NRCS Helps to Deliver Best Management Practices (BMPs) to Lake Tahoe

Molly Pulsifer of the Tahoe Resource Conservation District measures impervious areas to develop a BMP retrofit plan to assist Lake Tahoe (NRCS image -- click to enlarge)

For the past several years, the NRCS, the Tahoe Resource Conservation District, and the Nevada Tahoe Conservation District have been providing conservation assistance one property owner at a time in attempt to slow run-off into Lake Tahoe, considered to be one of the most beautiful lakes in the United States.  Over the years, population growth and development on the erosion-prone landscape surrounding the lake have caused runoff that has contributed fine sediment and unwanted nutrients to the lake. The once clear and pristine Lake Tahoe is currently losing clarity at a rate of about a foot a year.

In an attempt to reduce run-off and stem lake degradation, the Tahoe Regional Planning Agency passed an ordinance in 1992 requiring all property owners to infiltrate storm water originating on their property.  This requirement meant that about 30,000 single-family residential properties would need to be retrofitted with best management practices (BMPs). BMPs that homeowners are expected to implement include infiltration structures and land treatment for erosion control.  The deadline for all properties to be in compliance with the ordinance is October of 2008. NRCS, the Tahoe Resource Conservation District, and the Nevada Tahoe Conservation District have been providing conservation assistance to owners of about 1,500 properties annually and about 600 completed projects per field season.

With about 19,000 single-family residences still in need of assistance and the deadline for compliance rapidly approaching, NRCS soil scientists from the California South Lake Tahoe Field Office, are contributing their expertise to a multidisciplinary team of conservationists and engineers.  As an expert in the field of soils and soil survey mapping, the local NRCS soil scientists Jane Schmidt and Woody Loftis were able to use the recently published Soil Survey of the Tahoe Basin Area, California and Nevada (2007).  This document, rich in soils information, has proven to be an extremely valuable tool in the team’s planning efforts. By using the very extensive and detailed soil survey data, the team established an evaluation process that envisioned a triage approach to parcel analysis.  This analysis provided a breakdown of soil limitations that guided project managers in determining how to allocate their limited staffing resources more effectively.  The final result was an area-wide or community approach to the application of technical assistance.  Project managers could now make decisions that improved the quality of BMP retrofit plans and expedited the project.  This planning approach resulted in properties being divided into five categories described as follows.

On 29 percent of the properties, the soils are so rapidly permeable that designs are generally not necessary. Because of the nontechnical nature of the BMPs, the owners of these properties are simply provided a do-it-yourself packet.

On 11 percent of the properties, the soils are so slowly permeable that infiltration BMPs are not practical because of economic and/or technical constraints.  These properties required large ground-disturbing excavations and were set aside.  They show potential for a regional storm-water treatment approach.

On nine percent of the properties, the soils have a seasonal high water table, which is so high that other ordinances prevent the installation of infiltration BMPs.  These properties have been set aside and show potential for a regional storm-water treatment approach.

On seven percent of the properties, the soils are rocky or are shallow to bedrock.  These properties are difficult to excavate and unfortunately require a site visit to determine their suitability for infiltration systems.

On 44 percent of the properties, the soils did not exhibit any limiting factors. These properties became the focus of staff time and resources.  They are expected to involve significant staff involvement for BMP design because these are the properties where the staff can get the most for its time.

The number of properties requiring significant staff time was reduced by 56 percent (the total of the properties described in the first four bullets).  On 29 percent of the properties, the problems were so simple that all the staff had to do was to provide the property owners a do-it-yourself packet, and on 27 percent of the properties the problems were so difficult that the property owners were asked to wait for a new approach to be worked out.

The soil survey data in correlation with GIS portrayals of problem areas and areas of opportunity enabled NRCS and partners to focus their efforts on appropriate areas, increasing the number of BMP retrofit plans that could be done in a year and minimizing the collateral damage to the environment that could result from wholesale excavations for infiltration systems in marginal locations.

The field office has not only increased their efficiency by empowering a significant percentage of homeowners to accomplish the task with minimal staff effort, but also has improved the services to the rest of the landowners.  Furthermore, landowners who are situated on sites with severe soil limitations are given a temporary reprieve from the implementation date until new technology or regional storm-water treatment resources become available.
Your contact is NRCS editor Stan Anderson at 402-437-5357.