[Coral-List] Dredging

[Jeremy J. Sofonia]

Dear Bob,

Could the solution be something as simple as using a "sifting" or  
"screening" bucket attachment on your excavation equipment?

Here's a couple links to video clips provided by a company called  
Dirt Works that illustrate my thinking:

http://dirtworksattachments.com/video/SiftDirt.wmv
and
http://dirtworksattachments.com/video/SiftStone.wmv

Sounds to me like you'd want to keep the top bit.  You can do a quick  
Google search and find all sorts of options.  I would also suggest  
you discuss this further with your local contractors who are most  
familiar with the options available in earth moving equipment.  If  
you explain the goals of your work, they almost certainly could  
present you with more ideas and some good advice.

Kind Regards,

Jeremy




On 30/01/2007, at 3:28 AM, Robert Bourke wrote:

> Jeremy & C-Listers;
>
> Does anyone have experience with dredging for wetland rehabilitation
> adjacent to coral reef ecosystems?
>
> On Oahu, Hawaii there is an interesting system (Kaelepulu Pond /
> Enchanted Lake) with a vibrant wetland / estuary ecosystem that has  
> been
> completely surrounded by urban development and is impacted by  
> excessive
> sedimentation.  While sedimentation in the pond protects the adjacent
> reefs off of Kailua Beach, the progressive infilling is actually
> decreasing wetland bird habitat as these areas become fast-land
> supporting alien grass species.
>
> Is anyone aware of an actual working mechanism whereby excavated
> materials can be segregated, removing the mud fines with  
> replacement of
> the large material (algae, oyster shells) back onto the substrate?
>
> Aloha
>
> Bob Bourke
>
>
> -----Original Message-----
> From: coral-list-bounces at coral.aoml.noaa.gov
> [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Jeremy J.
> Sofonia
> Sent: Saturday, January 27, 2007 4:47 PM
> To: Andrew_Jamieson at URSCorp.com
> Cc: coral-list at coral.aoml.noaa.gov
> Subject: Re: [Coral-List] coral sedimentation thresholds for dredge
> inducedsedimentation
>
> Andrew,
>
> Wanted to add:
>
> Also important in estimating potential impacts to benthic primary
> producers is the type of dredge (e.g. cutter suction, trailer hopper,
> etc.), the size of the dredge (m^3), it's power, it's proximity to
> sensitive resources (such as corals), and the duration/ frequency they
> are operating.  Other operational details such as of 'side-  
> casting' and
> 'overflow' rates can also have significant effects (positive or
> negative).  Obviously spoil disposal locations and methods should also
> considered, but keeping in mind that sediments released during  
> disposal
> will behave differently than those suspended during cutting (i.e. less
> fines).
>
> If the program is to run in a working port facility, you'll want to  
> look
> at how local conditions are affected by ongoing operations such as
> berthing and other vessel movements (e.g. tugs can kick up a fair  
> bit of
> sediment/ turbidity in shallow areas).  Contamination such as TBT or
> heavy metals is not uncommon and proper disposal of these materials  
> also
> requires some forethought.
>
> Potential impacts to whales and other cetacens, as well as marine
> turtles should also be investigated.  These can be both direct (e.g.
> physical impact) and indirect (e.g. acoustic, lighting).  Seasonal
> timing of operations is therefore a key avoidance/ minimization  
> measure.
>
> Certainly a lot to think about, but with early (and regular)
> consultation with your environmental authorities, clear communication
> with the proponent, and some good science, the successful  
> management of
> these types of programs is certainly possible.
>
> Hope this was of some help,
>
> Jeremy
>
>
>
> JEREMY J. SOFONIA
> Senior Marine & Environmental Consultant SKM Australia Pty. Ltd.
>
> 7th Floor, Durack Centre
> 263 Adelaide Terrace
> Perth, WA 6000
>
> http://www.skm.com.au
>
>
>
> On 24/01/2007, at 5:43 PM, Andrew_Jamieson at URSCorp.com wrote:
>
>> Dear Coral Listers
>>
>> I am trying to track down any  research undertaken into tropical  
>> coral
>
>> sedimentation thresholds for dredge induced sedimentation - can  
>> anyone
>
>> direct me in the right direction ?
>>
>> Many thanks
>>
>>
>> Andrew Jamieson
>> Senior Environmental Scientist
>> andrew_jamieson at urscorp.com
>>
>>
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