The past, present, and future of blind inlets as a surface water best management practice

Authors: Penn, Chad; Gonzalez, Javier; Williams, Mark; Smith, Douglas; Livingston, Stanley

Submitted to: Critical Reviews in Environmental Science Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2019
Publication Date: 7/26/2019
Citation: Penn, C.J., Gonzalez, J.M., Williams, M.R., Smith, D.R., Livingston, S.J. 2019. The past, present, and future of blind inlets as a surface water best management practice. Critical Reviews in Environmental Science Technology. 50(7):743-768. https://doi.org/10.1080/10643389.2019.1642836.
DOI: https://doi.org/10.1080/10643389.2019.1642836

Interpretive Summary: The use of blind-inlets as a surface water Best Management Practice has gained recent popularity, although there is little information in the peer review literature regarding the performance of them. This paper provided a review and presented new information about the performance of a 12-yr old blind inlet (the oldest operating unit) through physical dissection. From this, new recommendations for future developments were given. The 12-yr old blind inlet removed at least 40% of the total phosphorus (P) and sediment that flowed into it. However, blind inlets do little for dissolved P, and they can be improved in this way by replacing the traditional limestone gravel with a P sorption material (PSM), thereby allowing it to serve as a P removal structure. The blind inlet was also able to remove herbicides, although this could also be improved by constructing future structures with addition of media such as biochar. A new blind inlet/P removal structure combo was shown as one way to additionally filter tile drain water with surface runoff.

Technical Abstract: Drainage of tile-riser inlets allow direct discharge of surface water into tile drainage systems, effectively bypassing soil filtration processes and negatively affecting water quality. Blind inlets have gained recent popularity in allowing for both depression drainage and removal of suspended particulate matter by filtration through a sand/gravel layer. This paper summarizes blind inlet development and all published studies, provides new data from dissection of the longest-operating blind inlet that was recently de-commissioned, and discusses new ideas for the future of blind inlets, given certain shortcomings. Previous studies, as well as current soil analysis of the 12-yr old blind inlet confirmed the ability of blind inlets to reduce sediment and particulate phosphorus (P), with an overall removal efficiency of at least 40% for each. In addition to sediment and PP, soil sampling revealed the ability of the blind inlet to capture several pesticides: glyphosate, atrazine, S-metolachlor, and metabolites. Traditional blind inlet sand media are unable to remove appreciable amounts of dissolved P compared to alternative media such as steel slag. Enhanced removal of dissolved constituents could be easily achieved through use of P sorption materials and organic materials such as biochar, as well as combination with tile-drain filters.