Frequently Asked Questions
Related to Drainage within Montgomery County MUD No. 89
1. What is the purpose of the Lakes within Legends Ranch?
The three lakes within Legends Ranch are both an amenity feature for the community and provide detention capacity for the drainage system. The lakes were designed to hold a static water elevation, which act as the amenity portion of the Lakes and does not account for any of the detention capacity. The detention capacity is calculated above the normal water surface elevation to the top of bank. During rain events, as the lakes collect water and the lake levels rise, water overflows into culverts which drain into the Central Drainage Channel.
2. Who is responsible for maintenance of the Lakes within Legends Ranch?
The three lakes are designed to hold water as an amenity feature for the community. The detention capacity is calculated above the normal water surface elevation. It is the responsibility of the Legends Ranch POA to clean/maintain the amenity feature of the lakes.
3. Where does the storm water drain from Legends Ranch?
The storm system within Legends Ranch include the streets, storm inlets, storm sewers and the detention portion of the three Lakes. The western portion of the Legends Ranch storm system, west of Legends Ridge Drive drain into the three Lakes, which drains into the Central Drainage Channel located immediately south of the Legends Ranch subdivision. The eastern portion of the Legends Ranch storm system, east of Legends Ridge Drive as well as The Enclave subdivision do not drain into the Lakes but drain directly into the Central Drainage Channel.
The Central Drainage Channel flows east into the Central Detention Pond located east of Birnham Woods Drive. This pond is drained via a storm water pump station located at the east end of the detention pond that ultimately flows into Stokes Gully and Woodsons Gully south of the Grand Parkway.
The Central Drainage Channel and Pump Station is shared between Montgomery County MUD No. 88, Montgomery County MUD No. 89 and Spring Creek UD and managed by Spring Creek UD.
4. How does the storm water pump station function?
The Central Detention Pond is 15 feet deep and provides approximately 443 acre-feet of detention volume and designed to contain a 100-year frequency storm event with a minimum of 1 foot of freeboard. The storm water pump station includes five pumps with a total capacity of 200,000 gallons per minute or 445 cfs. The detention pond also includes an emergency overflow weir designed to outflow events greater than the 25-year frequency storm event. The storm water pump station has an emergency generator sized to operate two of the five pumps, with the emergency scenario relying on the overflow weir.
The storm water pump station does not pump water directly for the three lakes within Legends Ranch nor do the pumps directly affect the street drainage. The lakes are designed to hold water at a constant water level as an amenity feature. During rain events, as the lakes collect water and the water levels rise, water overflows into culverts which drain into the Central Drainage Channel and ultimately pumped into Woodsons Gully.
5. Why may the water backup in the streets?
The storm sewer system within the District was designed to meet Montgomery County drainage requirements. As a general rule of thumb, the storm sewer system was designed to handle approximately 1 inch/hour of rainfall intensity. In the event that rainfall intensity exceeds the capacity of the storm sewer system, water may begin to rise in the streets. The streets themselves are a part of the drainage system and are designed to hold 12-18 inches of water as part of the capacity of the system. As soon as the rainfall intensity weakens, water in the streets will quickly begin to recede.