dredging works

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Recommendations for the management of

dredged materials in the Ports of Spain

Miguel La Casta Muoa

Civil Engineer

Tuesday 16th October


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Dredging projects developed by Spanish PortAuthorities are regulated by Spanish Ports Law:

Article 64: Dredging works

- Every dredging work or disposal of dredged materials

in ports needs the Port Authority permit.

- Dredging works will include an study of dredged

materials management and the disposal location and

treatment.

- The disposal of dredging materials outside the port

area needs a permit of the Maritime Administration.

(1)


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- Before disposal of dredged materials must bestudied the contaminant capacity of such disposal.

- Outside the port, dredging works need to include an

evaluation over the effects in coastal dynamics and

marine biosphere and works must be informed byFishery and Environmental administrations before the

dredging permit.

- Port Authority will submit all relevant data about

quantities disposed of dredged materials to Maritimeand Regional Administration.

(2)


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Quantities dredgedand disposed in

Spanish ports

between 1995-2004


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Recommendations for the management of dredged materialsin the Ports of Spain (CEDEX 1994)

1.- Scope and range of application

-The present recommendations are applicable for the disposalinto the sea of all materials which come from all dredging

operations undertaken within the State owned ports of Spain.

- These Recommendations are based on International

Conventions subscribed by Spain and on the Spanishlegislation.


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Recommendations for the management of dredged materialsin the Ports of Spain (CEDEX 1994)

2.- Categories of dredged materials

- Three categories of dredged material are established as afunction of the effects (chemical or biochemical nature) they

may produce on the marine biota.

- Category I can be freely disposed into the sea.

- Category II can be disposed in a controlled manner.

- Category III must be isolated from the sea.


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Recommendations for the management of dredgedmaterials in the Ports of Spain (CEDEX 1994)

3.- Types of disposal authorisations

- Normal disposal authorisation for category I materials.

- Special disposal authorisation for categories II and III


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4.- Levels of action

- Levels of action are defined as those limit values for theconcentration of toxic substances which serve to establish

the categories:

- Category I below level action 1

- Category II below level action 2

- Category III a) below 8 times level action 2- Category III b) up 8 times level action 2


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5.- Future plans of action

- In order to establish the levels of action to the regionalcharacteristics of the spanish coast the following studies will

be undertaken:

- Background level along the coast.

- Anthropogenic influence in material

- Refinement of biological techniques- Bioavailability of contaminants


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7.-Required studies for the management of dregded material

- Summary of the dredged project

- Characterisation of the sediments to be dredged- Comparative study of the disposal alternatives

- Selection and characterisation of the disposal site

- Effects of physical or mechanical nature on the legitimate

utilizations of the sea.

-Technique of contolled disposal- Monitoring and environmental surveillance programme

- Anticipated corrective measures

- Just in the case isolation technique


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Recommendations for themanagement of dredged

materials in the Ports of

Spain (CEDEX 1994)

8.-Procedure for management

of the dregded material


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9.- Characteristics of the zone to be dredged

-Type of dredging work- Space definition of the zone to be dredged

- Volume of the dredging

- Dredging method and proposed disposal

- Granulometry of the material to be extracted

- Approximate duration of the dredging


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10.- Dredged materials exempt for characterisation

In the absence of appreciable sources of contaminationmaterials can be exempt of characterisation if:

- The material is 90 % sand, gravel or rock

- The material is used in beach nourishment and

composed mainly by sand, gravel or shells.

- The amount of material does not exceed 15.000m3/year with local information about quality


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11.- Sample collection campaign

To obtain representative results of horizontal distribution ofthe sediments the minimum number of sampling stations will

be a function of the area to be dredged according with the

following formula:

N = x / 25 x

with a minimum of 4 sampling stations

If the dredged layer is very thick a corer type sampler must

be used


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12.- Characterisation of the sediments

The characterisation of the sediments is to be done in twoconsecutive phases:

- Phase I: Physical characterisation and content of

organic matter

- Phase II: Chemical characterisation


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13.- Deadlines for the validity of samples and analyses

- The results of the analyses are valid for two years.

- New samples in the area must be made if the works lasts

longer than two years.However, the number of stations may

be reduced by half in the part of the zone whose analyses

gave lower than level of action 1.


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14.- Evaluation of the analytical results

- The analytical results subject to direct and prior evaluationwill be evaluated according to levels of action defined in

point 4 taking into account the normalised concentrations.

- The normalised concentration depends on the number of

samples and on the fraction the analyses are made on.


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15.- Study of productive uses

- For all dredged materials included within categories I andII, a study must be made on the alternatives for productive

uses.


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16.- Selection of the disposal site

- The selection of a disposal site will be based on the effectsof physical or mechanical impacts of the material on the

legitimate uses of the sea.

- The information about the site should be as broad as

possible and special attention must be paid to the zone used

historically by the port as a disposal site.


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17.- Request of a normal disposal authorisation

- The document wich results from these Recommendationswill have the following format:

Introduction

Descriptive report of the dredging work

Characterisation of the sediments

Possibility of productive uses

Location of the disposal site

Sythesis of the report


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18.- Disposal category II materials into the sea

- The Category II dredged materials can be disposed intothe sea in a controlled manner prior special authorisation.

- Studies of the transport and dispersion of the fraction liable

to remain in suspension must be carried out not only during

the disposal but also in the long term.

- The special authorisation must include location indicated,

hypothesis of impact and a programme of environmental

monitoring and surveillance.


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19.- Study on the receiving site for category III materials

-For all Category III dredged materials a study on the

advisavility of undertaking the disposal on land or in seamust be done.

- This study will serve as a basis to develop a solution or a

safe technique of environmental management for later

studies.

- The management could be soft isolation, hard isolation or

treatment techniques.


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20.- Selection and description of the management technique

for disposal into the sea

- Category III dredged materials can only be disposed into

the sea by using isolation management techniques.

- The aim is to isolate the toxic substances contained in the

dredged material avoiding their bioavailability and

introduction into the trophic chain.


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21.- Impact hypothesis

- In order to dispose Category II material into the sea it isnecessary the formulation of an impact hypothesis which

predicts the physical, chemical and biological effects on the

marine environment.


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23.- Request for a special disposal authorisation

- The request will have the following format:Introduction

Descriptive report of the work

Characterisation of the sediments

Possibility of disposal on land

Description of the management technique

Impact hypothesis

Environmental surveillance programmes

Synthesis of the report


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