STRUCTURAL MEASURES: CONSTRUCTION, OPERATION, AND MAINTENANCE - Low Impact Development and Sustainable Stormwater Management - page 175

Table 8-1 Pavement Cost (per ft 2 ), San Diego County, California, 2005

Subbase Annual

Demolition and Pavement Total Maintenance

Cost Excavation Installation Cost Cost

Porous AC, 18 in. backfill $3.75 $1.88 $1.87 $6.50 $0.04

Standard AC, 6 in. backfill $2.13 $1.04 $1.32 $4.49 $0.06

Porous concrete, 15 in.
backfill

$3.19 $1.88 $6.34 $11.41 $0.02

Standard concrete, no
backfill

$1.51 — $3.42 $4.93 $0.01

TBD a

Porous pavers, 18 in.
backfill

$2.75 $1.88 $9.63 $14.26

a TBD, to be determined.

pervious pavement areas with subsurface infiltration beds often eliminate the
need (and associated costs, space, etc.) for large detention basins. When all of
these factors are considered, pervious pavement with infiltration has proven itself
less expensive than impervious pavement with associated traditional stormwater
management. Pavement and stormwater management of recent installations has
averaged between $2,000 and $2,500 per parking space.
Pervious asphalt, with additives, is generally 10 to 20% higher in cost than
standard asphalt on a unit area basis. Unit costs for pervious asphalt (without
an infiltration bed) range from about $1.75 to $3.50 per square foot. Pervious
concrete as a material is generally more expensive than asphalt and requires
more labor and experience for installation, due to specific material constraints.
Unit costs for a 6-in.-thick pervious concrete (without an infiltration bed) section
are typically between $6 and $7 per square foot. Pervious paver blocks vary
in cost depending on type and manufacturer, and the data provided are based
on average market costs. For greater accuracy, a site and market specific cost
estimate should be developed.
Table 8-1 summarizes the costs associated with a pervious pavement demon-
stration project completed at the San Diego County Operations Center in Kearny
Mesa. Phase I included pervious asphalt, concrete, and pavers, while phase II
included only pervious asphalt (different mixes than in phase I) and concrete.

8.2 BIOREMEDIATION SYSTEMS

Rain Gardens

Design Considerations Rain gardens allow flexible design and can vary
in complexity according to site conditions and runoff volume requirements.
Although a rain garden is a structural BMP, the initial location of bioremedi-
ation areas should respect the site design process, and they should be integrated