Here’s a solution to this problem.
During the September 2013 flood, water seeped into and flooded the low front part of our Unitarian Universalist Church of Boulder (UUCB) Earth-Room Sanctuary.
Fox Martin, age 9 in September 2013, standing in flooded UUCB Earth-Room Sanctuary
Rainwater falling on the north slope of the roof above the two Ministers’ Offices plus most all of the water falling on the east slope of the Earth-Room Sanctuary roof totals 1,125 square feet of roof* and it all funnels down onto the Memorial Garden’s tiled Patio outside the offices and onto the adjacent Memorial Garden. We believe water saturated the ground of the Memorial Garden on the north-east side of the Earth-Room and seeped down until its hydraulic pressure caused it to bubble up inside the Earth-Room. (Water literally seeks its own level.) Hilton observed water bubbling up through joints in the Sanctuary’s cement floor. At the time, he also looked at the bottom of the vertical stained glass Sanctuary window and did not see any water leaking in from the outside. Surprisingly, the outside base of the window was also fairly dry.
To prevent future flooding, draining rainwater away from the Patio and Memorial Garden should prevent our Earth-Room from flooding again. So, UUCB Member Fox Martin for his Eagle Scout Service Project will install this needed drainage. He will lead and supervise volunteer Boy Scouts in his troop along with their parents, some players from his Fairview High School football team, plus some Church members.
To capture the water coming off the subject roof, particularly the 90° corner of the roof where the RE Wing roof joins the Earth-Room roof, we need to install a 10 foot Trench Drain along the entire north edge of the tiled Patio and pipe it underground to a Catch/Distribution Basin with a 13 foot long 3 inch solid smooth PVC Drain Pipe.
page 2 Fox Martin’s Eagle Scout UUCB Rainwater Flood Drain Service Project
The Catch Basin will be directly north of the Patio at the lowest point in the Memorial Garden. Additional piping will then run underground north-westerly 80 to 90 feet and empty onto the lawn near the existing culvert on the south side of the east-west paved path north of the Church. That culvert slopes northward under the path and empties into the Wellman Canal ditch. During the flood of September 2013, Hilton looked and saw no water backing up from the ditch through the culvert and flowing south onto the Church lawn.
The catch basin in the Memorial Garden is some 13 inches higher than the culvert, so the pipe will drop 1 foot giving it the minimum recommended 1% drainage slope. (A one foot drop over 100 feet is 1%.)
All piping will drain by gravity and will be 3 inch solid white PVC sewer pipe (not perforated as it’s not a French drain).
* Using a June 4, 1999 survey plat (a portion of which is shown below) we calculate the subject roofs’ plan view area (the horizontal area as viewed straight down from the sky) to be 1,125 square feet.
For an area of 1,125 square feet, 9 inches of rain in one day equals 6,312 gallons. The maximum rainfall on 9/12/2013 was 9.08 inches** per https://water.usgs.gov/edu/activity-howmuchrain.html. 6,312 gallons per day
÷ 24 hours = 263 gallons per hour, or 4.4 gallons per minute.
A 3 inch solid smooth non-perforated PVC pipe at a 1% slope will drain 34 gallons of water per minute by gravity. So a 3 inch diameter pipe will work.
This Drain Project was approved for $500 by the UUCB Endowment Fund and by the UUCB Board of Trustees. We coordinated ahead of time with other concerned members as recommended. The work began Saturday, August 17th and was completed on Sunday, August 25, 2019. At one point to maintain the proper downward drainage slope the trench had to be dug fully 2 feet deep through ground that was hard, dry and rocky. The soil had likely not been disturbed since our church was built 56 years ago in 1963.
After the ground settles, the Building and Grounds Committee can re lay the concrete stepping stones and flagstones that were set aside. To maintain drainage in the Memorial Garden they may wish to add dirt to low places after settling occurs. Some sprinklers need to be reinstalled. weed barrier fabric has been installed over the 13 foot pipe in the Memorial Garden path. Additional weed barrier fabric has been left for Committee installation under the concrete stepping stones.
Hilton Fitt-Peaster and Fox Martin
updated August 27, 2019
page 3 Fox Martin’s Eagle Scout UUCB Rainwater Flood Drain Service Project
Boulder Flood 2013: Rain by day
Mon., Sept.9 0.25 inches
Tues, Sept. 10 1.02 inches
Weds., Sept. 11 1.92 inches
Thurs., Sept. 12 9.08 inches (**the maximum day)
Fri., Sept. 13 2.44 inches
Sat., Sept. 14 0.01 inches
Sun., Sept. 15 1.94 inches
Mon., Sept. 16 0.49 inches
Eight-day total 17.15 inches
Source: Meteorologist Matt Kelsch
Boulder Flood May 4–8, 1969 when UUCB Member Fred Cole believes the Earth-Room also flooded
Peak Day May 6 3.5 inches
SW of Boulder, total 13.05 inches in 86 hours (3½ days)
Boulder Flood May 9–15, 1957
Peak day, 5.9 2.61 inches
May 7, 1957 2.35 inches
page 4 Fox Martin’s Eagle Scout UUCB Rainwater Flood Drain Service Project
A January 12, 2019 email from Tim Piwonka-Corle, UUCB Building & Grounds Chair:
Hilton and Fox
I fully support this project. You can certainly add my personal endorsement. I have personally seen the problem with the drainage of the Memorial Garden behind the Ministers Office. The fact that you did not see any water seeping in next to the stained glass is very interesting (although not conclusive as I think that low area is still higher than the base of the sanctuary).
Even if the drainage does not help with water incursion into the sanctuary, I still think it is worthwhile to get the water away from the building where it accumulates in the Memorial Garden.
Best regards, Tim