Town releases report on downtown flooding

On the night of Tuesday, July 15, a sudden and substantial summer thunderstorm caused floodwaters to spill over the banks of Rumbaugh Creek near the intersection of Lewis and 1st streets, causing substantial damage to a number of businesses and homes on the east side of downtown Pagosa Springs.

At the July 17 town council meeting, Michael Howell, owner of the house on the southwest corner of the intersection, approached Town Manager Greg Schulte and offered an explanation for the cause. The next day, Friday, Schulte toured the area with Howell.

Howell offered the same tour and explanation to SUN staff the following Monday. “They reworked Lewis Street from the middle school, all the way down, and that section on First Street, they raised the height of that road well over two feet.”

The Lewis Street repaving project, which was completed last year, ran into more snags than could be summarized in this article, and further background research on the SUN’s website is recommended.

“I know that because I was arguing with Davis Engineering,” Howell continued, “that if they raise the height of that road, it actually put my foundation two feet below grade. Code requires you to build your house above road height, so water will run towards the road and drain off.”

Howell then took SUN staff on a tour of the area and explained what happened on the night of July 15.

All of the rainwater from the Snowball watershed area funnels down into Rumbaugh Creek, which is the ditch on the west side of 1st Street. At approximately 10 p.m. on the night of July 15, the amount of water flowing in the ditch exceeded the capacity of the culvert at the intersection of Lewis and 1st streets.

As a result, water began to back up, eventually covering the driveway of the next upstream property, nearly a hundred feet away. This pool of water then began flooding the backyard and basement of the house on the northwest corner of the intersection, across the street from Howell’s.

As the water overtopped the culvert and began to flow over the surface of Lewis Street, it quickly exceeded the capacity of the street’s gutters. Instead of turning west on Lewis Street and flowing into a newly installed storm drain, it jumped the curb and flowed directly into Howell’s house. It also flowed through the yard of Howell’s next-door neighbor.

All of this water then flowed across the alley and through the parking lot of the Rocky Mountain Knife Shop, where it began to pool and spread out. It soon crested U.S. 160, creating a flow of water nearly the entire length of the block from 1st Street to 2nd Street, flooding the businesses on the south side of the highway. The Pinewood Inn was perhaps the hardest hit.

Howell explained that in the past, before the Lewis Street repaving project, floodwater would turn east, flow across the surface of 1st Street, and empty back into Rumbaugh Creek behind the San Juan Historical Society Museum.

Soon after meeting with Howell, Schulte asked Davis Engineering to analyze the situation and make a formal report to the town explaining why the flood occurred and what role, if any, the Lewis Street redesign may have played in the event.

In a phone interview with SUN staff on Aug. 26, Schulte explained that the town had received the final report from Davis, but it had been sent directly to the town’s attorney, Bob Cole, and then distributed to town council. As a result, it was covered by attorney/client privilege and was not a public document.

At this week’s Town Council meeting, Schulte argued, “Upon review of the report, by both myself and the town attorney, we believe that it is appropriate to release that report.”

Town Council agreed, voting unanimously to waive attorney/client privilege and allow the document to become public. Schulte emailed a copy to SUN staff shortly after Tuesday’s meeting.

The five-page report, signed by Mike Davis and received by Cole’s office on July 31, contains an extensive technical description of the event, including everything from mathematical formulas for figuring out-flow capacities for ditches and culverts — including a variable that accounts for the amount of vegetation along both sides of the ditch — to definitions of two-, 10- and 100-year flood events.

In conclusion, the report states, “From the data presented above, it would appear that the First Street culvert for Rumbaugh Creek has the capacity to carry right at the 2-year peak runoff flow, and that the recent flood was significantly in excess of this amount, possibly between the 10 and 100-year events. The Town LUDC calls for major drainage structures to be designed for the 100-year peak flow, indicating (by present standards) that the Rumbaugh Creek culvert is severely undersized. We are uncertain how long the present structure has been in place, or how it was sized.”

The report also claims that, because of the magnitude of the flood, the design of the curbs and gutters along Lewis Street had little or no bearing on the outcome of the flood.

“With Lewis Street being designed to Town standards,” the report states, “and the failure occurring at the Rumbaugh Creek culvert, the issue at hand is the inadequate capacity of the culvert. At no time was DES informed that new street infrastructure should be designed to accommodate shortcomings in upstream drainage structures, nor would that normally be the case.”

As far as what should be done to prevent similar flooding in the future, the report states, “Short term recommendations would be to improve the drainage handling ability of the Rumbaugh Creek channel and culvert. Removal of the brush and trees would increase the capacity of the channel immediately upstream of the culvert. As the upstream and downstream culvert ends have been washed out and need attention, now might also be the time to refine culvert inlet/outlet hydraulics and protection (end sections, wingwalls, etc.). An additional localized consideration would be to add ‘training’ walls to direct overflows to the street. This might include fairly low concrete walls along portions of First Street and Lewis Street; however, this wouldn’t help additional properties further downstream, such as those along the south side of Pagosa Street (U.S. Highway 160), which also experienced flooding. Individual or groups of properties could also pursue the ‘training’ wall idea for their own protection if significant improvements to the Rumbaugh Creek crossing can’t be accomplished in the near future.

“Long term, it is recommended to refine the drainage study and anticipated peak runoff values at the First Street crossing (using survey data and a more robust model) to determine the size and type of structure required to pass the 100-year runoff peak. Using the 1,366 cfs indicated above might require a concrete box culvert around 12 feet wide and 12 feet high, which would be a significant undertaking.”

At Tuesday’s meeting, council member David Schanzenbaker said, “I just might question the concept of Davis Engineering preparing the report since they’re the inside player.”

“That’s true,” Schulte replied, “but they are the people who have the background information … and we believe it is appropriate for them to provide a response, since they were our contractor for that project.

“We’ve made this report public, and the people who choose to may take that report and give it to whomever they want and have their own analysis done.”

This story was posted on September 4, 2014.