Our Team

Although Riley is a relatively small company by industry standards, our staff is carefully and purposefully selected to provide a diverse and complementary set of skills that ensure the viability of our client’s projects. Our staff is comprised of highly educated registered engineers, scientists, and experienced technical staff including: 

  • Civil Engineers 
  • Water Resource Engineers 
  • Professional Hydrologist 
  • Certified Draftsmen 
  • Research Engineers/Scientists 

Riley’s company structure allows us to guarantee that our clients work with the most qualified personnel for the needs of each individual project. Because our staff is cross-trained we are able to provide a flexible combination of engineering services across disciplines that otherwise might not be possible in a large, structured hierarchy found in other companies.  Riley openly communicates with our clients at the outset of every project about the duties and qualifications of every staff member that will be working on their project. 
Ph.D., P.E. Principal

Ronson Chee

Ph.D. Candidate (ABD). Staff Engineer

Chris Horstmann

E.I.T. Staff Engineer

Michaela Long

P.E., P.H. Senior Engineer

Michael E. Zeller

Ph.D., P.E. Principal

Ronson Chee

Education: Bachelor of Science in Civil Engineering, University of Arizona, 2008 

Master of Science in Civil Engineering, University of Arizona, 2011 (Water Resources Emphasis) 

Doctor of Philosophy in Civil Engineering, University of Arizona, 2017 (Water Resources Emphasis) 

Licensure: Professional Engineer Arizona (No. 54056)  

Professional Engineer New Mexico (No. 26226) 

Years of Experience: 13  

Short Bio:   

Dr. Chee is the Founder and Principal of Riley. His experience as a water resource engineer is expansive and ranges from being a designer, to a project engineer/manager, as well as managing the company. He has experience in hydrology & hydraulics, water distribution systems, grading and drainage. As the Principal of Riley, he is responsible for managing day-to-day operations of the company and ensuring projects are technically sound and completed on time and on budget.  

Dr. Chee grew up on the Navajo Nation where he experienced firsthand the socioeconomic challenges caused by the lack of basic water infrastructure. This motivated Dr. Chee to pursue the field of civil engineering to improve living conditions and ensure that society has the necessary civil and water infrastructure to facilitate economic well-being. Civil engineering is his passion, and he has made it his life’s mission to serve and help improve the lives of others. In working towards this, in 2017, Dr. Chee became the first member of the Navajo Nation to earn a Doctor of Philosophy in Civil Engineering.   

Ph.D. Candidate (ABD). Staff Engineer

Chris Horstmann

Education:  

Bachelor of Architecture, University of Arizona, 2003 

Master of Science in Civil Engineering, University of Arizona, 2015 (Water Resources Emphasis) 

Doctor of Philosophy (ABD) in Civil Engineering, University of Arizona, 2020 (Water Resources Emphasis) 

Years of Experience: 7 

Short Bio:   

Mr. Horstman worked as a design/build architect focused on energy efficient & low-income housing until returning to the University of Arizona Civil & Architectural Engineering Department where he worked as a graduate student and research engineer. It was during this time that he joined Riley Engineering, having a shared commitment for developing water resources in rural and underserved communities. At Riley, Mr. Horstman brings his knowledge of ground/surface water hydrology, hydraulic infrastructure design, and scenario planning. His expertise lies in leveraging his computer programming and modeling skills to provide creative solutions to large scale water resources projects.  

Originally from Flagstaff, AZ, Mr. Horstman’s commitment to education and his community led him to help establish a K-12 water engineering competition. He remains active in this outreach program at Riley Engineering, helping students across Arizona understand their water supply through a hands-on engineering activity. Mr. Horstman’s graduate work has focused on surface and groundwater interactions along the San Pedro River in Southeastern Arizona and Northern Sonora, Mexico. Mr. Horstman maintains a focus on quality client/stakeholder interactions at Riley Engineering, developed through his experience collaborating with regulatory government agencies, NGOs, and a diverse array of clients. 

E.I.T. Staff Engineer

Michaela Long

Education: Bachelor of Science in Civil Engineering, University of Arizona, 2018 

Licensure: Engineer-in-Training Arizona (No. 12927) 

Years of Experience: 3 

Short Bio: 

Ms. Michaela Long is a Staff Engineer with areas of expertise in surface water hydrology, hydraulics and drainage design. As a Staff Engineer at Riley, she is responsible for: civil design using AutoCAD Civil 3D, performing technical calculations, hydrologic modeling, 1D/2D hydraulic modeling, preparation of technical reports, project proposals, design drawings, and construction cost estimates. 

Ms. Long is Navajo from Sanders, AZ and Klagetoh, AZ, both on the Navajo Nation. The latter half of her upbringing was spent on the Tohono O’odham Nation. She is proud of both of her upbringings and is deeply passionate about advancing water infrastructure on Navajo, Tohono O’odham and native nations in the Southwest. She pursued civil engineering with the intent of eventually returning to her Navajo home and assuming a role as a Civil Engineer and water resources  expert. Ms. Long is continuing her education and pursing a master’s and doctorate degrees in Civil Engineering. Ms. Long is also working on obtaining her Professional Engineering licensure. 

P.E., P.H. Senior Engineer

Michael E. Zeller

Education: Bachelor of Science in Physics, University of Arizona, 1968 

Licensure: Professional Engineer Arizona (No. 12481)  

Professional Hydrologist – American Institute of Hydrology (No. 698) 

Years of Experience: 48  

Short Bio:   

Mr. Zeller was formally a Principal Water Resources Engineer with the surface water group of a nationally known engineering firm and served in that capacity for more than 30 years.  Mr. Zeller has been responsible for the administration of numerous water-resources projects in Tucson, Pima County, and the southern Arizona region.  His principal fields of expertise are arid and semi-arid hydrology, hydraulics, erosion and sedimentation, urban drainage and flood control, floodplain management, stormwater management (which includes water-quality aspects of stormwater runoff), flood hazard studies, and water resources development. 

In his 46 years of professional experience, Mr. Zeller has served as Project Principal and/or Project Manager for well over one-thousand projects relating to hydrologic, hydraulic, and erosion and sedimentation problems within areas in and around Tucson, Pima County, and southern Arizona. Principal projects have included a river mechanics study for the Santa Cruz River in Tucson, project management of the Flood Control/Floodplain Management element of the Rillito Corridor Study, one of four principal elements of a $1.7 million dollar master plan study for a 110-square mile area in northern Tucson, development of a detention/retention design manual for use by both Pima County and the City of Tucson; development of a Floodplain and Drainage Standards Manual for the City of Tucson; development of scour procedures for pipeline crossings of watercourses for the Pima County Regional Wastewater and Reclamation Department; preparation of several river-management plans for major watercourses in Pima County and the City of Tucson; development of basin-management plans for the City of Tucson and Pima County; and the preparation of a master surface water plan for the City of Sierra Vista.  Mr. Zeller also authored the Pima County Hydrology Manual (currently referred to as “PC-HYDRO”) while employed as the Floodplain Manager of the Pima County Regional Flood Control District. 

Business Manager

Jerod Jimmie

Senior Designer

Daryl Edmunds

E.I.T. Staff Engineer

Gustavo Guerrero

Staff Technician

Christian Jimmie

Business Manager

Jerod Jimmie

Education: Bachelor of Science in Civil Engineering, University of Arizona, 2022 

Years of Experience: 4 

Short Bio:   

Jerod currently serves as the business manager at Riley bringing with him several years of administrative and business management experience. He also assists on design aspects for various water infrastructure projects while pursuing his Bachelor of Science degree in civil engineering from the University of Arizona with an emphasis in water resources engineering. In addition to water resources engineering, Jerod has a strong passion in infrastructure planning, where he aspires to help address civil infrastructure deficiencies in our state and on tribal lands, particularly the Navajo Nation. Jerod has the passion for water resources engineering and is excited to continue his education and gain more experience in the field.       

Senior Designer

Daryl Edmunds

Education: AAS in Architecture, Otero Junior College, 1972 

Years of Experience: 28 

Short Bio:   

Mr. Edmunds has a wealth of professional design and drafting experience for civil engineering projects ranging from land development and public works to mining.  He has worked on many projects throughout the southwestern United States. He is proficient in designing with AutoCAD Civil 3D. His experience includes preparation of: plats; grading and drainage plans; levee/berm design; channel design; paving plans; sewer and storm-drain plans; water plans; survey right-of-way plans; legal descriptions; roadway plans; waste-rock grading plans; heap-leach-pad grading plans, and reclamation contouring design drawings.  

E.I.T. Staff Engineer

Gustavo Guerrero

Education: Bachelor of Science in Civil Engineering, University of Arizona, 2019 

Licensure: Engineer-in-Training Arizona (No. 013107) 

Years of Experience: 3 

Short Bio: 

Mr. Guerrero is a Staff Engineer with expertise in grading and drainage, water distribution systems, and hydrology & Hydraulics. His area of specialty is open-channel hydraulics, drainage, distribution design and drafting. As a staff engineer at Riley, he is responsible for: developing CAD standards, civil designing using AutoCAD Civil 3D; hydraulic modeling using HEC-HMS, HEC-RAS, HY8, EPANET; preparation of technical reports, design drawings, specifications, and cost estimates. 

Mr. Guerrero entered the civil engineering field with the goal of improving lives by designing and improving water infrastructure to manage and provide water for rural environments. Growing up in California where oceans and lakes are not unfamiliar and later moving into the Sonoran Desert as a young teen, Mr. Guerrero gained an appreciation for all sources of water. As a college student deciding on a major, he knew that civil engineering would best allow him to make a beneficial contribution to society.  

Staff Technician

Christian Jimmie

Education: Bachelor of Science in Civil Engineering, Arizona State University, 2021 

Years of Experience: 1 

Short Bio: 

Christian is completing his civil engineering degree at Arizona State University. He started with Riley as an intern and has been involved with design aspects on a variety of water infrastructure projects. Christian is passionate about helping improve the quality of living for people by improving civil infrastructure and promoting economic development. He believes that improvements to water infrastructure is essential for reducing poverty and sustaining economic growth. He eventually wants to help his people on the Navajo Nation by improving infrastructure after completing his master’s degree in civil engineering at the University of Arizona.