CASE STUDY 39 — Magnolia Trails 360-Lot Residential Neighborhood | Full Civil Engineering Design

PROJECT OVERVIEW

JRH Engineering delivered complete civil engineering design for the Magnolia Trails neighborhood — a 360-lot residential development in Alvin, Texas, located in the floodplain with water and sanitary infrastructure 5,000 feet away. JRH purchased regional detention credits, sourced fill from on-site mitigation pond excavation, and brought water and sanitary in through an adjacent neighborhood — eliminating what would have been a 5,000-foot greenfield utility extension and compressing the development timeline significantly.

AT A GLANCE

Site Civil Design

● Full civil design for 360-lot subdivision including road layout, lot grading, utility design, and floodplain mitigation

● On-site mitigation pond excavation used as the fill source — dirt excavated for pond construction raised lot grades out of the floodplain, eliminating the cost of importing fill

● Street tie-in connected to TxDOT infrastructure

● Four-lane major collector roadway designed to serve the full development

Utility Infrastructure

● Water and sanitary brought through an existing adjacent neighborhood — avoiding the 5,000-foot greenfield extension entirely

● City of Alvin water main extended 13,100 linear feet to serve the development

● Sanitary sewer extended 4,530 linear feet within the City of Alvin service area

● MUD district coordination for utility service to 360 lots across multiple construction phases

Stormwater & Drainage

● Regional detention credits purchased from CNR3 — on-site detention pond construction eliminated

● On-site mitigation pond excavation provided fill material to raise lot grades above the Base Flood Elevation — one excavation serving two purposes simultaneously

● Floodplain LOMR-F process managed to remove residential lots from the FEMA flood zone

Permitting & Agency Coordination

● City of Alvin, TxDOT, MUD, and CNR3 approvals pursued simultaneously across four sub-project packages

● FEMA LOMR-F coordinated concurrently with subdivision civil permitting

● Mass grading, utility extension, paving, and Section 1 infrastructure delivered as separate coordinated contracts

THE CHALLENGE

A 360-lot subdivision in the floodplain with utilities 5,000 feet away is a complex, multi-front engineering challenge. Floodplain fill requirements, detention obligations, utility extension logistics, and a four-agency approval process all have to move in parallel — not sequentially — or the development timeline stretches beyond what the economics can support.

JRH's Approach

Every major decision was made to serve two purposes. The on-site mitigation pond excavation produced fill that raised lot grades — one operation solving both the pond construction and the fill sourcing problem. Regional detention credits eliminated the detention design and construction track. Utility routing through the adjacent neighborhood avoided a 5,000-foot greenfield extension. LOMR-F was processed concurrently with subdivision permitting. Four agencies were managed simultaneously across four coordinated construction packages.

The Result

A 360-lot residential subdivision delivered from floodplain raw land to construction-ready lots — with utilities sourced through an adjacent neighborhood, fill sourced from on-site excavation, and four agencies managed concurrently.

RESULTS

● 5,000-foot utility extension eliminated — water and sanitary brought through adjacent neighborhood instead of greenfield extension

● Fill cost reduced — on-site mitigation pond excavation provided fill to raise lot grades above BFE

● Regional detention purchase eliminated on-site pond design and construction across a 360-lot subdivision

● $11,327,391.82 combined construction value across four coordinated sub-project packages