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HomeMy WebLinkAboutPhotosFIELD REPORT Tighe&Bond -2- 2- Figure 2 - Downstream end of culvert Figure 3 - Upstream end of culvert FIELD REPORT Tighe&Bond -3- 3- Figure 4 - Collapsed stone blocking flow (downstream end) Figure 5 - Flow Migration around sidewalls of culvert with loss of backfill material. Loose mortar and unstable stones supported by a chain link fence. (downstream end) Collapsed Stone Alternate Flow Paths Alternate Flow Paths MAY 2021 BASS RIVER HEADWATERS RESTORATION 60% DESIGN REPORT i Bass River Headwaters Restoration Project, Yarmouth, MA 60% Design Report SUBMITTED TO Friends of the Bass River P.O. Box 303 West Dennis, MA 02670 May 2021 MAY 2021 BASS RIVER HEADWATERS RESTORATION 60% DESIGN REPORT 4 Many areas of Miss Thatcher’s Pond have filled in with organic material and aquatic vegetation, resulting in low levels of dissolved oxygen and elevated water temperatures. Water warmed in Miss Thatcher’s Pond flows downstream, degrading water quality through the rest of the Bass River watershed. While conducting our survey and site assessment, we observed ducks, geese, and swans in Miss Thatcher’s Pond. One resident spoke about large snapping turtles that he observed in the pond. Though no records are available, we assume that warm-water fish species currently live within the pond. Along the northern and eastern edges of Miss Thatcher’s Pond, an earthen berm was created to maintain water levels and separate the pond from Cells 2 and 4. This earthen berm remains intact, though portions of the berm are showing signs of deterioration with erosion around disused flow control structures. Two flow control structures had historically carried water from the pond to the cranberry bogs to the north, but these culverts have filled in and no longer support flow. A former pump house was located on the earthen berm with only a portion of its concrete walls now remaining. Figure 2. Miss Thatcher's Pond MAY 2021 BASS RIVER HEADWATERS RESTORATION 60% DESIGN REPORT 7 During the site assessment, we examined portions of the main channel with active flow for an indication of appropriate design channel sizing. Approximately 75 feet downstream of the fish ladder at Miss Thatcher’s Pond, trees have grown close to the channel and roots obscure portions of a nearby ditch leaving an active flow area of approximately 4 feet wide at the top of bank and 1 to 1.5 feet deep (Figure 6). Here, the water moves more swiftly than elsewhere, is close to the top of bank, and has created some scour around the roots. Further downstream where the water spreads into the adjacent vegetation, the active flow appears to be limited to an approximately 4-foot-wide channel between hummocks (Figure 6). Much of the cranberry bog landscape is now a mix of hummocks of vegetation and deep pockets of water. The vegetation in Cells 1 & 3 is a mix of sphagnum moss, shrubs, and red maple saplings over 20 feet in height. In Cells 2 & 4, higher water levels limit woody growth and vegetation is mainly herbaceous, primarily grasses, rushes, sedges, and sphagnum moss. Figure 5. Looking downstream along the top of a levee separating Cells 1 & 3 from Cells 2 & 4. The main channel within the Project Site runs along the left toe of the levee in Cell 3. MAY 2021 BASS RIVER HEADWATERS RESTORATION 60% DESIGN REPORT 8 Figure 6. Approximately 75 feet downstream of the fish ladder at Miss Thatcher’s Pond, vegetation and roots have constrained the channel to be approximately 4 feet wide at the top of bank (left). Further downstream, the effective flow through the hummocky vegetation is approximately 4 feet wide at the top of bank (right). Weir Road Culvert The Weir Road culvert, a stone masonry box culvert, has partially collapsed. On the downstream side of the road, the existing opening is 3.2 feet wide and 2.5 feet tall. On the upstream side of the road, the existing opening is 1.8 feet wide and 2 feet tall. The weir road crest elevation is 10.7 feet. In addition to its poor physical condition, the culvert restricts flood flows and elevates water levels upstream. Weir Road is classed as an Urban Local Road/ Rural Minor Collector. It mostly serves the residential areas that surround it. MAY 2021 BASS RIVER HEADWATERS RESTORATION 60% DESIGN REPORT 9 Figure 7. Culvert at Weir Road Cranberry Bogs Between Weir Road and Cheyenne Lane The Project Site downstream of Weir Road consists of another area of retired cranberry bog (Cell 5). Approximately 75 feet downstream of Weir Road, the channel splits in two with flow control structures regulating water elevations in each channel. A straightened ditch conveys a portion of the flows to the northeast, while a more natural-looking sinuous channel conveys water to the northwest. These two channels generally flow north/northeast and under the earthen berm and walkway between Cheyenne Lane and Knollwood Drive. Ditches through Cell 5 currently hold water and historically would have conveyed water from the ditch to the bog platform as needed for farming. The more natural-looking channel ranges in width from 12 to 18 feet and becomes undefined in the middle of this former bog. The levee adjacent to the ditch has been converted into a walking path for public use. The vegetation within Cell 5 has grown substantially since the bogs were abandoned. In the middle of the bog along the main channel, vegetation is primarily shrubs and grass hummocks where water levels are elevated as a result of the undersized and clogged culvert downstream (see below). Elsewhere, mature red maple and pitch pine trees have grown to more 30 feet in height. The lateral MAY 2021 BASS RIVER HEADWATERS RESTORATION 60% DESIGN REPORT 10 and perimeter farm ditches remain visible, though many have partially filled in with sphagnum moss. Small patches of the invasive plant Phragmites were observed in the northeastern portion of this bog. At the downstream end of Cell 5, the channel flows through an undersized, 18-inch corrugated metal culvert beneath the earthen berm and walkway between Cheyenne Lane and Knollwood Drive (Figure 8). The culvert is partially filled and restricts flows, increasing the water elevations upstream of the crossing. Figure 8. Looking upstream at the 18-inch corrugated metal pipe under the earthen berm and walkway between Cheyenne Lane and Knollwood Drive MAY 2021 BASS RIVER HEADWATERS RESTORATION 60% DESIGN REPORT 12 Figure 9. Abandoned farm equipment and mounds from excavating a farm ditch. 4. Data Collection and Review 4.1 DESKTOP DATA REVIEW We conducted a desktop review of existing data to understand the broader context of the site and restoration project and to identify design constraints and opportunities. Land Use/ Land Cover, Geology, and Soils The headwaters of the Bass River watershed comprise primarily forested and single-family residential areas. The remaining area is forested and non-forested wetlands with some commercial land to the south of Route 6. Residential development throughout the watershed has led to increased nitrogen and nutrient loads to the groundwater and subsequent surface water in Mill Pond and further downstream. No significant sources of industrial or commercial impacts to the soils or water are known except for the chemical use on the former cranberry bogs. We describe the results of our bog soil sampling and testing in Section 5.