Seep Spring Retrofit

~ Level 3 – Gravity-Fed Spring Water Collection System Retrofit ~

Level 3 – Spring Water Collection System Design & Implementation

Location: Forestville, CA

Project Scope: 7th Generation Design was invited to revamp an old spring site in Forestville, CA with an upgraded water collection and distribution system. The spring has been tapped and in use for a long time, as evidenced by the multiple iterations of collection piping and spring boxes found buried in the mud surrounding the active seep zone. Two horizontal wells had been drilled adjacent to the seep zone 3 years ago in an effort to boost waning supply, one of which had since ceased to function and the other had experienced ~ 70% reduction in flow rate. The seep zone was producing ~ 3 gallons per minute, all of which was flowing out of the area uncollected.

LEFT: Condition of seep zone during the initial site assessment. Mud in the seep was thigh deep and could easily steal a boot! The most recent spring box iteration can be seen in the upper right. RIGHT: The planned collection wall location and actively seeping footprint.

Work Performed

Site Assessment

  • First visit to the site was in July of 2021.
  • Initial flow rates and seep footprint measurements were taken to develop a plan to collect the water emerging along a 25′ hydrated edge.
  • Spring box location was surveyed and rudimentary collection wall dimensions were estimated to aid in creating a detailed implementation plan.

Collection & Distribution System Design

  • A collection system consisting of a 25′ HDPE wall and two separate collection intakes was designed to handle the dispersed flow while creating an arched wall shape that will bifurcate the natural seep and stand up well to earth movement over time.
  • Collection piping was composed of 1.5″ piping, ultimately joining together in a 2″ main line at the spring box.
  • 1″ overflow lines were set above each collection package in the event of a dramatic increase in spring production.
  • A spring box was set just above the input from the still functioning horizontal well to allow for easy inspection and splitting of the total flow between our client and the neighbor who also draws water from the spring.


  • The new collection wall, filter package materials (1 yard of 2-5″ cobble, 3 yards of 3/4″ drain rock), capping materials (3.2 oz. weedmat and HDX plastic sheeting), collection piping and spring box were installed over the course of three full days.
    • Day 1: Excavation and laser leveling of collection wall footprint, removal of excess mud. Transport and staging of 4 yards of rock for the collection package materials. Washing of the main filter package materials.
    • Day 2: Cutting and heat-shaping of the bamboo rhizome barrier HDPE collection wall. Preparation of clay cobs for lining the collection wall foundation. Installation of the wall, wall penetrations cut, and initial filter package material emplaced. Spring box sited and placed.
    • Day 3: Completion of filter packages. Addition of remaining drain rock, capping of spring with weedmat and HDX followed by 3-4″ of native soil. Completion of collection piping and integration with the spring box.
Side profile sketch of the collection and overflow piping, collection wall, filter package and cap.
Pre-assembled collection and overflow piping and spring box.
Completed filter package prior to capping. Visible pipes are shock ports for the collection and overflow intakes respectively.

Watch The Whole Process Start-To-Finish

Before & After

LEFT: The seep site during the first site assessment. RIGHT: The capped filter package behind the HDPE collection wall just prior to topping with native soil – piping yet to be fully hooked up.