San Angelo received 11.75 inches of rain in a single day in September 1936, and the South Concho River peaked at 111,000 cubic feet per second, according to the National Weather Service. No storm drain is sized for an event like that, but the record is the reason Texas engineers think carefully about where water goes when the system is overwhelmed. Storm drain installation is the work of building the inlets, pipes, junctions and outfalls that carry ordinary and design-level storms off a site and away from a building, and it is the scope that makes a parking lot usable after a thunderstorm.
We install storm drainage as part of a site package that also includes the paving, curb and grading that feed it. That ordering matters. A storm line laid in the wrong location relative to the final grade can leave an inlet that sits above the flow line, a trap that cannot be reached, or a pipe that conflicts with a footing. Because we build the lines and the pavement above them, we plan inlet tops to the curb or finish grade from the first survey stake.
Storm drain work runs from small private lines draining one lot to large reinforced concrete trunks in public right of way. We handle both, from corrugated or HDPE pipe in a retail pad to RCP boxes and large-diameter pipe in a municipal outfall.
What decides a storm system before it is drawn
The site's low point and the downstream connection decide most of the layout. If a site drains to a public storm sewer, the engineer has to show capacity in the receiving system, and the cost of any off-site upgrade lands on the project. If the site drains to a creek or channel, outfall design, scour protection and the permit for work near a waterway govern the schedule. We ask early where the water leaves, because a discharge point that moves means a new alignment and often a new plan review.
Soil is the second variable. Clay slows infiltration and sends more water to the pipes, while sandy ground absorbs more but can collapse in the trench. Where groundwater is shallow, buoyancy of empty pipe and structures has to be checked, and the contractor must be ready to dewater during construction. The dewatering plan belongs in the bid, not in a change order.
Drainage in the places where it matters most
The Texas Water Development Board describes the first state flood plan, produced under a 2019 law and assembled from 15 regional plans built by more than 350 planning group members across more than 550 public meetings; the board approved the amended regional plans in March 2024. The practical effect for builders is that local governments now have documented flood priorities, and drainage projects that line up with those plans find funding and approvals more easily.
Nowhere is the issue as visible as around Houston, which is described as a flat, marshy area with an extensive built drainage system and with low-permeability clay-silt prairie soils; flooding is described as a recurring problem there. With almost no natural fall, storm lines must be laid to tight grades, and detention often has to supplement conveyance. In places like San Angelo, the opposite problem arises: short, intense rain across hard ground, with channels that move water fast and carry debris.
Inlets, pipe, junctions and outfalls
A storm system starts at the inlet. Curb inlets, grate inlets and area drains collect surface flow, and each one is set to the exact top elevation that the paving plan requires. From the inlets, pipe runs to junction boxes and manholes, where lines change direction or size, and finally to an outfall or connection. We install reinforced concrete pipe, HDPE, corrugated metal and precast box sections, selected to the load, the cover and the owner's standard.
Each connection point has a detail that cannot be skipped. Boots or grouted connections at structures prevent soil from entering the line, and rip-rap or concrete aprons at outfalls keep a storm from undermining the pipe end. We form and pour cast-in-place inlets and headwalls where the precast catalog does not fit the plan. That work ties into our culverts and headwalls and the detention and retention scopes.
Where we install storm drainage
Large roofs and large paved yards produce a lot of water, which is why warehouse and distribution sites usually carry the heaviest storm package per acre. Roof drains tie into underground trunks that pass beneath truck courts and trailer parking, so pipe cover and the pavement section need to be designed together. We commonly coordinate these lines with the truck courts and dock aprons that sit above them.
Retail centers, schools, medical campuses and multifamily projects all need storm systems tied to their parking and landscaping. Municipal projects add a public review layer, and municipal and public works owners usually require the pipe to be televised before acceptance. We schedule that inspection with the pavement so that a failed joint does not force a second cut.
Permits, plans and construction stormwater
Storm drainage is reviewed by the municipality or county, and the plan usually goes through a drainage study that shows pre- and post-development flow. Work in or near a floodplain or waterway can add a floodplain development permit or approvals beyond the city. Construction itself requires erosion and sediment controls under the construction stormwater program, and our trade partners install and maintain those controls as the site is disturbed.
Inspection comes in stages. Bedding and pipe are examined before backfill, structures are checked for elevation and grout, and final inspection typically includes pipe cleanliness and, for public lines, a camera review. We keep the compaction results and as-built elevations together so the engineer of record can certify the system without a hunt for documents.
Review your drainage plan with us
Share the grading plan, the drainage study and the discharge point, and we will tell you what we see in the sequence and the risk before the pipe is priced.
Common Questions
How deep does a typical storm drain run?
Depth depends on the outfall and the site grades. Many private lines sit three to six feet deep at the outlet end and shallower near inlets. Where a connection is deep, the lines at the upstream end need adequate cover for wheel loads, and the pipe class is chosen accordingly.
Can you build a storm system in clay soil that stays wet?
Yes, but the construction sequence changes. We keep trenches short, place granular bedding to carry water to a sump, and compact backfill at the right moisture. Where wet soils persist, a stabilization layer under the pipe can prevent settling of the line.
What happens if the receiving storm sewer lacks capacity?
The engineer usually has to add detention on the site or upgrade the downstream pipe, and the owner pays for it. We recommend confirming capacity in the plan review stage, because an off-site upgrade can add months to the schedule.
Do you handle trench drains and area drains inside the building envelope?
We install the concrete trench drains and area drains outside and at the slab edge, and we coordinate with the plumbing contractor for any lines inside the building. The elevations have to line up between the two scopes, so we meet before the slab is formed.
How do you protect the system during construction?
Inlets receive filter protection from the day they are set, and pipe ends are plugged until the pavement is ready. Silt that enters a new line ends up in the pond or the creek, and the cleanout cost lands on the contractor who let it in.