August 2002Volume 9, Number 3

2 Interlocking Concrete Pavement Magazine August 2002

The Port Authority of New Yorkand New Jersey has constructedthe first port pavement in NorthAmerica to combine solid and per-

meable interlocking concrete pavementsfor container handling equipment.Located on the northwest corner ofStaten Island, New York, Howland HookMarine Terminal, expanded an existingcontainer terminal by 13 acres (5.3 ha).The Port Authority and several otherAmerican ports have used millions ofsquare feet (meters) interlocking concretepavements for container yards. While it isa standard pavement for overseas ports, itis becoming so for those in NorthAmerica. The unique aspect at HowlandHook is a test area of 0.25 acres (0.1 ha)of permeable interlocking concrete pave-ment to verify structural, hydraulic and

water quality improvement properties.The only other documented permeableport pavement in the western hemisphereis 1,320,000 (132,000 m2) at SantosContainer Port, Brazil.

Port Operations at Howland HookContainer movement operations includeTaylor top pick equipment, huge lifttrucks that use a telescoping beam andclamp on one end to grasp the top of asteel shipping container. The trucks lift40 ft (12 m) long containers and stacksthem four high on the pavement. Eachloaded container can weigh as much as50,000 lbs. (22,700 kg), so a four highstack concentrates at least that amountweight on the pavement at each cornerof the bottom container. When grabbed

by top pick, a container and the vehicletogether can result in a 215 kip (97,500Kg) load on the dual wheel axle. Theload on the front tires also increases sub-stantially during braking and turning.Besides movement and stacking of con-tainers with the heavy top picks, there are(highway and off-road) truck chassis thatreceive and transport containers to andfrom Howland Hook.

Engineered Pavement DesignThe interlocking concrete pavement isdesigned to provide service for at least200,000 passes of the top pick vehiclesover an estimated 20 years of service. Theresulting cross section taking these loadsand winter environment consists of 3 1/8

in. (80 mm) thick concrete pavers over aninch (25 mm) of bedding sand. The base

The Port Authority of New York and New Jersey placed some 13 acres (5.3) hectares of interlocking concrete pavements anda 0.25 acre (0.1 ha) test section of permeable interlocking concrete pavements for container yards.

Interlocking Concrete Pavement Magazine August 2002 3

consisted of an 8 in. (200 mm) of NewJersey Interagency EngineeringCommittee (NJIEC) mix 1-2A AsphaltConcrete Bottom Course constructed inaccordance with a Port Authority specifi-cation on an 18 in. (450 mm) thick recy-cled concrete aggregate base. This basewas compacted to at least 95% modifiedProctor density to achieve a CBR(California Bearing Ratio) of at least 60%.The base was placed over a sandy sub-grade reinforced with geogrids and geot-extile. This 24 in. (600 mm) layer isdesigned to spread loads over thedecades-old fill containing gypsum. Thegeogrids are designed to span any voidsthat result when the gypsum is dissolvedby water.

Structural design of the pavement wasdeveloped using the British Port

Federation (now the British PortsAssociation) design method. In addition,engineers used two other computerizedlayered elastic models to characterize theloads and resulting stresses and strains inthe pavement materials. The designerswere ERES Consultants of Champaign,Illinois and Nigel Nixon and Partners ofPlano, Texas. They examined variouslayer thicknesses and strengths using a 1in. (25 mm) rutting failure criteria. Theyfound the combination of materialstrengths to provide at least 20 years ofpavement service while maintainingdeformations below this criterion.

Mechanical Installation Members of the Interlocking ConcretePavement Institute (ICPI) supplied andinstalled the pavers and bedding course in

both areas. Figure 5 shows the screedingof the bedding sand and Figure 6 showsone of two machines used to place thepavers. The pavers were compacted intothe bedding sand, joints filled with sandand compacted again. The daily averageinstallation using two machines machinewas 15,000 sf (1,500 m2). This includesscreeding, installation of pavers and jointsand and compaction.

An Innovative Experiment withPermeable Interlocking ConcretePavement The Engineering Department of the PortAuthority took an innovative step bycombining the features of pavement andinfiltration trench in a test section of per-

Figure 1. A top pick provides movementof the containers at Howland Hookwhile exerting wheel loads in excess of50,000 lbs. (22,700 kg).

Figure 2. Unlike asphalt, concrete pavers can withstandloaded stacked containers that can exert over 50,000lbs. (22,700 kg) at the corners without indentations thatcould interfere with container movement operations.

Continued on p. 8

4 Interlocking Concrete Pavement Magazine August 2002

meable interlocking concrete pavement.As part of the larger interlocking pave-ment construction, a 0.25-acre (0.1 ha)section of permeable pavement combinesthe structural load-bearing capacity with asurface that allows runoff to infiltrate.The designers enabled an increase in use-able port pavement area by selecting asurface which functions as a pavement forcontainer storage and as a retentionpond.

The idea emerged from Principal CivilEngineer Walt Sieglen, Jr., P.E. with thePort Authority’s “Green Ports” TaskGroup. According to Mr. Sieglen, “Theexperiment supports the Port Authority’s

objective to reduce waterrunoff and non-point sourcewater pollution. If successful,we could see greater use ofpermeable interlocking con-crete pavements for portpaving in order to meet envi-ronmental conditions for newport facilities.” Besides theheavy loads, port containeroperations are noted for theirheavy loading of pollutants inrunoff. Oils, rubber, steel, andbrake compounds from thecontainer lift trucks, plus occa-sional minor leaks from con-tainers are washed into storm

sewers and to the adjacent bay. Like allindustrial facilities, port areas are subjectto federal and state mandates to reducestormwater runoff and non-point sourcepollution.

Pavement Surface as Retention AreaPermeable interlocking concrete pave-ments were of special interest to Mr.Sieglen because they capture the “firstflush” or the first 30 to 60 minutes ofrainfall, typically 0.5 to 1 inch (13 to 25mm). The runoff from the initial portionof the rainstorm has the highest concen-tration of pollutants. This portion is sub-

Figure 3. Cut away construction view of the base:soil subgrade covered with geogrid, recycled con-crete aggregate base, and asphalt ready (left) forbedding sand and concrete pavers.

ject to regulation by state environmentallaws through the use of best managementpractices (BMPs) for control of runoffquantities and water quality. For NewJersey, BMP designs should capture andtreat the first 1.25 inches of rainfall overtwo hours and for New York it is 0.5inches. (Stormwater drainage design forNew Jersey and New York is consideredby the Port Authority as projects may bebuilt in both states.) The permeability ofthe surface will well exceed these rainfallintensities even with some sediment inopenings from years of use.

Permeable interlocking concrete pave-ment was selected because of its ability toinfiltrate and reduce the concentration ofpollutants by filtering and oxidizing. Sincethe soil subgrade (an old landfill contain-ing gypsum) was moisture susceptible, therunoff flowing into the permeable basewould be treated there, pass into perforat-ed drain pipes, and then released into theAuthur Kill channel. While total runofffrom storms would not be substantiallyreduced from infiltration back into thesoil, the treatment of runoff in the basewas viewed as an advantage rather thancollecting it in storm sewers and deten-tion ponds. Ice and heaving of the pave-ment was not viewed as a problem due tothe low risk of the permeable basebecoming saturated.

Aggregate Base CourseJointing Sand

Asphalt Bottom CourseConcrete PaversBedding Sand

Openings With Permeable FillPermeable Concrete Pavers

Permeable Bedding Mix5 in. (125 mm) Permeable Asphalt Base

3 in. (75 mm) Impermeable Asphalt Layer

1 in. (25 mm)

8 in. (200 mm)

18 in. (450 mm)

6 in. (150 mm)

Sand SubgradeGeogrid & Geotextile Subgrade Reinforcement

IMPERMEABLE SECTION PERMEABLE TYPICAL TEST SECTION Edge Restraint

Typical Subdrain

3 1/8 in. (80 mm)

5 in. (125 mm)3 in. (75 mm)

Figure 4. The pavements have a common base course of recycled concrete aggre-gate, one surface is impermeable and the other is permeable.

Figure 5. Powered screeding of the bed-ding sand accelerates its installation.

Permeable Pavements Now in First Port Application Continued from p. 7

Interlocking Concrete Pavement Magazine August 2002 5

The typical construction for impervi-ous port pavement includes a network ofsurface drain inlets and undergroundpipes often directed to retention ponds.The inlets, pipes, and ponds hold thewater for a time, allowing the sediment tosettle, and slowly releasing the remainingwater. They take on sediment over timeand have to be cleaned periodically byremoving the sediment and disposing itin a landfill.

A full-scale installation of permeableinterlocking concrete pavement would

provide long-term spreading of sediment-filled runoff over a wider area. The sedi-ment is spread by the runoff and collect-ed in the first few inches of open-gradedbase in and under the pavers, and can beperiodically removed from the surfacewith vacuum cleaning. However, theactual cycle for cleaning will be influencedby a realistic assessment of doing thiswork in busy container terminal.

The Howland Hook test area specifiedan ASTM No. 9 open-graded aggregatein the openings of the pavers and directly

under them as a bedding material. The 1-inch (25 mm) thick bedding was placeddirectly on the 5 inch (125 mm) thicklayer of permeable Plant Mix Macadam(NJIEC I-1). This layer directs water tosubdrains at the perimeter of the area. Asmall well is located at the low end of thedrains for monitoring water levels andsampling. The permeable layer of asphaltis placed over 3 inches (75 mm) ofimpermeable I-2A asphalt and 18 inches(450 mm) of recycled concrete aggregatebase. The location of the test area exposesit to both stacked containers and top picktraffic.

Lower Maintenance CostsExpected to Offset Higher Initial CostsPerformance at Howland Hook will beevaluated by the Port Authority. Theseincludes costs for regular vacuuming ofthe surface to remove dried sediment andrepairs to damaged pavers. Costs willcompared to those associated with a con-ventional pavement such as cleaning dropinlets, pipes, and detention ponds. Theadjacent impervious concrete pavers witha conventional drainage system will pro-vide a source of maintenance cost datafrom an impervious surface. It is antici-pated that the savings by not building

Figure 6. Mechanical equipment placesthe concrete pavers that are manufac-tured in the pavement laying pattern.

Figure 7. The two pavements are sepa-rated by a significant concrete edgerestraint.

Permeable CBP Test

Area(0.25 Ac.)

SD

SD SD

SD

SD

SD

SD

SD

Manhole for Monitoring & Sampling at Accessible Location

Connection of Subdrains to Drainage System

Cleanout (Typ.) at Accessible Location

ImpermeableCBP

Pavement

Concrete Edge Restraint All Around • Creates bathtub to prevent infiltration water from entering subgrade. • Isolates permeable pavers from other pavements. • Delineates test location.

Subdrain All Around • Collects infiltration • Slope follows grades

D

85 ft

(26

m)

65 ft

( 20

m)

40 ft

(12

m)

5 ft (1.5 m)

100 ft (30 m)

Figure 8. Plan of permeable interlocking concrete pavementtest area.

Figure 9. The permeable pavement test area is surrounded bysolid interlocking concrete pavement. The pavers against thecurb haven’t yet been cut to fit against it.

6 Interlocking Concrete Pavement Magazine August 2002

and maintaining a conventional drainagesystem and detention pond for waterquality purposes will be greater than theadditional periodic expense for vacuumingthe surface and replacement of the aggre-gate in various places.

The test area could also be used toobtain water quality data to support per-mit applications for future projects to

develop new, environmen-tally friendly port facilities.A successful test woulddemonstrate that perme-able pavers area a cost-effective alternative toconventional impermeablepavements and stormwatertreatment systems.

A New Application? When placed on an open-graded base, and on soilsubgrade for infiltration,permeable interlockingconcrete pavements aretypically for low trafficareas. ICPI has a designmanual for such applica-

tions mentioned elsewhere in this issue.The unique aspect of the Howland Hookproject is its test of permeable pavementfor port and other heavy-duty loads.Economics dictated by limited land areaand stormwater runoff laws will increas-ingly drive the decision to use permeableinterlocking concrete pavements in a vari-ety of applications.

Figure 10. Essential to all permeable pavements, theHowland project included an observation well to monitorwater levels, drainage rates, and sample water quality.