Chapters 1 - U.S. Fish and Wildlife Service

Refuge Resources
A 45-acre area to the north of Bolsa Avenue and south of the railroad tracks (referred to as the
Bolsa Cell) was separated from unobstructed tidal influence at some point in the past by the
construction of Bolsa Avenue. According to existing topography and utilities drawings prepared
for the Port of Long Beach (Moffatt and Nichol, Engineers 1988) in preparation for developing
restoration plans for various portions of the Refuge, tidal influence, although limited, was
maintained within the Bolsa Cell through a series of culverts. Two 30-inch-diameter culverts (the
western culverts) were identified under Bolsa Avenue about 300 feet to the east of the intersection
of Bolsa Avenue and Kitts Highway, and three 30-inch-diameter culverts (the central culverts)
were present under Bolsa Avenue about half way between Kitts Highway and Case Road. Despite
a muted tidal range, tidal exchange in the Bolsa Cell supported, and continues to support, high
marsh habitat and a large population of Belding savannah sparrows.
To avoid any impacts to the wetland habitat in the Bolsa Cell as a result of the Port of Long Beach
mitigation project, restoration plans included preserving the majority of the Bolsa Cell. The
restoration project did require that the western end of the Bolsa Cell be converted into a channel
(referred to as the mitigation channel) to convey water from Anaheim Bay to Forrestal and Case
Road Ponds. To create this 300-foot-wide channel required that the remainder of the Bolsa Cell be
separated from the channel by a dike extending north from Bolsa Avenue to the railroad tracks
located along the northern edge of the Cell. The mitigation channel continues to convey tidal flows
from the main wetlands complex to the south of Bolsa Avenue via a series of large culverts into the
restored areas in Forrestal Pond and Case Road Pond(refer to Figure 4-11). The two western
culverts that had previously provided tidal exchange into the western end of the Cell were
demolished. To continue to provide tidal exchange to the western end of the Cell, two 30-inch pipe
culverts were placed in the new dike and the three 30-inch-diameter central culverts were retained.
Over the years, various changes have been made to the two culverts that connect the mitigation
channel to the Bolsa Cell in an effort to address water levels in the Cell, as well as water quality
issues. Shortly after completion of the restoration project, first one and then both culverts were
sealed at the request of the Service over concerns that the water level in the Cell was too high (Sea
Dyn, Inc. 1993). The central culverts were unaffected by this action.
In 1993, the Service once again raised concerns regarding the habitat quality in the Bolsa Cell, this
time citing issues related to degraded water quality and unacceptably low water levels. Modeling
of the hydraulic circulation within the Bolsa Cell concluded that the tidal range within the Cell
following the sealing of the two culverts was lower than the historical range by approximately 0.9
feet (Sea Dyn, Inc. 1993). Based on the modeling results, which indicated that higher high tide
water levels nearly identical to pre-restoration conditions might be achieved by reestablishing the
connection between the Bolsa Cell and the mitigation channel, the culverts were re-opened.
Although no data are currently available to verify the prediction of the 1993 modeling, the model
did predict that reopening the culverts would not result in the lower low water levels that occurred
in the Cell prior to restoration (Sea Dyn, Inc. 1993). These lower low water levels could only be
achieved by restoring a direct connection between the Bolsa Cell and Anaheim Bay, which would
require installing new culverts under Bolsa Avenue near the western end of the Bolsa Cell.
Even after the culverts were reopened, the Bolsa Cell continues to experience fluctuations in tidal
flow and water quality due to biofouling (the accumulation of mussels within the culvert) and pipe
corrosion. Biofouling has restricted tidal flow through the culverts which in turn has resulted in a
lower tidal range and degraded water quality. Water levels and water quality are restored once
the culverts are clean out. Currently, the culverts are in very poor condition, showing significant
signs of deterioration. This is resulting in tidal seepage around the culverts, which could ultimately
Draft Comprehensive Conservation Plan/Environmental Assessment 4-19