A good parking lot or driveway is a worthwhile asset, but water can ruin that investment faster than heavy traffic ever could. Drainage is not merely an adjunct to the design; it is the hidden system that assures year after year performance of the asphalt or concrete. The control of water on the surface and in the base prevents early failures, loss of liability and lessens the life expenses. Here is the difference between a surface which lasts decades and one which fails in a few seasons of rain.
Why Drainage Matters in Paving
Water is the enemy of pavement. It infiltrates cracks or lies in lower spots, weakening sub-base, breaking down the asphalt binders and hastening the joints in the concrete. So, it is only a matter of time until you have deeper ruts, wider cracks and, worse yet, costly repairs that could have been prevented with better grading and outlet ways. Check this site to know how water infiltrates cracks.
Good drainage methods consider your site as a whole water system – surface flow, inlets, pipe, landscaped areas all working together. With well aligned parts, you shed water quickly, saving foundations and landscaping and improving safety by eliminating areas of ponding causing slips and hydroplaning. A fraction of what you will spend on emergency repairs and asphalt paving maintenance may be the amount that is budgeted for drainage.
Common Water Damage Signs
You don’t need a forwarding crew to see early indications of water damage. A weekly walk through after rain can reveal small troubles before they become major repairs. Watch the entrances, high-traffic lanes, and edges of paving and landscaping or building where these meet.
- Continuing pools that do not go away 24-48 hours after a storm have an improper slope or settlement.
- Ruts or alligator cracking in wheel paths indicate water has softened the base.
- Ravel or pulverized aggregate and use of sand-like substances mean the binder was lost by being wet and dry.
- Pumping obtained at joints (mud or fines pulled up by traffic) shows that there is water back of the slab or mat.
- Moss or algae seen in shaded areas means chronic moisture pneumonia dangers.
Take pictures of these and note dates, so that your maintenance person will be able to trace the causes of trouble and fix the causes, rather than the symptoms.
Slope Design for Driveways
The performance of the driveway starts with the cross slope which is the gentle pitch to cause surface water to go where it should. This should be from 1-2% (about 1/8- 1/4 inch in one foot) away from buildings into approved outlets or swales. Long drives have best yields if controlled under a common center crown which divides flow to both sides; or short distances may have flow to one side if it protects the adjacent structures.
The slope to or from the buildings must coordinate with roof downspouts. Never let water converges onto a driveway from downspouts. The latter should be taken from the buildings to a storm inlet regularly via splash blocks or pipe. Make sure that all run-off goes to a system of collecting water. Block walls or concrete curbs and gutters help confine flow and protect the edges against erosion and wear by vehicles.
Where roadways meet public streets or garage entrances, smooth transitions and properly set inlets will prevent ponding that can freeze (in cold climates) or stain or weaken joints.
Drainage Solutions for Parking Lots
Parking lots have large flat areas where even the slightest grading error will create large ponds. Good design combines surface grading with structures that capture and quickly convey water. Plan for maximum storms, but also for frequent rains — that is where the greatest misery lies in the long run.
- Cross slope and gentle crowns: 1.5% to 2% across driving aisles and parking bays to keep pavement drained without being a impediment to walking or pushing a cart.
- Trench drains at entrances: for loading docks, garage approaches, or ADA maximums that must be kept nearly flat.
- Inlets and catch basins: spacing them so that each serves a moderate drainage area and verify that the rims are high enough so that water enters them and does not go around them.
- Sub-surface underdrains: perforated pipe in wrapped stone where the soils drain poorly, and/or the water table is high.
- Vegetated swales or bioretention: to slow, filter and infiltrate runoff as well as for obtaining local permits and sustainability objectives.
When the site is complicated, bring in an asphalt contractor Anaheim Hills for the grades, inlets and pipe capacity and to verify that the thickness of pavement is sufficient where the water concentrates.
The incorporation of these features early in the game keep one in compliance with ADA grade limits and still furnish water control along the pedestrian routes.
Preventing Base Erosion
Surface water is only part of the story; the really bad stuff happens below. Protect the sub-base by not allowing infiltration to take place and by not allowing the fines to escape from the base. That is done best by proper subgrade preparation — compacted subgrades at the right moisture density, sound aggregate base, layers of separation if required.
In those areas where there are springs, or perched water tables, underdrains should be included to lower the moisture around the pavement layers. Where soils are soft or unevenly mixed, use of geotextile separations or base stabilization with cement or asphalt treated base can keep the fines from migrating and retain strength.
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Routine surface maintenance keeps water out. Proper timing of sealcoating and sealing cracks prevents infiltration, slows oxidization, and stops the lesser type of cracks from becoming inlets for storm water ingress. Keep joints caulked, keep inlets clean, keep edges away from lawn irrigation which saturates the base from time to time.
Treat the phase of drainage as an ongoing discipline, and not a single event. A simple pavement management plan will solve the alleviation problem — annual inspections, prioritized maintenance, and capital expenditures, will add life to the service life, keep costs stable and keep your property looking professional.
