Wan
Sai Kung Clear Water Bay 1st, Clear Water Bay 2nd, Trio, Silverstrand, Kiu Tsui

15.In addition, the advice on the effect of rainfall will also be provided in the webpage on "Beach Water Quality in Hong Kong" and in the weekly press release for the beach grades.


Environmental Protection Department
March 1999


 

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