Diverting Rain Water

December 24, 2010
It’s rainy season here in Santa Cruz.  So far we’ve had 14 days of rain this month (December).  November had 9 days of rain and October had 6 days of rain.  Ever since we learned that there is evidence of high water pooled under the house (from home inspection we did during escrow) we’ve been thinking about mitigating the impact from the winter rain on the house.  Excessive moisture fuel mold growth and wet wood will compromise the integrity of the structure.  So, we want to divert the rain water away from the house.
A while ago we talked to Robert, prior owner of the house, and he mentioned that there is a drainage tube that was placed parallel between the house and the driveway to divert the pooled water in the back of the yard towards the street into the storm drain.  This drainage tube is now covered up in grass and hardly visible.  We don’t intend to use this if we can help it.  Why?  Because (a) Rainwater could be harvested and used to water the plants on the property; and (b) Large volume of rainwater discharging in to the storm drain cause problems such as erosion and degraded wildlife habitat.  Allow me to digress on this second point.  
Have you seen a label next to the storm drain?  It may say, “No Dumping Flows to Bay,” or a variation of this message.  This means that the liquid that goes into the storm drain does not get treated at sewage treatment plants.  The storm drain water simply goes into a local watershed, transporting whatever it picks up along the way to the stream, ocean, etc.  OK, that’s not big news and we’re not dumping automobile engine oil in the storm drain.  Still, there are indirect ways that we may be contributing to the water pollution.  Maybe it’s the fertilizer to keep the grass green or the pesticide used to kill weeds.  Perhaps it’s the bitumen or asphalt on our roof that is slowly degrading in the sun and transported by the rain.  We want to minimize these pollutants from getting into our watershed and also avoid erosion from high volume of storm water moving quickly through the system.  All right, enough of my rant about avoiding directing rain water into storm drain and back to the house…
We also talked to our neighbor about rain water and “flooding” in the backyard during storms.  In the past few years they have done a major renovation to their home by removing several feet of soil from their crawlspace and converting the crawlspace into a beautiful basement that opens out to the backyard.  During their project they found that the soil has high clay content that does not drain well and found the water table to be high.
Next, went on a quest for water table data.   First, we tried the water department with the city of Santa Cruz.  They pointed us to the public works department.  The people at the public works department was friendly and helpful, but they didn’t have water table data.  One of the engineers mentioned that ordering a soils report from a soils professional would be the way to get complete analysis and it would be very expensive.  A low cost alternative would be to simply dig a hole of 3-6 feet in the backyard and see if we hit water.  So that’s what we did.
About a month ago Kurt dug a hole of about 8 inches in diameter using a post hole digger — one in the back yard and one in the front yard to see if the water table is high as the rumor has it to be.  It was.  It was a clear day and the soil dug up was still moist from the rain over the weekend.  He stopped digging after 30 inches or so.  Observing that the dirt at the bottom was visible he walked away.  Then 30 minutes later he looked in the hole and saw 2 inches of standing water at the bottom! 
What to do with this?  We have a crawlspace that potentially floods.  The soil in our area has high clay content and does not drain well.  The water table is high in our area.  We want to avoid sending rain water down the storm drain. Hmm….
Since our first priority is to “protect the house” we took a temporary measure to divert the rainwater from the downspout away from the foundation of the house.  We will keep these downspout extension tubes in place until spring.
We plan to include a landscape designer as part of the overall design team so that rainwater harvesting system can be integrated into the overall design.  Right now we are thinking of putting rain pillows under the deck on the south side of the house.  Eventually the yard will be covered with mulch that will absorb rainwater and native plants that require little or no watering (once established).  The timing of actual implementation of the landscaping design will be after the house completion.
By the way, there is a great free resource for rainwater management for single family homes called, “Watershed Stewardship Toolkit,” prepared by Coastal Watershed Council.  It’s an easy to read document with specific examples for the things we are considering, such as rain pillows or cisterns, vegetated swales or rain garden, soil amendments and more.  This document is available from CWC’s stewardship page on their website.

About the Author

Chie Kawahara

Chie is one of the co-creator of Midori Haus. When she is not sharing her stories of transforming an old house and giving tours, she enjoys trail running and hiking.