HomeMy WebLinkAboutSUP 06-10X2A; AGUA HEDIONDA OUTER LAGOON MAINTENANCE; SUMMARY OF CALIFORNIA GRUNION MONITORING MARCH 31- APRIL 3 2018; 2018-04-04 Merkel & Associates, Inc.
5434 Ruffin Road, San Diego, CA 92123
Tel: 858/560-5465 Fax: 858/560-7779
e-mail: associates@merkelinc.com
April 4 2018
M&A #14‐051‐06
Ms. Sheila Henika
Cabrillo Power I LLC
4600 Carlsbad Blvd
Carlsbad, CA 92008
Re: Summary of California Grunion (Leuresthes tenuis) Monitoring for the Agua Hedionda Lagoon
2018 Outer Lagoon Maintenance Dredging (March 31‐April 3, 2018)
Dear Ms. Henika:
Cabrillo Power I LLC (Cabrillo Power) is conducting maintenance dredging within the outer lagoon at
Agua Hedionda Lagoon, Carlsbad, California. The project consists of maintenance dredging of the outer
lagoon with placement of the dredged material at receiver sites located on Middle Beach and South
Beach. The dredging is part of an ongoing effort by Cabrillo Power to prevent intruding sands from
forming sandbars in the Outer Lagoon.
Beach nourishment (i.e., the placement of sand onto existing beaches) can benefit California grunion
(Leuresthes tenuis) by increasing potential spawning habitat; however, construction activities can
potentially bury grunion eggs or change the beach profile such that juvenile grunion are unable to return
to the ocean. Monitoring for grunion and implementation of impact minimization measures is usually
required when beach nourishment or construction is scheduled to overlap or follow within two weeks of
a grunion spawning activity.
Dredging for the Agua Hedionda Lagoon 2018 Outer Lagoon Maintenance Dredging Project was initiated
on Monday, February 19, 2018 and is scheduled to be completed by April 15, 2018. This schedule
overlaps with the early portion of the grunion spawning season. Deposition of dredged materials
moved from Middle Beach to South Beach on April 2, 2018 (Figure 1). Monitoring was conducted on
Middle and South Beach for California Grunion (Leuresthes tenuis) during the third grunion run of 2018
(March 31‐April 3).
No grunion were observed on the first two nights of the run. Grunion were observed spawning in low
numbers throughout Middle Beach on the third and fourth nights of the run and in low to high numbers
on South Beach on the third and fourth nights of the run (Table 1, Figure 2).
Table 1. Number of grunion sightings observed during the survey.
Approximate Group Size* Date Weather Number of
Sightings Low High
Walker
Scale
March 31, 2018 Partly cloudy, Calm,
Swell 3 to 4 ft 0 0 0 0
April 1, 2018 Partly cloudy, Light Winds,
Swell 3 to 4 ft 0 0 0 0
April 2, 2018 Partly Cloudy, Light Winds,
Swell 1 to 2 ft 20 1 >1,000 3
April 3, 2018 Partly cloudy, Light Winds,
Swell 1 to 2 ft 29 1 ~500 2
*if grunion observed
Project Vicinity Map
Agua Hedionda Lagoon 2018 Outer Lagoon Maintenance DredgingM
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M&A #14-051-06
Merkel & Associates, Inc.
0 500 1,000250Feet
Final Grunion Monitoring Results(March 31- April 3, 2018)
Agua Hedionda Lagoon 2018 Maintenance Dredging
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M&A #14-051-06
Merkel & Associates, Inc.
Grunion Monitoring Results (April 2, 2018)
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grunion range
#*Discharge locationGrunion Monitoring Results (April 3, 2018)Walker Scale
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0 500 1,000250Feet
Agua Hedionda Lagoon 2018 Outer Lagoon Maintenance Dredging Project April 4, 2018
Merkel & Associates, Inc. #14‐051‐06 4
Based on the results of the survey, several recommendations should be considered:
1. Avoid construction activities below the high water mark in areas where grunion were
observed (see Figure 2).
2. Continue fills towards the north end of South Beach as this is the furthest removed from the
beach area that has been used for spawning.
3. Since grunion eggs hatch in approximately 10 days, there are no restrictions regarding
equipment mobilization or construction below the high water mark after April 13 until the
time of the next scheduled grunion run and contingent on the findings of monitoring.
4. The next scheduled grunion run is April 16‐19, 2018. If dredging is still ongoing at that time,
grunion monitoring should be conducted.
If you have any questions regarding the monitoring, please call me at (858) 560‐5465.
Sincerely,
Keith W. Merkel
Principal Consultant