Evers Road Bridge-Rain Event and Update
As you know, we have spent the past seven months constructing a proper bridge for Evers Road at Huebner Creek. The roadway was opened last week to get traffic moving for school, but the construction is still underway – they expected to be complete by September 28th, but this rainfall will cause another delay.
Overnight, the bridge had to be closed due to an extraordinary amount of rainfall upstream and in Leon Valley. The Fire Department recorded 9 inches of rain in a ten hour period of time. The rain gauge at Public Works recorded 8 ¾ inches of rain. The Fire Department reports that the rainfall was so intense, that the street runoff around the bridge/creek could not get into the creek fast enough. Please be advised that, due to ground saturation and more rainfall expected, the roadway may have to be closed again.
Because of the limited amount of real estate and the hydraulic calculations for flooding in the Evers/Poss Road area, we were not able to build a bridge that would withstand a 100 year flood event. In fact, the bridge will only hold a five year flood event, which is what we typically experience. That equates to a 2-3 inch rain fall event. Although the bridge is higher than the old low water crossing, building it high enough to hold a 100 year flood event would have caused the city to buy out property and would have also caused a rise in flood waters downstream, which would have put more homes at risk of flooding.
The original low water crossing had to be replaced because it was on the verge of falling apart from being flooded and collecting debris, which damaged the structure. The metal 36” round culverts were tearing away, portions of base under the roadway were washing away, and the concrete rip rap on the top of the crossing were completely disconnected from the structure. It was just a matter of time until the whole thing collapsed. In addition, the low water crossing required the road to be closed every time we had a 1 inch rainfall event, which resulted in the Fire Department having to close the roadway over 20 times in 2017.
As we have said, the bridge is still not complete – the contractor is still installing concrete rip rap on both sides of the park side of the bridge, and the pedestrian crossing, then they will spray hydromulch on the north side to revegetate the area. There is a rock filter dam in the creek bed on the park side that will be removed once the project is complete, which will allow the water and debris to flow more freely. The rock filter dam is a part of the Stormwater Prevention Plan, as required by TxDOT.
The Public Works Department has applied for and received funds from the United States Corp of Engineers (USACE) to perform a feasibility study on reshaping Huebner Creek to reduce the amount of flooding we experience. Huebner Creek is made up of 9 ½ square miles of watershed, both in San Antonio and in Leon Valley. The City will be partnering with the San Antonio River Authority and USACE to see if there are improvements that can be made in both cities to finally control our creek and reduce or eliminate the threat of flooding.