Transportation, drainage plans help city prepare for future growth



Everything presented Monday to the City Council regarding the drainage and transportation master plans falls into the hypothetical category today.

Roads may or may not be built, detention areas may or may not be dug, but the plans on paper alone give the city staff a useful tool in guiding the growth of Liberty Hill. Both plans passed unanimously.

The transportation master plan, which includes data on traffic counts and patterns, key challenges and a recommended network of new roadways, was presented by John Dean with Bowman Consulting

“We’ve identified existing and planned development, current congestion and mobility challenges, planned infrastructure projects and then talked with neighboring jurisdictions including Williamson County and the City of Leander,” Dean said.

It is not a plan of projects that are sure to be constructed, but proposals for long-range planning.

“Everyone of these proposed projects would take multiple council actions to move forward at all,” Dean said. “A lot of these roads are 20 years out, but it is important to have a map like this because as developers come in, if you don’t secure the right of way now and they put structures there, you’ve effectively taken away the option for the city to build a road there.”

Area traffic counts on key roadways show exponential growth in recent decades. Since 1990, traffic counts on SH 29 west of town has increased from 5,200 trips per day to 11,703 in 2015. During that same time, counts on SH 29 east of Liberty Hill shot up from 6,800 to 25,657.
Loop 332 jumped from 1,000 daily trips in 1990 to 2,836 in 2015, and RR 1869 in town went from 2,100 to 5,507.

“We want to provide mobility options,” Dean said. “I know congestion is getting to be an issue at a lot of different intersections and on different roadways in town, so we want to anticipate that and do our best to plan for it and provide alternatives.”

The adopted master plan focuses on collector and arterials roads.

Collector streets have a proposed right of way width of 70 feet. Typical design for these roads is two, 12-foot travel lanes with a nine-foot shoulder on each side, but could also have two 12-foot travel lanes plus a third 14-foot center turn lane with a two-foot shoulder.

Stubblefield, once completed, will be identified as an example of a collector.

“Arterials are more significant roadways and are intended to carry traffic over longer distances,” Dean said. “Typically you don’t want access to residential property on an arterial and you want to limit access to commercial property. It may happen, but you don’t want driveways every 10 feet because it really limits the functionality of the roadway.”

The right of way width for arterials is 100 feet, with typically four 11-foot lanes with a six-foot shoulder and a 16-foot center turn lane. It can also have a raised median in the center rather than a turn lane.

SH 29 is what Dean mentioned as an example of an existing arterial.

Having the different roadways identified as either collectors or arterials, with a defined right of way along a general mapped path will help the city in working with developers and acquiring right of way in advance of development.

“The entire purpose for doing this type of planning is to establish those corridors and as the development community comes in and starts planning with the city, we’re able to identify (the ROW plans) and not pay the huge amounts we would if we did nothing and let development happen without identifying the need for transportation lanes in the future,” City Administrator Greg Boatright said.

A number of corridors are identified in the master plan, many of which will be meant to help move traffic better in areas like up and down County Road 200.

A bypass from SH 29 on the east, connecting to CR 200 north of the railroad tracks is one option on the drawing board.

The map will include many options for future traffic control and relief of congestion, such as an extension of Long Run and Sundance Trail, both on the north side of town, east and west. The idea is for Sundance Trail to connect with RR 1869 closer to US 183 in the east and cross CR 200, connecting near SH 29 to the west.

The Stubblefield extension will eventually loop around the south side of town; then could meet and cross SH 29 to connect to the Long Run extension.

Putting drainage in detention
Working through phase two of the drainage master plan, K. Friese and Associates has identified the different drainage basins in the city, which also helps predict where strategic detention locations can be placed to make the most impact on drainage issues.

The first presentation was on the city’s drainage basins, demonstrating where stormwater tends to naturally go as it runs into tributaries.

“It is a really unique geography, from a drainage perspective, that the city has,” said Chad Cormack with K. Friese & Associates. “You don’t have any other cities that drain to you, which is a common problem, so we really have full control over our drainage basins and how we are going to regulate stormwater.”

By identifying the different basins, the city can zero in on the particular issues with each.

“It will aid future regulation,” Cormack said. “Each one of these basins has different characteristics. Some of the basins have a lot of problem areas already, some of them lend themselves well to regional detention, and some of them are undeveloped.”

Once the drainage basins were identified, planning for potential regional detention areas was next.

“As the city develops, there is going to be a need to detain the stormwater so we don’t increase the flooding that already exists, and so that we don’t create flooding that is not there,” Cormack said.

The models developed showed 15 locations across the city suited for detention ponds.

“These are just recommended locations,we are not advising you go out and acquire easements yet, and these are really flexible on where they can be located,” Cormack said. “It’s really just kind of a conversation starter with developers.”

Examples of where detention ponds may be in the future include a pair of locations near downtown and Liberty Hill Elementary north of Main Street and south of the railroad tracks; on the north side of SH 29 near CR 214; in front of the high school; on the western edge of City Park; along the west side of RR 1869 north of SH 29; and on the north side of SH 29 between US 183 and Sunset Ridge Drive.

The hope is that through this plan, site-based detention will not be the focus, as many developments won’t justify it on their own, but that the focus can be on a larger area and address the impact of numerous sites on an area overall.

In phase 1 of the city’s drainage master plan, K. Friese & Associates identified 17 problem areas in the city, which have been ranked based criteria to include the impact on property, streets, overlap with other projects, funding sources and the need for outside entity coordination.

“We came up with 17 problem areas,” Cormack said. “We ranked them to determine how we would tackle these drainage issues throughout the city. Phase 2 is developing solutions on how we will address these issues throughout the city.”

The top five problem areas according to the rankings include Jenks Branch, downtown flooding, East Carson Ave., Liberty Trails Apartments and the City Park and CR 200.