[Mintwood-place] Kalorama Playground Surface Meant for Cars Not Kids
eddie_becker at yahoo.com
Mon Jun 22 11:05:18 EDT 2009
Dear Director Hartsock,
This is a request to the Department of Parks and Recreation to seek independent confirmation, from a qualified children’s playground designer, that the installation of Geoblock Porous Pavement System in KaloramaPark, is appropriate for use as a children’s play surface
The major “improvement” in the Kalorama Park Erosion Control Project is the resurfacing of the hard surfaced playing field adjacent to the basketball court with a safe, soft and lush grass covered multi-use playing field. The playing field could be used as a toddler soccer practice, fir catch, net games like volleyball, Frisbee, adult exercise and yoga, etc.
But my research indicates that the primary use for the Geoblock Porous Pavement System is to as the surface designed primarily for parking lots. And unless one of the contemplated uses for is to turn the field at Kalorama into a parking lot, then Geoblock is inappropriate, high maintenance, not very good at growing grass, nor drought resistant, unattractive, and dangerous mainly for children because of its hard surfaces and tripping hazard with its open squares.
The work around suggested by the designer at the Fund for Kalorama Park and the DPR project manager when I raised this question at the public meeting was to place an additional 2”or more layers of sod and grass a top of the plastic Geoblock makes even less sense. First off Geoblock is intended to withstand high compaction by cars; the weight is supported by the rigid vertical Geoblock walls, and with a clump of grass growing in between the root ball growing in the protected cup. Under heavy use the top layer of sod and grass atop the Geoblock will be crushed against the rigid tops of the Geoblock walls.
But overall the upper layer of grass will far less chance of survival. A layer of sod and grass placed over the Geoblock restricts robust rooting in a variety of ways.
Adhesion to the subsurface will be interrupted by the plastic Geoblock layer, which is 88% open at the top but only 56% on the bottom. This will restrict deep rooting of the grass, and the ability of the upper layer to hold to the sub-layer.
Limiting the ability of deep root growth results compromises drought resistance as fewer roots can penetrate to deeper water rich soil. The Geoblock layer will make grass failure more likely after a draught.
Furthermore, the top layer of grass is not well rooted. The design of the Geoblock’s 2.25”square walled boxes restrict root growth to a vertical direction, the side walls block lateral (horizontal) rooting, combined with the smooth plastic surface of walls, much of the root is held in the Geoblock cup. The grass is more easily pulled out then if the top layer were well rooted to a proper base – specifically designed to support, drain, nourish and root the upper layer grass. Good introduction to building robust playing fields
To see pictures you may have to open word attachment.
Geoblock is a good product and should be used to replace some of the impermeable sidewalks, and make the park more wheelchairs assessable, where appropriate, thereby increasing the overall water filtering capacity of the Park.
“Geoblock® Porous Pavement System
The Geoblock® System is a series of permeable, high-strength, interlocking units designed to offer turf protection and load support in traffic areas. The units create a flexible structural bridge system within the topsoil layer to support and distribute concentrated loads.
Though Geoblock 2 can grow grass far better then an impermeable hard top parking surface, it is not suitable nor was it intended or is it recommended by the manufacturer as a playing field.
1) It can grow grass but not very well.
2) It will not look very attractive – most of the time is will look like a bad hair plugs
3) It is not suitable as a playing field
4) Will require more maintenance
5) It is a hard surface with openings that catch shoe tips therefore unsuitable as a children’s playground surface. .
Grass can’t grow as well
1) The 1.2”high Geoblock 2 cell walls limit grass reproduction by preventing the spread of root runners (Rhizomes), if the grass in a cell dies out, it will have to be reseeded because root runners are restricted by the Geoblock cell walls.
The best playing field grass, like Kentucky Bluegrass, provides a well rooted carpet tightly connected with Rhizomes
2) Only 56% of the bottom of the Geoblock is open. So deep rooting is limited. Deep grass anchoring is limited so fewer roots can get to the deeper water. The grass will be less successful in surviving draught and other types of stress (dog urine).
See Table 1 page 3 (though the bottom number says 1 of 7) for cell specs
1) 88% of the cell is open while 22% is vertically rigid plastic strong enough to support a car. Not something you’d want to hit your head on, even with grass growing though the Geoblock opening. .
2) Each block is a 2.25”X 2.25”and 3”on the diagonal, a tripping hazard for most shoes especially children and toddlers.
3) The surface is unsuitable for sliding, meaning that if someone is running fast then trips and falls, instead of sliding (and sliding is good at dissipating the forward energy) they may be stopped quite suddenly when the palm of the hand or the point of a knee is jammed against the Geoblock wall surface. So instead of a nasty bruise expect more broken bones.
GEOBLOCK 2 Specification http://www.reynoldspkg.com/alcoa-geo/catalog/pdfs/Geoblock2_Spec_Summary.pdf
A central goal of the current Erosion Control and Site Improvement at KaloramaParkis the replacement of the impervious black top field adjacent to the basketball court.
Good introduction to Athletic Fields—Specification outline, construction, and maintenance http://turfgrassmanagement.psu.edu/athletic_fields.cfm
Eddie Becker eddie_becker AT yahoo.com
E-mail me with any questions or if you need this document to be sent to you as an attachment so you can get all the photos
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