The NB I-5 off-ramp at Imperial Highway will be permanently closed starting this Sunday. Here’s the press release from Caltrans:

Caltrans will permanently close the northbound Santa Ana Freeway (Interstate 5) off-ramp at Imperial Highway on Sunday, September 8 at 11:59 p.m.   Northbound I-5 motorists will have access to the Norwalk Boulevard, Rosecrans Avenue and Florence Avenue off-ramps.
The closure will allow construction to continue for the new southbound I-5 off-ramp at Imperial Highway and other structural work.  The on-going construction is part of the $1.6 billion I-5 South Corridor Improvement Projects to widen the freeway by adding one general purpose lane and one High Occupancy Vehicle (HOV) or carpool lane, in both directions from the Los Angeles County/Orange County line to I-605.
Other work and local street closures:
Overnight, Full Closure of Imperial Highway (near I-5 undercrossing) from 10 p.m. to 6 a.m.
Nightly, Sunday, Sept. 8  through Friday, Sept. 13
(two of two lanes will be closed in each direction)
The work involves drilling in the center median on Imperial Highway for large (80-inch diameter and 100-feet deep) Cast in Drill Hole (CIDH) foundations for the new Imperial Highway off-ramp bridge. The CIDH work includes drilling, excavating earth, setting rebar and pouring concrete.   For the safety of the public and for work crews, full street closures are necessary during this work at this location.
Full Closure of a portion of South Firestone Blvd
Daytime:  Week of Monday, September 9 through Friday, Sept.13  from  7 a.m. to 3:30 p.m.
Overnight:  Monday, September 16 through Thurs. Sept. 19 from 6 p.m. to 5 a.m.
Location:  on S. Firestone Blvd, abutting southbound I-5 near the former Shoemaker Ave. Bridge.
The work involves placing falsework, or temporary wood formwork, for the new Shoemaker Bridge.
The I-5 South Corridor Improvement Projects are overseen by Caltrans and funding is administered by Metro. Caltrans thanks the motoring public and the City of Norwalk residents and businesses for their patience during construction.
The public is encouraged to sign-up to receive email notifications on freeway lane and ramp closures and local city street closures by calling the I-5 South Corridor Improvement Projects Toll-Free Information line at (855) 454-6335 or by visiting www.I-5info.com

Freeway Traffic Information:  For timely, accurate and accessible real-time freeway traffic information and travel times, visit Caltrans Quick Map http://quickmap.dot.ca.gov/  Caltrans Quick Map