Ponding next to drainage basin 4

[arabojan]

Hi everybody
Currently I am designing a drainage system for a commercial site, which is located an rural area without any adjacent buildings, we have no restriction for extending our site, so if we need we can use surroundings lands, but problem is that all the proposed and predeveloped area's water is ponding just next to the site and it seems to be no way to get out of that water, my question is what system can I use for keeping and discharging that water, I am thinking about a system with evaporation and detention pond together, but there is problem about detention pond water to discharge.

 

[francesca]

Is the area where the water is ponding a wetland?

The simple solution is to purchase the area where water ponds and excavate as necessary to hold the additional volume, but of course this is not necessarily viable if the area is a wetland. If it's a karst area then a Class V injection well in the retention basin would help infiltration, but if it's not a defined sinkhole it can be fun trying to excavate to bedrock to correctly install the injection well.

 

[RWF7437]

Where is your project ?
What laws govern your design ?
Is water ponding because your project has blocked the natural flow or is this a natural low area which would pond water whether or not your project is built ?

You need to know what you can legally do before proposing any technical solution.

good luck

 

[arabojan]

The area where water is ponding is wetland and natural low area, but it isn't under any jurisdiction or agency protection and our proposed road is going to pass over it, we are following Spokane County, Washington regulations,

Subsurface condition
Our exploration generally ecointered 2 subsurface soil units at the site: 1) uncontrolled fill 2)alluvium.
Groundwater levels were measured in the piezometer on august 29, 2006 to be about 5 1/2 feet below existing ground surface. however based on our site experience gorund water can rise seasonally about 2 feet.
we encountered alluvium in each of the exploration locations consisting of clay.Generally the alluvium transitioned from hard to very soft at around 15 feet.

thanks for quick relpy

 

[RWF7437]

Thank you for the clarification.

If you are in the U.S. as you say, and the area is a wetland, as shown or catalogged by the State of Washington you ARE subject to both State and Federal law regarding wetlands. You must either avoid disturbing the wetland, hire a wetlands expert to certify that it is not a wetland, or provide additional wetland area to compensate for any wetland destroyed by your construction.

Your project is under someone's jurisdiction.... probably Spokane County. You should contact them and discuss what you would like to do and what they will ALLOW you to do.

good luck

 

[arabojan]

I am sure that the wetland in the project area is not under any jurisdiction, By studying more I found out that there is a creek nearby, is it possible to discharge the water by a channal to the creek?

 

[RWF7437]

You wrote:

"I am sure that the wetland in the project area is not under any jurisdiction, By studying more I found out that there is a creek nearby, is it possible to discharge the water by a channal to the creek? "

What makes you "sure" the wetland is not under anyone's jurisdiction ? Have you asked the County ? the City ? the State of Washington ? or the Corps of Engineers? Do not proceed unless and until you do. I work on Oregon where the Agency resonsible for wetlands regulation is the Division of State Lands. There must be a parallel agency in Washington.

Not sure what you mean by "studying more". Have you been to the site ? If not go there. It is suicide in Civil Engineering to fail to visit the site. One site visit would probably have told you there was a nearby creek and saved whatever "studying" you did. If your site drains naturally to that creek you can probably, in fact you almost certainly must, drain to it. State drainage law will probably require this.

good luck

 

[RWF7437]

http://depts.washington.edu/hortlib/resources/hort_web_sites/wetlandsguide.pdf

 

[francesca]

If the site does not drain naturally to the creek (e.g. if the wetland does not fill to a point and then drain to the creek) it would be considered an inter-basin transfer to drain the site to the creek and is probably not allowed. Onsite retention or buying land adjacent to the wetland and extending the wetland as indicated by a wetlands expert to incorporate your additional runoff volume would be your options.

Wetlands are definitely regulated, and there are more stringent NPDES (Construction Stormwater Permit) requirements, too.

 

[cvg]

not to mention USACE 404 permit...

 

[civilperson]

After getting all regulatory permits and approvals, try a draw down structure which maintains the water level at predevelopment levels and discharges excess water through a pipe/drain to the nearby creek water basin.

 

[arabojan]

I decided to include the infiltration to my evaporation pond calculation, which is 0.5 in/day to reduce my pond size that without is 700000 square feet,after applying this reduction, my pond size is 400000sf with a depth about 1.5ft ( with 1 ft free board, total depth 2.5)
My question is can I apply infiltration on evaporation pond? if we can which months of the year infiltration exist with regarding Eastern Washington state climate?
What another method do you guys suggest to decrease the depth of the pond?

 

[francesca]

If there is existing standing water, you'd be hard pressed to convince me you can get half an inch of infiltration per day in a saturated soil. Around here you have to assume zero outflow and design a retention basin to hold the entire (24 hour) storm volume.

I do not have experience designing evaporation basins, so I'd be interested to know what the standard is for design storm duration, as you're not going to get much evaporation while it's still raining and in Washington State I bet it can rain an inch or two a day for over a week... not to mention snow melt.

If you want to decrease the depth of the pond, make it wider or longer.

 

[bltseattle]

I suggest you:
(a) double check the wetland status of the standing water area you described - a wetland delineation by a consultant would be in order because you don't want the inspector bringing this up during construction. THis recently happened in Seattle, no wetland delineation was done because the designers were *sure* that the new training center was not in a wetland, now the city has spent like $6,000,000 to restore impacted areas after being sued.
(b) Review the Ecology Stormwater Management Manual for Eastern Washington. This addresses when you can release water to streams with/without detention, and there are lots of special cases for Eastern Washington. Following this manual, even if the local agency does not require it, is likely considered state-of-the-art and will reduce design liability of potential downstream impacts and help you to avoid water rights issues. Reviewing this manual should also inform you as to terms more consistent with the practice; "evaporation pond" is not a standard BMP; referring to your facilities using the standard terms will help reviewers and this forum to understand your stormwater management design.

 

[arabojan]

yes there water table is 5.5 feet below the existing ground, and in august it raise 2 feet more, actually I don’t believe that we can discharge the water by infilration,but I have not a good reason, because may be we can explain that the infiltration water is flowing with ground water routes, and in this way we can have discharge out of the basin, I use the eastern Washington department of ecology manual and spread sheet for calculation o retention pond that is easily downloadable and rain gage that that the project is located for input data.

 

[trey25624]

You can never be sure unless you talk to whoever regulates wetlands in your state. I find it hard to believe you have wetlands either on or off your site and you can do whatever you want with them. This sounds like a disaster waiting to happen.

Your question about the pond, you should be asking the local county drain commission those questions. You might think you have a great design and they will rip it apart because it doesn't meet their standards. It sounds like you are ignoring the fact that you will have regulations and reviews on your site to deal with. Get the proper government agencies involved asap.

 

[arabojan]

the project is located in native americans property so they are not under any jursdiction, there is a wetland next to property that is under jurisdiction of army corps but the wetland inside property is not protected by any agency, the design that I am doing is not going to be reviewd by any county or agency, just i want to be design right

 

[tsgrue]

.

Interesting. You might want to review: "Wisconsin v. Environmental Protection Agency, et al", US Supreme Court, Docket No 01-1247.

Or, you could contact US Army Corps of Engineers Seattle District Regulatory Branch (

http://www.nws.usace.army.mil/PublicMenu/Menu.cfm?sitename=REG&pagename=Home_Page)

.



tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation

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