School & University Drainage

One parcel, nine drainage sites, one facilities director

Walk a K–12 campus or a university quadrangle with a drainage eye and the buildings stop being architecture. What is left is a set of unrelated surfaces sharing a parcel and a budget line. The roof is the largest catchment on most school properties: 70,000 sq ft of one-story elementary roof releases about 43,600 gallons per inch of rain through a dozen leaders, most of them landing on lawn that children cross twice a day. Then the bus loop, which is also the fire lane. The car-rider canopy, dripping a concentrated line exactly where kids step out of vehicles. The quad, where a passing period puts several hundred people across the same twelve square yards in four minutes. The courtyard between the wings, which on a 1960s plan is a bathtub whose only outlet runs beneath occupied space. Then the dining patio, the cafeteria dock, the dumpster pad, the field gates, the portables and the lots.

Three things separate a campus from any other commercial site we quote. The occupants: many of the people crossing your drains are small, distracted, in a crowd or on wheels, so standing water and a bad grate stop being maintenance items and become incident reports. The calendar: nobody closes a bus loop in October, so the work either lands in a fixed summer window or it does not happen. The memory: campus drainage is bought once on a bond cycle and then lived with for thirty years by a grounds crew of three covering forty acres, so whatever you spec has to be serviceable by people who were not in the design meeting.

The mistake that follows from all three, and the one we see most often: somebody standardizes one grate part number across the property because it simplifies the bid. Two summers later a wide-slot vehicular iron grate is sitting in the walk between the gym and the cafeteria, catching every caster and cane on campus, correctly specified — for the bus loop 400 ft away.

Where campus water actually goes between the bell and the bus loop

Campus water concentrates in the same places with tiresome reliability, and few of them are where the original site plan put the storm structures.

• Under roof leaders and canopy drip lines. A big roof gathers enormous area and releases it at a handful of points — not sheet flow, a hose — and at the car-rider door it lands in a loading zone. See downspout drainage for the discharge point itself.
• Along the bus loop gutter line. Loops are crowned to shed outward, so the whole loop reports to one or two curb lows sized decades ago for a smaller school.
• Interior courtyards — the highest-consequence catchment on older campuses. No grade, no daylight, one outlet under a building; when it backs up, water enters a corridor rather than a lawn.
• Ramp and stair bottoms at portables, the wettest square yards on many campuses and rarely on the drainage plan, because the portables arrived after it was drawn.
• The field-to-hardscape seam — gate, track edge, bleacher apron — where a well-drained field dumps onto a walk that is not.
• The dining patio and dumpster pad, where the water is the smaller half of the problem and the debris load is the larger one.

It all sorts into two moves. Intercept a moving sheet with a channel set across its path; collect a standing pool with a basin at the true low point. Most campus failures we get asked to fix are one doing the other's job — a basin cannot stop a 60 ft sheet coming off a plaza, and a channel three feet uphill of the real sag stays dry while the sag holds ice all winter.

Run the volume math zone by zone, before anyone picks a channel width

Two numbers carry almost all of this. Every 1,000 sq ft of impervious surface yields about 623 gallons per inch of rain — an acre of pavement is roughly 27,000 gallons per inch — and that sizes a holding problem. Then 1 in. per hour on one acre is about 1 cubic foot per second, roughly 449 gallons per minute, and that sizes a moving problem, which is what actually governs a trench drain. A 200,000 sq ft high school roof is about 124,600 gallons in a 1 in. storm; a three-acre bus loop and staff lot in a 2 in./hr cell is running near 6 cfs, about 2,700 gpm, inside twenty minutes.

The campus-specific instruction: run every zone as its own catchment through the runoff calculator, with the method in Sizing for Storms: Estimating Runoff, and add every upstream surface that drains into the zone rather than the zone alone — the courtyard is not 2,000 sq ft of brick, it is 2,000 sq ft of brick plus the two roof planes that empty into it. Treating a campus as one number is how a courtyard ends up with a drain sized for a patio.

The outlet is the bottleneck, and on a campus it is older than the staff

When a district tells us a drain is clogged, the drain is usually fine and the outlet was never big enough. A 4 in. line at 1% slope carries roughly 85 to 110 gpm running full; a 6 in. line at the same slope carries close to three times that, because capacity climbs with diameter to about the eight-thirds power. Widening the channel while leaving a 4 in. outlet buys a longer puddle, not a working system.

The campus twist is record drawings. On a 1968 building that courtyard outlet may be clay or cast iron, root-choked, running under a slab and shown on no drawing anyone can find, so put a camera down it before you size anything new. Then pitch carrier pipe at 1/8 in. to 1/4 in. per foot and treat debris as a design input: pine straw, mulch, cafeteria wrappers, infield sand and an astonishing volume of October leaves are guaranteed, so spec silt buckets and reachable cleanouts up front. And in freeze climates, the October puddle at the gym door is the January ice sheet at the gym door, where 600 people exit at once.

What drains an athletic field — and why it is not on our invoice

Campuses raise the subsurface question more than any vertical we serve, because a school property is roughly half pavement and half turf. So, plainly: a natural-grass playing surface is drained from below, and that system is not something we sell. A modern sand-based field is an engineered profile — a specified sand rootzone over a gravel or choker layer, over a grid of perforated pipe bedded in gravel trenches running to collector mains. Spacing follows the profile, on the order of 15 to 20 ft on center under a sand-capped athletic field and much tighter, near 5 ft, under a USGA-specification green on a university golf property. Sand-slit work on chronically wet practice fields is the same trade. All of it — perforated pipe in gravel, the french-drain family broadly — is designed by an agronomist or sports field engineer and installed by a turf contractor. That work is real and belongs in the bond package, but we do not sell perforated pipe, gravel-trench subsurface systems or rootzone materials, and nothing in our catalog should ever be called a french drain. The same goes under synthetic turf, where the drainage layer, base and perimeter collector all come from the turf installer.

What we sell is the surface layer around it, and that is the half campus packages routinely under-spec. Water the profile cannot infiltrate fast enough has to be collected somewhere, and so does everything the field sheds onto the hardscape at its edge: catch basins at the true low points of practice fields and grounds, a channel line at the field gate, track edge and bleacher apron, and the outlets, grates and fittings that carry both to discharge. The two are complements — a field with a flawless profile still floods at the gate if nobody put a basin there, and the gate is where the crowd walks. Stadium and recreation drainage covers the venue side of a university athletics property.

The parts of a campus we do not drain

An honest scope is worth more to a facilities director than a broad one, because the gaps are what blow up a summer schedule in week six.

• Subsurface field and turf systems, per the section above. Turf contractor, start to finish.
• Pumps, lift stations and sumps. Sunken courtyards, below-grade receiving wells and natatorium pits often need pumped discharge because there is no gravity outlet to be had. We sell no pumps, floats or controls, and we would rather say so than quote around it.
• Separators and interceptors. The grease interceptor at the kitchen, the oil-water separator at a bus garage or vo-tech shop, the grit interceptor at a wash slab: downstream, and by others. Our channel delivers flow to them; the vessel is plumbing and civil scope.
• Hygienic interior drainage. An interior food-production room under a sanitation program needs engineered sanitary stainless channel — crevice-free, sloped invert, built for daily wash-down and inspection. We do not sell that line, and nothing we sell should be represented as meeting FSMA, USDA, NSF, 3-A or EHEDG expectations. What we serve is the general-duty and exterior side of campus food service: dock apron, dumpster pad, wash slab, service drive — see dumpster pad drainage.
• Detention, retention and treatment — ponds, chambers, bioswales, water-quality units — are civil scope; we supply the collection layer feeding them. Roof drain bodies and interior leaders are plumbing scope, and we pick the water up where the leader daylights, which is usually where the erosion is.

Load class by campus zone, and the window each one has to be built in

Channel body and grate carry separate ratings, and the finished rating assumes full concrete encasement per the manufacturer's instructions. A single campus uses most of the EN 1433 range, which is exactly why one part number never covers it. Class A 15 (15 kN, about 3,400 lb) is landscape-only, and "no vehicle will ever cross it" is a promise a mower breaks by August. Class B 125 (125 kN, about 28,000 lb) is the honest floor anywhere people walk, because sweepers and stocking carts run those routes whether or not anyone planned for it. Class C 250 (250 kN, about 56,000 lb) covers drive aisles, car-rider lines and service routes. Class D 400 (400 kN, about 90,000 lb) is the number for buses, refuse trucks, semis and fire apparatus. Class E 600 and F 900 (600 and 900 kN, about 135,000 and 202,000 lb) show up rarely, at a university utility yard or central plant. US drawings often speak AASHTO instead, where H-20 is a 16,000 lb wheel load and HS-25 is 20,000 lb — a different test regime rather than a formal equivalence, so treat the crossover as a shop heuristic and let the engineer of record stamp the spec. Detail is in the Load Class Recommendation Guide.

Every walk between two buildings is an accessible route

This is the rating skipped most often and the one with the sharpest consequences here. On an accessible route, grate openings are limited to 1/2 in. in the direction of travel, with elongated openings perpendicular to the dominant path — which rules out most wide-slot iron and rules in heel-proof mesh, perforated and composite honeycomb tops. Our practical test is narrower than a heel: a wheelchair caster, a walker foot and a rolling backpack wheel all find the same opening, at the door of every building, several hundred times a day. Read Understanding the ADA before anyone signs off on a walkway grate, and ADA and pedestrian drainage for surface detail. When a district asks us to value-engineer, this is the line we push back on.

Buying it: the summer window, the submittal package and the PO

Product selection is the easy half of a campus job. The hard half is landing the work inside a window nobody controls, bought through a process with its own calendar. Schools and universities across the country order from us, so this side is familiar ground.

Work backward from the first bell. A typical district has ten to eleven weeks between bells; a balanced or year-round calendar may give three or four, which changes the answer from "trench the loop" to "phase the loop over two summers." Saw cutting and setting channel to grade is fast. Concrete is not, and the load class rates the installed assembly rather than the part on the pallet, so the encasement and its cure belong on the schedule as their own line item. Start quoting in March or April: the stocked NDS, BG Filcoten and Stegmeier lines ship as ordered, but the quote-only ACO lines are configured per project, so a June inquiry for a June install is the one avoidable mistake in this process.

Split the package by zone, not by lump sum. Quote the bus loop, the quad, the courtyard and the dock as separate line groups. When the number comes back high — and it will — a zoned quote lets you defer the staff lot on purpose instead of quietly downgrading the grate at the accessible entry, which is the substitution we see attempted every summer.

Send what you have, in whatever form it exists. A full drawing set is ideal; a zone list with run lengths, load class, invert depths and outlet locations is entirely workable. We come back within one business day with quantities, part numbers, manufacturer cut sheets and the published load class documentation a submittal package needs. If the spec is written around a named system, tell us whether it is sole-source or "or equal," because that decides whether we quote the named line or the closest stocked equivalent — and if it names ACO or Josam, it is a quote from the start. Two logistics details that cost districts real money in July: confirm who is on site with a forklift to receive a pallet, and confirm the delivery address is the maintenance yard, not a school office locked for the season.

Zone by zone: what we spec on a campus, and why

Our picks, typed by the zone they serve rather than by brand, each assuming the catchment numbers above came first. Choose load class and opening geometry, then take the top from the grate catalog rather than an application page — channel grates by system, ductile iron and steel for vehicular and heel-proof duty, cast iron where a campus standard names it, atrium grates in planted areas, square and round grates on basins, decorative grates where a donor plaza demands one.

One line item worth protecting before value engineering starts: the locking and service hardware on every run above — Filcoten silt buckets and anti-vandalism locks, ACO QuickLok bars and tamper-resistant bolts, the Dura-Slope ProFit grate lock and trash bucket — plus any valve boxes you can drop into the same grounds trenches while they are already open. Retrofitting that hardware after the first grate goes missing costs more than specifying it would have, and the missing grate is the one that generates the incident report.

What to have in hand before the pre-bid walk