Replies

1. 
   TomT226 | Oct 15, 2005 01:54pm | #1

   I've got 30 years surveying experience, and seen many drainage problems like this that HO's tried to fix.  IMHO, you need to get a good profile of the tracts, and adjacent streets and alleys, to calculate the runoff from the impervious cover.  You'd be surprised how much water 1" of rain will drop on an acre of land.  If your tracts are much lower than the street, and the street has an adaquate storm sewer system, then you may need a holding pond type of flow reduction device.  The berms are probably a good idea, but if they divert water into adjoiners and damage occurs, you could have legal problems.

   Get a topographic survey done of your tracts, including the street fronting your tracts, and a portion of the adjoiners.  Work with the surveyor so as to reduce the cost, and give him a clear idea of your objectives.  Request a scaled drawing so that you and the surveyor/engineer may calculate the runoff and decide where to put the holding pond.  You may even find that your local government's design and construction of the street and drainage areas are the problem, and that improvements need to be made on those areas.  Make sure all easements are located as some areas have restrictions on construction that may obstruct access to them.

   I have worked on several of these, and a holding pond was constructed with flow reducers, and decks were placed over these to offset the loss of usable area.  Poured in place rip-rap and rock/gravel bottoms reduce maintainance.

   Good luck.

1. 
   Clyde | Oct 15, 2005 03:25pm | #2

   Thanks for your response.  I KNOW that the city's lack of drainage is the problem.  They know.  But it will take a long time (5-10 years) before they even begin to look at doing something.  (We have a mayor who brags about not having raised taxes in 10 years, but nothing ever gets done either.)

   So in the meantime, I have to address the problem.  You mention pouring something.  What specifically.  Yes, I had thought about placing it uder an area where I also want a deck, but wonderered about the stability of the footings/piers for the deck.  Would it be compromised unless I contain the "catch pond" in some way?

1. 
   storme | Oct 15, 2005 05:09pm | #3

   if you end up looking at pond liners check out everliner:http://www.everliner.com/ev_pond.htmlgood folks.-s

2. 
   TomT226 | Oct 16, 2005 01:55pm | #4

   First things first.  I don't know what size city your tract is in, but it may have a "Watershed Management" department, or something similar.  If you do, you need to find out the saturation point of your soil.  This factor, combined with the slope of your tract will determine how much (and at what velocity) the runoff from you tract will be.  This is very important in sizing your "holding pond."  This factor is known as "Q," if memory serves.  The "Q" is calculated at different rainfall rates.  When your soil reaches saturation point, 100% of the rainfall is runoff.  Holding devices are generally used to slow the velocity of the runoff so as not to overwhelm downstream drainage structures.

   In your case, it seems that you want to get rid of the runoff as soon as possible.  A holding device will not provide this.  If you have a drainage feature at the low end of your tract, you should consider constructing a swale through your tract to facilitate the rapid removal of the runoff into this feature.  To slow the flow you can construct "meanders" (curves) into this if you wish.  Grading a slope between existing structures to fall into the feature will help also.

   If you go with the "holding pond," it must not hold water all the time.  You could excavate, drill and pour footers with sonotube, then form and pour concrete rip-rap in the bottom graded so as to drain all water out.  Use the footers to attach your decking material above the projected high water line.

   Don't want to beat a dead horse, but a topographic survey of your land would really help you out with this problem.  Plus, if you had legal issues down the road, a recent survey showing the "Q" and the topo will be very, very useful.

   Check with the USGS to see if they have some 25, 50, and 100 year flood plain info on your area.