County of Kaua’i Wastewater Management Division
This multi-year project included planning and site selection, grant funding applications, design and construction support of a LID parking lot retrofit for groundwater recharge in the sole source Santa Margarita aquifer. The Santa Margarita has become overdrafted, in part, because of urbanization which has also resulted in significant hydromodification of Carbonero Creek.
Planning included identifying potential locations for LID retrofit considering complex subsurface geology, property size and ownership, proximity to deeper aquifers, and site drainage. The grant Concept Proposal for the grant application included further development of LID retrofit measures at five of the high-potential areas within Scotts Valley. Measures considered included pervious pavement, bioretention, downspout disconnection for planter boxes, and rainwater/stormwater storage and infiltration.
Funding was awarded and KJ provided design including hydrologic analysis, engineering calculations, preparation of plans, specifications and cost estimates, CEQA compliance coordination and construction support for LID retrofit at the Transit Center Parking Lot. The project included biofiltration, pervious pavement, rain garden, sediment/erosion reduction source control, collection including overflow facilities, and enhanced high volume infiltration gallery and provisions to add adjacent areas in the future. The facilities targeted returning recharge to align more closely with preurbanization conditions. Estimated recharge will be 5 AFY on average capturing all storms 1.6” or less (about 2/3 of annual rainfall). Measures considered will both improve water quality and enhance groundwater recharge in an overdrafted aquifer.
