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Too Green: Arboretum Cleanup Begins

By Dateline Staff on August 23, 2016 in University

Quick Summary

  • Contractor called in to remove weeds from waterway’s far west end and Lake Spafford
  • Next, a different contractor will start flow improvement project in waterway’s east half
  • Water will cascade through a set of weirs over newly engineered 15-inch drop in elevation

We recently told you about forthcoming improvements to the Arboretum Waterway’s east half. But what about the rest of the waterway, where algae and aquatic weeds seem to be taking over?

Good news: The UC Davis Arboretum and Public Garden has brought in a company that specializes in pond maintenance and aquatic plant removal. The contractor, Loomis-based Fuentes Pond Maintenance, started in Monday (Aug. 22) on the duckweed and azolla in the larger, open areas of the waterway at its far west end, and will do the same in Lake Spafford. Campus grounds personnel are spreading the vegetation on a vacant field north of the Equestrian Center.

Aquatic weeds are contained in the Arboretum Waterway.
Plants are corralled in the west end of the Arboretum Waterway Monday (Aug. 22). (Andrew Fulks/UC Davis)

Permanent fixes in the waterway’s west half are a few years off, though, because the Arboretum Waterway Maintenance and Enhancement Project is divided into phases — and the first one stretches between the waterway's eastern terminus near downtown Davis, and the Redwood Grove near Lake Spafford.

The university called for bids on Phase 1, and San Rafael-based Valentine Corp. won out. The company’s typical projects include buildings and bridges, cofferdams and marine wharves, storm and flood-control systems, underwater concrete and piling repairs, and bulkheads and retaining walls.

Officials said Phase 1 will begin in late August or early September with the construction of a cofferdam near Wyatt Deck to close off Lake Spafford during construction. Fish and turtles will be moved to the lake before the contractor drains the waterway east of the cofferdam.

The contractor will then dredge and grade the waterway channel to give it a 15-inch elevation drop, and build five weirs along the way — so water can cascade through the arboretum, east to west. At the point where the waterway opens into Lake Spafford, water will be pumped back to the eastern terminus, to maintain a constant flow.

That’s the problem with the waterway as it exists now: There is little to no flow, allowing algae to hang around and weeds to take hold. Note: The waterway is not a creek — it’s a long, narrow pond that captures storm runoff.

Earthen banks and a brick path

In rebuilding the waterway channel, Valentine Corp. will strengthen the banks, transforming them from rock and wire-basket construction to earthen slopes planted with native vegetation.

Phase 1 also includes a renovated path — made of brick — on the south side of the waterway. This path, meeting the requirements of the Americans with Disabilities Act, will connect with a brick path in the Arboretum GATEway Garden (behind the Davis Commons shopping center).

Construction in the east half of the waterway is expected to last until around the end of the year. Detours for pedestrians and bicyclists will be in place when pathways are inaccessible.

The contract with Valentine Corp. is for $1.8 million, to be paid with deferred maintenance funds.

Cascade and marsh in the west half

The waterway’s west half has a flow problem, too, despite having an added water source — treated water from the campus’s wastewater treatment plant. The water is approved for discharge into the Arboretum Waterway and the South Fork of Putah Creek. (The campus pumps water into the creek when the waterway rises to a certain level.)

The treated water, of course, is nutrient rich — which contributes to the growth of algae and weeds.

The arboretum’s long-term plan — over the next four years — is to have the water cascading through part of the west half of the arboretum, just like what’s being done in the east half: Regrade the channel and build a set of weirs, and recirculate the water by pumping it from the bottom of the cascade back to the top.

The west half cascade would stretch between Lake Spafford and the Putah Creek Lodge. From there to the western terminus of the waterway, the plan calls for the creation of an emergent marsh, open water and riparian forest habitat, with a boardwalk and viewing platforms, according to the Arboretum Waterway Maintenance and Enhancement Project FAQs.

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About the author(s)

Dateline Staff Dave Jones, editor, can be reached at 530-752-6556 or Cody Kitaura, news and media relations specialist, can be reached at 530-752-1932 or