Guidelines on the Use of Alternative Computer Models
in Air Quality Assessment
[The
information contained in this Appendix is meant to assist the Applicant in
performing the air quality assessment. The Applicant must exercise professional
judgment in applying this general information for the Project.]
1. Background
1.1 In Hong Kong, a number of
Gaussian plume models are commonly employed in regulatory applications such as
application for specified process licences and environmental impact assessments
(EIAs). These frequently used
models (as listed in Schedule 1 attached; hereafter referred to as Schedule 1
models) have no regulatory status but form the basic set of tools for
local-scale air quality assessment in Hong Kong.
1.2
However, no single model is sufficient to cover all situations encountered in
regulatory applications. In order to ensure that the best model available is
used for each regulatory application and that a model is not arbitrarily
applied, the project proponent (and/or its environmental consultants) should
assess the capabilities of various models available and adopt one that is most
suitable for the project concerned.
1.3 Examples of
situations where the use of an alternative model is warranted include:
(i) the complexity of the situation to be modelled far exceeds the capability of the Schedule 1 models; and
(ii) the performance of an alternative model is comparable or better than the Schedule 1 models.
1.4
This paper outlines the demonstration / submission required in order to support
the use of an alternative air quality model for regulatory applications for
Hong Kong.
2. Required Demonstration / Submission
2.1 Any model that is proposed for
air quality applications and not listed amongst the Schedule 1 models will be
considered by EPD on a case-by-case basis. In such cases, the proponent
will have to provide the followings for EPD's review:
(i) Technical details of the proposed model; and
(ii) Performance evaluation of the proposed model
Based on the above
information, EPD will determine the acceptability of the proposed model for a
specific or general applications. The
onus of providing adequate supporting materials rests entirely with the
proponent.
2.2 To provide technical details of
the proposed model, the proponent should submit documents containing at least
the following information:
(i) mathematical formulation and data requirements of the model;
(ii) any previous performance evaluation of the model; and
(iii) a complete set of model input and output file(s) in commonly used electronic format.
2.3 On performance evaluation, the required approach and extent of demonstration varies depending on whether a Schedule 1 model is already available and suitable in simulating the situation under consideration. In cases where no Schedule 1 model is found applicable, the proponent must demonstrate that the proposed model passes the screening test as set out in USEPA Document "Protocol for Determining the Best Performing Model" (Ref. 1).
2.4 For cases where a Schedule 1
model is applicable to the project under consideration but an alternative model
is proposed for use instead, the proponent must demonstrate either that:
(i)
the highest
and second highest concentrations predicted by the proposed model are within 2
percent of the estimates obtained from an applicable Schedule 1 model (with
appropriate options chosen) for all receptors for the project under
consideration; or
(ii)
the
proposed model has superior performance against an applicable Schedule 1 model
based on the evaluation procedure set out in USEPA Document
"Protocol for Determining the Best Performing Model" (Ref. 1).
2.5
Should EPD find the information on technical details alone sufficient to
indicate the acceptability of the proposed model, information on further
performance evaluation as specified in Sections 2.3 and 2.4 above would not be
necessary.
2.6
If the proposed model is an older version of one of the Schedule 1 models or
was previously included in Schedule 1, the technical documents mentioned in
Section 2.2 are normally not required. However, a performance demonstration of
equivalence as stated in Section 2.4 (i) would become necessary.
2.7
If EPD is already in possession of some of the documents that describe the
technical details of the proposed model, submission of the same by the
proponent is not necessary. The proponent may check with EPD to avoid sending
in duplicate information.
Schedule
1
Air Quality Models Generally Accepted by
Hong Kong Environmental Protection Department for
Regulatory Applications as at 1 July 1998*
Industrial Source Complex Dispersion
Model - Short Term Version 3 (ISCST3)
or the latest version developed by U.S. Environmental Protection Agency
California Line Source Dispersion Model
Version 4 (CALINE4) or
the latest version developed by Department of Transportation, State of
California, U.S.A.
Fugitive Dust Model (FDM) or the latest version developed by U.S.
Environmental Protection Agency
Ref. (1): William M. Cox, "Protocol for Determining the Best Performing Model" Publication No. EPA-454/R-92-025; U.S. Environmental Protection Agency, Research Triangle Park, NC.
* EPD is continually reviewing the latest
development in air quality models and will update this Schedule accordingly.