# Dredging Question **URL:** \ **Category:** Factual Questions\ **Created:** [July 26, 2015, 3:57pm UTC](https://boards.straightdope.com/t/dredging-question/726236 "2015-07-26T15:57:58Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Potestas](https://avatars.discourse-cdn.com/v4/letter/p/50afbb/32.png) [@Potestas](https://boards.straightdope.com/u/Potestas)\ **Post date:** [July 26, 2015, 3:57pm UTC](https://boards.straightdope.com/t/dredging-question/726236/1 "2015-07-26T15:57:58Z")
Say I own an island handed down to me over the generations and I want to dredge sand from the ocean floor to make my island a bit bigger. My question is how much would it cost on average to hire a dredge to do something like that? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [July 26, 2015, 4:20pm UTC](https://boards.straightdope.com/t/dredging-question/726236/2 "2015-07-26T16:20:46Z")
Poking around online it seems like the cost is typically somewhere between $5 and $10 per cubic yard. So basically a football field sized area, assuming 100x50x50 yards and $5 per cubic yard, works out to $1.25 million. This of course will vary a lot depending on your actual water depth, any local environmental rules (you may need to pay for an environmental impact study), permitting, and all sorts of other things, but I think it’s a decent starting point for a rough ballpark figure. How big is your island and how much bigger do you want to make it? ---
**Author:** ![Potestas](https://avatars.discourse-cdn.com/v4/letter/p/50afbb/32.png) [@Potestas](https://boards.straightdope.com/u/Potestas)\ **Post date:** [July 26, 2015, 4:24pm UTC](https://boards.straightdope.com/t/dredging-question/726236/3 "2015-07-26T16:24:19Z")
> [@engineer\_comp\_geek](#): > > Poking around online it seems like the cost is typically somewhere between $5 and $10 per cubic yard. > > So basically a football field sized area, assuming 100x50x50 yards and $5 per cubic yard, works out to $1.25 million. > > This of course will vary a lot depending on your actual water depth, any local environmental rules (you may need to pay for an environmental impact study), permitting, and all sorts of other things, but I think it’s a decent starting point for a rough ballpark figure. > > How big is your island and how much bigger do you want to make it? My island is 63 acres of mostly mountainous area surrounded by a coral reef on the north side of the island with the southern island have a small stretch of beach. I want to increase the southern side of the island by at least 20 to 25 acres so I can create a few guest cottages for vacation rental income. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [July 26, 2015, 4:27pm UTC](https://boards.straightdope.com/t/dredging-question/726236/4 "2015-07-26T16:27:34Z")
Increasing your island’s size this way will require constant maintenance. The island is the shape and size it is because that’s what the underlying rock will support. Adding more sand will just mean that you will constantly need to re-drege, as the ocean wears it away… ---
**Author:** ![Potestas](https://avatars.discourse-cdn.com/v4/letter/p/50afbb/32.png) [@Potestas](https://boards.straightdope.com/u/Potestas)\ **Post date:** [July 26, 2015, 4:30pm UTC](https://boards.straightdope.com/t/dredging-question/726236/5 "2015-07-26T16:30:46Z")
> [@beowulff](#): > > Increasing your island’s size this way will require constant maintenance. The island is the shape and size it is because that’s what the underlying rock will support. Adding more sand will just mean that you will constantly need to re-drege, as the ocean wears it away… I plan to put gravel and other rock into the first layer of sand that is dredged to hold it in place and then add just a few very fine sand and rock layers before the majority of the sand is spread out in order to hold it in place. I assumed that the tide line would change so long as the sand dredged was above the water line providing enough elevation to ensure that it is not submerged during regular tidal patterns. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [July 27, 2015, 5:48pm UTC](https://boards.straightdope.com/t/dredging-question/726236/6 "2015-07-27T17:48:35Z")
I think the answer here would have to be “It depends.” Important factors include: [ul]Distance of your island from commercial dredging operations[/ul] [ul]Distance from the nearest area of abundant sand/rock to the place where you want it put[/ul] [ul]Depth of the water from which material will be dredged[/ul] [ul]Steepness of the shore area you wish to augment (this will determine how much material will be needed)[/ul] [ul]Weather patterns during the dredging project[/ul] ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [July 27, 2015, 6:55pm UTC](https://boards.straightdope.com/t/dredging-question/726236/7 "2015-07-27T18:55:22Z")
You forgot [ul] [li]Time and expense for the environmental impact statements[/li][/ul] ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [July 27, 2015, 7:07pm UTC](https://boards.straightdope.com/t/dredging-question/726236/8 "2015-07-27T19:07:59Z")
Also • Time and expense to obtain a permit from the Corps of Engineers • Cost of mitigation measures required by the Corps of Engineers Assuming the island in question is within U.S. jurisdiction. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [July 27, 2015, 8:03pm UTC](https://boards.straightdope.com/t/dredging-question/726236/9 "2015-07-27T20:03:14Z")
Any reason you can’t put the cottages on pilings? I’ve seen pictures of vacation cottages on pilings and they seemed to be very popular.