Texas Department of Transportation (TxDOT) shows the way
By Ashish D. Patel, PE
Following extreme storm events such as Hurricane Harvey, Tropical Storm Imelda, and Hurricane Laura in recent years, the Texas Department of Transportation (TxDOT) engaged planning, engineering, and program management firm Lockwood, Andrews & Newnam, Inc. (LAN) in December 2020 to perform a facility evaluation study of selected facilities in five coastal districts – Beaumont, Corpus Christi, Houston, Pharr, and Yoakum – before the 2021 hurricane season (In Texas, June 1 is the beginning of hurricane season).
Subsequently, LAN performed a comprehensive FEMA Level 1 assessment of 52 facilities in these coastal districts and provided recommendations to improve their resilience against probable future hurricane, wind, and flood hazards. As TxDOT improves the resiliency of its vulnerable facilities in these coastal districts, the agency will be better prepared to serve the needs of its residents during future hurricanes and storms.
The evaluated facilities were built anywhere from 1939 to 2020. Facilities varied from wood structure to steel framed structure to pre-engineered structure to cold formed steel structure to concrete structure to combination thereof. There was no uniformity. Many facilities were beyond the originally designed service life and went through one or multiple repairs/renovations over the years. There was limited historical documentation and the data available on the structural, architectural, and mechanical, electrical and plumbing (MEP) systems for many of these facilities was inadequate beyond a previous ADA assessment. For some of the buildings, there was no historical documentation or data available.
LAN’s scope of work was limited to FEMA Level 1 assessment which included:
- Reviewing historical information files (i.e., as-built drawings and specifications, submittals, previous leakage, and repair reports) including but not limited to wind and flood load rating per current building codes.
- Discussing with personnel familiar with the building to determine whether it has leaks or has other known issues and obtain historical information that is not in the file.
- Conducting a field investigation.
- Reporting findings.
However, the Level 1 assessment doesn’t include any destructive investigations or non-destructive testing. As a result, buildings lacking as-builts or construction documents required more assumptions for analyses of structural, architectural, MEP and other building component systems.
One of the primary goals of the evaluation was to come up with recommendations along with cost estimates to improve resiliency of existing facilities against hurricane, wind, and flood without disrupting their normal operations. Hurricane, wind, and flood are probabilistic environmental hazards and its quantification is a blend of statistics, physics, past measurements or data collected during such events and engineering judgment based on years of experience. The engineering knowledge of these environmental hazards is still evolving. Many of these buildings were built in an era when the knowledge about environmental hazards was either non-existent or was in its infancy.
Further complicating the evaluation was the performance variability of building materials, assessment scope limited to FEMA level 1 assessment, limited availability of existing record drawings, and limited information about design parameters on the existing record drawings. Considerations such as the cost of improvement recommendations versus building a new facility and determining the time needed to execute the project presented another layer of challenge.
While there are several FEMA reference standards and building codes that provide guidance on the various challenges described above, it is anything but a straightforward process to unify all of that and come up with a systematic, cost-effective solution that can be rapidly employed.
Standardizing the site-specific data collection process involved interviewing several long-tenured TxDOT employees in a short time. Often, that was the only way to get information about past performance of the facilities during extreme events, past repairs/retrofits/renovations, and existing hurricane and flood preparedness plans.
Another challenge was classifying the asset integrity for hurricane/wind and flood in a way that can be easily understood by the local TxDOT employees and upper management, while also being consistent with the applicable building codes and FEMA reference standards. Most of the mainstream media reporting of the environmental hazard events pertaining to hurricane and flood relates to Saffir-Simpson Hurricane Category for hurricane/wind and 100 year or 500-year classifications for flood events. For engineering analysis and design, building codes and FEMA reference standards do not directly correlate to those mainstream media narratives.
Picture a building built in 1939 which is long beyond its service life and has gone through several re-roofing exercises still standing but not in sync with current code requirements. Coming up with recommendations to improve its resiliency against future hurricane/wind and flood events without making extensive retrofits or building a new facility from the ground up was a major undertaking.
Three teams of assessors comprising professional engineers and architects were employed for this project. The three assessment teams utilized a field reconnaissance checklist, which was incorporated into the report section of each building. Teams were assembled with a balance of skills to address identification and documentation of building assemblies, structural components, and critical infrastructure.
To gather necessary facilities data, the assessment team first reviewed available site plans and building drawings. Assessment teams then conducted site visits to all 52 buildings in the five coastal districts. The work performed at each site included:
- Discussion with local staff to explain the facility evaluation and inquire about historic storms, protective shutters, generators, and the existence of drawings, if not provided previously.
- Verification, documentation, and measurement of exterior envelopes, including walls and roofs, if accessible.
- Exploration of accessible attics, mezzanines, and roofs to verify and document structural components.
A correlation was made between Saffir-Simpson Hurricane Wind Scale and hurricane/wind resiliency level determined based on the building codes. Illustration is provided in the images below.
Also, a correlation was made between a 100-year flood event, a 500-year level flood event and the flood resiliency level determined based on the building codes. Illustration is provided in the image below.
Following the field assessments, the teams performed engineering analyses to determine the resiliency level of each asset against hurricane, wind, and flood hazards as per the applicable building code at the time of construction. The resiliency level of each asset against hurricane, wind, and flood hazards as per the current building code (IBC 2018) was also determined. A comparison was made between the resiliency level of each asset as per the applicable building code at the time of construction and as per the current building code (IBC 2018). An example for an individual facility is shown below. These comparison tables were used as a part of process to determine whether the individual facility is sufficient or deficient per current building standards.
Recommendations to Improve Resiliency
Based on holistic evaluation including but not limited to engineering analyses and architectural review, recommendations were provided for each asset to improve resilience against probable future hurricane, wind, and flood events. Repair recommendations were also provided for distressed items observed during field assessments.
While it is not possible to provide an exhaustive list of all the recommendations for 52 facilities here, a brief list is provided below:
- Partial or full roof replacement (particularly at existing ballasted roofing systems) including repairs to roof support members.
- Hurricane-rated storm shutters on doors or windows that were deficient to meet current building code requirements for wind loading.
- Removable flood barrier walls instead of retrofitting existing buildings to meet current building code requirements at deficient facilities. This recommendation provided a cost-effective alternative to retrofitting the building and allowed operational space outside the building during a flood event. This recommendation also allows a future liner addition over the removable barrier walls to protect against scour and erosion.
- Sectional and rolling door replacement in places where storm shutters were not feasible.
- Positive anchorage of rooftop equipment in places where anchorage was not sufficient.
- New emergency generator system in places that didn’t have one.
- New emergency generator enclosure in places with inadequate enclosures.
- Standby generator to cover for potential malfunctioning of the emergency generator. A cam locking box was also recommended to facilitate a back-up portable generator connection.
- Independent water supply such as a well or on-site water storage at emergency operation facilities.
- Protection of storage tanks, piping and pumps against wind-borne debris using either protective enclosures or placing them underground.
- Portable toilets placed inside the facility before the onset of a hurricane.
- Addition of backflow preventers to sewer lines.
- Addition of walls and hurricane-rated overhead doors at currently open equipment sheds.
- Periodic inspection of various systems and facility components.
In addition, an Engineer’s Opinion of Probable Cost (EOPC) was also provided for the recommendations (example for an individual facility below).
In August, Hurricane Ida came ashore 60 miles south of New Orleans as a Category 4 hurricane and made landfall on the 16th anniversary of Hurricane Katrina. According to news reports, New Orleans didn’t suffer the kind of catastrophic flooding that happened during Hurricane Katrina. It is not just a result of good fortune, but it is at least in part the result of flood protection measures put in place after Hurricane Katrina. However, in the hurricane’s aftermath, significant parts of New Orleans suffered loss of power. Understanding this issue, our project team not only recommended barrier walls but also backup power generators with camlock boxes to improve the resiliency of TxDOT coastal facilities.
It is my sincere hope that this project will show the way to other DOTs, public agencies, and private corporations to consider the potential negative effects of climate change seriously and ensure that resiliency is built into their facilities and infrastructure. By building in resiliency, we can reduce mass suffering, property damage, injuries, deaths, and disruptions to public life during extreme events.
Ashish D. Patel, P.E. is a senior structural engineer and a subject matter expert with Lockwood, Andrews & Newnam, Inc (LAN), a national planning, engineering and program management firm. He can be reached at firstname.lastname@example.org.