Chan Partners Engineering


Chan & Partners Engineering, LLC

Consulting Civil Engineers


Dam Engineering

SC Robertson Dam (Lake Limestone) and DeCordova Bend Dam (Lake Granbury) Breach Analyses and Inundation Mappings

The Brazos River Authority (BRA) owns, operates and maintains a series of dams along the Brazos River. The dams have high-hazard classifications because of the consequences of dam failures, and because of their sizes and hazard ratings are subject to State Dam Safety criteria. One of the dam safety criteria is that high-hazard dams must have written Emergency Action Plans with detailed supplemental breach inundation mappings. The BRA hired a preeminent hydrologic & hydraulic engineering firm (Halff & Associates, Inc.) to prepare the complicated breach analyses (using HEC-RAS hydraulic modeling) and detailed breach flood inundation mappings for S.C. Robertson Dam (Lake Limestone) and DeCordova Bend Dam (Lake Granbury) for “sunny-day” breach failure conditions and for Probable Maximum Flood (PMF) design flood conditions. S.C. Robertson Dam has a 8,130 feet long embankment section with a maximum fill height of 60 feet and has a concrete gravity spillway with 5 radial gates and a stilling basin. DeCordova Bend Dam has a 1,400 feet long compacted fill embankment section with a maximum fill height of 63 feet and has a concrete Ambursen-type spillway with 16 radial gates and a stilling basin. Breach analyses and breach flood inundation mappings were performed using HEC-RAS hydraulic program.

CPE, as a sub-consultant to Halff & Associates, calculated the breach parameters for both dams, for the embankment sections and for the gated spillway sections, for the “sunny-day” and for PMF design flood hydraulic conditions. CPE performed data research of the configurations of the two dams, including reviews of the construction as-built drawings and performed site visits to confirm field conditions and to confirm the locations and types of reasonable breach scenarios.


City of Austin Stormwater Pond Safety Program - Austin, Texas

The City of Austin owns and maintains at least 63 high hazard dam structures across the City.  State and City dam safety criteria require these high hazard dams to be able to safely pass the Probable Maximum Flood (PMF) without failing. The project team performed preliminary design assessments of the 63 dams to determine whether or not the dams are capable of safely passing the PMF, and if not, to perform preliminary designs of mitigation efforts to allow the dams to safely pass the PMF.

CPE assisted project team in developing the hydrologic models for the 63 dams as part of the preliminary design services. Based on available information and site visits, delineated drainage boundaries for each of the 63 structures, CPE calculated times of concentration for contributing runoff and developed HEC HMS models. Performed “peer review” of the proposed FNI methodologies for preliminary risk assessment from a theoretical breach and the overall structure ranking. CPE provided input to the methodologies including providing technical publications on calculating breach width and breach side slopes, flowchart diagram to depict various evaluation steps, and a “sensitivity analysis” for dam breach velocity related to attenuation length. Prepared memorandums summarizing the results of the peer review. Under final design services, CPE assisted project team in developing hydrologic and hydraulic models for Pond Dams 26, 220, 267, 337, 581, and 726.


Scenic Brook Flood Control Project, Hydrologic Modeling & Dam Hazard Analysis - Austin Texas

The Scenic Brook neighborhood is located on the Scenic Brook Tributary to Williamson Creek in the City of Austin. The neighborhood has been plagued by frequent local flooding. Plummer & Associates (APA) was retained by the City to develop mitigation measures. As part of the solution, APA identified a stormwater detention pond up gradient from South Brook Drive to reduce peak flowrates entering the neighborhood.

CPE developed the SCS TR-20 model for the existing and future condition for the 2-, 5-, 10-, 25-, and 100-year storms. Coordinated with TCEQ staff on dam safety requirements. Coordinated with APA staff in adjusting detention pond outlet structures to meet flood control objectives and TCEQ requirements. Developed dam safety analysis using the Probable Maximum Flood (PMF) storm event. Prepared engineering report documenting the project approach and conclusions. The detention pond consisted of a concrete retaining wall embankment, is approximately 16’ high and has a flood storage volume of about 22 acre-feet.


Brazos River Authority, DeCordova Bend Dam and S.C. Robertson Dam

The project is the development of breach parameters for DeCordova Bend Dam (Lake Granbury) and S.C. Robertson Dam (Lake Limestone).

As subconsultant to Prime Firm, CPE was the project engineer for determination of HEC-RAS breach parameters for the two Brazos River Authority high hazard dams.


Individual Experience of John King (while with Freese & Nichols):

DAM DESIGN AND REHABILITATION

Dam Modernization Program – Upper Brushy Creek WCID
Program Manager for the programming studies, preliminary designs, final designs and investigations and construction phase services for the ongoing modernization and rehabilitation of the District’s 23 dams.

Program Study – Upper Brushy Creek WCID
Project manager and project engineer for the development of the programming requirements for the District to implement its dam safety modernization program, including the requirements to implement the “Cafeteria Plan”. This study was performed under grant funding from the Texas Water Development Board.

Evaluation of High Hazard Dams – Brushy Creek WCID #1
Project manager and project engineer for the initial assessments of the WCID’s 46 dams in the Brushy Creek Watershed in Williamson and Milam Counties, Texas.

Pond Dams Inventory Project – City of Austin, Texas
Project manager for the preliminary assessments of 129 pond dams owned by the City, including assessments of dam related risks, priority rankings of dam modifications to comply with state dam safety criteria, and identification of pond dam safety program implementation requirements.

Dam Modernization Program – Lower Colorado River Authority
Project Manager for the $50 million dam modernizations of the LCRA’s six Highland Lakes Dams: Buchanan Dam, Inks Dam, Wirtz Dam, Starcke Dam, Mansfield Dam, and Tom Miller Dam.

Applewhite Dam and Spillway – San Antonio Water System
Project engineer for the design of Applewhite Dam and Spillway.

Richland Creek Dam – Tarrant County Water Control and Improvement District No. 1
Assistant and resident engineer for Richland Creek Dam, spillway and intake pump station, as well as relocation of a section of 3.2 miles of Burlington Northern Railroad track.

Starcke Dam – Lower Colorado River Authority
Project manager for design of floating bulkhead dewatering system and spillway pier modifications to the dam.

Longhorn and Decker Dams – City of Austin, Texas
Dam safety inspection and assessments of Longhorn Dam and Decker Dam. Duties included functioning as the firm’s representative shareholder (owner) for the project; ensuring the City’s project manager that the firm devoted sufficient resources; monitoring the project for compliance with the contractual scope, schedule and budget; served as the backup to the firm’s project manager to make the firm available and responsive to the City at all times; oversaw the firm’s internal quality assurance on the project; and in many cases served on the study and design team. Mr. King also assisted the firm’s project manager in coordinating the work between the City’s project manager and the City’s utility group at each dam site and assisted  the City in making assessments when 1997 floods damaged several spillway gates at Longhorn Dam.

BREACH ANALYSES AND RISK ASSESSMENTS

Dam Modernization Program – Lower Colorado River Authority
Project manager for the HEC-RAS breach analyses and risk assessments of potential breaches of Mansfield Dam and Tom Miller Dam.

Evaluation of High Hazard Dams – Upper Brushy Creek WCID
Project manager for the preliminary breach analyses, inundation mappings, and population-at-risk assessments for 19 high hazard dams in the Brushy Creek Watershed. Project Manager for HEC-RAS breach analyses and inundation mapping for 6 high hazard dams in the Brushy Creek Watershed.

Pond Dam Inventory Project – City of Austin, Texas
Project Manager for the preliminary breach analyses, inundation mappings, and population-at-risk assessments for 61 high hazard dams owned by the City.

DAM INSPECTIONS

Statewide High Hazard Dams – Texas Commission on Environmental Quality
Project manager for the inspections and assessments on behalf of the TCEQ of 245 high hazard dams statewide in 2000, 2001, and 2005.

Wesley Seale Dam – City of Corpus Christi, Texas
Project manager of inspection and assessment of spillway gates and spillways.

Highland Lake Dams – Lower Colorado River Authority
Project manager of assessments of flood damage to the dams.

Lake Mackenzie Dam – Mackenzie Municipal Water Authority
Project engineer for the inspection of Lake Mackenzie Dam.

Richland Creek Dam, Eagle Mountain Dam, and Lake Bridgeport Spillway – Tarrant County Water Control and Improvement District No. 1
Project engineer for the inspection of Richland Creek Dam and Spillway, Eagle Mountain Dam, and Lake Bridgeport Spillway.

Cedar Creek Dam and Spillway – Tarrant County Water Control and Improvement District No. 1
Project Engineer for the inspection of Cedar Creek Dam and Spillway.

Lake Nocona Dam – North Montague County Municipal Water District
Project manager of inspection and assessment of dam.

Nutt Dam – TU Electric
Project manager of the inspection of the dam.

Squaw Creek Dam – TU Electric
Project manager of instrumentation assessment of the dam.

CONSTRUCTION CONTRACT MANAGEMENT

Hubbard Creek Dam – West Central Texas Municipal Water District
Construction manager for riprap repair at Hubbard Creek Dam.

Comanche Trail Lake Dam – City of Big Spring, Texas
Construction manager for the repair and upgrade of Comanche Trail Lake Dam.

Lake Como Dam – City of Fort Worth, Texas
Construction manager for the rehabilitation of Lake Como Dam.

Applewhite Water Supply Dam – San Antonio Water System
Construction manager of construction of the Applewhite Supply Dam, Spillway and Neal Road relocation.

Eagle Mountain Dam – Tarrant County Water Control and Improvement District No. 1
Construction manager for riprap repair at Eagle Mountain Dam.

MAPPING

Dam Modernization Program – Upper Brushy Creek WCID
Program manager for the development of the digital mapping database for the District’s 23 dams and their watersheds, as well as the periodic updates as the local government entities have their jurisdictions within the watershed re-flown.

Mapping of the Applewhite Water Supply Project – San Antonio Water System
Project manager for computerized topographic mapping of the Applewhite Water Supply Project reservoir and mitigation areas.

REGULATORY
Executive Director’s Task Force on Dam Safety – Texas Commission on Environmental Quality
Member of the TCEQ task force that first developed and recommended changes to the state’s dam safety criteria to allow implementation of a “Cafeteria Plan”.

Dam Safety Hydrologic and Hydraulic Design Criteria Manual – Texas Commission on Environmental Quality
Project manager for the ongoing development of the proposed new hydrologic and hydraulic design criteria for assessment and design of dams in Texas.

John King, P.E.
(Vice President)

Specializes in the design of water retaining / storage structures such as reservoirs, dams, and levees.

Mr. King has considerable experience in the rehabilitation of concrete and earthen dams.

Prior to joining Chan & Partners Engineering, LLC, Mr. King served as the project manager and project engineer for a number of large-scale public works projects including planning, design and construction for roads, utilities, railroads, wastewater collection systems, dams, and reservoir while with Freese & Nichols. Inc.