HomeMy WebLinkAboutSUP 06-10X2A; AGUA HEDIONDA OUTER LAGOON MAINTENANCE; SUMMARY OF CALIFORNIA GRUNION MONITORING MARCH 1-4, 2018; 2018-03-06 Merkel & Associates, Inc.
5434 Ruffin Road, San Diego, CA 92123
Tel: 858/560-5465 Fax: 858/560-7779
e-mail: associates@merkelinc.com
March 6, 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 1‐4, 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 is
currently occurring on Middle Beach and will move to South Beach once approximately 79 percent of
the material has been placed (Figure 1). Monitoring was conducted on Middle and South Beach for
California Grunion (Leuresthes tenuis) during the first grunion run of 2018 (March 1‐4).
No grunion were observed on the first, second, or last nights of the run. Grunion were observed in low
numbers on the third night of the run, with occasional spawning occurring observed (Figure 2, Table 1).
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 1-4, 2018)
Agua Hedionda Lagoon 2018 Outer Lagoon Maintenance Dredging
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M&A #14-051-06
Merkel & Associates, Inc.
Grunion Monitoring Results (March 3, 2018)Walker Scale
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0 500 1,000250Feet
Agua Hedionda Lagoon 2018 Outer Lagoon Maintenance Dredging Project March 6, 2018
Merkel & Associates, Inc. #14‐051‐06 4
Table 1. Number of grunion sightings observed during the survey.
Approximate Group Size* Date Weather Number of
Sightings Low High
Walker
Scale
March 1, 2018 Partly cloudy, Light Winds,
Swell 1 to 3ft 0 N/A N/A 0
March 2, 2018 Partly cloudy, Light Winds,
Swell 1 to 3 ft 0 N/A N/A 0
March 3, 2018 Rainy, Light Winds,
Swell 1 to 3 ft 100‐500 10 40 1
March 4, 2018 Clear, Light Winds,
Swell 1 to 3 ft 0 N/A N/A 0
*if grunion observed
Based on the results of the survey, several recommendations should be considered:
1.Preferentially fill the top (supra‐tidal portion of the beach) to the maximum extent reasonable
(considering recreational condition needs) in order to minimize sand volume placement into the
surf.
2.To avoid filling in areas supporting grunion, remain a minimum of 50 feet away from any of the
spawning areas on the upcoast side of discharge and 200 feet away from spawning areas on the
downcoast side of the discharge.
3.The next scheduled grunion run is March 17‐20, 2018 and given the anticipated construction
schedule, grunion monitoring should be conducted.
4.In areas where active beach discharge is planned to occur following the next grunion run, build
up a high berm within the surf zone prior to each night of the run. As the run progresses, the
eroding scarp will prevent grunion from using these segments of the beach for spawning and
will avoid any conflicts with spawning. The berm will need to be built up each night of the run.
Potential pooling areas behind the berm should be aovided.
If you have any questions regarding the monitoring, please call me at (858) 560‐5465.
Sincerely,
Keith W. Merkel
Principal Consultant